在之前我们分析了Android6.0系统在启动时安装应用程序的过程，这些应用程序安装好之后，Launcher应用就负责把它们在桌面上展示出来。

一、AMS启动Launcher

Launcher应用是在AMS的systemReady方法中直接调用startHomeActivityLocked启动的，下面是systemReady启动Launcher的代码。

startHomeActivityLocked(mCurrentUserId, "systemReady");我们来看下这个函数，先调用了getHomeIntent方法来获取Intent，然后也是调用resolveActivityInfo函数从PKMS获取ActivityInfo，接着当进程没有启动的话，调用ActivityStackSupervisor的startHomeActivity函数

boolean startHomeActivityLocked(int userId, String reason) { if (mFactoryTest == FactoryTest.FACTORY_TEST_LOW_LEVEL && mTopAction == null) { // We are running in factory test mode, but unable to find // the factory test app, so just sit around displaying the // error message and don't try to start anything. return false; } Intent intent = getHomeIntent();//获取intent ActivityInfo aInfo = resolveActivityInfo(intent, STOCK_PM_FLAGS, userId);//获取ActivityInfo if (aInfo != null) { intent.setComponent(new ComponentName( aInfo.applicationInfo.packageName, aInfo.name)); // Don't do this if the home app is currently being // instrumented. aInfo = new ActivityInfo(aInfo); aInfo.applicationInfo = getAppInfoForUser(aInfo.applicationInfo, userId); ProcessRecord app = getProcessRecordLocked(aInfo.processName, aInfo.applicationInfo.uid, true); if (app == null || app.instrumentationClass == null) {//进程没有启动调用 EventLog.writeEvent(EventLogTags.AM_PROC_START,"AMS -> startHomeActivityLocked startHomeActivity then startActivityLock : "+ aInfo.processName); intent.setFlags(intent.getFlags() | Intent.FLAG_ACTIVITY_NEW_TASK); mStackSupervisor.startHomeActivity(intent, aInfo, reason); } } return true; }

我们先来看看getHomeIntent这个函数。

Intent getHomeIntent() { Intent intent = new Intent(mTopAction, mTopData != null ? Uri.parse(mTopData) : null); intent.setComponent(mTopComponent); if (mFactoryTest != FactoryTest.FACTORY_TEST_LOW_LEVEL) { intent.addCategory(Intent.CATEGORY_HOME); } return intent; }

然后我们来看下ActivityStackSupervisor的startHomeActivity函数，它也是调用了startActivityLocked来启动Activity的，在之前的博客分析过这个函数这里我们就不介绍了。

void startHomeActivity(Intent intent, ActivityInfo aInfo, String reason) { moveHomeStackTaskToTop(HOME_ACTIVITY_TYPE, reason); startActivityLocked(null /* caller */, intent, null /* resolvedType */, aInfo, 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 */, null /* outActivity */, null /* container */, null /* inTask */); if (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. scheduleResumeTopActivities(); } }

二、Launcher启动

接着我们来看下Launcher的AndroidManifest.xml，我们看下其主Activity有一个category为android.intent.category.HOME

<application android:name="com.android.launcher2.LauncherApplication" android:label="@string/application_name" android:icon="@mipmap/ic_launcher_home" android:hardwareAccelerated="true" android:largeHeap="@bool/config_largeHeap" android:supportsRtl="true"> <activity android:name="com.android.launcher2.Launcher" android:launchMode="singleTask" android:clearTaskOnLaunch="true" android:stateNotNeeded="true" android:resumeWhilePausing="true" android:theme="@style/Theme" android:windowSoftInputMode="adjustPan" android:screenOrientation="nosensor"> <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"/> </intent-filter> </activity> ......

在Launcher.java的onCreate函数中调用了mModel.startLoader函数

protected void onCreate(Bundle savedInstanceState) { ...... if (!mRestoring) { if (sPausedFromUserAction) { // If the user leaves launcher, then we should just load items asynchronously when // they return. mModel.startLoader(true, -1); } else { // We only load the page synchronously if the user rotates (or triggers a // configuration change) while launcher is in the foreground mModel.startLoader(true, mWorkspace.getCurrentPage()); } } ......

