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基于android R源码 Navigationbar加载流程_安卓14 navigationbar启动流程

作者：weixin_40725706 | 2024-03-11 13:13:54

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安卓14 navigationbar启动流程

Android 中关于navigationbar相关的模式主要分为三种：手势导航，“双按钮”导航，“三按钮”导致，下面主要总结下对应的启动流程以及遇到的问题。

（1）NavigationbarView 绘制

NavigationbarView在创建statusbar的时候统一被创建，具体代码流程如下：

../framework/base/packages/SystemUI/src/com/android/systemui/statusbar/phone/StatusBar.java

StatusBar启动后就会执行start方法调用的时候会执行createAndAddWindow()

  1. public void createAndAddWindows(@Nullable RegisterStatusBarResult result) {
  2.     makeStatusBarView(result);
  3. ..
  4. }

然后执行makeStatusBarView()

  1. protected void makeStatusBarView(@Nullable RegisterStatusBarResult result) {
  2. ..
  3. createNavigationBar(result);//这个方法就是创建navigationbar的入口
  4. ..
  5. }
  1. protected void createNavigationBar(@Nullable RegisterStatusBarResult result) {
  2.     mNavigationBarController.createNavigationBars(true /* includeDefaultDisplay */, result);
  3. }

../framework/base/packages/SystemUI/src/com/android/systemui/statusbar/NavigationBarController.java

createNavigationBar()

  1. public void createNavigationBars(final boolean includeDefaultDisplay,
  2.         RegisterStatusBarResult result) {
  3. //获取当前的display的数据
  4. Display[] displays = mDisplayManager.getDisplays();
  5. //执行for循环添加navigationbarview
  6.     for (Display display : displays) {
  7.         if (includeDefaultDisplay || display.getDisplayId() != DEFAULT_DISPLAY) {
  8.             void createNavigationBar(Display display, RegisterStatusBarResult result) {
  9.         if (display == null) {
  10.             return;
  11.         }
  12.  
  13.         final int displayId = display.getDisplayId();
  14.         final boolean isOnDefaultDisplay = displayId == DEFAULT_DISPLAY;
  15.         final IWindowManager wms = WindowManagerGlobal.getWindowManagerService();
  16.  
  17.         try {
  18. //framework通过属性”qemu.hw.mainkeys”来定义是否显示navigationbar
  19.             if (!wms.hasNavigationBar(displayId)) {
  20.                 return;
  21.             }
  22.         } catch (RemoteException e) {
  23.             // Cannot get wms, just return with warning message.
  24.             Log.w(TAG, "Cannot get WindowManager.");
  25.             return;
  26.         }
  27.         final Context context = isOnDefaultDisplay
  28.                 ? mContext
  29.                 : mContext.createDisplayContext(display);
  30.         //navigationbarview其实是fragement，添加到系统view中
  31.         NavigationBarFragment.create(context, (tag, fragment) -> {
  32.             NavigationBarFragment navBar = (NavigationBarFragment) fragment;
  33.  
  34.             // Unfortunately, we still need it because status bar needs LightBarController
  35.             // before notifications creation. We cannot directly use getLightBarController()
  36.             // from NavigationBarFragment directly.
  37.             LightBarController lightBarController = isOnDefaultDisplay
  38.                     ? Dependency.get(LightBarController.class)
  39.                     : new LightBarController(context,
  40.                             Dependency.get(DarkIconDispatcher.class),
  41.                             Dependency.get(BatteryController.class));
  42.             navBar.setLightBarController(lightBarController);
  43.  
  44.             // TODO(b/118592525): to support multi-display, we start to add something which is
  45.             //                    per-display, while others may be global. I think it's time to add
  46.             //                    a new class maybe named DisplayDependency to solve per-display
  47.             //                    Dependency problem.
  48.             AutoHideController autoHideController = isOnDefaultDisplay
  49.                     ? Dependency.get(AutoHideController.class)
  50.                     : new AutoHideController(context, mHandler);
  51.             navBar.setAutoHideController(autoHideController);
  52.             navBar.restoreSystemUiVisibilityState();
  53.             mNavigationBars.append(displayId, navBar);
  54.  
  55.             if (result != null) {
  56.                 navBar.setImeWindowStatus(display.getDisplayId(), result.mImeToken,
  57.                         result.mImeWindowVis, result.mImeBackDisposition,
  58.                         result.mShowImeSwitcher);
  59.             }
  60.         });
  61.     }
  62. (display, result);//创建navigationbar
  63.         }
  64.     }
  65. }

../frameworks/base/packages/SystemUI/src/com/android/systemui/statusbar/PHONE/NavigationBarFragment.java

Create()(之前执行NavigationBarFragment/onCreate/onCreateView/onViewCreate的顺序)，最终add了fragment的onCreateView加载的布局

  1. public static View create(Context context, FragmentListener listener) {
  2. //设置view添加的属性
  3.         WindowManager.LayoutParams lp = new WindowManager.LayoutParams(
  4.                 LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT,
  5.                 WindowManager.LayoutParams.TYPE_NAVIGATION_BAR,
  6.                 WindowManager.LayoutParams.FLAG_TOUCHABLE_WHEN_WAKING
  7.                         | WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE
  8.                         | WindowManager.LayoutParams.FLAG_NOT_TOUCH_MODAL
  9.                         | WindowManager.LayoutParams.FLAG_WATCH_OUTSIDE_TOUCH
  10.                         | WindowManager.LayoutParams.FLAG_SPLIT_TOUCH
  11.                         | WindowManager.LayoutParams.FLAG_SLIPPERY,
  12.                 PixelFormat.TRANSLUCENT);
  13.         lp.token = new Binder();
  14.         lp.setTitle("NavigationBar" + context.getDisplayId());
  15.         lp.accessibilityTitle = context.getString(R.string.nav_bar);
  16.         lp.windowAnimations = 0;
  17.         lp.privateFlags |= WindowManager.LayoutParams.PRIVATE_FLAG_COLOR_SPACE_AGNOSTIC;
  18.  
  19.         View navigationBarView = LayoutInflater.from(context).inflate(
  20.                 R.layout.navigation_bar_window, null);//加载navigation_bar_window布局
  21.  
  22.         if (DEBUG) Log.v(TAG, "addNavigationBar: about to add " + navigationBarView);
  23.         if (navigationBarView == null) return null;
  24.  
  25.         final NavigationBarFragment fragment = FragmentHostManager.get(navigationBarView)
  26.                 .create(NavigationBarFragment.class);
  27.         navigationBarView.addOnAttachStateChangeListener(new View.OnAttachStateChangeListener() {
  28.             @Override
  29.             public void onViewAttachedToWindow(View v) {
  30.                 final FragmentHostManager fragmentHost = FragmentHostManager.get(v);
  31.                 //使用fragment切换R.id.navigation_bar_frame,这个id定义在navigation_bar_window.xml中
  32.                 fragmentHost.getFragmentManager().beginTransaction()
  33.                         .replace(R.id.navigation_bar_frame, fragment, TAG)
  34.                         .commit();
  35.                 fragmentHost.addTagListener(TAG, listener);
  36.             }
  37.  
  38.             @Override
  39.             public void onViewDetachedFromWindow(View v) {
  40.                 FragmentHostManager.removeAndDestroy(v);
  41.             }
  42.         });
  43.         context.getSystemService(WindowManager.class).addView(navigationBarView, lp);
  44.         return navigationBarView;
  45.     }

来看WindowManager加载的这个view的布局：navigation_bar_window.xml，发现根布局是自定义的view类NavigationBarFrame

  1. <com.android.systemui.statusbar.phone.NavigationBarFrame
  2.     xmlns:android="http://schemas.android.com/apk/res/android"
  3.     xmlns:systemui="http://schemas.android.com/apk/res-auto"
  4.     android:id="@+id/navigation_bar_frame"
  5.     android:theme="@style/Theme.SystemUI"
  6.     android:layout_height="match_parent"
  7.     android:layout_width="match_parent">
  8.  
  9. </com.android.systemui.statusbar.phone.NavigationBarFrame>

