RecentsActivity启动分析二

接着上一篇RecentsActivity启动分析一继续分析RecentsActivity。先给大家看布局的结构图

简单的画了RecentsView部分，如下图所示

那接着就从RecentsActivity的构造方法开始分析

@Override
public void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);//初始化RecentsTaskLoaderRecentsTaskLoader.initialize(this);//获取SystemServicesProxy的对象SystemServicesProxy ssp = RecentsTaskLoader.getInstance().getSystemServicesProxy();mConfig = RecentsConfiguration.reinitialize(this, ssp);// 初始化AppWidgetHostmAppWidgetHost = new RecentsAppWidgetHost(this, Constants.Values.App.AppWidgetHostId);//设置布局setContentView(R.layout.recents);//控件初始化mRecentsView = (RecentsView) findViewById(R.id.recents_view);mRecentsView.setCallbacks(this);mRecentsView.setSystemUiVisibility(View.SYSTEM_UI_FLAG_LAYOUT_STABLE |View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN |View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION);mEmptyViewStub = (ViewStub) findViewById(R.id.empty_view_stub);mDebugOverlayStub = (ViewStub) findViewById(R.id.debug_overlay_stub);mScrimViews = new SystemBarScrimViews(this, mConfig);inflateDebugOverlay();// Bind the search app widget when we first start up//绑定搜索框mSearchWidgetInfo = ssp.getOrBindSearchAppWidget(this, mAppWidgetHost);// Register the broadcast receiver to handle messages when the screen is turned off//注册广播接收器，接收来自系统的广播，处理系统消息IntentFilter filter = new IntentFilter();filter.addAction(Intent.ACTION_SCREEN_OFF);filter.addAction(SearchManager.INTENT_GLOBAL_SEARCH_ACTIVITY_CHANGED);registerReceiver(mSystemBroadcastReceiver, filter);//清除近期应用的按钮ImageButton clearButton = (ImageButton) findViewById(R.id.clear_button);clearButton.setOnClickListener(new OnClickListener() {@Overridepublic void onClick(View v) {new Thread(new Runnable() {@Overridepublic void run() {//清除所有任务removeAllTasks();}}).start();}});am = (ActivityManager) getSystemService(Context.ACTIVITY_SERVICE);pm = getPackageManager();
}

这个函数主要就是初始化控件，注册广播。

onStart()

@Override
protected void onStart() {super.onStart();MetricsLogger.visible(this, MetricsLogger.OVERVIEW_ACTIVITY);//获取RecentsTaskLoader实例RecentsTaskLoader loader = RecentsTaskLoader.getInstance();//获取SystemServiceProxy实例，这个类主要承接了RecentsActivity和系统服务的交互，包含获取最近任务列表，启动制定任务所在的应用等等。 SystemServicesProxy ssp = loader.getSystemServicesProxy();//通知可见性改变Recents.notifyVisibilityChanged(this, ssp, true);//注册广播接收器接收处理来自Service的消息：隐藏、打开Recent Apps界面IntentFilter filter = new IntentFilter();filter.addAction(Recents.ACTION_HIDE_RECENTS_ACTIVITY);filter.addAction(Recents.ACTION_TOGGLE_RECENTS_ACTIVITY);filter.addAction(Recents.ACTION_START_ENTER_ANIMATION);registerReceiver(mServiceBroadcastReceiver, filter);// Register any broadcast receivers for the task loaderloader.registerReceivers(this, mRecentsView);//更新recent tasksupdateRecentsTasks();// If this is a new instance from a configuration change, then we have to manually trigger// the enter animation state, or if recents was relaunched by AM, without going through// the normal mechanismsboolean wasLaunchedByAm = !mConfig.launchedFromHome && !mConfig.launchedFromAppWithThumbnail;if (mConfig.launchedHasConfigurationChanged || wasLaunchedByAm) {onEnterAnimationTriggered();}if (!mConfig.launchedHasConfigurationChanged) {mRecentsView.disableLayersForOneFrame();}
}

重点来看两点:

(1)Recents.notifyVisibilityChanged(this, ssp, true);

既然是Recents类，我们就到该类中寻找这个被调用的函数

/** Notifies the callbacks that the visibility of Recents has changed. */
public static void notifyVisibilityChanged(Context context, SystemServicesProxy ssp,boolean visible) {if (ssp.isForegroundUserOwner()) {visibilityChanged(visible);} else {Intent intent = createLocalBroadcastIntent(context,ACTION_PROXY_NOTIFY_RECENTS_VISIBLITY_TO_OWNER);intent.putExtra(EXTRA_RECENTS_VISIBILITY, visible);context.sendBroadcastAsUser(intent, UserHandle.OWNER);}
}

调用了sRecentsComponentCallbacks.onVisibilityChanged(visible)，RecentsComponent.Callbacks是RecentsComponent的内部接口，由BaseStatusBar类实现，那这样就是调用了BaseAtatusBar类中的onVisibilityChanged函数.

