Android系统启动流程(4) —— 解析Launcher启动过程_no home screen found for intent

    private ActivityInfo resolveActivityInfo(Intent intent, int flags, int userId) {
        ActivityInfo ai = null;
        ComponentName comp = intent.getComponent();
        try {
            if (comp != null) {
                // Factory test.             
                ai = AppGlobals.getPackageManager().getActivityInfo(comp, flags, userId);
            } else {
                ResolveInfo info = AppGlobals.getPackageManager().resolveIntent(
                        intent,
                        intent.resolveTypeIfNeeded(mContext.getContentResolver()),
                        flags, userId);
 
                if (info != null) {
                    ai = info.activityInfo;
                }
            }
        } catch (RemoteException e) {
            // ignore
        }
 
        return ai;
    }

<manifest
    xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.android.launcher3">
    <uses-sdk android:targetSdkVersion="23" android:minSdkVersion="21"/>
    ...
 
    <application
        android:backupAgent="com.android.launcher3.LauncherBackupAgent"
        android:fullBackupOnly="true"
        android:fullBackupContent="@xml/backupscheme"
        android:hardwareAccelerated="true"
        android:icon="@drawable/ic_launcher_home"
        android:label="@string/derived_app_name"
        android:theme="@style/LauncherTheme"
        android:largeHeap="@bool/config_largeHeap"
        android:restoreAnyVersion="true"
        android:supportsRtl="true" >
 
        <!--
        Main launcher activity. When extending only change the name, and keep all the
        attributes and intent filters the same
        -->
        <activity
            android:name="com.android.launcher3.Launcher"
            android:launchMode="singleTask"
            android:clearTaskOnLaunch="true"
            android:stateNotNeeded="true"
            android:windowSoftInputMode="adjustPan"
            android:screenOrientation="nosensor"
            android:configChanges="keyboard|keyboardHidden|navigation"
            android:resizeableActivity="true"
            android:resumeWhilePausing="true"
            android:taskAffinity=""
            android:enabled="true">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.HOME" />
                <category android:name="android.intent.category.DEFAULT" />
                <category android:name="android.intent.category.MONKEY"/>
                <category android:name="android.intent.category.LAUNCHER_APP" />
            </intent-filter>
        </activity>      
       ...
 
    </application>
</manifest>

       可以看到intent-filter设置了<category android:name="android.intent.category.HOME" /> 属性，这样名称为com.android.launcher3.Launcher的Activity 就成为了主 Activity。 从前面 AMS的startHomeActivityLocked方法的注释5处，我们知如 Launcher 没有启动就会调用ActivityStarter的startHomeActivityLocked 方法来启动Launcher ，如下所示：

frameworks/base/services/core/java/com/android/server/am/ActivityStarter.java

    void startHomeActivityLocked(Intent intent, ActivityInfo aInfo, String reason) {
        // 将Launcher放入HomeStack中
        mSupervisor.moveHomeStackTaskToTop(reason); // ... 1
        mLastHomeActivityStartResult = startActivityLocked(null /*caller*/, intent,
                null /*ephemeralIntent*/, null /*resolvedType*/, aInfo, null /*rInfo*/,
                null /*voiceSession*/, null /*voiceInteractor*/, null /*resultTo*/,
                null /*resultWho*/, 0 /*requestCode*/, 0 /*callingPid*/, 0 /*callingUid*/,
                null /*callingPackage*/, 0 /*realCallingPid*/, 0 /*realCallingUid*/,
                0 /*startFlags*/, null /*options*/, false /*ignoreTargetSecurity*/,
                false /*componentSpecified*/, mLastHomeActivityStartRecord /*outActivity*/,
                null /*inTask*/, "startHomeActivity: " + reason); // ... 2
        if (mSupervisor.inResumeTopActivity) {
            // If we are in resume section already, home activity will be initialized, but not
            // resumed (to avoid recursive resume) and will stay that way until something pokes it
            // again. We need to schedule another resume.
            mSupervisor.scheduleResumeTopActivities();
        }
    }

       在注释1处将 Launcher放入HomeStack 中，HomeStack 是在 ActivityStackSupervisor 中定义的用于存储Launcher的变量 。接着调用注释2处的startActivityLocked方法来启动Launcher, 剩余的过程会和普通Activity 启动过程类似，后面会出Activity启动过程相关文章，这里就先不做讲解。最终进Launcher的onCreate 方注中，到这里 Launcher就启动完成了。

    3 Launcher 中应用图标显示过程

       Launcher 完成启动后会做很多的工作，作为桌面它会显示应用程序图标， 这与应用程序开发有所关联，应用程序图标是用户进入应用程的入口，因此我们有必要了解 Launcher 是如何显示应用程序图标的。

  @Override
    protected void onCreate(Bundle savedInstanceState) {
       
        ...
       