我们进入NavigationBarFrame类。发现类里并不是我们的预期，就是一个FrameLayout，对DeadZone功能下的touch事件做了手脚，不管了。

NavigationBarFragment的生命周期呢。onCreateView()里，导航栏的真正的rootView。

  1. public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container,
  2.             Bundle savedInstanceState) {
  3.         return inflater.inflate(R.layout.navigation_bar, container, false);
  4.     }

进入导航栏的真正根布局：navigation_bar.xml，NavigationBarView 和 NavigationBarInflaterView 都要仔细研读

  1. <com.android.systemui.statusbar.phone.NavigationBarView
  2.     xmlns:android="http://schemas.android.com/apk/res/android"
  3.     xmlns:systemui="http://schemas.android.com/apk/res-auto"
  4.     android:layout_height="match_parent"
  5.     android:layout_width="match_parent"
  6.     android:background="@drawable/system_bar_background">
  7.  
  8.     <com.android.systemui.statusbar.phone.NavigationBarInflaterView
  9.         android:id="@+id/navigation_inflater"
  10.         android:layout_width="match_parent"
  11.         android:layout_height="match_parent" />
  12.  
  13. </com.android.systemui.statusbar.phone.NavigationBarView>

../frameworks/base/packages/SystemUI/src/com/android/systemui/statusbar/phone/NavigationBarInflaterView .java

先看构造方法，因为加载xml布局首先走的是初始化（是先执行NavigationBarView再加载NavigationBarInflaterView）

  1. //监听模式变换
  2. public class NavigationBarInflaterView extends FrameLayout implements NavigationModeController.ModeChangedListener {
  3. public NavigationBarInflaterView(Context context, AttributeSet attrs) {
  4.         super(context, attrs);
  5.         createInflaters();//根据屏幕旋转角度创建子view（单个back home or recent）的父布局
  6.         mOverviewProxyService = Dependency.get(OverviewProxyService.class);
  7.         mNavBarMode = Dependency.get(NavigationModeController.class).addListener(this);
  8. }
  9. void createInflaters() {
  10.         mLayoutInflater = LayoutInflater.from(mContext);
  11.         Configuration landscape = new Configuration();
  12.         landscape.setTo(mContext.getResources().getConfiguration());
  13.         landscape.orientation = Configuration.ORIENTATION_LANDSCAPE;
  14.         mLandscapeInflater = LayoutInflater.from(mContext.createConfigurationContext(landscape));
  15.     }

再看onFinishInflate()方法，这是view的生命周期，每个view被inflate之后都会回调

  1. protected void onFinishInflate() {
  2.         super.onFinishInflate();
  3.         inflateChildren();//加载navigation_layout/navigation_layout_verital布局，此布局复写用于定义控件点击范围
  4.         clearViews();
  5.         inflateLayout(getDefaultLayout());//关键方法：加载了 back.home.recent三个按钮的layout
  6. }
  7. protected String getDefaultLayout() {
  8.         final int defaultResource = QuickStepContract.isGesturalMode(mNavBarMode)
  9.                 ? R.string.config_navBarLayoutHandle//手势下显示的字符结构
  10.                 : mOverviewProxyService.shouldShowSwipeUpUI()//是否显示上滑动的显示字符结构
  11.                         ? R.string.config_navBarLayoutQuickstep
  12.                         : R.string.config_navBarLayout;
  13.         return getContext().getString(defaultResource);
  14.     }

看inflateLayout()：里面的newLayout参数很重要！！！根据上一个方法看到getDefaultLayout()，他return了一个在xml写死的字符串。字符样式显示如下：

<string name="config_navBarLayout" translatable="false">left[.5W],back[1WC];home;recent[1WC],right[.5W]</string>

再看inflateLayout方法，他解析分割了xml里配置的字符串，并传给了inflateButtons方法

  1. protected void inflateLayout(String newLayout) {
  2.         mCurrentLayout = newLayout;
  3.         if (newLayout == null) {
  4.             newLayout = getDefaultLayout();
  5.         }
  6.         String[] sets = newLayout.split(GRAVITY_SEPARATOR, 3);//根据“；”号分割成长度为3的数组
  7.         if (sets.length != 3) {
  8.             Log.d(TAG, "Invalid layout.");
  9.             newLayout = getDefaultLayout();
  10.             sets = newLayout.split(GRAVITY_SEPARATOR, 3);
  11.         }
  12.         String[] start = sets[0].split(BUTTON_SEPARATOR);//根据“，”号分割，包含 left[.5W]和back[1WC]
  13.         String[] center = sets[1].split(BUTTON_SEPARATOR);//包含home
  14.         String[] end = sets[2].split(BUTTON_SEPARATOR);//包含recent[1WC]和right[.5W]
  15.         // Inflate these in start to end order or accessibility traversal will be messed up.
  16.         inflateButtons(start, mHorizontal.findViewById(R.id.ends_group),
  17.                 false /* landscape */, true /* start */);
  18.         inflateButtons(start, mVertical.findViewById(R.id.ends_group),
  19.                 true /* landscape */, true /* start */);
  20.  
  21.         inflateButtons(center, mHorizontal.findViewById(R.id.center_group),
  22.                 false /* landscape */, false /* start */);
  23.         inflateButtons(center, mVertical.findViewById(R.id.center_group),
  24.                 true /* landscape */, false /* start */);
  25.  
  26.         addGravitySpacer(mHorizontal.findViewById(R.id.ends_group));//插入空格符
  27.         addGravitySpacer(mVertical.findViewById(R.id.ends_group));//插入空格符
  28.  
  29.         inflateButtons(end, mHorizontal.findViewById(R.id.ends_group),
  30.                 false /* landscape */, false /* start */);
  31.         inflateButtons(end, mVertical.findViewById(R.id.ends_group),
  32.                 true /* landscape */, false /* start */);
  33.  
  34.         updateButtonDispatchersCurrentView();
  35.     }

再看inflateButtons()方法，遍历加载inflateButton：

  1. private void inflateButtons(String[] buttons, ViewGroup parent, boolean landscape,
  2.             boolean start) {
  3.         for (int i = 0; i < buttons.length; i++) {
  4.             inflateButton(buttons[i], parent, landscape, start);
  5.         }
  6. }
  7.  
  8. protected View inflateButton(String buttonSpec, ViewGroup parent, boolean landscape,
  9.             boolean start) {
  10.         LayoutInflater inflater = landscape ? mLandscapeInflater : mLayoutInflater;
  11.         View v = createView(buttonSpec, parent, inflater);//这个是根据上面传来的字符加载不同布局
  12.         if (v == null) return null;
  13.  
  14.         v = applySize(v, buttonSpec, landscape, start);//根据返回字符的解析，来确认图标显示的大小
  15.         parent.addView(v);//addView到父布局
  16.         addToDispatchers(v);
  17.         View lastView = landscape ? mLastLandscape : mLastPortrait;
  18.         View accessibilityView = v;
  19.         if (v instanceof ReverseRelativeLayout) {
  20.             accessibilityView = ((ReverseRelativeLayout) v).getChildAt(0);
  21.         }
  22.         if (lastView != null) {
  23.             accessibilityView.setAccessibilityTraversalAfter(lastView.getId());
  24.         }
  25.         if (landscape) {
  26.             mLastLandscape = accessibilityView;
  27.         } else {
  28.             mLastPortrait = accessibilityView;
  29.         }
  30.         return v;
  31.     }

