Android系統默認Home應用程序（Launcher）的啓動過程源代碼分析

在前面一篇文章中，我們分析了Android系統在啓動時安裝應用程序的過程，這些應用程序安裝好之後，還需要有一個Home應用程序來負責把它們在桌面上展示出來，在Android系統中，這個默認的Home應用程序就是Launcher了，本文將詳細分析Launcher應用程序的啓動過程。

Android系統的Home應用程序Launcher是由ActivityManagerService啓動的，而ActivityManagerService和PackageManagerService一樣，都是在開機時由SystemServer組件啓動的，SystemServer組件首先是啓動ePackageManagerServic，由它來負責安裝系統的應用程序，具體可以參考前面一篇文章Android應用程序安裝過程源代碼分析，系統中的應用程序安裝好了以後，SystemServer組件接下來就要通過ActivityManagerService來啓動Home應用程序Launcher了，Launcher在啓動的時候便會通過PackageManagerServic把系統中已經安裝好的應用程序以快捷圖標的形式展示在桌面上，這樣用戶就可以使用這些應用程序了，整個過程如下圖所示：

點擊查看大圖

下面詳細分析每一個步驟。

Step 1. SystemServer.main

這個函數定義在frameworks/base/services/java/com/android/server/SystemServer.java文件中，具體可以參考前面一篇文章Android應用程序安裝過程源代碼分析的Step 1。

Step 2. SystemServer.init1

這個函數是一個JNI方法，實現在 frameworks/base/services/jni/com_android_server_SystemServer.cpp文件中，具體可以參考前面一篇文章Android應用程序安裝過程源代碼分析的Step 2。

Step 3. libsystem_server.system_init

函數system_init實現在libsystem_server庫中，源代碼位於frameworks/base/cmds/system_server/library/system_init.cpp文件中，具體可以參考前面一篇文章Android應用程序安裝過程源代碼分析的Step 3。

Step 4. AndroidRuntime.callStatic

這個函數定義在frameworks/base/core/jni/AndroidRuntime.cpp文件中，具體可以參考前面一篇文章Android應用程序安裝過程源代碼分析的Step 4。

Step 5. SystemServer.init2

這個函數定義在frameworks/base/services/java/com/android/server/SystemServer.java文件中，具體可以參考前面一篇文章Android應用程序安裝過程源代碼分析的Step 5。

Step 6. ServerThread.run

這個函數定義在frameworks/base/services/java/com/android/server/SystemServer.java文件中，具體可以參考前面一篇文章Android應用程序安裝過程源代碼分析的Step 6。

Step 7. ActivityManagerService.main

這個函數定義在frameworks/base/services/java/com/android/server/am/ActivityManagerServcie.java文件中：

public final class ActivityManagerService extends ActivityManagerNative   
implements Watchdog.Monitor, BatteryStatsImpl.BatteryCallback {   
......   
 
public static final Context main(int factoryTest) {   
AThread thr = new AThread();   
thr.start();   
 
synchronized (thr) {   
while (thr.mService == null) {   
try {   
thr.wait();   
} catch (InterruptedException e) {   
}   
}   
}   
 
ActivityManagerService m = thr.mService;   
mmSelf = m;   
ActivityThread at = ActivityThread.systemMain();   
mSystemThread = at;   
Context context = at.getSystemContext();   
m.mContext = context;   
m.mFactoryTest = factoryTest;   
m.mMainStack = new ActivityStack(m, context, true);   
 
m.mBatteryStatsService.publish(context);   
m.mUsageStatsService.publish(context);   
 
synchronized (thr) {   
thr.mReady = true;   
thr.notifyAll();   
}   
 
m.startRunning(null, null, null, null);   
 
return context;   
}   
 
......   
}

public final class ActivityManagerService extends ActivityManagerNative implements Watchdog.Monitor, BatteryStatsImpl.BatteryCallback { ...... public static final Context main(int factoryTest) { AThread thr = new AThread(); thr.start(); synchronized (thr) { while (thr.mService == null) { try { thr.wait(); } catch (InterruptedException e) { } } } ActivityManagerService m = thr.mService; mSelf = m; ActivityThread at = ActivityThread.systemMain(); mSystemThread = at; Context context = at.getSystemContext(); m.mContext = context; m.mFactoryTest = factoryTest; m.mMainStack = new ActivityStack(m, context, true); m.mBatteryStatsService.publish(context); m.mUsageStatsService.publish(context); synchronized (thr) { thr.mReady = true; thr.notifyAll(); } m.startRunning(null, null, null, null); return context; } ...... } 這個函數首先通過AThread線程對象來內部創建了一個ActivityManagerService實例，然後將這個實例保存其成員變量mService中，接着又把這個ActivityManagerService實例保存在ActivityManagerService類的靜態成員變量mSelf中，最後初始化其它成員變量，就結束了。

