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上一篇文章中分析了系統(tǒng)是如何把桌面應(yīng)用拉起的。（見(jiàn)Android 9.0 Launcher源碼分析（一）——系統(tǒng)啟動(dòng)Launcher流程）
現(xiàn)在接上文朦乏，分析一下Launcher應(yīng)用的啟動(dòng)流程岳颇。
首先把Launcher的onCreate貼出來(lái)。
@Override
protected void onCreate(Bundle savedInstanceState) {
if (DEBUG_STRICT_MODE) {
StrictMode.setThreadPolicy(new StrictMode.ThreadPolicy.Builder()
.detectDiskReads()
.detectDiskWrites()
.detectNetwork() // or .detectAll() for all detectable problems
.penaltyLog()
.build());
StrictMode.setVmPolicy(new StrictMode.VmPolicy.Builder()
.detectLeakedSqlLiteObjects()
.detectLeakedClosableObjects()
.penaltyLog()
.penaltyDeath()
.build());
}
TraceHelper.beginSection("Launcher-onCreate");
super.onCreate(savedInstanceState);
TraceHelper.partitionSection("Launcher-onCreate", "super call");
LauncherAppState app = LauncherAppState.getInstance(this);
mOldConfig = new Configuration(getResources().getConfiguration());
mModel = app.setLauncher(this);
initDeviceProfile(app.getInvariantDeviceProfile());
mSharedPrefs = Utilities.getPrefs(this);
mIconCache = app.getIconCache();
mAccessibilityDelegate = new LauncherAccessibilityDelegate(this);
mDragController = new DragController(this);
mAllAppsController = new AllAppsTransitionController(this);
mStateManager = new LauncherStateManager(this);
UiFactory.onCreate(this);
mAppWidgetManager = AppWidgetManagerCompat.getInstance(this);
mAppWidgetHost = new LauncherAppWidgetHost(this);
mAppWidgetHost.startListening();
mLauncherView = LayoutInflater.from(this).inflate(R.layout.launcher, null);
setupViews();
mPopupDataProvider = new PopupDataProvider(this);
mRotationHelper = new RotationHelper(this);
mAppTransitionManager = LauncherAppTransitionManager.newInstance(this);
boolean internalStateHandled = InternalStateHandler.handleCreate(this, getIntent());
if (internalStateHandled) {
if (savedInstanceState != null) {
// InternalStateHandler has already set the appropriate state.
// We dont need to do anything.
savedInstanceState.remove(RUNTIME_STATE);
}
}
restoreState(savedInstanceState);
// We only load the page synchronously if the user rotates (or triggers a
// configuration change) while launcher is in the foreground
int currentScreen = PagedView.INVALID_RESTORE_PAGE;
if (savedInstanceState != null) {
currentScreen = savedInstanceState.getInt(RUNTIME_STATE_CURRENT_SCREEN, currentScreen);
}
if (!mModel.startLoader(currentScreen)) {
if (!internalStateHandled) {
// If we are not binding synchronously, show a fade in animation when
// the first page bind completes.
mDragLayer.getAlphaProperty(ALPHA_INDEX_LAUNCHER_LOAD).setValue(0);
}
} else {
// Pages bound synchronously.