我们来看createView()方法：以home按键为例，加载了home的button,其实是加载了 R.layout.home 的layout布局

  1. private View createView(String buttonSpec, ViewGroup parent, LayoutInflater inflater) {
  2.         View v = null;
  3.         String button = extractButton(buttonSpec);
  4.         if (LEFT.equals(button)) {
  5.             button = extractButton(NAVSPACE);
  6.         } else if (RIGHT.equals(button)) {
  7.             button = extractButton(MENU_IME_ROTATE);
  8.         }
  9.         if (HOME.equals(button)) {
  10.             v = inflater.inflate(R.layout.home, parent, false);
  11.         } else if (BACK.equals(button)) {
  12.             v = inflater.inflate(R.layout.back, parent, false);
  13.         } 
  14.         .....
  15.         else if (button.startsWith(KEY)) {
  16.             String uri = extractImage(button);
  17.             int code = extractKeycode(button);
  18.             v = inflater.inflate(R.layout.custom_key, parent, false);
  19.             ((KeyButtonView) v).setCode(code);
  20.             if (uri != null) {
  21.                 if (uri.contains(":")) {
  22.                     ((KeyButtonView) v).loadAsync(Icon.createWithContentUri(uri));
  23.                 } else if (uri.contains("/")) {
  24.                     int index = uri.indexOf('/');
  25.                     String pkg = uri.substring(0, index);
  26.                     int id = Integer.parseInt(uri.substring(index + 1));
  27.                     ((KeyButtonView) v).loadAsync(Icon.createWithResource(pkg, id));
  28.                 }
  29.             }
  30.         }
  31.         return v;
  32. }
  33.  
  34. //home.xml
  35. <com.android.systemui.statusbar.policy.KeyButtonView
  36.     xmlns:android="http://schemas.android.com/apk/res/android"
  37.     xmlns:systemui="http://schemas.android.com/apk/res-auto"
  38.     android:id="@+id/home"
  39.     android:layout_width="@dimen/navigation_key_width"
  40.     android:layout_height="match_parent"
  41.     android:layout_weight="0"
  42.     systemui:keyCode="3"//systemui自定义的属性，模拟的keycode码
  43.     android:scaleType="center"
  44.     android:contentDescription="@string/accessibility_home"
  45.     android:paddingStart="@dimen/navigation_key_padding"
  46.     android:paddingEnd="@dimen/navigation_key_padding"
  47.     />

SystemUI\src\com\android\systemui\statusbar\policy\KeyButtonView.java

先来看KeyButtonView的构造方法，我们之前xml的systemui:keyCode=”3”方法在这里获取。再来看Touch事件，通过sendEvent()方法可以看出，back等view的点击touch事件不是自己处理的，而是交由系统以实体按键（keycode）的形式处理的.

当然KeyButtonView类还处理了支持长按的button,按键的响声等，这里忽略。

至此，导航栏按键事件我们梳理完毕。

  1. public KeyButtonView(Context context, AttributeSet attrs, int defStyle, InputManager manager,
  2.             UiEventLogger uiEventLogger) {
  3.         super(context, attrs);
  4.         mUiEventLogger = uiEventLogger;
  5.  
  6.         TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.KeyButtonView,
  7.                 defStyle, 0);
  8.  
  9.         mCode = a.getInteger(R.styleable.KeyButtonView_keyCode, KEYCODE_UNKNOWN);
  10.  
  11.         mPlaySounds = a.getBoolean(R.styleable.KeyButtonView_playSound, true);
  12.  
  13.         TypedValue value = new TypedValue();
  14.         if (a.getValue(R.styleable.KeyButtonView_android_contentDescription, value)) {
  15.             mContentDescriptionRes = value.resourceId;
  16.         }
  17.  
  18.         a.recycle();
  19.  
  20.         setClickable(true);
  21.         mAudioManager = (AudioManager) context.getSystemService(Context.AUDIO_SERVICE);
  22.  
  23.         mRipple = new KeyButtonRipple(context, this);
  24.         mOverviewProxyService = Dependency.get(OverviewProxyService.class);
  25.         mInputManager = manager;
  26.         setBackground(mRipple);
  27.         setWillNotDraw(false);
  28.         forceHasOverlappingRendering(false);
  29.     }
  30.     
  31.     //touch事件处理
  32.     public boolean onTouchEvent(MotionEvent ev) {
  33.         final boolean showSwipeUI = mOverviewProxyService.shouldShowSwipeUpUI();
  34.         final int action = ev.getAction();
  35.         int x, y;
  36.         if (action == MotionEvent.ACTION_DOWN) {
  37.             mGestureAborted = false;
  38.         }
  39.         if (mGestureAborted) {
  40.             setPressed(false);
  41.             return false;
  42.         }
  43.         ...
  44.         
  45.       }
  46.       
  47.       private void sendEvent(int action, int flags, long when) {
  48.         mMetricsLogger.write(new LogMaker(MetricsEvent.ACTION_NAV_BUTTON_EVENT)
  49.                 .setType(MetricsEvent.TYPE_ACTION)
  50.                 .setSubtype(mCode)
  51.                 .addTaggedData(MetricsEvent.FIELD_NAV_ACTION, action)
  52.                 .addTaggedData(MetricsEvent.FIELD_FLAGS, flags));
  53.         logSomePresses(action, flags);
  54.         //back键单独处理
  55.         if (mCode == KeyEvent.KEYCODE_BACK && flags != KeyEvent.FLAG_LONG_PRESS) {
  56.             Log.i(TAG, "Back button event: " + KeyEvent.actionToString(action));
  57.             if (action == MotionEvent.ACTION_UP) {
  58.                 mOverviewProxyService.notifyBackAction((flags & KeyEvent.FLAG_CANCELED) == 0,
  59.                         -1, -1, true /* isButton */, false /* gestureSwipeLeft */);
  60.             }
  61.         }
  62.         final int repeatCount = (flags & KeyEvent.FLAG_LONG_PRESS) != 0 ? 1 : 0;
  63. //这里根据mCode new了一个KeyEvent事件，通过injectInputEvent使事件生效。
  64.         final KeyEvent ev = new KeyEvent(mDownTime, when, action, mCode, repeatCount,
  65.                 0, KeyCharacterMap.VIRTUAL_KEYBOARD, 0,
  66.                 flags | KeyEvent.FLAG_FROM_SYSTEM | KeyEvent.FLAG_VIRTUAL_HARD_KEY,
  67.                 InputDevice.SOURCE_KEYBOARD);
  68.  
  69.         int displayId = INVALID_DISPLAY;
  70.  
  71.         // Make KeyEvent work on multi-display environment
  72.         if (getDisplay() != null) {
  73.             displayId = getDisplay().getDisplayId();
  74.         }
  75.         // Bubble controller will give us a valid display id if it should get the back event
  76.         BubbleController bubbleController = Dependency.get(BubbleController.class);
  77.         int bubbleDisplayId = bubbleController.getExpandedDisplayId(mContext);
  78.         if (mCode == KeyEvent.KEYCODE_BACK && bubbleDisplayId != INVALID_DISPLAY) {
  79.             displayId = bubbleDisplayId;
  80.         }
  81.         if (displayId != INVALID_DISPLAY) {
  82.             ev.setDisplayId(displayId);
  83.         }
  84.         //keycode通过系统处理
  85.         mInputManager.injectInputEvent(ev, InputManager.INJECT_INPUT_EVENT_MODE_ASYNC);
  86.     }

设置图片的icon到底在哪？我们之前一直阅读的是NavigationBarInflaterView，根据布局我们还有一个类没有看，NavigationBarView