        LauncherAppState app = LauncherAppState.getInstance(this); // ... 1
 
        // Load configuration-specific DeviceProfile
        mDeviceProfile = app.getInvariantDeviceProfile().getDeviceProfile(this);
        if (isInMultiWindowModeCompat()) {
            Display display = getWindowManager().getDefaultDisplay();
            Point mwSize = new Point();
            display.getSize(mwSize);
            mDeviceProfile = mDeviceProfile.getMultiWindowProfile(this, mwSize);
        }
 
        mOrientation = getResources().getConfiguration().orientation;
        mSharedPrefs = Utilities.getPrefs(this);
        mIsSafeModeEnabled = getPackageManager().isSafeMode();
 
        mModel = app.setLauncher(this); // ...2
 
        ...
 
        if (!mModel.startLoader(currentScreen)) { // ... 3 
            // If we are not binding synchronously, show a fade in animation when
            // the first page bind completes.
            mDragLayer.setAlpha(0);
        } else {
            // Pages bound synchronously.
            mWorkspace.setCurrentPage(currentScreen);
 
            setWorkspaceLoading(true);
        }
 
        ...
 
    }
 

    LauncherModel setLauncher(Launcher launcher) {
        getLocalProvider(mContext).setLauncherProviderChangeListener(launcher);
        mModel.initialize(launcher); // ... 1
        return mModel;
    }

    public void initialize(Callbacks callbacks) {
        synchronized (mLock) {
            Preconditions.assertUIThread();
            mCallbacks = new WeakReference<>(callbacks);
        }
    }

    ...   
 
    // 创建了具有消息循环的线程HandlerThread对象
    @Thunk static final HandlerThread sWorkerThread = new HandlerThread("launcher-loader"); // ... 1
    static {
        sWorkerThread.start();
    }
    @Thunk static final Handler sWorker = new Handler(sWorkerThread.getLooper()); // ... 2
 
     ...
 
     public boolean startLoader(int synchronousBindPage) {
        // Enable queue before starting loader. It will get disabled in Launcher#finishBindingItems
        InstallShortcutReceiver.enableInstallQueue(InstallShortcutReceiver.FLAG_LOADER_RUNNING);
        synchronized (mLock) {
            // Don't bother to start the thread if we know it's not going to do anything
            if (mCallbacks != null && mCallbacks.get() != null) {
                final Callbacks oldCallbacks = mCallbacks.get();
                // Clear any pending bind-runnables from the synchronized load process.
                mUiExecutor.execute(new Runnable() {
                            public void run() {
                                oldCallbacks.clearPendingBinds();
                            }
                        });
 
                // If there is already one running, tell it to stop.
                stopLoader();
                LoaderResults loaderResults = new LoaderResults(mApp, sBgDataModel,
                        mBgAllAppsList, synchronousBindPage, mCallbacks);  // ... 3
                if (mModelLoaded && !mIsLoaderTaskRunning) {
                    // Divide the set of loaded items into those that we are binding synchronously,
                    // and everything else that is to be bound normally (asynchronously).
                    loaderResults.bindWorkspace();
                    // For now, continue posting the binding of AllApps as there are other
                    // issues that arise from that.
                    loaderResults.bindAllApps();
                    loaderResults.bindDeepShortcuts();
                    loaderResults.bindWidgets();
                    return true;
                } else {
                    startLoaderForResults(loaderResults); // ... 4
                }
            }
        }
        return false;
    }

    public void startLoaderForResults(LoaderResults results) {
        synchronized (mLock) {
            stopLoader();
            mLoaderTask = new LoaderTask(mApp, mBgAllAppsList, sBgDataModel, results); // ... 1
            runOnWorkerThread(mLoaderTask); // ... 2
        }
    }