Step 8. PackageManagerService.main

這個函數定義在frameworks/base/services/java/com/android/server/PackageManagerService.java文件中，具體可以參考前面一篇文章Android應用程序安裝過程源代碼分析的Step 7。執行完這一步之後，系統中的應用程序的所有信息都保存在PackageManagerService中了，後面Home應用程序Launcher啓動起來後，就會把PackageManagerService中的應用程序信息取出來，然後以快捷圖標的形式展示在桌面上，後面我們將會看到這個過程。

Step 9. ActivityManagerService.setSystemProcess

這個函數定義在frameworks/base/services/java/com/android/server/am/ActivityManagerServcie.java文件中：

public final class ActivityManagerService extends ActivityManagerNative   
implements Watchdog.Monitor, BatteryStatsImpl.BatteryCallback {   
......   
 
public static void setSystemProcess() {   
try {   
ActivityManagerService m = mSelf;   
 
ServiceManager.addService("activity", m);   
ServiceManager.addService("meminfo", new MemBinder(m));   
if (MONITOR_CPU_USAGE) {   
ServiceManager.addService("cpuinfo", new CpuBinder(m));   
}   
ServiceManager.addService("permission", new PermissionController(m));   
 
ApplicationInfo info =   
mSelf.mContext.getPackageManager().getApplicationInfo(   
"android", STOCK_PM_FLAGS);   
mSystemThread.installSystemApplicationInfo(info);   
 
synchronized (mSelf) {   
Proce***ecord app = mSelf.newProce***ecordLocked(   
mSystemThread.getApplicationThread(), info,   
info.processName);   
app.persistent = true;   
app.pid = MY_PID;   
app.maxAdj = SYSTEM_ADJ;   
mSelf.mProcessNames.put(app.processName, app.info.uid, app);   
synchronized (mSelf.mPidsSelfLocked) {   
mSelf.mPidsSelfLocked.put(app.pid, app);   
}   
mSelf.updateLruProcessLocked(app, true, true);   
}   
} catch (PackageManager.NameNotFoundException e) {   
throw new RuntimeException(   
"Unable to find android system package", e);   
}   
}   
......   
}   
public final class ActivityManagerService extends ActivityManagerNative  
        implements Watchdog.Monitor, BatteryStatsImpl.BatteryCallback {  
    ......  
 
    public static void setSystemProcess() {  
        try {  
            ActivityManagerService m = mSelf;  
 
            ServiceManager.addService("activity", m);  
            ServiceManager.addService("meminfo", new MemBinder(m));  
            if (MONITOR_CPU_USAGE) {  
                ServiceManager.addService("cpuinfo", new CpuBinder(m));  
            }  
            ServiceManager.addService("permission", new PermissionController(m));  
 
            ApplicationInfo info =  
                mSelf.mContext.getPackageManager().getApplicationInfo(  
                "android", STOCK_PM_FLAGS);  
            mSystemThread.installSystemApplicationInfo(info);  
 
            synchronized (mSelf) {  
                Proce***ecord app = mSelf.newProce***ecordLocked(  
                    mSystemThread.getApplicationThread(), info,  
                    info.processName);  
                app.persistent = true;  
                app.pid = MY_PID;  
                app.maxAdj = SYSTEM_ADJ;  
                mSelf.mProcessNames.put(app.processName, app.info.uid, app);  
                synchronized (mSelf.mPidsSelfLocked) {  
                    mSelf.mPidsSelfLocked.put(app.pid, app);  
                }  
                mSelf.updateLruProcessLocked(app, true, true);  
            }  
        } catch (PackageManager.NameNotFoundException e) {  
            throw new RuntimeException(  
                "Unable to find android system package", e);  
        }  
    }  
    ......  
}