  1. public NavigationBarView(Context context, AttributeSet attrs) {
  2.         super(context, attrs);
  3.  
  4.         ...
  5.         // Set up the context group of buttons
  6.         mContextualButtonGroup = new ContextualButtonGroup(R.id.menu_container);
  7.         final ContextualButton imeSwitcherButton = new ContextualButton(R.id.ime_switcher,
  8.                 R.drawable.ic_ime_switcher_default);
  9.         final RotationContextButton rotateSuggestionButton = new RotationContextButton(
  10.                 R.id.rotate_suggestion, R.drawable.ic_sysbar_rotate_button);
  11.         final ContextualButton accessibilityButton =
  12.                 new ContextualButton(R.id.accessibility_button,
  13.                         R.drawable.ic_sysbar_accessibility_button);
  14.         mContextualButtonGroup.addButton(imeSwitcherButton);
  15.         if (!isGesturalMode) {
  16.             mContextualButtonGroup.addButton(rotateSuggestionButton);
  17.         }
  18.         mContextualButtonGroup.addButton(accessibilityButton);
  19.  
  20.         mOverviewProxyService = Dependency.get(OverviewProxyService.class);
  21.         //此类主要功能是手势模式下上滑后出现的提示
  22.         mRecentsOnboarding = new RecentsOnboarding(context, mOverviewProxyService);
  23.         mFloatingRotationButton = new FloatingRotationButton(context);
  24.         mRotationButtonController = new RotationButtonController(context,
  25.                 R.style.RotateButtonCCWStart90,
  26.                 isGesturalMode ? mFloatingRotationButton : rotateSuggestionButton,
  27.                 mRotationButtonListener);
  28.  
  29.         mConfiguration = new Configuration();
  30.         mTmpLastConfiguration = new Configuration();
  31.         mConfiguration.updateFrom(context.getResources().getConfiguration());
  32. 	  //pin页面的提示类
  33.         mScreenPinningNotify = new ScreenPinningNotify(mContext);
  34.         //navigationbar的颜色控制类
  35.         mBarTransitions = new NavigationBarTransitions(this, Dependency.get(CommandQueue.class));
  36. //mButtonDispatchers是维护这些home/back/recent图标view的管理类，会传递到他的		 				child,NavigationBarInflaterView类中
  37.         mButtonDispatchers.put(R.id.back, new ButtonDispatcher(R.id.back));
  38.         mButtonDispatchers.put(R.id.home, new ButtonDispatcher(R.id.home));
  39.         mButtonDispatchers.put(R.id.home_handle, new ButtonDispatcher(R.id.home_handle));
  40.         mButtonDispatchers.put(R.id.recent_apps, new ButtonDispatcher(R.id.recent_apps));
  41.         mButtonDispatchers.put(R.id.ime_switcher, imeSwitcherButton);
  42.         mButtonDispatchers.put(R.id.accessibility_button, accessibilityButton);
  43.         mButtonDispatchers.put(R.id.rotate_suggestion, rotateSuggestionButton);
  44.         mButtonDispatchers.put(R.id.menu_container, mContextualButtonGroup);
  45.         mDeadZone = new DeadZone(this);
  46.  
  47.         mNavColorSampleMargin = getResources()
  48.                         .getDimensionPixelSize(R.dimen.navigation_handle_sample_horizontal_margin);
  49.         //手势模式下屏幕左右滑动的EdgeBack类
  50.         mEdgeBackGestureHandler = new EdgeBackGestureHandler(context, mOverviewProxyService,
  51.                 mSysUiFlagContainer, mPluginManager, this::updateStates);
  52.         //获取范围类的RegionSampling来变化显示是light/dark
  53.         mRegionSamplingHelper = new RegionSamplingHelper(this,
  54.                 new RegionSamplingHelper.SamplingCallback() {
  55.                     @Override
  56.                     public void onRegionDarknessChanged(boolean isRegionDark) {
  57.                         getLightTransitionsController().setIconsDark(!isRegionDark ,
  58.                                 true /* animate */);
  59.                     }
  60.                     @Override
  61.                     public Rect getSampledRegion(View sampledView) {
  62.                         if (mOrientedHandleSamplingRegion != null) {
  63.                             return mOrientedHandleSamplingRegion;
  64.                         }
  65.                         updateSamplingRect();
  66.                         return mSamplingBounds;
  67.                     }
  68.                     @Override
  69.                     public boolean isSamplingEnabled() {
  70.                         return isGesturalModeOnDefaultDisplay(getContext(), mNavBarMode);
  71.                     }
  72.                 });
  73.     }

下面说明下navigationbarview图标如此加载，当加载完成后会执行onAttachedToWindow，这个方法中对图标进行添加

  1. protected void onAttachedToWindow() {
  2.         super.onAttachedToWindow();
  3.         requestApplyInsets();
  4.   //设置图标的入口方法
  5.         reorient();
  6.         //模式变化时各个类对于onNavigationModeChanged状态的处理
  7.         onNavigationModeChanged(mNavBarMode);
  8.         setUpSwipeUpOnboarding(isQuickStepSwipeUpEnabled());
  9.         if (mRotationButtonController != null) {
  10.             mRotationButtonController.registerListeners();
  11.         }
  12.  
  13.         mEdgeBackGestureHandler.onNavBarAttached();
  14.         getViewTreeObserver().addOnComputeInternalInsetsListener(mOnComputeInternalInsetsListener);
  15. }
  16.  
  17. public void reorient() {
  18. 		//view gone对应的布局
  19.         updateCurrentView();
  20.  
  21.         ((NavigationBarFrame) getRootView()).setDeadZone(mDeadZone);
  22.         mDeadZone.onConfigurationChanged(mCurrentRotation);
  23.  
  24.         // force the low profile & disabled states into compliance
  25.         mBarTransitions.init();
  26.  
  27.         // Resolve layout direction if not resolved since components changing layout direction such
  28.         // as changing languages will recreate this view and the direction will be resolved later
  29.         if (!isLayoutDirectionResolved()) {
  30.             resolveLayoutDirection();
  31.         }
  32.         //更新navButtonIcon图标
  33.         updateNavButtonIcons();
  34.  
  35.         getHomeButton().setVertical(mIsVertical);
  36. }
  37.  
  38. public void updateNavButtonIcons() {
  39.         // We have to replace or restore the back and home button icons when exiting or entering
  40.         // carmode, respectively. Recents are not available in CarMode in nav bar so change
  41.         // to recent icon is not required.
  42.         final boolean useAltBack =
  43.                 (mNavigationIconHints & StatusBarManager.NAVIGATION_HINT_BACK_ALT) != 0;
  44.         KeyButtonDrawable backIcon = mBackIcon;
  45.         orientBackButton(backIcon);
  46.         KeyButtonDrawable homeIcon = mHomeDefaultIcon;
  47.         if (!mUseCarModeUi) {
  48.             orientHomeButton(homeIcon);
  49.         }
  50.         //设置home/back的button image
  51.         getHomeButton().setImageDrawable(homeIcon);
  52.         getBackButton().setImageDrawable(backIcon);
  53.         
  54. 		//根据是否分屏模式来显示recent对应的图标
  55.         updateRecentsIcon();
  56.  
  57.         // Update IME button visibility, a11y and rotate button always overrides the appearance
  58.         mContextualButtonGroup.setButtonVisibility(R.id.ime_switcher,
  59.                 (mNavigationIconHints & StatusBarManager.NAVIGATION_HINT_IME_SHOWN) != 0);
  60.  
  61.         mBarTransitions.reapplyDarkIntensity();
  62. 		...
  63.         // When screen pinning, don't hide back and home when connected service or back and
  64.         // recents buttons when disconnected from launcher service in screen pinning mode,
  65.         // as they are used for exiting.
  66.        //判断当前是否为pinning状态
  67.         final boolean pinningActive = ActivityManagerWrapper.getInstance().isScreenPinningActive();
  68.         if (mOverviewProxyService.isEnabled()) {
  69.             // Force disable recents when not in legacy mode
  70.             disableRecent |= !QuickStepContract.isLegacyMode(mNavBarMode);
  71.             if (pinningActive && !QuickStepContract.isGesturalMode(mNavBarMode)) {
  72.                 disableBack = disableHome = false;
  73.             }
  74.         } else if (pinningActive) {//pinning状态禁用back/home
  75.             disableBack = disableRecent = false;
  76.         }
  77.  
  78.         ViewGroup navButtons = getCurrentView().findViewById(R.id.nav_buttons);
  79.         if (navButtons != null) {
  80.             LayoutTransition lt = navButtons.getLayoutTransition();
  81.             if (lt != null) {
  82.                 if (!lt.getTransitionListeners().contains(mTransitionListener)) {
  83.                     lt.addTransitionListener(mTransitionListener);
  84.                 }
  85.             }
  86.         }
  87. 		//根据是否禁用来显示对应的button
  88.         getBackButton().setVisibility(disableBack       ? View.INVISIBLE : View.VISIBLE);
  89.         getHomeButton().setVisibility(disableHome       ? View.INVISIBLE : View.VISIBLE);
  90.         getRecentsButton().setVisibility(disableRecent  ? View.INVISIBLE : View.VISIBLE);
  91.         getHomeHandle().setVisibility(disableHomeHandle ? View.INVISIBLE : View.VISIBLE);
  92.         notifyActiveTouchRegions();
  93.     }