(2)updateRecentsTasks();

/** Updates the set of recent tasks */
void updateRecentsTasks() {// If AlternateRecentsComponent has preloaded a load plan, then use that to prevent// reconstructing the task stackRecentsTaskLoader loader = RecentsTaskLoader.getInstance();RecentsTaskLoadPlan plan = Recents.consumeInstanceLoadPlan();if (plan == null) {//创建加载任务计划plan = loader.createLoadPlan(this);}// Start loading tasks according to the load planif (!plan.hasTasks()) {/*preloadTasks方法中调用了RecentsTaskLoadPlan类的preLoadPlan函数，在该函数中调用preloadRawTask函数继而调用mSystemServicesProxy.getRecentTasks函数得到rawtasks，并不是正在显示的UI，是原始数据配合UI显示*/}RecentsTaskLoadPlan.Options loadOpts = new RecentsTaskLoadPlan.Options();loadOpts.runningTaskId = mConfig.launchedToTaskId;loadOpts.numVisibleTasks = mConfig.launchedNumVisibleTasks;loadOpts.numVisibleTaskThumbnails = mConfig.launchedNumVisibleThumbnails;loader.loadTasks(this, plan, loadOpts);ArrayList<TaskStack> stacks = plan.getAllTaskStacks();mConfig.launchedWithNoRecentTasks = !plan.hasTasks();if (!mConfig.launchedWithNoRecentTasks) {mRecentsView.setTaskStacks(stacks);}// Create the home intent runnableIntent homeIntent = new Intent(Intent.ACTION_MAIN, null);homeIntent.addCategory(Intent.CATEGORY_HOME);homeIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK |Intent.FLAG_ACTIVITY_RESET_TASK_IF_NEEDED);mFinishLaunchHomeRunnable = new FinishRecentsRunnable(homeIntent,ActivityOptions.makeCustomAnimation(this,mConfig.launchedFromSearchHome ? R.anim.recents_to_search_launcher_enter :R.anim.recents_to_launcher_enter,mConfig.launchedFromSearchHome ? R.anim.recents_to_search_launcher_exit :R.anim.recents_to_launcher_exit));// Mark the task that is the launch targetint taskStackCount = stacks.size();int launchTaskIndexInStack = 0;if (mConfig.launchedToTaskId != -1) {for (int i = 0; i < taskStackCount; i++) {TaskStack stack = stacks.get(i);ArrayList<Task> tasks = stack.getTasks();int taskCount = tasks.size();for (int j = 0; j < taskCount; j++) {Task t = tasks.get(j);if (t.key.id == mConfig.launchedToTaskId) {t.isLaunchTarget = true;launchTaskIndexInStack = tasks.size() - j - 1;break;}}}}// Update the top level view's visibilitiesif (mConfig.launchedWithNoRecentTasks) {if (mEmptyView == null) {mEmptyView = mEmptyViewStub.inflate();}mEmptyView.setVisibility(View.VISIBLE);mRecentsView.setSearchBarVisibility(View.GONE);} else {if (mEmptyView != null) {mEmptyView.setVisibility(View.GONE);}if (mRecentsView.hasValidSearchBar()) {mRecentsView.setSearchBarVisibility(View.VISIBLE);} else {refreshSearchWidgetView();}}// Animate the SystemUI scrims into viewmScrimViews.prepareEnterRecentsAnimation();……
}

这个函数主要做了三件事:
(1)调用RecentsTaskLoader的loadTasks函数获取相关最近使用应用的相关信息。

/** Begins loading the heavy task data according to the specified options. */
public void loadTasks(Context context, RecentsTaskLoadPlan plan,RecentsTaskLoadPlan.Options opts) {if (opts == null) {throw new RuntimeException("Requires load options");}plan.executePlan(opts, this, mLoadQueue);if (!opts.onlyLoadForCache) {mNumVisibleTasksLoaded = opts.numVisibleTasks;mNumVisibleThumbnailsLoaded = opts.numVisibleTaskThumbnails;// Start the loadermLoader.start(context);}
}