mWorkspace.setCurrentPage(currentScreen);
setWorkspaceLoading(true);
}
// For handling default keys
setDefaultKeyMode(DEFAULT_KEYS_SEARCH_LOCAL);
setContentView(mLauncherView);
getRootView().dispatchInsets();
// Listen for broadcasts
registerReceiver(mScreenOffReceiver, new IntentFilter(Intent.ACTION_SCREEN_OFF));
getSystemUiController().updateUiState(SystemUiController.UI_STATE_BASE_WINDOW,
Themes.getAttrBoolean(this, R.attr.isWorkspaceDarkText));
if (mLauncherCallbacks != null) {
mLauncherCallbacks.onCreate(savedInstanceState);
}
mRotationHelper.initialize();
TraceHelper.endSection("Launcher-onCreate");
}
我們從頭開(kāi)始看叮贩，在super.onCreate過(guò)后击狮，首先調(diào)用了LauncherAppState.getInstance(this)來(lái)初始化一個(gè)單例對(duì)象。LauncherAppState里面保存了一些比較常用的對(duì)象妇汗，方便其他地方通過(guò)單例來(lái)獲取帘不，比如IconCache（圖標(biāo)緩存）说莫、LauncherModel（負(fù)責(zé)數(shù)據(jù)加載和處理各種回調(diào)）等杨箭。getInstance函數(shù)如下，注意這里初始化使用的application的Context储狭，因?yàn)閱卫鳛閟tatic對(duì)象互婿，生命周期是與application生命周期一樣長(zhǎng)的，如果這里使用了Activity的Context辽狈，會(huì)導(dǎo)致activity退出后慈参，該Context依然被單例持有而無(wú)法回收，于是出現(xiàn)內(nèi)存泄露刮萌。
public static LauncherAppState getInstance(final Context context) {
if (INSTANCE == null) {
if (Looper.myLooper() == Looper.getMainLooper()) {
INSTANCE = new LauncherAppState(context.getApplicationContext());
} else {
try {
return new MainThreadExecutor().submit(new Callable<LauncherAppState>() {
@Override
public LauncherAppState call() throws Exception {
return LauncherAppState.getInstance(context);
}
}).get();
} catch (InterruptedException|ExecutionException e) {
throw new RuntimeException(e);
}
}
}
return INSTANCE;
}
繼續(xù)看LauncherAppState的初始化過(guò)程驮配。這里面其實(shí)就是各個(gè)對(duì)象的實(shí)例創(chuàng)建過(guò)程，并且注冊(cè)了一些系統(tǒng)事件的監(jiān)聽(tīng)。
private LauncherAppState(Context context) {
if (getLocalProvider(context) == null) {
throw new RuntimeException(
"Initializing LauncherAppState in the absence of LauncherProvider");
}
Log.v(Launcher.TAG, "LauncherAppState initiated");
Preconditions.assertUIThread();
mContext = context;
mInvariantDeviceProfile = new InvariantDeviceProfile(mContext);
mIconCache = new IconCache(mContext, mInvariantDeviceProfile);
mWidgetCache = new WidgetPreviewLoader(mContext, mIconCache);
mModel = new LauncherModel(this, mIconCache, AppFilter.newInstance(mContext));
LauncherAppsCompat.getInstance(mContext).addOnAppsChangedCallback(mModel);
// Register intent receivers
IntentFilter filter = new IntentFilter();
filter.addAction(Intent.ACTION_LOCALE_CHANGED);
// For handling managed profiles
filter.addAction(Intent.ACTION_MANAGED_PROFILE_ADDED);
filter.addAction(Intent.ACTION_MANAGED_PROFILE_REMOVED);
filter.addAction(Intent.ACTION_MANAGED_PROFILE_AVAILABLE);
filter.addAction(Intent.ACTION_MANAGED_PROFILE_UNAVAILABLE);
filter.addAction(Intent.ACTION_MANAGED_PROFILE_UNLOCKED);
if (FeatureFlags.IS_DOGFOOD_BUILD) {
filter.addAction(ACTION_FORCE_ROLOAD);
}
mContext.registerReceiver(mModel, filter);
UserManagerCompat.getInstance(mContext).enableAndResetCache();
new ConfigMonitor(mContext).register();
if (!mContext.getResources().getBoolean(R.bool.notification_badging_enabled)) {
mNotificationBadgingObserver = null;
} else {
// Register an observer to rebind the notification listener when badging is re-enabled.