上述图标切换在横竖屏切换，分辨率变化中都会对图标进行切换，具体实现在navigationbarview/navigationbarInflateview中

../framework/base/package/SystemUI/src/com/android/systemui/statusbar/phone/NavigationBarFragment.java

最后一个问题navigationbar button的click事件在何处添加的,当布局加载完成后会回调onViewCreated

  1. public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
  2.         super.onViewCreated(view, savedInstanceState);
  3.         mNavigationBarView = (NavigationBarView) view;
  4.         ...
  5. 		
  6. 	  //back/home/recent 设置click事件方法入口	
  7.         prepareNavigationBarView();
  8.         checkNavBarModes();
  9. 		
  10. 	   //亮/灭屏/用户切换 navigatinbarview变化
  11.         IntentFilter filter = new IntentFilter(Intent.ACTION_SCREEN_OFF);
  12.         filter.addAction(Intent.ACTION_SCREEN_ON);
  13.         filter.addAction(Intent.ACTION_USER_SWITCHED);
  14.         mBroadcastDispatcher.registerReceiverWithHandler(mBroadcastReceiver, filter,
  15.                 Handler.getMain(), UserHandle.ALL);
  16.         
  17.         notifyNavigationBarScreenOn();
  18.  
  19.         mOverviewProxyService.addCallback(mOverviewProxyListener);
  20.         updateSystemUiStateFlags(-1);
  21. 		
  22. 		...
  23. }
  24.  
  25. private void prepareNavigationBarView() {
  26.             //设置navigationbar相关图标背景
  27.         mNavigationBarView.reorient();
  28.       //设置recentsButton的setOnClickListener/setOnTouchListener/setOnLongClickListener监听
  29.         ButtonDispatcher recentsButton = mNavigationBarView.getRecentsButton();
  30.         recentsButton.setOnClickListener(this::onRecentsClick);
  31.         recentsButton.setOnTouchListener(this::onRecentsTouch);
  32.         recentsButton.setLongClickable(true);
  33.         recentsButton.setOnLongClickListener(this::onLongPressBackRecents);
  34.        //设置backButton 的setLongClickable属性，backbutton具体操作在keyButtonView中实现
  35.         ButtonDispatcher backButton = mNavigationBarView.getBackButton();
  36.         backButton.setLongClickable(true);
  37. //设置homeButton 的setOnTouchListener/setOnLongClickListener监听
  38.         ButtonDispatcher homeButton = mNavigationBarView.getHomeButton();
  39.         homeButton.setOnTouchListener(this::onHomeTouch);
  40.         homeButton.setOnLongClickListener(this::onHomeLongClick);
  41.             //盲人模式下accessibilityButton的setOnClickListener/setOnLongClickListener监听
  42.         ButtonDispatcher accessibilityButton = mNavigationBarView.getAccessibilityButton();
  43.         accessibilityButton.setOnClickListener(this::onAccessibilityClick);
  44.         accessibilityButton.setOnLongClickListener(this::onAccessibilityLongClick);
  45.         updateAccessibilityServicesState(mAccessibilityManager);
  46.  
  47.         updateScreenPinningGestures();
  48.     }

至此，SystemUI的虚拟导航栏模块代码流程结束。

总结：创建一个window属性的父view，通过读取解析xml里config的配置，addView需要的icon，src图片资源通过代码设置，touch事件以keycode方式交由系统处理。

Settings中切换系统导航的流程分析

手机/平板等设备系统导航默认为“三按钮”导航,那么切换流程是如何实现的的，下面主要分析下“三按钮”导航切换到“双按钮”导航，“三按钮”导航切换到手势导航的流程。

  1. “三按钮”导航切换到“双按钮”导航分析

原生系统导航Preference定义在accessibility_settings.xml中，具体路径如下：

../packages/apps/Settings/res/xml/accessibility_settings.xml

  1. <Preference
  2.             android:fragment="com.android.settings.gestures.SystemNavigationGestureSettings"//系统导航的fragment
  3.             android:key="gesture_system_navigation_input_summary_accessibility"
  4.             android:persistent="false"
  5.             android:title="@string/system_navigation_title"
  6.             settings:searchable="false"
  7.             settings:controller="com.android.settings.gestures.SystemNavigationPreferenceController"/>//对应的控制类

由于SystemNavigationGestureSettings.java继承之RadioButtonPickerFragment,radioClick最后调用的是

setDefaultKey方法

  1. protected boolean setDefaultKey(String key) {
  2.   //通过overlaymanager设置对应不同的模式
  3.         setCurrentSystemNavigationMode(mOverlayManager, key);
  4.   //根据不同的navigationmode设置不同的video资源
  5.         setIllustrationVideo(mVideoPreference, key);
  6.         if (TextUtils.equals(KEY_SYSTEM_NAV_GESTURAL, key) && (
  7.                 isAnyServiceSupportAccessibilityButton() || isNavBarMagnificationEnabled())) {
  8.             Intent intent = new Intent(getActivity(), SettingsTutorialDialogWrapperActivity.class);
  9.             intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
  10.             startActivity(intent);
  11.         }
  12.         return true;
  13. }
  14.  
  15. static void setCurrentSystemNavigationMode(IOverlayManager overlayManager, String key) {
  16.         String overlayPackage = NAV_BAR_MODE_GESTURAL_OVERLAY;
  17.         switch (key) {
  18.             case KEY_SYSTEM_NAV_GESTURAL:
  19.                 overlayPackage = NAV_BAR_MODE_GESTURAL_OVERLAY;
  20.                 break;
  21.             case KEY_SYSTEM_NAV_2BUTTONS:
  22.                 overlayPackage = NAV_BAR_MODE_2BUTTON_OVERLAY;
  23.                 break;
  24.             case KEY_SYSTEM_NAV_3BUTTONS:
  25.                 overlayPackage = NAV_BAR_MODE_3BUTTON_OVERLAY;
  26.                 break;
  27.         }
  28.  
  29.         try {
  30.            //3键切为2键后 执行系统setEnabledExclusiveInCategory方法
  31. overlayManager.setEnabledExclusiveInCategory(overlayPackage, USER_CURRENT);
  32.         } catch (RemoteException e) {
  33.             throw e.rethrowFromSystemServer();
  34.         }
  35.     }

../frameworks/base/core/java/android/content/om/OverlayManager.java

  1.  public void setEnabledExclusiveInCategory(@NonNull final String packageName,
  2.             @NonNull UserHandle user) throws SecurityException, IllegalStateException {
  3.         try {
  4.             if (!mService.setEnabledExclusiveInCategory(packageName, user.getIdentifier())) {
  5.                 throw new IllegalStateException("setEnabledExclusiveInCategory failed");
  6.             }
  7.         } catch (SecurityException e) {
  8.             rethrowSecurityException(e);
  9.         } catch (RemoteException e) {
  10.             throw e.rethrowFromSystemServer();
  11.         }
  12.     }

../frameworks/base/services/core/java/com/android/server/om/OverlayManagerService.java

  1. public boolean setEnabledExclusiveInCategory(@Nullable String packageName,final int userIdArg) {
  2. 				...
  3.                 try {
  4.                     synchronized (mLock) {
  5.                         try {
  6.                             mImpl.setEnabledExclusive(packageName,
  7.                                     true /* withinCategory */, realUserId)
  8.                                 .ifPresent(mPropagateOverlayChange);
  9.                             return true;
  10.                         } catch (OperationFailedException e) {
  11.                             return false;
  12.                         }
  13.                     }
  14.                     ...
  15.         }
  16.  
  17. private final Consumer<PackageAndUser> mPropagateOverlayChange = (pair) -> {
  18.         //更新setting文件
  19.         persistSettings();
  20.         FgThread.getHandler().post(() -> {
  21.             List<String> affectedTargets = updatePackageManager(pair.packageName, pair.userId);
  22.             updateActivityManager(affectedTargets, pair.userId);
  23.             //发送overlaychange广播，systemui会接收到此广播
  24. broadcastActionOverlayChanged(pair.packageName, pair.userId);
  25.         });
  26. };
  27.  
  28. private void broadcastActionOverlayChanged(@NonNull final String targetPackageName,
  29.             final int userId) {
  30.   //发送ACTION_OVERLAY_CHANGED的广播
  31.         final Intent intent = new Intent(ACTION_OVERLAY_CHANGED,
  32.                 Uri.fromParts("package", targetPackageName, null));
  33.             //设置此flag限制只有动态注册才能接收次action
  34.         intent.setFlags(Intent.FLAG_RECEIVER_REGISTERED_ONLY_BEFORE_BOOT);
  35.         try {
  36.             ActivityManager.getService().broadcastIntent(null, intent, null, null, 0, null, null,
  37.                     null, android.app.AppOpsManager.OP_NONE, null, false, false, userId);
  38.         } catch (RemoteException e) {
  39.             // Intentionally left empty.
  40.         }
  41.     }