這個函數首先是將這個ActivityManagerService實例添加到ServiceManager中去託管，這樣其它地方就可以通過ServiceManager.getService接口來訪問這個全局唯一的ActivityManagerService實例了，接着又通過調用mSystemThread.installSystemApplicationInfo函數來把應用程序框架層下面的android包加載進來，這裏的mSystemThread是一個ActivityThread類型的實例變量，它是在上面的Step 7中創建的，後面就是一些其它的初始化工作了。

Step 10. ActivityManagerService.systemReady

這個函數是在上面的Step 6中的ServerThread.run函數在將系統中的一系列服務都初始化完畢之後才調用的，它定義在frameworks/base/services/java/com/android/server/am/ActivityManagerServcie.java文件中：

public final class ActivityManagerService extends ActivityManagerNative
implements Watchdog.Monitor, BatteryStatsImpl.BatteryCallback {
......
public void systemReady(final Runnable goingCallback) {
......
synchronized (this) {
......
mMainStack.resumeTopActivityLocked(null);
}
}
......
}

public final class ActivityManagerService extends ActivityManagerNative implements Watchdog.Monitor, BatteryStatsImpl.BatteryCallback { ...... public void systemReady(final Runnable goingCallback) { ...... synchronized (this) { ...... mMainStack.resumeTopActivityLocked(null); } } ...... } 這個函數的內容比較多，這裏省去無關的部分，主要關心啓動Home應用程序的邏輯，這裏就是通過mMainStack.resumeTopActivityLocked函數來啓動Home應用程序的了，這裏的mMainStack是一個ActivityStack類型的實例變量。

Step 11. ActivityStack.resumeTopActivityLocked

這個函數定義在frameworks/base/services/java/com/android/server/am/ActivityStack.java文件中：

public class ActivityStack {   
......   
 
final boolean resumeTopActivityLocked(ActivityRecord prev) {   
// Find the first activity that is not finishing.   
ActivityRecord next = topRunningActivityLocked(null);   
 
......   
 
if (next == null) {   
// There are no more activities! Let's just start up the   
// Launcher...   
if (mMainStack) {   
return mService.startHomeActivityLocked();   
}   
}   
 
......   
}   
 
......   
}

public class ActivityStack { ...... final boolean resumeTopActivityLocked(ActivityRecord prev) { // Find the first activity that is not finishing. ActivityRecord next = topRunningActivityLocked(null); ...... if (next == null) { // There are no more activities! Let's just start up the // Launcher... if (mMainStack) { return mService.startHomeActivityLocked(); } } ...... } ...... } 這裏調用函數topRunningActivityLocked返回的是當前系統Activity堆棧最頂端的Activity，由於此時還沒有Activity被啓動過，因此，返回值爲null，即next變量的值爲null，於是就調用mService.startHomeActivityLocked語句，這裏的mService就是前面在Step 7中創建的ActivityManagerService實例了。

Step 12. ActivityManagerService.startHomeActivityLocked

這個函數定義在frameworks/base/services/java/com/android/server/am/ActivityManagerServcie.java文件中：

public final class ActivityManagerService extends ActivityManagerNative   
implements Watchdog.Monitor, BatteryStatsImpl.BatteryCallback {   
......   
 
boolean startHomeActivityLocked() {   
......   
 
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);   
}   
ActivityInfo aInfo =   
intent.resolveActivityInfo(mContext.getPackageManager(),   
STOCK_PM_FLAGS);   
if (aInfo != null) {   
intent.setComponent(new ComponentName(   
aInfo.applicationInfo.packageName, aInfo.name));   
// Don't do this if the home app is currently being   
// instrumented.   
Proce***ecord app = getProce***ecordLocked(aInfo.processName,   
aInfo.applicationInfo.uid);   
if (app == null || app.instrumentationClass == null) {   
intent.setFlags(intent.getFlags() | Intent.FLAG_ACTIVITY_NEW_TASK);   
mMainStack.startActivityLocked(null, intent, null, null, 0, aInfo,   
null, null, 0, 0, 0, false, false);   
}   
}   
 
return true;   
}   
 
......