mNotificationBadgingObserver = new SettingsObserver.Secure(
mContext.getContentResolver()) {
@Override
public void onSettingChanged(boolean isNotificationBadgingEnabled) {
if (isNotificationBadgingEnabled) {
NotificationListener.requestRebind(new ComponentName(
mContext, NotificationListener.class));
}
}
};
mNotificationBadgingObserver.register(NOTIFICATION_BADGING);
}
}
回到剛才的Launcher創(chuàng)建流程壮锻，LauncherAppState初始化完成后琐旁，有這樣一句mModel = app.setLauncher(this)，這里調(diào)用了mModel.initialize(launcher)猜绣，這里將傳過(guò)來(lái)的Callbacks對(duì)象（也就是Launcher灰殴，Launcher實(shí)現(xiàn)了Callbacks接口）保存為了弱引用。同樣是基于避免內(nèi)存泄露的考慮掰邢。還記得上文提到的LauncherAppState牺陶，LauncherModel是其內(nèi)部的一個(gè)成員變量，生命周期也是比Launcher這個(gè)Activity要長(zhǎng)的辣之。
public void initialize(Callbacks callbacks) {
synchronized (mLock) {
Preconditions.assertUIThread();
mCallbacks = new WeakReference<>(callbacks);
}
}
繼續(xù)Launcher的create掰伸，之后是initDeviceProfile(app.getInvariantDeviceProfile())，DeviceProfile是與Launcher布局相關(guān)的一個(gè)重要類怀估，這里面保存了所有布局相關(guān)數(shù)據(jù)比如圖標(biāo)大小碱工、頁(yè)面寬高、各種padding等等奏夫。然后創(chuàng)建一些其他對(duì)象后怕篷，終于inflate了R.layout.launcher。繼續(xù)往下就執(zhí)行到一個(gè)關(guān)鍵函數(shù)mModel.startLoader(currentScreen)酗昼，前面執(zhí)行的都是諸如對(duì)象創(chuàng)建廊谓、View的inflate等邏輯，并沒(méi)有涉及到數(shù)據(jù)相關(guān)的內(nèi)容麻削，此函數(shù)就是開(kāi)啟Launcher數(shù)據(jù)加載的一個(gè)調(diào)用蒸痹。
之后又是一些初始化的邏輯。所以我們前面啰嗦一大堆呛哟，其實(shí)onCreate干的事情簡(jiǎn)單說(shuō)來(lái)就是初始化對(duì)象叠荠、加載布局、注冊(cè)一些事件監(jiān)聽(tīng)扫责、以及開(kāi)啟數(shù)據(jù)加載榛鼎。
接著看數(shù)據(jù)加載與綁定流程。數(shù)據(jù)加載的調(diào)用實(shí)際是這樣的startLoader()→startLoaderForResults()鳖孤。從如下代碼中可知者娱，數(shù)據(jù)加載時(shí)在一個(gè)工作線程去做的，這是很正常的一個(gè)選擇苏揣，避免阻塞主線程黄鳍。
public void startLoaderForResults(LoaderResults results) {
synchronized (mLock) {
stopLoader();
mLoaderTask = new LoaderTask(mApp, mBgAllAppsList, sBgDataModel, results);
runOnWorkerThread(mLoaderTask);
}
}
private static void runOnWorkerThread(Runnable r) {
if (sWorkerThread.getThreadId() == Process.myTid()) {
r.run();
} else {
// If we are not on the worker thread, then post to the worker handler
sWorker.post(r);
}
}
在工作線程跑的是一個(gè)LoaderTask類，實(shí)現(xiàn)了Runnable接口平匈。我們直接來(lái)看其run函數(shù)的定義框沟。
public void run() {
synchronized (this) {
// Skip fast if we are already stopped.
if (mStopped) {
return;
}
}
TraceHelper.beginSection(TAG);
try (LauncherModel.LoaderTransaction transaction = mApp.getModel().beginLoader(this)) {
TraceHelper.partitionSection(TAG, "step 1.1: loading workspace");
loadWorkspace();
verifyNotStopped();
TraceHelper.partitionSection(TAG, "step 1.2: bind workspace workspace");
mResults.bindWorkspace();
// Notify the installer packages of packages with active installs on the first screen.