mLoader是RecentsTaskLoader的对象，在它的构造方法中进行一些初始化操作

private RecentsTaskLoader(Context context) {mMaxThumbnailCacheSize = context.getResources().getInteger(R.integer.config_recents_max_thumbnail_count);mMaxIconCacheSize = context.getResources().getInteger(R.integer.config_recents_max_icon_count);int iconCacheSize = Constants.DebugFlags.App.DisableBackgroundCache ? 1 :mMaxIconCacheSize;int thumbnailCacheSize = Constants.DebugFlags.App.DisableBackgroundCache ? 1 :mMaxThumbnailCacheSize;// Create the default assetsBitmap icon = Bitmap.createBitmap(1, 1, Bitmap.Config.ARGB_8888);icon.eraseColor(0x00000000);mDefaultThumbnail = Bitmap.createBitmap(1, 1, Bitmap.Config.ARGB_8888);mDefaultThumbnail.setHasAlpha(false);mDefaultThumbnail.eraseColor(0xFFffffff);mDefaultApplicationIcon = new BitmapDrawable(context.getResources(), icon);// Initialize the proxy, cache and loadersmSystemServicesProxy = new SystemServicesProxy(context);mPackageMonitor = new RecentsPackageMonitor();mLoadQueue = new TaskResourceLoadQueue();mApplicationIconCache = new DrawableLruCache(iconCacheSize);mThumbnailCache = new BitmapLruCache(thumbnailCacheSize);mActivityLabelCache = new StringLruCache(100);mContentDescriptionCache = new StringLruCache(100);mLoader = new TaskResourceLoader(mLoadQueue, mApplicationIconCache, mThumbnailCache,mDefaultThumbnail, mDefaultApplicationIcon);}

初始化了三个缓存，主要用于缓存应用图标，名称，截屏。mLoadQueue是一个用于缓存任务的队列。mLoader是
TaskResourceLoader的对象，它的构造函数中启动了一个线程HandlerThread，在它的Run函数中一直循环从mLoadQueue中读取任务并获取任务所对应的截图，并缓存到mThumbnailCache中，然后通知TaskView加载截图并显示。

/** Restarts the loader thread */
void start(Context context) {mContext = context;mCancelled = false;mSystemServicesProxy = new SystemServicesProxy(context);// Notify the load thread to start loadingsynchronized(mLoadThread) {mLoadThread.notifyAll();}
}
@Override
public void run() {while (true) {if (mCancelled) {// We have to unset the context here, since the background thread may be using it// when we call stop()mContext = null;// If we are cancelled, then wait until we are started againsynchronized(mLoadThread) {try {mLoadThread.wait();} catch (InterruptedException ie) {ie.printStackTrace();}}} else {RecentsConfiguration config = RecentsConfiguration.getInstance();SystemServicesProxy ssp = mSystemServicesProxy;// If we've stopped the loader, then fall through to the above logic to wait on// the load threadif (ssp != null) {// Load the next item from the queuefinal Task t = mLoadQueue.nextTask();if (t != null) {Drawable cachedIcon = mApplicationIconCache.get(t.key);Bitmap cachedThumbnail = mThumbnailCache.get(t.key);……if (!mCancelled) {// Notify that the task data has changedfinal Drawable newIcon = cachedIcon;final Bitmap newThumbnail = cachedThumbnail == mDefaultThumbnail? null : cachedThumbnail;mMainThreadHandler.post(new Runnable() {@Overridepublic void run() {t.notifyTaskDataLoaded(newThumbnail, newIcon);}});}}}……}}
}

t是Task类的对象，调用notifyTaskDataLoaded的函数中最终调用mCb.onTaskDataLoaded函数,mCb是Task.TaskCallbacks内部接口类的对象，而TaskView实现了这个接口，也就是调用用TaskView中的onTaskDataLoaded函数。

@Override
public void onTaskDataLoaded() {if (mThumbnailView != null && mHeaderView != null) {// Bind each of the views to the new task datamThumbnailView.rebindToTask(mTask);mHeaderView.rebindToTask(mTask);// Rebind any listenersAccessibilityManager am = (AccessibilityManager) getContext().getSystemService(Context.ACCESSIBILITY_SERVICE);if (Constants.DebugFlags.App.EnableTaskFiltering || (am != null && am.isEnabled())) {mHeaderView.mApplicationIcon.setOnClickListener(this);}mHeaderView.mDismissButton.setOnClickListener(this);if (mConfig.multiStackEnabled) {mHeaderView.mMoveTaskButton.setOnClickListener(this);}mActionButtonView.setOnClickListener(this);mHeaderView.mApplicationIcon.setOnLongClickListener(this);}mTaskDataLoaded = true;
}

(2)调用mRecentsView.setTaskStacks，把获得的TaskStack设置到RecentsView中创建TaskStackView

public void setTaskStacks(ArrayList<TaskStack> stacks) {……for (int i = mTaskStackViews.size(); i < numStacks; i++) {TaskStack stack = stacks.get(i);TaskStackView stackView = new TaskStackView(getContext(), stack);stackView.setCallbacks(this);addView(stackView);mTaskStackViews.add(stackView);}……
}

(3)如果没有最近使用的应用信息则显示空的提示信息，如果有就隐藏显示应用信息。

阅读代码前给自己留了个小问题：不显示Recent Apps界面上方的搜索框，当然这个问题很简单，直接在onCreate()函数中将 mSearchWidgetInfo = ssp.getOrBindSearchAppWidget(this, mAppWidgetHost);这个语句注释掉即可，这个语句就是负责搜索框的绑定。

RecentsActivity的分析就到这里结束了，刚接触源码不久，所以只做了简单分析，记录学习的过程，有问题的话欢迎一起讨论。有时间的话我会补上时序图，毕竟看图便可一目了然。

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