函數首先創建一個CATEGORY_HOME類型的Intent，然後通過Intent.resolveActivityInfo函數向PackageManagerService查詢Category類型爲HOME的Activity，這裏我們假設只有系統自帶的Launcher應用程序註冊了HOME類型的Activity（見packages/apps/Launcher2/AndroidManifest.xml文件）：

<manifest   
xmlns:android="http://schemas.android.com/apk/res/android"   
package="com.android.launcher"   
android:sharedUserId="@string/sharedUserId"   
>   
 
......   
 
<application   
android:name="com.android.launcher2.LauncherApplication"   
android:process="@string/process"   
android:label="@string/application_name"   
android:icon="@drawable/ic_launcher_home">   
 
<activity   
android:name="com.android.launcher2.Launcher"   
android:launchMode="singleTask"   
android:clearTaskOnLaunch="true"   
android:stateNotNeeded="true"   
android:theme="@style/Theme"   
android:screenOrientation="nosensor"   
android:windowSoftInputMode="stateUnspecified|adjustPan">   
<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>   
 
......   
</application>   
</manifest>   
<manifest 
    xmlns:android="http://schemas.android.com/apk/res/android" 
    package="com.android.launcher" 
    android:sharedUserId="@string/sharedUserId" 
    > 
 
    ......  
 
    <application 
        android:name="com.android.launcher2.LauncherApplication" 
        android:process="@string/process" 
        android:label="@string/application_name" 
        android:icon="@drawable/ic_launcher_home"> 
 
        <activity 
            android:name="com.android.launcher2.Launcher" 
            android:launchMode="singleTask" 
            android:clearTaskOnLaunch="true" 
            android:stateNotNeeded="true" 
            android:theme="@style/Theme" 
            android:screenOrientation="nosensor" 
            android:windowSoftInputMode="stateUnspecified|adjustPan"> 
            <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> 
 
        ......  
    </application> 
</manifest>

因此，這裏就返回com.android.launcher2.Launcher這個Activity了。由於是第一次啓動這個Activity，接下來調用函數getProce***ecordLocked返回來的Proce***ecord值爲null，於是，就調用mMainStack.startActivityLocked函數啓動com.android.launcher2.Launcher這個Activity了，這裏的mMainStack是一個ActivityStack類型的成員變量。

Step 13. ActivityStack.startActivityLocked

這個函數定義在frameworks/base/services/java/com/android/server/am/ActivityStack.java文件中，具體可以參考Android應用程序啓動過程源代碼分析一文，這裏就不詳述了，在我們這個場景中，調用這個函數的最後結果就是把com.android.launcher2.Launcher啓動起來，接着調用它的onCreate函數。

Step 14. Launcher.onCreate

這個函數定義在packages/apps/Launcher2/src/com/android/launcher2/Launcher.java文件中：

public final class Launcher extends Activity
implements View.OnClickListener, OnLongClickListener, LauncherModel.Callbacks, AllAppsView.Watcher {
......
@Override
protected void onCreate(Bundle savedInstanceState) {
......
if (!mRestoring) {
mModel.startLoader(this, true);
}
......
}
......
}

public final class Launcher extends Activity implements View.OnClickListener, OnLongClickListener, LauncherModel.Callbacks, AllAppsView.Watcher { ...... @Override protected void onCreate(Bundle savedInstanceState) { ...... if (!mRestoring) { mModel.startLoader(this, true); } ...... } ...... } 這裏的mModel是一個LauncherModel類型的成員變量，這裏通過調用它的startLoader成員函數來執行加應用程序的操作。

Step 15. LauncherModel.startLoader

這個函數定義在packages/apps/Launcher2/src/com/android/launcher2/LauncherModel.java文件中：

public class LauncherModel extends BroadcastReceiver {   
......   
 
public void startLoader(Context context, boolean isLaunching) {   
......   
 
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) {   
// If there is already one running, tell it to stop.   
LoaderTask oldTask = mLoaderTask;   
if (oldTask != null) {   
if (oldTask.isLaunching()) {   
// don't downgrade isLaunching if we're already running   
isLaunching = true;   
}   
oldTask.stopLocked();   
}   
mLoaderTask = new LoaderTask(context, isLaunching);   
sWorker.post(mLoaderTask);   
}   
}   
}   
 