TraceHelper.partitionSection(TAG, "step 1.3: send first screen broadcast");
sendFirstScreenActiveInstallsBroadcast();
// Take a break
TraceHelper.partitionSection(TAG, "step 1 completed, wait for idle");
waitForIdle();
verifyNotStopped();
// second step
TraceHelper.partitionSection(TAG, "step 2.1: loading all apps");
loadAllApps();
TraceHelper.partitionSection(TAG, "step 2.2: Binding all apps");
verifyNotStopped();
mResults.bindAllApps();
verifyNotStopped();
TraceHelper.partitionSection(TAG, "step 2.3: Update icon cache");
updateIconCache();
// Take a break
TraceHelper.partitionSection(TAG, "step 2 completed, wait for idle");
waitForIdle();
verifyNotStopped();
// third step
TraceHelper.partitionSection(TAG, "step 3.1: loading deep shortcuts");
loadDeepShortcuts();
verifyNotStopped();
TraceHelper.partitionSection(TAG, "step 3.2: bind deep shortcuts");
mResults.bindDeepShortcuts();
// Take a break
TraceHelper.partitionSection(TAG, "step 3 completed, wait for idle");
waitForIdle();
verifyNotStopped();
// fourth step
TraceHelper.partitionSection(TAG, "step 4.1: loading widgets");
mBgDataModel.widgetsModel.update(mApp, null);
verifyNotStopped();
TraceHelper.partitionSection(TAG, "step 4.2: Binding widgets");
mResults.bindWidgets();
transaction.commit();
} catch (CancellationException e) {
// Loader stopped, ignore
TraceHelper.partitionSection(TAG, "Cancelled");
}
TraceHelper.endSection(TAG);
}
非常清晰明了藏古，一步一步通過(guò)注釋和Log都標(biāo)出來(lái)了。Launcher里面數(shù)據(jù)比較多忍燥，包括所有應(yīng)用的圖標(biāo)和應(yīng)用數(shù)據(jù)校翔，所有應(yīng)用的Widget數(shù)據(jù)，桌面已添加的用戶數(shù)據(jù)等灾前，隨著Android大版本演進(jìn)防症，還有DeepShortcuts等新的數(shù)據(jù)類型。如果按照常規(guī)的加載做法哎甲，等加載數(shù)據(jù)完成后再顯示到View蔫敲，耗時(shí)就太長(zhǎng)了。為了優(yōu)化體驗(yàn)炭玫，Launcher于是采用了分批加載奈嘿、分批綁定的做法。這是大家在應(yīng)用開(kāi)發(fā)時(shí)可以借鑒的一種優(yōu)化方案吞加。整體的加載綁定流程如下裙犹。
我們以其中的加載與綁定桌面內(nèi)容為例來(lái)進(jìn)行說(shuō)明，后面的三步在弄明白第一步如何做之后也就是業(yè)務(wù)邏輯上的差異衔憨，不再贅述叶圃。
加載桌面內(nèi)容，調(diào)用函數(shù)為loadWorkspace()践图。這個(gè)函數(shù)很長(zhǎng)掺冠，這里就不貼代碼了。簡(jiǎn)述一下其流程码党。
首先我們要知道一個(gè)BgDataModel類德崭，這個(gè)類用于把所有數(shù)據(jù)對(duì)應(yīng)的實(shí)例管理起來(lái)。如下面代碼揖盘，可以看到有workspaceItems（所有應(yīng)用圖標(biāo)數(shù)據(jù)對(duì)應(yīng)的ItemInfo）眉厨，appWidgets（所有AppWidgets數(shù)據(jù)對(duì)應(yīng)的LauncherAppWidgetInfo）等等。
public final LongArrayMap<ItemInfo> itemsIdMap = new LongArrayMap<>();
public final ArrayList<ItemInfo> workspaceItems = new ArrayList<>();
public final ArrayList<LauncherAppWidgetInfo> appWidgets = new ArrayList<>();
public final LongArrayMap<FolderInfo> folders = new LongArrayMap<>();
public final ArrayList<Long> workspaceScreens = new ArrayList<>();
public final Map<ShortcutKey, MutableInt> pinnedShortcutCounts = new HashMap<>();
public boolean hasShortcutHostPermission;
public final MultiHashMap<ComponentKey, String> deepShortcutMap = new MultiHashMap<>();
public final WidgetsModel widgetsModel = new WidgetsModel();
然后正式來(lái)看loadWorkspace兽狭。
- 通過(guò)