../frameworks/base/packages/SystemUI/src/com/android/systemui/statusbar/phone/NavigationModeController.java

  1. public NavigationModeController(Context context,DeviceProvisionedController deviceProvisionedController,
  2. ConfigurationController configurationController,@UiBackground Executor uiBgExecutor) {
  3. ...
  4. 	   //初始化中添加ACTION_OVERLAY_CHANGED广播监听
  5.         IntentFilter overlayFilter = new IntentFilter(ACTION_OVERLAY_CHANGED);
  6.         overlayFilter.addDataScheme("package");
  7.         overlayFilter.addDataSchemeSpecificPart("android", PatternMatcher.PATTERN_LITERAL);
  8.         mContext.registerReceiverAsUser(mReceiver, UserHandle.ALL, overlayFilter, null, null);
  9.         ...
  10.         }
  11.  
  12. private BroadcastReceiver mReceiver = new BroadcastReceiver() {
  13.         @Override
  14.         public void onReceive(Context context, Intent intent) {
  15.             updateCurrentInteractionMode(true /* notify */);
  16.         }
  17. };
  18.  
  19. public void updateCurrentInteractionMode(boolean notify) {
  20.         mCurrentUserContext = getCurrentUserContext();
  21.         //获取当前导航栏的模式
  22.         int mode = getCurrentInteractionMode(mCurrentUserContext);
  23.         //如果是手势的话执行switchToDefaultGestureNavOverlayIfNecessary
  24.         if (mode == NAV_BAR_MODE_GESTURAL) {
  25.             switchToDefaultGestureNavOverlayIfNecessary();
  26.         }
  27.         mUiBgExecutor.execute(() ->
  28.             Settings.Secure.putString(mCurrentUserContext.getContentResolver(),
  29.                     Secure.NAVIGATION_MODE, String.valueOf(mode)));
  30. 		//回调通知onNavigationModeChanged navigationbar改变
  31.         if (notify) {
  32.             for (int i = 0; i < mListeners.size(); i++) {
  33.                 //这个回调很多类注册了，我们只要关注navigationbarFragment/navigationbarview的回调
  34.                 mListeners.get(i).onNavigationModeChanged(mode);            
  35. }
  36.         }
  37.     }

../frameworks/base/packages/SystemUI/src/com/android/systemui/statusbar/phone/NavigatinbarFragment.java

  1. public void onNavigationModeChanged(int mode) {
  2.         mNavBarMode = mode;
  3.         updateScreenPinningGestures();
  4.         ...
  5.         // Workaround for b/132825155, for secondary users, we currently don't receive configuration
  6.         // changes on overlay package change since SystemUI runs for the system user. In this case,
  7.         // trigger a new configuration change to ensure that the nav bar is updated in the same way.
  8.         int userId = ActivityManagerWrapper.getInstance().getCurrentUserId();
  9.         if (userId != UserHandle.USER_SYSTEM) {
  10.             mHandler.post(() -> {
  11.                 FragmentHostManager fragmentHost = FragmentHostManager.get(mNavigationBarView);
  12.           //监听到navigatinbarmodechange重新加载fragment,重新执行布局
  13.                 fragmentHost.reloadFragments();
  14.             });
  15.         }
  16.     }

至此在setting中切换导航栏模式的流程就如上所述。

  1. “双按钮”导航/“三按钮”导航切换到手势导航

“双按钮”导航/“三按钮”导航切换到手势导航，流程与（2）上述基本相同，切换后navigationbar的高度会发生变化，具体的代码在NavigationBarView.java

  1.   protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
  2.         int w = MeasureSpec.getSize(widthMeasureSpec);
  3.         int h = MeasureSpec.getSize(heightMeasureSpec);
  4.         if (DEBUG) Log.d(TAG, String.format(
  5.                 "onMeasure: (%dx%d) old: (%dx%d)", w, h, getMeasuredWidth(), getMeasuredHeight()));
  6.  
  7.         final boolean newVertical = w > 0 && h > w
  8.                 && !isGesturalMode(mNavBarMode);
  9.       //方向变化后重新加载图标 
  10.  if (newVertical != mIsVertical) {
  11.             mIsVertical = newVertical;
  12.             if (DEBUG) {
  13.                 Log.d(TAG, String.format("onMeasure: h=%d, w=%d, vert=%s", h, w,
  14.                         mIsVertical ? "y" : "n"));
  15.             }
  16.             reorient();
  17.             notifyVerticalChangedListener(newVertical);
  18.         }
  19.               //如果是2.，3键模式，navigationbar heigh的高度是不变的，当切换到手势模式下时，navigationbar height		    会变小，一般为16dp
  20.         if (isGesturalMode(mNavBarMode)) {
  21.             // Update the nav bar background to match the height of the visible nav bar
  22.             int height = mIsVertical
  23.                     ? getResources().getDimensionPixelSize(
  24.                             com.android.internal.R.dimen.navigation_bar_height_landscape)
  25.                     : getResources().getDimensionPixelSize(
  26.                             com.android.internal.R.dimen.navigation_bar_height);
  27.             int frameHeight = getResources().getDimensionPixelSize(
  28.                     com.android.internal.R.dimen.navigation_bar_frame_height);
  29.             mBarTransitions.setBackgroundFrame(new Rect(0, frameHeight - height, w, h));
  30.         }
  31.  
  32.         super.onMeasure(widthMeasureSpec, heightMeasureSpec);
  33.     }

  1. 手势导航上滑源码分析

Android Ｏ之前的虚拟按键，基本的控制方法都是在SystemUI中做处理的，在Android R上为了在手势导航操作时其动画更加流畅，与Launcher互动效果更好，google的设计师就把手势导航相关的操作放到了Launcher3中,而且为了与SystemUI进行信息同步，利用两个aidl的文件利用binder做Launcher3与Systemui之前的进程通信。

在分析之前我们来看下AndroidManifest的一个开机启动属性android:directBootAware="true"这个属性对于手势导航的启动是有决定性的作用，有了这属性，其无论是应用还是服务都能第一时间启动，它保证了手势导航功能在系统准备好之前做好初始化。

  1. <application
  2.         android:name=".SystemUIApplication"
  3.         android:persistent="true"//该应用是可持久的，也即是常驻的应用
  4.         android:allowClearUserData="false"//是否允许清楚用户数据
  5.         android:backupAgent=".backup.BackupHelper"
  6.         android:killAfterRestore="false"//kill之后是否restore
  7.         android:hardwareAccelerated="true"
  8.         android:label="@string/app_label"
  9.         android:icon="@drawable/icon"
  10.         android:process="com.android.systemui"
  11.         android:supportsRtl="true"
  12.         android:theme="@style/Theme.SystemUI"
  13.         android:defaultToDeviceProtectedStorage="true"
  14.         android:directBootAware="true"
  15. >

而Launcher3是只对TouchInteractionService进行了设置，而且TouchInteractionService设置了一个action “android.intent.action.QUICKSTEP_SERVICE”，这为SystemUI绑定TouchInteractionService提供了向导。

下面先看下Launcher3与SystemUI之间做对接的服务，这两个服务为　SystemUI (OverviewProxyService)和Launcher3(TouchInteractionService) 。

OverviewProxyService：Class to send information from overview to launcher with a binder

