Android4.4 Framework分析——Android默许Home应用Launcher3的加载过程分析

本文主要介绍Android4.4默认Home应用Launcher3的启动过程和Launcher3的数据加载过程。Launcher的启动是开机时，ActivityManagerService准备好后开始的，下图是它的启动序列图：

step1，SystemServer中，ActivityManagerService准备好了。

step3，

    boolean resumeTopActivitiesLocked(ActivityStack targetStack, ActivityRecord target,            Bundle targetOptions) {        if (targetStack == null) {            targetStack = getFocusedStack(); //获得mHomeStack        }        boolean result = false;        for (int stackNdx = mStacks.size() - 1; stackNdx >= 0; --stackNdx) {            final ActivityStack stack = mStacks.get(stackNdx);            if (isFrontStack(stack)) {                if (stack == targetStack) {                    result = stack.resumeTopActivityLocked(target, targetOptions);                } else {                    stack.resumeTopActivityLocked(null);                }            }        }        return result;    }

step6，

   boolean startHomeActivityLocked(int userId) {        if (mHeadless) {            // Added because none of the other calls to ensureBootCompleted seem to fire            // when running headless.            ensureBootCompleted();            return false;        }        Intent intent = getHomeIntent(); //HOME intent        ActivityInfo aInfo =            resolveActivityInfo(intent, STOCK_PM_FLAGS, userId);//查找home应用信息        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);//home应用未启动，返回null            if (app == null || app.instrumentationClass == null) {                intent.setFlags(intent.getFlags() | Intent.FLAG_ACTIVITY_NEW_TASK);                mStackSupervisor.startHomeActivity(intent, aInfo); //step7            }        }        return true;    }

    Intent getHomeIntent() {        Intent intent = new Intent(mTopAction, mTopData != null ? Uri.parse(mTopData) : null);        intent.setComponent(mTopComponent);        if (mFactoryTest != SystemServer.FACTORY_TEST_LOW_LEVEL) {            intent.addCategory(Intent.CATEGORY_HOME);//Home应用的标志        }        return intent;    }

的step14之后的过程。

step11~step14，开始异步加载应用图标，工作线程sWorkerThread。

step15~step20，加载workspace的图标，step16读取LauncherProvider的Favorites数据，favorites表的数据是Launcher数据库创建时从default_workspace.xml解析读取的。step18绑定图标信息。

step22，睡眠等待空闲进程，然后加载主菜单的所有app图标。

step23，从睡眠中醒来，准备加载所有app图标，包括widget等。

step24，

        private void loadAllApps() {            final long loadTime = DEBUG_LOADERS ? SystemClock.uptimeMillis() : 0;            .....            final PackageManager packageManager = mContext.getPackageManager();            final Intent mainIntent = new Intent(Intent.ACTION_MAIN, null); //在PackageManagerService查询所有要显示在桌面上的app            mainIntent.addCategory(Intent.CATEGORY_LAUNCHER);            // Clear the list of apps            mBgAllAppsList.clear();            // Query for the set of apps            final long qiaTime = DEBUG_LOADERS ? SystemClock.uptimeMillis() : 0;            List<ResolveInfo> apps = packageManager.queryIntentActivities(mainIntent, 0);            if (DEBUG_LOADERS) {                Log.d(TAG, "queryIntentActivities took "                        + (SystemClock.uptimeMillis()-qiaTime) + "ms");                Log.d(TAG, "queryIntentActivities got " + apps.size() + " apps");            }            // Fail if we don't have any apps            if (apps == null || apps.isEmpty()) {                return;            }            // Sort the applications by name            final long sortTime = DEBUG_LOADERS ? SystemClock.uptimeMillis() : 0;            Collections.sort(apps,                    new LauncherModel.ShortcutNameComparator(packageManager, mLabelCache));//按应用名称排序            // Create the ApplicationInfos            for (int i = 0; i < apps.size(); i++) {                ResolveInfo app = apps.get(i);                // This builds the icon bitmaps.                mBgAllAppsList.add(new AppInfo(packageManager, app,                        mIconCache, mLabelCache));            }            // Huh? Shouldn't this be inside the Runnable below?            final ArrayList<AppInfo> added = mBgAllAppsList.added;            mBgAllAppsList.added = new ArrayList<AppInfo>();            // Post callback on main thread            mHandler.post(new Runnable() {                public void run() {                    final long bindTime = SystemClock.uptimeMillis();                    final Callbacks callbacks = tryGetCallbacks(oldCallbacks);                    if (callbacks != null) {                        callbacks.bindAllApplications(added); //step26，绑定                        if (DEBUG_LOADERS) {                            Log.d(TAG, "bound " + added.size() + " apps in "                                + (SystemClock.uptimeMillis() - bindTime) + "ms");                        }                    } else {                        Log.i(TAG, "not binding apps: no Launcher activity");                    }                }            });        }

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