LauncherSettings.Favorites.CONTENT_URI查詢Favorites表的所有內(nèi)容憾股，拿到cursor。 - 遍歷cursor椭符，進(jìn)行數(shù)據(jù)的整理荔燎。每一行數(shù)據(jù)都有一個(gè)對(duì)應(yīng)的itemType耻姥，標(biāo)志著這一行的數(shù)據(jù)對(duì)應(yīng)的是一個(gè)應(yīng)用销钝、還是一個(gè)Widget或文件夾等。不同的類型會(huì)進(jìn)行不同的處理琐簇。
- 對(duì)于圖標(biāo)類型（itemType是
ITEM_TYPE_SHORTCUT蒸健，ITEM_TYPE_APPLICATION座享，ITEM_TYPE_DEEP_SHORTCUT），首先經(jīng)過(guò)一系列判斷似忧，判斷其是否還可用（比如應(yīng)用在Launcher未啟動(dòng)時(shí)被卸載導(dǎo)致不可用）渣叛，不可用的話就標(biāo)記為可刪除，繼續(xù)循環(huán)盯捌。如果可用的話淳衙，就根據(jù)當(dāng)前cursor的內(nèi)容，生成一個(gè)ShortcutInfo對(duì)象饺著，保存到BgDataModel箫攀。 - 對(duì)于文件夾類型（itemType是
ITEM_TYPE_FOLDER），直接生成一個(gè)對(duì)應(yīng)的FolderInfo對(duì)象幼衰，保存到BgDataModel靴跛。 - 對(duì)于AppWidget（itemType是
ITEM_TYPE_APPWIDGET，ITEM_TYPE_CUSTOM_APPWIDGET）渡嚣，也需要經(jīng)過(guò)是否可用的判斷梢睛，但是可用條件與圖標(biāo)類型是有差異的。如果可用识椰，生成一個(gè)LauncherAppWidgetInfo對(duì)象绝葡，保存到BgDataModel。 - 經(jīng)過(guò)上述流程腹鹉，現(xiàn)在所有數(shù)據(jù)庫(kù)里讀出的內(nèi)容已經(jīng)分類完畢挤牛，并且保存到了內(nèi)存（BgDataModel）中。然后開(kāi)始處理之前標(biāo)記為可刪除的內(nèi)容种蘸。顯示從數(shù)據(jù)庫(kù)中刪除對(duì)應(yīng)的行墓赴，然后還要判斷此次刪除操作是否帶來(lái)了其他需要?jiǎng)h除的內(nèi)容。比如某個(gè)文件夾或者某一頁(yè)只有一個(gè)圖標(biāo)航瞭，這個(gè)圖標(biāo)因?yàn)槟承┰虮粍h掉了诫硕，那么此文件夾或頁(yè)面也需要被刪掉。
至此數(shù)據(jù)加載完畢刊侯，開(kāi)始要進(jìn)行綁定了章办，也就是mResults.bindWorkspace()
此函數(shù)在LoaderResults類中。函數(shù)在執(zhí)行數(shù)據(jù)綁定之前滨彻，會(huì)執(zhí)行這樣一段代碼藕届。
// Separate the items that are on the current screen, and all the other remaining items
ArrayList<ItemInfo> currentWorkspaceItems = new ArrayList<>();
ArrayList<ItemInfo> otherWorkspaceItems = new ArrayList<>();
ArrayList<LauncherAppWidgetInfo> currentAppWidgets = new ArrayList<>();
ArrayList<LauncherAppWidgetInfo> otherAppWidgets = new ArrayList<>();
filterCurrentWorkspaceItems(currentScreenId, workspaceItems, currentWorkspaceItems,
otherWorkspaceItems);
filterCurrentWorkspaceItems(currentScreenId, appWidgets, currentAppWidgets,
otherAppWidgets);
sortWorkspaceItemsSpatially(currentWorkspaceItems);
sortWorkspaceItemsSpatially(otherWorkspaceItems);
這段代碼做的事情是，把Launcher啟動(dòng)后默認(rèn)顯示出來(lái)那一頁(yè)所擁有的數(shù)據(jù)篩選到currentWorkspaceItems與currentAppWidgets亭饵，其他頁(yè)的數(shù)據(jù)篩選到otherWorkspaceItems與otherAppWidgets休偶。然后對(duì)每個(gè)list，按照從上到下辜羊，從左到右的順序進(jìn)行排序踏兜。然后可以開(kāi)始綁定了词顾。下面代碼的Callbacks就是Launcher activity實(shí)例，首先通知Launcher要開(kāi)始綁定了（callbacks.startBinding()）碱妆，然后先把空頁(yè)面添加到View tree中（callbacks.bindScreens(orderedScreenIds)）肉盹，之后先綁定默認(rèn)頁(yè)的所有元素（下段代碼的最后一句）。當(dāng)然這些所有的操作都是通過(guò)mUiExecutor放到主線程執(zhí)行的疹尾。
// Tell the workspace that we're about to start binding items
r = new Runnable() {
public void run() {
Callbacks callbacks = mCallbacks.get();
if (callbacks != null) {
callbacks.clearPendingBinds();
callbacks.startBinding();
}
}
};
mUiExecutor.execute(r);
// Bind workspace screens
mUiExecutor.execute(new Runnable() {
@Override
public void run() {
Callbacks callbacks = mCallbacks.get();
if (callbacks != null) {
callbacks.bindScreens(orderedScreenIds);
}
}
});
Executor mainExecutor = mUiExecutor;
// Load items on the current page.