是随着SystemUI应用启动而生成的，作为一个单例类存在于SystemUI这种系统应用中，而非一个正常的”Service“

OverviewProxyService的构造函数如下：

  1. public OverviewProxyService(Context context, CommandQueue commandQueue,
  2.             NavigationBarController navBarController, NavigationModeController navModeController,
  3.             NotificationShadeWindowController statusBarWinController, SysUiState sysUiState,
  4.             PipUI pipUI, Optional<Divider> dividerOptional,
  5.             Optional<Lazy<StatusBar>> statusBarOptionalLazy,
  6.             BroadcastDispatcher broadcastDispatcher) {
  7.         super(broadcastDispatcher);
  8.         //配置mRecentsComponentName的值com.android.launcher3/com.android.quickstep.RecentsActivity，默认值在framework res下
  9.         mRecentsComponentName = ComponentName.unflattenFromString(context.getString(
  10.                 com.android.internal.R.string.config_recentsComponentName));
  11.         //指向launcher3来接收ACTION_QUICKSTEP
  12.         mQuickStepIntent = new Intent(ACTION_QUICKSTEP)
  13.                 .setPackage(mRecentsComponentName.getPackageName());
  14. ....
  15.  
  16.         // 添加navigationbar mode 切换的监听
  17.         mNavBarMode = navModeController.addListener(this);
  18.  
  19.         // 添加 launcher package changes的监听
  20.         IntentFilter filter = new IntentFilter(Intent.ACTION_PACKAGE_ADDED);
  21.         filter.addDataScheme("package");
  22.         filter.addDataSchemeSpecificPart(mRecentsComponentName.getPackageName(),
  23.                 PatternMatcher.PATTERN_LITERAL);
  24.         filter.addAction(Intent.ACTION_PACKAGE_CHANGED);
  25.         mContext.registerReceiver(mLauncherStateChangedReceiver, filter);
  26.  
  27.         // Listen for status bar state changes
  28.         statusBarWinController.registerCallback(mStatusBarWindowCallback);
  29.         mScreenshotHelper = new ScreenshotHelper(context);
  30.  
  31.         // Listen for tracing state changes
  32.         commandQueue.addCallback(new CommandQueue.Callbacks() {
  33.             @Override
  34.             public void onTracingStateChanged(boolean enabled) {
  35.                 mSysUiState.setFlag(SYSUI_STATE_TRACING_ENABLED, enabled)
  36.                         .commitUpdate(mContext.getDisplayId());
  37.             }
  38.         });
  39.  
  40.         // Listen for user setup
  41.         startTracking();
  42.  
  43.         // Connect to the service
  44.         updateEnabledState();
  45.         startConnectionToCurrentUser();
  46.     }

OverviewProxyService中实现了ISystemUiProxy.aidl，如下所示：

SystemUI/src/com/android/systemui/recents/OverviewProxyService.java

  1. private ISystemUiProxy mSysUiProxy = new ISystemUiProxy.Stub() {
  2.         @Override
  3.         public void startScreenPinning(int taskId) {//开始固定屏幕
  4.             if (!verifyCaller("startScreenPinning")) {
  5.                 return;
  6.             }
  7.             long token = Binder.clearCallingIdentity();
  8.             try {
  9.                 mHandler.post(() -> {
  10.                     mStatusBarOptionalLazy.ifPresent(
  11.                             statusBarLazy -> statusBarLazy.get().showScreenPinningRequest(taskId,
  12.                                     false /* allowCancel */));
  13.                 });
  14.             } finally {
  15.                 Binder.restoreCallingIdentity(token);
  16.             }
  17.         }
  18.         @Override
  19.         public void stopScreenPinning() {//停止固定屏幕
  20.             if (!verifyCaller("stopScreenPinning")) {
  21.                 return;
  22.             }
  23.             long token = Binder.clearCallingIdentity();
  24.             try {
  25.                 mHandler.post(() -> {
  26.                     try {
  27.                         ActivityTaskManager.getService().stopSystemLockTaskMode();
  28.                     } catch (RemoteException e) {
  29.                         Log.e(TAG_OPS, "Failed to stop screen pinning");
  30.                     }
  31.                 });
  32.             } finally {
  33.                 Binder.restoreCallingIdentity(token);
  34.             }
  35.         }
  36. 		...
  37.     };
  38.      /***还有很多其他功能，在ISystemUiProxy.aidl文件中都有功能相关的描述
  39.         SystemUI/shared/src/com/android/systemui/shared/recents/ISystemUiProxy.aidl***/

mSysUiProxy是作为binder服务端存在的,在SystemUI等待着类似屏幕固定,分屏，最近任务展示等方法的回调。而mSysUiProxy与Launcher3与进行通信的开端便是“ServiceConnection”服务的链接绑定，如下所示：

SystemUI/src/com/android/systemui/recents/OverviewProxyService.java

  1.   /*service对应的action,用于绑定服务*/
  2. private static final String ACTION_QUICKSTEP = "android.intent.action.QUICKSTEP_SERVICE";
  3. //OverviewProxyService构造函数中调用startConnectionToCurrentUser()来binder Service
  4.     private void internalConnectToCurrentUser() {
  5.         /*断开之间的所有链接*/
  6.         disconnectFromLauncherService();
  7.  
  8.         // If user has not setup yet or already connected, do not try to connect
  9.         if (!mDeviceProvisionedController.isCurrentUserSetup() || !isEnabled()) {
  10.             Log.v(TAG_OPS, "Cannot attempt connection, is setup "
  11.                 + mDeviceProvisionedController.isCurrentUserSetup() + ", is enabled "
  12.                 + isEnabled());
  13.             return;
  14.         }
  15.         mHandler.removeCallbacks(mConnectionRunnable);
  16.         /*Intent填入指定的action*/
  17.         Intent launcherServiceIntent = new Intent(ACTION_QUICKSTEP)
  18.                 .setPackage(mRecentsComponentName.getPackageName());
  19.         try {
  20.             /*绑定服务*/
  21.             mBound = mContext.bindServiceAsUser(launcherServiceIntent,
  22.                     mOverviewServiceConnection,
  23.                     Context.BIND_AUTO_CREATE | Context.BIND_FOREGROUND_SERVICE_WHILE_AWAKE,
  24.                     UserHandle.of(mDeviceProvisionedController.getCurrentUser()));
  25.         } catch (SecurityException e) {
  26.             Log.e(TAG_OPS, "Unable to bind because of security error", e);
  27.         }
  28.         if (mBound) {
  29.             // Ensure that connection has been established even if it thinks it is bound
  30.             mHandler.postDelayed(mDeferredConnectionCallback, DEFERRED_CALLBACK_MILLIS);
  31.         } else {
  32.             // Retry after exponential backoff timeout
  33.             retryConnectionWithBackoff();
  34.         }
  35.     }
  36.  
  37.     private final ServiceConnection mOverviewServiceConnection = new ServiceConnection() {
  38.         @Override
  39.         public void onServiceConnected(ComponentName name, IBinder service) {
  40.             mConnectionBackoffAttempts = 0;
  41.             mHandler.removeCallbacks(mDeferredConnectionCallback);
  42.             try {
  43.                 service.linkToDeath(mOverviewServiceDeathRcpt, 0);
  44.             } catch (RemoteException e) {
  45.                 // Failed to link to death (process may have died between binding and connecting),
  46.                 // just unbind the service for now and retry again
  47.                 Log.e(TAG_OPS, "Lost connection to launcher service", e);
  48.                 disconnectFromLauncherService();
  49.                 retryConnectionWithBackoff();
  50.                 return;
  51.             }
  52.  
  53.             mCurrentBoundedUserId = mDeviceProvisionedController.getCurrentUser();
  54.              /*获取IOverviewProxy的代理*/
  55.             mOverviewProxy = IOverviewProxy.Stub.asInterface(service);
  56.  
  57.             Bundle params = new Bundle();
  58.             params.putBinder(KEY_EXTRA_SYSUI_PROXY, mSysUiProxy.asBinder());
  59.             params.putFloat(KEY_EXTRA_WINDOW_CORNER_RADIUS, mWindowCornerRadius);
  60.             params.putBoolean(KEY_EXTRA_SUPPORTS_WINDOW_CORNERS, mSupportsRoundedCornersOnWindows);
  61.             try {
  62.                 /*把ISystemUiProxy推荐给Launcher3*/
  63.                 mOverviewProxy.onInitialize(params);
  64.             } catch (RemoteException e) {
  65.                 mCurrentBoundedUserId = -1;
  66.                 Log.e(TAG_OPS, "Failed to call onInitialize()", e);
  67.             }
  68.             dispatchNavButtonBounds();
  69.  
  70.             // Update the systemui state flags
  71.             updateSystemUiStateFlags();
  72.  
  73.             notifyConnectionChanged();
  74.         }
  75.  
  76.         @Override
  77.         public void onNullBinding(ComponentName name) {
  78.             Log.w(TAG_OPS, "Null binding of '" + name + "', try reconnecting");
  79.             mCurrentBoundedUserId = -1;
  80.             retryConnectionWithBackoff();
  81.         }
  82.  
  83.         @Override
  84.         public void onBindingDied(ComponentName name) {
  85.             Log.w(TAG_OPS, "Binding died of '" + name + "', try reconnecting");
  86.             mCurrentBoundedUserId = -1;
  87.             retryConnectionWithBackoff();
  88.         }
  89.  
  90.         @Override
  91.         public void onServiceDisconnected(ComponentName name) {
  92.             // Do nothing
  93.             mCurrentBoundedUserId = -1;
  94.         }
  95.     }