    private static void runOnWorkerThread(Runnable r) {
        if (sWorkerThread.getThreadId() == Process.myTid()) {
            r.run(); // 如果当前线程是工作线程，直接执行run方法
        } else {
            // If we are not on the worker thread, then post to the worker handler
            // 如果当前线程不是工作现在，那么post到工作线程处理。
            sWorker.post(r); 
        }
    }

    public void run() {
        synchronized (this) {
            // Skip fast if we are already stopped.
            if (mStopped) {
                return;
            }
        }
 
        try (LauncherModel.LoaderTransaction transaction = mApp.getModel().beginLoader(this)) {
            long now = 0;
            if (DEBUG_LOADERS) Log.d(TAG, "step 1.1: loading workspace");
            // 加载工作区信息
            loadWorkspace(); // ... 1
 
            verifyNotStopped();
            if (DEBUG_LOADERS) Log.d(TAG, "step 1.2: bind workspace workspace");
 
            // 绑定工作区信息
            mResults.bindWorkspace(); // ... 2
 
            // Take a break
            if (DEBUG_LOADERS) {
                Log.d(TAG, "step 1 completed, wait for idle");
                now = SystemClock.uptimeMillis();
            }
            waitForIdle();
            if (DEBUG_LOADERS) Log.d(TAG, "Waited " + (SystemClock.uptimeMillis() - now) + "ms");
            verifyNotStopped();
 
            // second step
            if (DEBUG_LOADERS) Log.d(TAG, "step 2.1: loading all apps");
 
            // 加载系统已经安装的应用程序信息
            loadAllApps(); // ... 3
 
            if (DEBUG_LOADERS) Log.d(TAG, "step 2.2: Binding all apps");
            verifyNotStopped();
 
            // 绑定Appinfo
            mResults.bindAllApps(); // ... 4
            
            ...
 
        } catch (CancellationException e) {
            // Loader stopped, ignore
            if (DEBUG_LOADERS) {
                Log.d(TAG, "Loader cancelled", e);
            }
        }
    }

    private void loadAllApps() {
       
        ...
 
        // Clear the list of apps
        mBgAllAppsList.clear();
        for (UserHandle user : profiles) {
            
            ...
 
            final List<LauncherActivityInfo> apps = mLauncherApps.getActivityList(null, user);
            ...
  
            for (int i = 0; i < apps.size(); i++) {
                LauncherActivityInfo app = apps.get(i);
                // This builds the icon bitmaps.
                mBgAllAppsList.add(new AppInfo(app, user, quietMode), app); // ... 1
            }
 
            ManagedProfileHeuristic.onAllAppsLoaded(mApp.getContext(), apps, user);
        }
 
        ... 
    }

 public void bindAllApps() {
        // shallow copy
        // 将mBgAllAppList中的data属性克隆一份
        @SuppressWarnings("unchecked")
        final ArrayList<AppInfo> list = (ArrayList<AppInfo>) mBgAllAppsList.data.clone();
 
        Runnable r = new Runnable() {
            public void run() {
                Callbacks callbacks = mCallbacks.get();
                if (callbacks != null) {
                    // 这里的callbacks就是Launcher的对象
                    callbacks.bindAllApplications(list); // ... 1
                }
            }
        };
        mUiExecutor.execute(r);
    }

 public void bindAllApplications(final ArrayList<AppInfo> apps) {
 
        ...
 
        if (mAppsView != null) {
            Executor pendingExecutor = getPendingExecutor();
            if (pendingExecutor != null && mState != State.APPS) {
                // Wait until the fade in animation has finished before setting all apps list.
                pendingExecutor.execute(r);
                return;
            }
 
            mAppsView.setApps(apps); // ... 1
        }
       
        ...
    }

    public void setApps(List<AppInfo> apps) {
        mApps.setApps(apps);
    }

    @Override
    protected void onFinishInflate() {
        super.onFinishInflate();
       
        ...
 
        mAppsRecyclerView = findViewById(R.id.apps_list_view); // ... 1
        mAppsRecyclerView.setApps(mApps); // ... 2
        mAppsRecyclerView.setLayoutManager(mLayoutManager);
        mAppsRecyclerView.setAdapter(mAdapter); //  ... 3
       
        ...
    }