Android 12系统源码_WindowInsets （一）WindowInsets相关类和功能介绍_android windowinsets

一、什么是WindowInsets？

WindowInsets源码解释为Window Content的一系列插值集合，可以理解为可以将其理解为不同的窗口装饰区域类型，比如一个Activity相对于手机屏幕需要空出的地方以腾给StatusBar、Ime、NavigationBar等系统窗口，具体表现为该区域需要的上下左右的宽高。

WindowInsets包括三类：SystemWindowInsets、StableInsets、WIndowDecorInsets

• SystemWindowInsets：全窗口下，被navigationbar、statusbar、ime或其他系统窗口覆盖的区域
• StableInsets：全窗口下，被系统UI覆盖的区域
• WIndowDecorInsets：系统预留属性

二、InsetsState

2.1 InsetsState简单介绍

1、保存系统中所有的Insets的状态，他是状态描述者，持有系统中可以产生Window Insets的window状态，它主要持有以下几种类型的Insets：

frameworks/base/core/java/android/view/InsetsState.java

public class InsetsState implements Parcelable {
    public static final int ITYPE_INVALID = -1;

    static final int FIRST_TYPE = 0;

    public static final int ITYPE_STATUS_BAR = FIRST_TYPE;//状态栏
    public static final int ITYPE_NAVIGATION_BAR = 1;//导航栏
    public static final int ITYPE_CAPTION_BAR = 2;

    public static final int ITYPE_TOP_GESTURES = 3;
    public static final int ITYPE_BOTTOM_GESTURES = 4;
    public static final int ITYPE_LEFT_GESTURES = 5;
    public static final int ITYPE_RIGHT_GESTURES = 6;

    public static final int ITYPE_TOP_MANDATORY_GESTURES = 7;
    public static final int ITYPE_BOTTOM_MANDATORY_GESTURES = 8;
    public static final int ITYPE_LEFT_MANDATORY_GESTURES = 9;
    public static final int ITYPE_RIGHT_MANDATORY_GESTURES = 10;

    public static final int ITYPE_LEFT_DISPLAY_CUTOUT = 11;
    public static final int ITYPE_TOP_DISPLAY_CUTOUT = 12;
    public static final int ITYPE_RIGHT_DISPLAY_CUTOUT = 13;
    public static final int ITYPE_BOTTOM_DISPLAY_CUTOUT = 14;

    public static final int ITYPE_LEFT_TAPPABLE_ELEMENT = 15;
    public static final int ITYPE_TOP_TAPPABLE_ELEMENT = 16;
    public static final int ITYPE_RIGHT_TAPPABLE_ELEMENT = 17;
    public static final int ITYPE_BOTTOM_TAPPABLE_ELEMENT = 18;

    public static final int ITYPE_IME = 19;//输入法

    public static final int ITYPE_CLIMATE_BAR = 20;
    public static final int ITYPE_EXTRA_NAVIGATION_BAR = 21;

    static final int LAST_TYPE = ITYPE_EXTRA_NAVIGATION_BAR;
    public static final int SIZE = LAST_TYPE + 1;
    
  	//mSources变量维护所有产生Insets的window（也就是InsetsSource）的状态。
    private final InsetsSource[] mSources = new InsetsSource[SIZE];
 }

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2.2 InsetsState发生变化

1、InsetsState发生变化的时候，会回调ViewRootImpl的内部类W的insetsChanged方法，相关代码如下所示。

frameworks/base/core/java/android/view/ViewRootImpl.java

public final class ViewRootImpl implements ViewParent,
        View.AttachInfo.Callbacks, ThreadedRenderer.DrawCallbacks,
        AttachedSurfaceControl {
        
static class W extends IWindow.Stub {
        private final WeakReference<ViewRootImpl> mViewAncestor;
        private final IWindowSession mWindowSession;

        W(ViewRootImpl viewAncestor) {
            mViewAncestor = new WeakReference<ViewRootImpl>(viewAncestor);
            mWindowSession = viewAncestor.mWindowSession;
        }
        //Insets发生了变化
        @Override
        public void insetsChanged(InsetsState insetsState, boolean willMove, boolean willResize) {
            final ViewRootImpl viewAncestor = mViewAncestor.get();
            if (viewAncestor != null) {
            	//触发ViewRootImpl的dispatchInsetsChanged方法
                viewAncestor.dispatchInsetsChanged(insetsState, willMove, willResize);
            }
        } 
      }
       //ViewRootImpl的内部Handler
       final ViewRootHandler mHandler = new ViewRootHandler();

      private void dispatchInsetsChanged(InsetsState insetsState, boolean willMove,
            boolean willResize) {
        if (Binder.getCallingPid() == android.os.Process.myPid()) {
            insetsState = new InsetsState(insetsState, true /* copySource */);
        }
        if (mTranslator != null) {
            mTranslator.translateInsetsStateInScreenToAppWindow(insetsState);
        }
        if (insetsState != null && insetsState.getSourceOrDefaultVisibility(ITYPE_IME)) {
            ImeTracing.getInstance().triggerClientDump("ViewRootImpl#dispatchInsetsChanged",
                    getInsetsController().getHost().getInputMethodManager(), null /* icProto */);
        }
        SomeArgs args = SomeArgs.obtain();
        args.arg1 = insetsState;
        args.argi1 = willMove ? 1 : 0;
        args.argi2 = willResize ? 1 : 0;
        //发送MSG_INSETS_CHANGED消息事件，触发ViewRootHandler的handleMessage方法。
        mHandler.obtainMessage(MSG_INSETS_CHANGED, args).sendToTarget();
    }  
    //系统Insets的控制器
    private final InsetsController mInsetsController;
    final class ViewRootHandler extends Handler {
        @Override
        public void handleMessage(Message msg) {
            try {
                handleMessageImpl(msg);
            } finally {
                Trace.traceEnd(Trace.TRACE_TAG_VIEW);
            }
        }
        private void handleMessageImpl(Message msg) {
            switch (msg.what) {
              	...代码省略...
                case MSG_INSETS_CHANGED: {
                    SomeArgs args = (SomeArgs) msg.obj;
                    mWillMove = args.argi1 == 1;
                    mWillResize = args.argi2 == 1;
                    //触发InsetsController的onStateChanged方法
                    mInsetsController.onStateChanged((InsetsState) args.arg1);
                    args.recycle();
                    break;
                }
               ...代码省略...
           }
	}
}
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ViewRootImpl经过层层调用，最终会调用InsetsController的onStateChanged方法。

2、InsetsController的onStateChanged方法如下所示。

frameworks/base/core/java/android/view/InsetsController.java

public class InsetsController implements WindowInsetsController, InsetsAnimationControlCallbacks {

    public boolean onStateChanged(InsetsState state) {
        boolean stateChanged = !mState.equals(state, true /* excludingCaptionInsets */,
                        false /* excludeInvisibleIme */)
                || !captionInsetsUnchanged();
        if (!stateChanged && mLastDispatchedState.equals(state)) {
            return false;
        }
        if (DEBUG) Log.d(TAG, "onStateChanged: " + state);
        mLastDispatchedState.set(state, true /* copySources */);

        final InsetsState lastState = new InsetsState(mState, true /* copySources */);
        updateState(state);
        applyLocalVisibilityOverride();

        if (!mState.equals(lastState, false /* excludingCaptionInsets */,
                true /* excludeInvisibleIme */)) {
            if (DEBUG) Log.d(TAG, "onStateChanged, notifyInsetsChanged");
            mHost.notifyInsetsChanged();
            startResizingAnimationIfNeeded(lastState);
        }
        return true;
    }
}
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