startLoader函数会post一个Runnable消息，我们来看下它的run方法

public void startLoader(boolean isLaunching, int synchronousBindPage) { synchronized (mLock) { if (DEBUG_LOADERS) { Log.d(TAG, "startLoader isLaunching=" + isLaunching); } // Clear any deferred bind-runnables from the synchronized load process // We must do this before any loading/binding is scheduled below. mDeferredBindRunnables.clear(); // Don't bother to start the thread if we know it's not going to do anything if (mCallbacks != null && mCallbacks.get() != null) { // If there is already one running, tell it to stop. // also, don't downgrade isLaunching if we're already running isLaunching = isLaunching || stopLoaderLocked(); mLoaderTask = new LoaderTask(mApp, isLaunching); if (synchronousBindPage > -1 && mAllAppsLoaded && mWorkspaceLoaded) { mLoaderTask.runBindSynchronousPage(synchronousBindPage); } else { sWorkerThread.setPriority(Thread.NORM_PRIORITY); sWorker.post(mLoaderTask); } } } }

在它的run方法中会调用loadAndBindAllApps函数，在loadAndBindAllApps函数中又会调用loadAllAppsByBatch函数

public void run() { synchronized (mLock) { mIsLoaderTaskRunning = true; } final Callbacks cbk = mCallbacks.get(); final boolean loadWorkspaceFirst = cbk != null ? (!cbk.isAllAppsVisible()) : true; keep_running: { // Elevate priority when Home launches for the first time to avoid // starving at boot time. Staring at a blank home is not cool. synchronized (mLock) { if (DEBUG_LOADERS) Log.d(TAG, "Setting thread priority to " + (mIsLaunching "BACKGROUND")); Process.setThreadPriority(mIsLaunching ? Process.THREAD_PRIORITY_DEFAULT : Process.THREAD_PRIORITY_BACKGROUND); } // First step. Load workspace first, this is necessary since adding of apps from // managed profile in all apps is deferred until onResume. See http://b/17336902. if (loadWorkspaceFirst) { if (DEBUG_LOADERS) Log.d(TAG, "step 1: loading workspace"); loadAndBindWorkspace(); } else { Log.d(TAG, "step 1: special: loading all apps"); loadAndBindAllApps(); }

我们先来看下loadAndBindAllApps函数，这个函数先进入while循环，然后调用了LauncherApps的getActivityList函数，后面又会调用callbacks的bindAllApplications

private void loadAllAppsByBatch() { final long t = DEBUG_LOADERS ? SystemClock.uptimeMillis() : 0; ...... mBgAllAppsList.clear(); final int profileCount = profiles.size(); for (int p = 0; p < profileCount; p++) { ...... while (i < N && !mStopped) { if (i == 0) { final long qiaTime = DEBUG_LOADERS ? SystemClock.uptimeMillis() : 0; apps = mLauncherApps.getActivityList(null, user); ...... mHandler.post(new Runnable() { public void run() { final long t = SystemClock.uptimeMillis(); if (callbacks != null) { if (firstProfile) { callbacks.bindAllApplications(added); } else { callbacks.bindAppsAdded(added); } if (DEBUG_LOADERS) { Log.d(TAG, "bound " + added.size() + " apps in " + (SystemClock.uptimeMillis() - t) + "ms"); } } else { Log.i(TAG, "not binding apps: no Launcher activity"); } } }); ......

我们先来看LauncherApps的getActivityList函数，它先用mService成员变量调用getLauncherActivities函数获取到list<ResolveInfo>，然后封装在ArrayList<LauncherActivityInfo> 中。

public List<LauncherActivityInfo> getActivityList(String packageName, UserHandle user) { List<ResolveInfo> activities = null; try { activities = mService.getLauncherActivities(packageName, user); } catch (RemoteException re) { throw new RuntimeException("Failed to call LauncherAppsService"); } if (activities == null) { return Collections.EMPTY_LIST; } ArrayList<LauncherActivityInfo> lais = new ArrayList<LauncherActivityInfo>(); final int count = activities.size(); for (int i = 0; i < count; i++) { ResolveInfo ri = activities.get(i); long firstInstallTime = 0; try { firstInstallTime = mPm.getPackageInfo(ri.activityInfo.packageName, PackageManager.GET_UNINSTALLED_PACKAGES).firstInstallTime; } catch (NameNotFoundException nnfe) { // Sorry, can't find package } LauncherActivityInfo lai = new LauncherActivityInfo(mContext, ri, user, firstInstallTime); if (DEBUG) { Log.v(TAG, "Returning activity for profile " + user + " : " + lai.getComponentName()); } lais.add(lai); } return lais; }

其service是class LauncherAppsImpl extends ILauncherApps.Stub 下面是getLauncherActivities函数，肯定也是通过PKMS来获取相关Activity的ResolveInfo的。

