Android应用启动过程-Launcher源码浅析
本文参考的源码（7.1.1_r6）java
Launcher也是一个应用程序，和咱们的App没有什么区别，当用户点击应用图标时候，启动其余的App，本文主要为分析Activity的启动流程打基础。android
Launcher.java代码量比较多，大约4500多行，可是里面的逻辑并不复杂，不过我这里分析它的意义主要为了更好理解后面的知识，了解Launcher具体的流程才是重要的，不要沉迷代码中没法自拔！bash
先来张图：app
在线源码地址
AndroidManifest.xml Launcher.java LauncherModel.java AllAppsContainerView.javaide
分析
先看下它的manifest文件，这里面的内容很少，Launcher类是一个Activity，只是比咱们普通的app多一个 <category android:name="android.intent.category.HOME" />函数
<?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> 复制代码
为了研究方便，删除了大量代码，完整的请查阅源码。布局
先查看onCreate方法post
class Launcher {
AllAppsContainerView mAppsView;// 桌面app的布局（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();
}
}
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跟踪mModel.startLoader() 方法，mModel是一个LauncherModel类， class LauncherModel extends BroadcastReceiver 这个类是一个BroadcastReceiver，可是没有发如今Manifest中注册，注意上面的 app.setLauncher(this)方法，是的，它是在LauncherAppState 里面动态注册的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);
}
}
复制代码
这个不是重点，继续追踪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;
}
复制代码
该类中synchronized 块有个mLoaderTask = new LoaderTask();查看LoaderTask源码，发现LoaderTask是LauncherModel的内部类，并且是Runnable 类型，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;
}
}
}
复制代码
step 1: loading workspace step 2: loading all apps step 3: loading deep shortcuts 日志写的很是清楚，就是加载全部app，图标之类的。
private void loadAndBindAllApps() {
// ............ 略
loadAllApps();
}
复制代码
下面逻辑是载入桌面全部app，并使用handler切换UI线程而后给全部应用bind回调函数。
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);
}
}
}
复制代码
Launcher的布局控件 咱们最开始提到Launcher的一个成员变量，AllAppsContainerView，这个类是一个自定义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;
复制代码
其中BaseContainerView extends FrameLayout，比较简单。 咱们看下它的成员变量-> AllAppsRecyclerView，这是个自定义的RecyclerView，说明它是用RecyclerView对桌面apps布局的。 查看AllAppsGridAdapter ，由于RecyclerView的事件监听 通常是在这里面设置的：
public AllAppsGridAdapter(Launcher launcher, AlphabeticalAppsList apps, View.OnClickListener
iconClickListener, View.OnLongClickListener iconLongClickListener) {
// 略 ..............
}
复制代码
AllAppsGridAdapter的构造函数的参数和AllAppsContainerView的构造函数的方法体来次对比：
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);
}
复制代码
惊喜发现-> AllAppsGridAdapter 构造函数的第三个参数是mLauncher，并且是View.OnClickListener类型。
再次回到Launcher，Launcher实现了 View.OnClickListener，直接找到 public void onClick(View v)方法，到这步就很是简单了，next->next->next...
这些步骤的代码就无须贴了，最终会执行到startActivity，即分析 Activity启动流程的重要入口。
onClick->onClickAppShortcut->startAppShortcutOrInfoActivity->startActivitySafely->startActivity
复制代码
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