Android應用啓動過程-Launcher源碼淺析
本文參考的源碼（7.1.1_r6）java
Launcher也是一個應用程序，和咱們的App沒有什麼區別，當用戶點擊應用圖標時候，啓動其餘的App，本文主要爲分析Activity的啓動流程打基礎。android
Launcher.java代碼量比較多，大約4500多行，可是裏面的邏輯並不複雜，不過我這裏分析它的意義主要爲了更好理解後面的知識，瞭解Launcher具體的流程纔是重要的，不要沉迷代碼中沒法自拔！bash
先來張圖：app
在線源碼地址
AndroidManifest.xml Launcher.java LauncherModel.java AllAppsContainerView.javaide
分析
先看下它的manifest文件，這裏面的內容很少，Launcher類是一個Activity，只是比咱們普通的app多一個 <category android:name="android.intent.category.HOME" />函數
<?xml version="1.0" encoding="utf-8"?>
<manifest
xmlns:android="http://schemas.android.com/apk/res/android"
package="com.android.launcher3">
<uses-sdk android:targetSdkVersion="23" android:minSdkVersion="21"/>
<permission
android:name="com.android.launcher3.permission.READ_SETTINGS"
android:permissionGroup="android.permission-group.SYSTEM_TOOLS"
android:protectionLevel="normal"
android:label="@string/permlab_read_settings"
android:description="@string/permdesc_read_settings"/>
<permission
android:name="com.android.launcher3.permission.WRITE_SETTINGS"
android:permissionGroup="android.permission-group.SYSTEM_TOOLS"
android:protectionLevel="signatureOrSystem"
android:label="@string/permlab_write_settings"
android:description="@string/permdesc_write_settings"/>
<uses-permission android:name="com.android.launcher.permission.READ_SETTINGS" />
<uses-permission android:name="com.android.launcher.permission.WRITE_SETTINGS" />
<uses-permission android:name="com.android.launcher3.permission.READ_SETTINGS" />
<uses-permission android:name="com.android.launcher3.permission.WRITE_SETTINGS" />
<application
android:backupAgent="com.android.launcher3.LauncherBackupAgent"
android:fullBackupOnly="true"
android:fullBackupContent="@xml/backupscheme"
android:hardwareAccelerated="true"
android:icon="@mipmap/ic_launcher_home"
android:label="@string/derived_app_name"
android:largeHeap="@bool/config_largeHeap"
android:restoreAnyVersion="true"
android:supportsRtl="true" >
<activity
android:name="com.android.launcher3.Launcher"
android:launchMode="singleTask"
android:clearTaskOnLaunch="true"
android:stateNotNeeded="true"
android:theme="@style/LauncherTheme"
android:windowSoftInputMode="adjustPan"
android:screenOrientation="nosensor"
android:configChanges="keyboard|keyboardHidden|navigation"
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"/>
</intent-filter>
</activity>
<!--
The settings activity. When extending keep the intent filter present
-->
<activity
android:name="com.android.launcher3.SettingsActivity"
android:label="@string/settings_button_text"
android:autoRemoveFromRecents="true">
<intent-filter>
<action android:name="android.intent.action.APPLICATION_PREFERENCES" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
<!--
The settings provider contains Home's data, like the workspace favorites. The permissions should be changed to what is defined above. The authorities should also be changed to represent the package name. --> <provider android:name="com.android.launcher3.LauncherProvider" android:authorities="com.android.launcher3.settings" android:exported="true" android:writePermission="com.android.launcher3.permission.WRITE_SETTINGS" android:readPermission="com.android.launcher3.permission.READ_SETTINGS" /> </application> </manifest> 複製代碼
爲了研究方便，刪除了大量代碼，完整的請查閱源碼。佈局
先查看onCreate方法post
class Launcher {
AllAppsContainerView mAppsView;// 桌面app的佈局（重要）
@Override
protected void onCreate(Bundle savedInstanceState) {
// 省略.....
if (mLauncherCallbacks != null) {
mLauncherCallbacks.preOnCreate();
}
super.onCreate(savedInstanceState);
LauncherAppState app = LauncherAppState.getInstance();
mModel = app.setLauncher(this);
setContentView(R.layout.launcher);
setupViews();
lockAllApps();
// We only load the page synchronously if the user rotates (or triggers a
// configuration change) while launcher is in the foreground
if (!mModel.startLoader(mWorkspace.getRestorePage())) {
// If we are not binding synchronously, show a fade in animation when
// the first page bind completes.
mDragLayer.setAlpha(0);
} else {
setWorkspaceLoading(true);
}
// On large interfaces, or on devices that a user has specifically enabled screen rotation,
// we want the screen to auto-rotate based on the current orientation
setOrientation();
}
}
複製代碼
跟蹤mModel.startLoader() 方法，mModel是一個LauncherModel類， class LauncherModel extends BroadcastReceiver 這個類是一個BroadcastReceiver，可是沒有發如今Manifest中註冊，注意上面的 app.setLauncher(this)方法，是的，它是在LauncherAppState 裏面動態註冊的ui
class LauncherAppState {
private LauncherAppState() {
// .....................