bindWorkspaceItems(currentWorkspaceItems, currentAppWidgets, mainExecutor);
最后一句的內(nèi)容如下上忍，也是通過(guò)callbacks調(diào)用在Launcher中的bindItems函數(shù)。
private void bindWorkspaceItems(final ArrayList<ItemInfo> workspaceItems,
final ArrayList<LauncherAppWidgetInfo> appWidgets,
final Executor executor) {
// Bind the workspace items
int N = workspaceItems.size();
for (int i = 0; i < N; i += ITEMS_CHUNK) {
final int start = i;
final int chunkSize = (i+ITEMS_CHUNK <= N) ? ITEMS_CHUNK : (N-i);
final Runnable r = new Runnable() {
@Override
public void run() {
Callbacks callbacks = mCallbacks.get();
if (callbacks != null) {
callbacks.bindItems(workspaceItems.subList(start, start+chunkSize), false);
}
}
};
executor.execute(r);
}
// Bind the widgets, one at a time
N = appWidgets.size();
for (int i = 0; i < N; i++) {
final ItemInfo widget = appWidgets.get(i);
final Runnable r = new Runnable() {
public void run() {
Callbacks callbacks = mCallbacks.get();
if (callbacks != null) {
callbacks.bindItems(Collections.singletonList(widget), false);
}
}
};
executor.execute(r);
}
}
bindItems函數(shù)我們看一下其中的關(guān)鍵代碼纳本。根據(jù)不同的itemType來(lái)生產(chǎn)不同的View睡雇，然后通過(guò)addInScreenFromBind函數(shù)將View add到相應(yīng)的ViewGroup去。
@Override
public void bindItems(final List<ItemInfo> items, final boolean forceAnimateIcons) {
...
switch (item.itemType) {
case LauncherSettings.Favorites.ITEM_TYPE_APPLICATION:
case LauncherSettings.Favorites.ITEM_TYPE_SHORTCUT:
case LauncherSettings.Favorites.ITEM_TYPE_DEEP_SHORTCUT: {
ShortcutInfo info = (ShortcutInfo) item;
view = createShortcut(info);
break;
}
case LauncherSettings.Favorites.ITEM_TYPE_FOLDER: {
view = FolderIcon.fromXml(R.layout.folder_icon, this,
(ViewGroup) workspace.getChildAt(workspace.getCurrentPage()),
(FolderInfo) item);
break;
}
case LauncherSettings.Favorites.ITEM_TYPE_APPWIDGET:
case LauncherSettings.Favorites.ITEM_TYPE_CUSTOM_APPWIDGET: {
view = inflateAppWidget((LauncherAppWidgetInfo) item);
if (view == null) {
continue;
}
break;
}
default:
throw new RuntimeException("Invalid Item Type");
}
...
workspace.addInScreenFromBind(view, item);
...