......   
}

public class LauncherModel extends BroadcastReceiver { ...... public void startLoader(Context context, boolean isLaunching) { ...... 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) { // If there is already one running, tell it to stop. LoaderTask oldTask = mLoaderTask; if (oldTask != null) { if (oldTask.isLaunching()) { // don't downgrade isLaunching if we're already running isLaunching = true; } oldTask.stopLocked(); } mLoaderTask = new LoaderTask(context, isLaunching); sWorker.post(mLoaderTask); } } } ...... } 這裏不是直接加載應用程序，而是把加載應用程序的操作作爲一個消息來處理。這裏的sWorker是一個Handler，通過它的post方式把一個消息放在消息隊列中去，然後系統就會調用傳進去的參數mLoaderTask的run函數來處理這個消息，這個mLoaderTask是LoaderTask類型的實例，於是，下面就會執行LoaderTask類的run函數了。

Step 16. LoaderTask.run

這個函數定義在packages/apps/Launcher2/src/com/android/launcher2/LauncherModel.java文件中：

public class LauncherModel extends BroadcastReceiver {   
......   
 
private class LoaderTask implements Runnable {   
......   
 
public void run() {   
......   
 
keep_running: {   
......   
 
// second step   
if (loadWorkspaceFirst) {   
......   
loadAndBindAllApps();   
} else {   
......   
}   
 
......   
}   
 
......   
}   
 
......   
}   
 
......   
}

這裏調用loadAndBindAllApps成員函數來進一步操作。

Step 17. LoaderTask.loadAndBindAllApps
這個函數定義在packages/apps/Launcher2/src/com/android/launcher2/LauncherModel.java文件中：

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public class LauncherModel extends BroadcastReceiver {   
......   
 
private class LoaderTask implements Runnable {   
......   
 
private void loadAndBindAllApps() {   
......   
 
if (!mAllAppsLoaded) {   
loadAllAppsByBatch();   
if (mStopped) {   
return;   
}   
mAllAppsLoaded = true;   
} else {   
onlyBindAllApps();   
}   
}   
 
 
......   
}   
 
......   
}

public class LauncherModel extends BroadcastReceiver { ...... private class LoaderTask implements Runnable { ...... private void loadAndBindAllApps() { ...... if (!mAllAppsLoaded) { loadAllAppsByBatch(); if (mStopped) { return; } mAllAppsLoaded = true; } else { onlyBindAllApps(); } } ...... } ...... } 由於還沒有加載過應用程序，這裏的mAllAppsLoaded爲false，於是就繼續調用loadAllAppsByBatch函數來進一步操作了。

Step 18. LoaderTask.loadAllAppsByBatch
這個函數定義在packages/apps/Launcher2/src/com/android/launcher2/LauncherModel.java文件中：

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public class LauncherModel extends BroadcastReceiver {   
......   
 
private class LoaderTask implements Runnable {   
......   
 
private void loadAllAppsByBatch() {   
......   
 
final Intent mainIntent = new Intent(Intent.ACTION_MAIN, null);   
mainIntent.addCategory(Intent.CATEGORY_LAUNCHER);   
 
final PackageManager packageManager = mContext.getPackageManager();   
List<ResolveInfo> apps = null;   
 
int N = Integer.MAX_VALUE;   
 
int startIndex;   
int i=0;   
int batchSize = -1;   
while (i < N && !mStopped) {   
if (i == 0) {   
mAllAppsList.clear();   
......   
apps = packageManager.queryIntentActivities(mainIntent, 0);   
 
......   
 
N = apps.size();   
 
......   
 
if (mBatchSize == 0) {   
batchSize = N;   
} else {   
batchSize = mBatchSize;   
}   
 
......   
 
Collections.sort(apps,   
new ResolveInfo.DisplayNameComparator(packageManager));   
}   
 
startIndex = i;   
for (int j=0; i<N && j<batchSize; j++) {   
// This builds the icon bitmaps.   
mAllAppsList.add(new ApplicationInfo(apps.get(i), mIconCache));   
i++;   
}   
 
final boolean first = i <= batchSize;   
final Callbacks callbacks = tryGetCallbacks(oldCallbacks);   
final ArrayList<ApplicationInfo> added = mAllAppsList.added;   
mAllAppsList.added = new ArrayList<ApplicationInfo>();   
 
mHandler.post(new Runnable() {   
public void run() {   
final long t = SystemClock.uptimeMillis();   
if (callbacks != null) {   
if (first) {   
callbacks.bindAllApplications(added);   
} else {   
callbacks.bindAppsAdded(added);   
}   
......   
} else {   
......   
}   
}   
});   
 