@Override public List<ResolveInfo> getLauncherActivities(String packageName, UserHandle user) throws RemoteException { ensureInUserProfiles(user, "Cannot retrieve activities for unrelated profile " + user); if (!isUserEnabled(user)) { return new ArrayList<ResolveInfo>(); } final Intent mainIntent = new Intent(Intent.ACTION_MAIN, null); mainIntent.addCategory(Intent.CATEGORY_LAUNCHER); mainIntent.setPackage(packageName); long ident = Binder.clearCallingIdentity(); try { List<ResolveInfo> apps = mPm.queryIntentActivitiesAsUser(mainIntent, 0 /* flags */, user.getIdentifier()); return apps; } finally { Binder.restoreCallingIdentity(ident); } }

最后回调Launcher.java的bindAllApplications函数，最后在这个函数中可以在桌面上展示系统中所有的应用程序了。

public void bindAllApplications(final ArrayList<ApplicationInfo> apps) { Runnable setAllAppsRunnable = new Runnable() { public void run() { if (mAppsCustomizeContent != null) { mAppsCustomizeContent.setApps(apps); } } }; // Remove the progress bar entirely; we could also make it GONE // but better to remove it since we know it's not going to be used View progressBar = mAppsCustomizeTabHost. findViewById(R.id.apps_customize_progress_bar); if (progressBar != null) { ((ViewGroup)progressBar.getParent()).removeView(progressBar); // We just post the call to setApps so the user sees the progress bar // disappear-- otherwise, it just looks like the progress bar froze // which doesn't look great mAppsCustomizeTabHost.post(setAllAppsRunnable); } else { // If we did not initialize the spinner in onCreate, then we can directly set the // list of applications without waiting for any progress bars views to be hidden. setAllAppsRunnable.run(); } }

三、显示应用图标

我们再来看下Launcher的onClick函数，当调用showWorkspace可以显示所有应用的图标。

public void onClick(View v) { // Make sure that rogue clicks don't get through while allapps is launching, or after the // view has detached (it's possible for this to happen if the view is removed mid touch). if (v.getWindowToken() == null) { return; } if (!mWorkspace.isFinishedSwitchingState()) { return; } Object tag = v.getTag(); if (tag instanceof ShortcutInfo) { // Open shortcut final Intent intent = ((ShortcutInfo) tag).intent; int[] pos = new int[2]; v.getLocationOnScreen(pos); intent.setSourceBounds(new Rect(pos[0], pos[1], pos[0] + v.getWidth(), pos[1] + v.getHeight())); boolean success = startActivitySafely(v, intent, tag); if (success && v instanceof BubbleTextView) { mWaitingForResume = (BubbleTextView) v; mWaitingForResume.setStayPressed(true); } } else if (tag instanceof FolderInfo) { if (v instanceof FolderIcon) { FolderIcon fi = (FolderIcon) v; handleFolderClick(fi); } } else if (v == mAllAppsButton) { if (isAllAppsVisible()) { showWorkspace(true); } else { onClickAllAppsButton(v); } } }

在showWorkspace中会显示所有的图标

void showWorkspace(boolean animated, Runnable onCompleteRunnable) { if (mState != State.WORKSPACE) { boolean wasInSpringLoadedMode = (mState == State.APPS_CUSTOMIZE_SPRING_LOADED); mWorkspace.setVisibility(View.VISIBLE); hideAppsCustomizeHelper(State.WORKSPACE, animated, false, onCompleteRunnable); // Show the search bar (only animate if we were showing the drop target bar in spring // loaded mode) if (mSearchDropTargetBar != null) { mSearchDropTargetBar.showSearchBar(wasInSpringLoadedMode); } // We only need to animate in the dock divider if we're going from spring loaded mode showDockDivider(animated && wasInSpringLoadedMode); // Set focus to the AppsCustomize button if (mAllAppsButton != null) { mAllAppsButton.requestFocus(); } } mWorkspace.flashScrollingIndicator(animated); // Change the state *after* we've called all the transition code mState = State.WORKSPACE; // Resume the auto-advance of widgets mUserPresent = true; updateRunning(); // Send an accessibility event to announce the context change getWindow().getDecorView() .sendAccessibilityEvent(AccessibilityEvent.TYPE_WINDOW_STATE_CHANGED); }

而点击应用图标，最终会调用Launcher.java的startActivitySafely来启动应用。这里调用的startActivity就是Activity的startActivity函数。

boolean startActivitySafely(View v, Intent intent, Object tag) { boolean success = false; try { success = startActivity(v, intent, tag); } catch (ActivityNotFoundException e) { Toast.makeText(this, R.string.activity_not_found, Toast.LENGTH_SHORT).show(); Log.e(TAG, "Unable to launch. tag=" + tag + " intent=" + intent, e); } return success; }

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