}
默認(rèn)頁(yè)的元素綁定完了饮醇，然后繼續(xù)綁定其他頁(yè)的元素它抱。這里我們從注釋也可以看出，Launcher為了讓默認(rèn)頁(yè)盡快顯示朴艰，自定義了一個(gè)ViewOnDrawExecutor观蓄，這里面會(huì)讓綁定其他頁(yè)的操作在綁定完第一頁(yè)的元素并且第一次onDraw執(zhí)行完之后才執(zhí)行。讀者有興趣的話可以去看看這個(gè)Executor的實(shí)現(xiàn)祠墅。
// In case of validFirstPage, only bind the first screen, and defer binding the
// remaining screens after first onDraw (and an optional the fade animation whichever
// happens later).
// This ensures that the first screen is immediately visible (eg. during rotation)
// In case of !validFirstPage, bind all pages one after other.
final Executor deferredExecutor =
validFirstPage ? new ViewOnDrawExecutor() : mainExecutor;
mainExecutor.execute(new Runnable() {
@Override
public void run() {
Callbacks callbacks = mCallbacks.get();
if (callbacks != null) {
callbacks.finishFirstPageBind(
validFirstPage ? (ViewOnDrawExecutor) deferredExecutor : null);
}
}
});
bindWorkspaceItems(otherWorkspaceItems, otherAppWidgets, deferredExecutor);
經(jīng)過(guò)其他頁(yè)的綁定之后侮穿，桌面數(shù)據(jù)的加載與綁定也就到此為止。接下來(lái)就是之前提到的另外三步后續(xù)加載與綁定內(nèi)容了毁嗦，不再贅述亲茅。但是在本文結(jié)束前，還想說(shuō)一個(gè)值得一提的地方狗准。
桌面數(shù)據(jù)的加載與綁定完之后克锣，我們看這里執(zhí)行了一個(gè)waitForIdle的函數(shù)，然后才是繼續(xù)執(zhí)行第二步腔长。這個(gè)函數(shù)是做什么的呢袭祟？
// Take a break
TraceHelper.partitionSection(TAG, "step 1 completed, wait for idle");
waitForIdle();
verifyNotStopped();
// second step
TraceHelper.partitionSection(TAG, "step 2.1: loading all apps");
loadAllApps();
我們看下它的實(shí)現(xiàn)。
protected synchronized void waitForIdle() {
// Wait until the either we're stopped or the other threads are done.
// This way we don't start loading all apps until the workspace has settled
// down.
LooperIdleLock idleLock = mResults.newIdleLock(this);
// Just in case mFlushingWorkerThread changes but we aren't woken up,
// wait no longer than 1sec at a time
while (!mStopped && idleLock.awaitLocked(1000));
}
public class LooperIdleLock implements MessageQueue.IdleHandler, Runnable {
private final Object mLock;
private boolean mIsLocked;
public LooperIdleLock(Object lock, Looper looper) {
mLock = lock;
mIsLocked = true;
if (Utilities.ATLEAST_MARSHMALLOW) {
looper.getQueue().addIdleHandler(this);
} else {
// Looper.myQueue() only gives the current queue. Move the execution to the UI thread
// so that the IdleHandler is attached to the correct message queue.
new LooperExecutor(looper).execute(this);
}
}
@Override
public void run() {
Looper.myQueue().addIdleHandler(this);
}
@Override
public boolean queueIdle() {
synchronized (mLock) {
mIsLocked = false;
mLock.notify();
}
return false;
}
public boolean awaitLocked(long ms) {
if (mIsLocked) {
try {
// Just in case mFlushingWorkerThread changes but we aren't woken up,
// wait no longer than 1sec at a time
mLock.wait(ms);
} catch (InterruptedException ex) {
// Ignore
}
}
return mIsLocked;
}
}
這里面涉及到一個(gè)應(yīng)用啟動(dòng)優(yōu)化的技術(shù)捞附。我們知道應(yīng)用的啟動(dòng)優(yōu)化可以有延遲加載巾乳、懶加載、異步加載等手段鸟召。而用一個(gè)名為IdleHandler的類胆绊，就可以比較方便的實(shí)現(xiàn)延遲加載。這個(gè)后面有空的話再來(lái)細(xì)說(shuō)吧欧募，本文就先到這里压状。
下一篇將分析Launcher布局相關(guān)內(nèi)容。