......   
}   
 
......   
}   
 
......   
}   
 
......   
}

函數首先構造一個CATEGORY_LAUNCHER類型的Intent：

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final Intent mainIntent = new Intent(Intent.ACTION_MAIN, null);
mainIntent.addCategory(Intent.CATEGORY_LAUNCHER);

接着從mContext變量中獲得PackageManagerService的接口

final PackageManager packageManager = mContext.getPackageManager();   
    final PackageManager packageManager = mContext.getPackageManager();  
 
 
下一步就是通過這個PackageManagerService.queryIntentActivities接口來取回所有Action類型爲Intent.ACTION_MAIN，並且Category類型爲Intent.CATEGORY_LAUNCHER的Activity了。  
 
我們先進入到PackageManagerService.queryIntentActivities函數中看看是如何獲得這些Activity的，然後再回到這個函數中來看其餘操作。  
 
 
Step 19. PackageManagerService.queryIntentActivities  
 
這個函數定義在frameworks/base/services/java/com/android/server/PackageManagerService.java文件中：  
 
 
view plaincopy to clipboardprint?  
class PackageManagerService extends IPackageManager.Stub {   
......   
 
public List<ResolveInfo> queryIntentActivities(Intent intent,   
String resolvedType, int flags) {   
......   
 
synchronized (mPackages) {   
String pkgName = intent.getPackage();   
if (pkgName == null) {   
return (List<ResolveInfo>)mActivities.queryIntent(intent,   
resolvedType, flags);   
}   
 
......   
}   
 
......   
}   
 
......   
}   
class PackageManagerService extends IPackageManager.Stub {  
    ......  
 
    public List<ResolveInfo> queryIntentActivities(Intent intent,  
            String resolvedType, int flags) {  
        ......  
 
        synchronized (mPackages) {  
            String pkgName = intent.getPackage();  
            if (pkgName == null) {  
                return (List<ResolveInfo>)mActivities.queryIntent(intent,  
                        resolvedType, flags);  
            }  
 
            ......  
        }  
 
        ......  
    }  
 
    ......  
}

回憶前面一篇文章Android應用程序安裝過程源代碼分析，系統在前面的Step 8中啓動PackageManagerService時，會把系統中的應用程序都解析一遍，然後把解析得到的Activity都保存在mActivities變量中，這裏通過這個mActivities變量的queryIntent函數返回符合條件intent的Activity，這裏要返回的便是Action類型爲Intent.ACTION_MAIN，並且Category類型爲Intent.CATEGORY_LAUNCHER的Activity了。

回到Step 18中的 LoaderTask.loadAllAppsByBatch函數中，從queryIntentActivities函數調用處返回所要求的Activity後，便調用函數tryGetCallbacks(oldCallbacks)得到一個返CallBack接口，這個接口是由Launcher類實現的，接着調用這個接口的.bindAllApplications函數來進一步操作。注意，這裏又是通過消息來處理加載應用程序的操作的。

Step 20. Launcher.bindAllApplications

這個函數定義在packages/apps/Launcher2/src/com/android/launcher2/Launcher.java文件中：

public final class Launcher extends Activity   
implements View.OnClickListener, OnLongClickListener, LauncherModel.Callbacks, AllAppsView.Watcher {   
......   
 
private AllAppsView mAllAppsGrid;   
 
......   
 
public void bindAllApplications(ArrayList<ApplicationInfo> apps) {   
mAllAppsGrid.setApps(apps);   
}   
 
......   
}   
public final class Launcher extends Activity  
        implements View.OnClickListener, OnLongClickListener, LauncherModel.Callbacks, AllAppsView.Watcher {  
    ......  
 
    private AllAppsView mAllAppsGrid;  
 
    ......  
 
    public void bindAllApplications(ArrayList<ApplicationInfo> apps) {  
        mAllAppsGrid.setApps(apps);  
    }  
 
    ......  
}

這裏的mAllAppsGrid是一個AllAppsView類型的變量，它的實際類型一般就是AllApps2D了。

Step 21. AllApps2D.setApps

這個函數定義在packages/apps/Launcher2/src/com/android/launcher2/AllApps2D.java文件中：

public class AllApps2D   
extends RelativeLayout   
implements AllAppsView,   
AdapterView.OnItemClickListener,   
AdapterView.OnItemLongClickListener,   
View.OnKeyListener,   
DragSource {   
 