// 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);
// For extracting colors from the wallpaper
if (Utilities.isNycOrAbove()) {
// TODO: add a broadcast entry to the manifest for pre-N.
filter.addAction(Intent.ACTION_WALLPAPER_CHANGED);
}
sContext.registerReceiver(mModel, filter);
}
}
複製代碼
這個不是重點，繼續追蹤mModel.startLoader()方法。this
public boolean startLoader(int synchronousBindPage) {
// Enable queue before starting loader. It will get disabled in Launcher#finishBindingItems
InstallShortcutReceiver.enableInstallQueue();
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.
runOnMainThread(new Runnable() {
public void run() {
oldCallbacks.clearPendingBinds();
}
});
// If there is already one running, tell it to stop.
stopLoaderLocked();
mLoaderTask = new LoaderTask(mApp.getContext(), synchronousBindPage);
// TODO: mDeepShortcutsLoaded does not need to be true for synchronous bind.
if (synchronousBindPage != PagedView.INVALID_RESTORE_PAGE && mAllAppsLoaded
&& mWorkspaceLoaded && mDeepShortcutsLoaded && !mIsLoaderTaskRunning) {
mLoaderTask.runBindSynchronousPage(synchronousBindPage);
return true;
} else {
sWorkerThread.setPriority(Thread.NORM_PRIORITY);
sWorker.post(mLoaderTask);
}
}
}
return false;
}
複製代碼
該類中synchronized 塊有個mLoaderTask = new LoaderTask();查看LoaderTask源碼，發現LoaderTask是LauncherModel的內部類，並且是Runnable 類型，直接查看其run方法。
private class LoaderTask implements Runnable {
// .............
public void run() {
synchronized (mLock) {
if (mStopped) {
return;
}
mIsLoaderTaskRunning = true;
}
// Optimize for end-user experience: if the Launcher is up and // running with the
// All Apps interface in the foreground, load All Apps first. Otherwise, load the
// workspace first (default).
keep_running: {
if (DEBUG_LOADERS) Log.d(TAG, "step 1: loading workspace");
loadAndBindWorkspace();
if (mStopped) {
break keep_running;
}
waitForIdle();
// second step
if (DEBUG_LOADERS) Log.d(TAG, "step 2: loading all apps");
loadAndBindAllApps();
waitForIdle();
// third step
if (DEBUG_LOADERS) Log.d(TAG, "step 3: loading deep shortcuts");
loadAndBindDeepShortcuts();
}
// Clear out this reference, otherwise we end up holding it until all of the
// callback runnables are done.
mContext = null;
synchronized (mLock) {
// If we are still the last one to be scheduled, remove ourselves.
if (mLoaderTask == this) {
mLoaderTask = null;
}
mIsLoaderTaskRunning = false;
mHasLoaderCompletedOnce = true;
}
}
}
複製代碼
step 1: loading workspace step 2: loading all apps step 3: loading deep shortcuts 日誌寫的很是清楚，就是加載全部app，圖標之類的。
private void loadAndBindAllApps() {
// ............ 略
loadAllApps();
}
複製代碼
下面邏輯是載入桌面全部app，並使用handler切換UI線程而後給全部應用bind回調函數。
private void loadAllApps() {
// ............ 略
mBgAllAppsList.clear();
for (UserHandleCompat user : profiles) {
// ............ 略
final List<LauncherActivityInfoCompat> apps = mLauncherApps.getActivityList(null, user);
for (int i = 0; i < apps.size(); i++) {
LauncherActivityInfoCompat app = apps.get(i);
// This builds the icon bitmaps.
mBgAllAppsList.add(new AppInfo(mContext, app, user, mIconCache, quietMode));
}
// ............ 略
}
final ArrayList<AppInfo> added = mBgAllAppsList.added;
callbacks.bindAllApplications(added);
mHandler.post(new Runnable() {
final Callbacks callbacks = tryGetCallbacks(oldCallbacks);
if (callbacks != null) {
callbacks.bindAllApplications(added);
}
}
}
複製代碼
Launcher的佈局控件 咱們最開始提到Launcher的一個成員變量，AllAppsContainerView，這個類是一個自定義ViewGroup，以下：
/**
* The all apps view container.
*/
public class AllAppsContainerView extends BaseContainerView implements DragSource,
LauncherTransitionable, View.OnLongClickListener, AllAppsSearchBarController.Callbacks {
private static final int MIN_ROWS_IN_MERGED_SECTION_PHONE = 3;
private static final int MAX_NUM_MERGES_PHONE = 2;
private final Launcher mLauncher;
private final AlphabeticalAppsList mApps;
private final AllAppsGridAdapter mAdapter;
private final RecyclerView.LayoutManager mLayoutManager;
private final RecyclerView.ItemDecoration mItemDecoration;
// The computed bounds of the container
private final Rect mContentBounds = new Rect();
private AllAppsRecyclerView mAppsRecyclerView;
複製代碼
其中BaseContainerView extends FrameLayout，比較簡單。 咱們看下它的成員變量-> AllAppsRecyclerView，這是個自定義的RecyclerView，說明它是用RecyclerView對桌面apps佈局的。 查看AllAppsGridAdapter ，由於RecyclerView的事件監聽 通常是在這裏面設置的：
public AllAppsGridAdapter(Launcher launcher, AlphabeticalAppsList apps, View.OnClickListener
iconClickListener, View.OnLongClickListener iconLongClickListener) {
// 略 ..............
}
複製代碼
AllAppsGridAdapter的構造函數的參數和AllAppsContainerView的構造函數的方法體來次對比：
public AllAppsContainerView(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
// 略 ....
mLauncher = Launcher.getLauncher(context);
mApps = new AlphabeticalAppsList(context);
mAdapter = new AllAppsGridAdapter(mLauncher, mApps, mLauncher, this);
mApps.setAdapter(mAdapter);
}
複製代碼
驚喜發現-> AllAppsGridAdapter 構造函數的第三個參數是mLauncher，並且是View.OnClickListener類型。
再次回到Launcher，Launcher實現了 View.OnClickListener，直接找到 public void onClick(View v)方法，到這步就很是簡單了，next->next->next...
這些步驟的代碼就無須貼了，最終會執行到startActivity，即分析 Activity啓動流程的重要入口。
onClick->onClickAppShortcut->startAppShortcutOrInfoActivity->startActivitySafely->startActivity
複製代碼
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