在mOverviewServiceConnection的onServiceConnected方法中，又看到了另外一个aidl的实现"IOverviewProxy"。这个对象是在服务绑定后通过binder传递过来的，那么"IOverviewProxy"的服务端就应该在Launcher3中了。当"IOverviewProxy"出现在SystemUI中的第一时间，mSysUiProxy就迫不及待的把自己打包好放到了Bundle(mSysUiProxy这个服务者在很尽责的推销自己嘛)，然后又由mOverviewProxy反向传递给了Launcher3。

TouchInteractionService：Service connected by system-UI for handling touch interaction.

TouchInteractionService 是Launcher3中的Service，注册于AndroidManifest中，服务有directBootAware属性，为开机即启动的服务。

  1. <service
  2.             android:name="com.android.quickstep.TouchInteractionService"
  3.             android:permission="android.permission.STATUS_BAR_SERVICE"
  4.             android:directBootAware="true" >
  5.             <intent-filter>
  6.                 <action android:name="android.intent.action.QUICKSTEP_SERVICE" />
  7.             </intent-filter>
  8.         </service>

下面就要看下IOverviewProxy在TouchInteractionService中的实现了：

  1. private final IBinder mMyBinder = new IOverviewProxy.Stub() {
  2.         public void onActiveNavBarRegionChanges(Region region) {
  3.             mActiveNavBarRegion = region;
  4.         }
  5.         /*从SystemUI而来，携带着在SystemUI中实现的ISystemUiProxy*/
  6.         public void onInitialize(Bundle bundle) {
  7.             mISystemUiProxy = ISystemUiProxy.Stub
  8.                     .asInterface(bundle.getBinder(KEY_EXTRA_SYSUI_PROXY));
  9.             MAIN_THREAD_EXECUTOR.execute(TouchInteractionService.this::initInputMonitor);
  10.             MAIN_THREAD_EXECUTOR.execute(TouchInteractionService.this::onSystemUiProxySet);
  11.         }
  12.  
  13.         @Override
  14.         public void onOverviewToggle() {
  15.             mOverviewCommandHelper.onOverviewToggle();
  16.         }
  17.  
  18.         @Override
  19.         public void onOverviewShown(boolean triggeredFromAltTab) {
  20.             mOverviewCommandHelper.onOverviewShown(triggeredFromAltTab);
  21.         }
  22.  
  23.         @Override
  24.         public void onOverviewHidden(boolean triggeredFromAltTab, boolean triggeredFromHomeKey) {
  25.             if (triggeredFromAltTab && !triggeredFromHomeKey) {
  26.                 // onOverviewShownFromAltTab hides the overview and ends at the target app
  27.                 mOverviewCommandHelper.onOverviewHidden();
  28.             }
  29.         }
  30.  
  31.         /***一些最近任务界面，Back按键等事件的互通，具体
  32.         SystemUI/shared/src/com/android/systemui/shared/recents/IOverviewProxy.aidl***/
  33.     };
  34.  
  35.     @Override
  36.     public IBinder onBind(Intent intent) {
  37.         Log.d(TAG, "Touch service connected");
  38.         /*当绑定成功后，反馈给SystemUI的IOverviewProxy*/
  39.         return mMyBinder;
  40.     }

当上面的IOverviewProxy函数onInitialize执行完成之后，SystemUI也就和Launcher3胜利会师了，从而进入了你中有我，我中有你的状态。整个流程如下图所示：

当Launcher3成功与SystemUI能够正常通信之后Launcher3就开始注册屏幕Touch事件的监听了。

Launcher3/quickstep/recents_ui_overrides/src/com/android/quickstep/TouchInteractionService.java

  1. private final IBinder mMyBinder = new IOverviewProxy.Stub() {
  2.         @BinderThread
  3.         public void onInitialize(Bundle bundle) {
  4.       //获取binder代理
  5.             ISystemUiProxy proxy = ISystemUiProxy.Stub.asInterface(
  6.                     bundle.getBinder(KEY_EXTRA_SYSUI_PROXY));
  7.             MAIN_EXECUTOR.execute(() -> {
  8.                 SystemUiProxy.INSTANCE.get(TouchInteractionService.this).setProxy(proxy);
  9.                 //监听屏幕触摸事件
  10. TouchInteractionService.this.initInputMonitor();
  11.                 preloadOverview(true /* fromInit */);
  12.             });
  13.             sIsInitialized = true;
  14.         }
  15.  
  16. private void initInputMonitor() {
  17.         disposeEventHandlers();
  18.         if (mDeviceState.isButtonNavMode() || !SystemUiProxy.INSTANCE.get(this).isActive()) {
  19.             return;
  20.         }
  21.         Bundle bundle = SystemUiProxy.INSTANCE.get(this).monitorGestureInput("swipe-up",
  22.                 mDeviceState.getDisplayId());
  23. //这个地方就是注册监听触摸事件的地方了
  24.         mInputMonitorCompat = InputMonitorCompat.fromBundle(bundle, KEY_EXTRA_INPUT_MONITOR);
  25.         mInputEventReceiver = mInputMonitorCompat.getInputReceiver(Looper.getMainLooper(),
  26.                 mMainChoreographer, this::onInputEvent);
  27.         mRotationTouchHelper.updateGestureTouchRegions();
  28.     }

从上面看到，Launcher3处理触摸事件的方法是onInputEvent，其会根据系统处于不同的状态而生成不同的事件处理器，以下是具体的代码实现：

../packages/apps/Launcher3/quickstep/recents_ui_overrides/src/com/android/quickstep/TouchInteractionService.java

  1. private void onInputEvent(InputEvent ev) {
  2.         if (!(ev instanceof MotionEvent)) {
  3.             Log.e(TAG, "Unknown event " + ev);
  4.             return;
  5.         }
  6.         MotionEvent event = (MotionEvent) ev;
  7.  
  8.         TestLogging.recordMotionEvent(
  9.                 TestProtocol.SEQUENCE_TIS, "TouchInteractionService.onInputEvent", event);
  10.  
  11.         if (!mDeviceState.isUserUnlocked()) {
  12.             return;
  13.         }
  14.  
  15.         Object traceToken = TraceHelper.INSTANCE.beginFlagsOverride(
  16.                 TraceHelper.FLAG_ALLOW_BINDER_TRACKING);
  17.  
  18.         final int action = event.getAction();
  19.         if (action == ACTION_DOWN) {
  20.             if (TestProtocol.sDebugTracing) {
  21.                 Log.d(TestProtocol.NO_SWIPE_TO_HOME, "TouchInteractionService.onInputEvent:DOWN");
  22.             }
  23. ....
  24. }

Laucher3中处理手势相关操作，具体后续会继续研究下对应的处理流程。

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