......   
 
public void setApps(ArrayList<ApplicationInfo> list) {   
mAllAppsList.clear();   
addApps(list);   
}   
 
public void addApps(ArrayList<ApplicationInfo> list) {   
final int N = list.size();   
 
for (int i=0; i<N; i++) {   
final ApplicationInfo item = list.get(i);   
int index = Collections.binarySearch(mAllAppsList, item,   
LauncherModel.APP_NAME_COMPARATOR);   
if (index < 0) {   
index = -(index+1);   
}   
mAllAppsList.add(index, item);   
}   
mAppsAdapter.notifyDataSetChanged();   
}   
 
......   
}

函數setApps首先清空mAllAppsList列表，然後調用addApps函數來爲上一步得到的每一個應用程序創建一個ApplicationInfo實例了，有了這些ApplicationInfo實例之後，就可以在桌面上展示系統中所有的應用程序了。

到了這裏，系統默認的Home應用程序Launcher就把PackageManagerService中的應用程序加載進來了，當我們在屏幕上點擊下面這個圖標時，就會把剛纔加載好的應用程序以圖標的形式展示出來了：

點擊這個按鈕時，便會響應Launcher.onClick函數：

public final class Launcher extends Activity   
implements View.OnClickListener, OnLongClickListener, LauncherModel.Callbacks, AllAppsView.Watcher {   
......   
 
public void onClick(View v) {   
Object tag = v.getTag();   
if (tag instanceof ShortcutInfo) {   
......   
} else if (tag instanceof FolderInfo) {   
......   
} else if (v == mHandleView) {   
if (isAllAppsVisible()) {   
......   
} else {   
showAllApps(true);   
}   
}   
}   
 
......   
}   
public final class Launcher extends Activity  
        implements View.OnClickListener, OnLongClickListener, LauncherModel.Callbacks, AllAppsView.Watcher {  
    ......  
 
    public void onClick(View v) {  
        Object tag = v.getTag();  
        if (tag instanceof ShortcutInfo) {  
            ......  
        } else if (tag instanceof FolderInfo) {  
            ......  
        } else if (v == mHandleView) {  
            if (isAllAppsVisible()) {  
                ......  
            } else {  
                showAllApps(true);  
            }  
        }  
    }  
 
    ......  
} 接着就會調用showAllApps函數顯示應用程序圖標：  
 
 
 
view plaincopy to clipboardprint?  
public final class Launcher extends Activity   
implements View.OnClickListener, OnLongClickListener, LauncherModel.Callbacks, AllAppsView.Watcher {   
......   
 
void showAllApps(boolean animated) {   
mAllAppsGrid.zoom(1.0f, animated);   
 
((View) mAllAppsGrid).setFocusable(true);   
((View) mAllAppsGrid).requestFocus();   
 
// TODO: fade these two too   
mDeleteZone.setVisibility(View.GONE);   
}   
 
......   
}

這樣我們就可以看到系統中的應用程序了：

當點擊上面的這些應用程序圖標時，便會響應AllApps2D.onItemClick函數：

view plain copy to clipboard print ?

public class AllApps2D   
extends RelativeLayout   
implements AllAppsView,   
AdapterView.OnItemClickListener,   
AdapterView.OnItemLongClickListener,   
View.OnKeyListener,   
DragSource {   
 
......   
 
public void onItemClick(AdapterView parent, View v, int position, long id) {   
ApplicationInfo app = (ApplicationInfo) parent.getItemAtPosition(position);   
mLauncher.startActivitySafely(app.intent, app);   
}   
 
 
......   
}   
public class AllApps2D  
    extends RelativeLayout  
    implements AllAppsView,  
        AdapterView.OnItemClickListener,  
        AdapterView.OnItemLongClickListener,  
        View.OnKeyListener,  
        DragSource {  
 
    ......  
 
    public void onItemClick(AdapterView parent, View v, int position, long id) {  
        ApplicationInfo app = (ApplicationInfo) parent.getItemAtPosition(position);  
        mLauncher.startActivitySafely(app.intent, app);  
    }  
 
 
    ......  
}

Android系統默認Home應用程序（Launcher）的啓動過程源代碼分析

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