繼上一篇Android系統啓動流程分析之安裝應用文章接着分析系統啓動應用的過程.
Android系統的啓動流程簡要分析裏已經介紹了SystemServer在main方法裏創建了一個線程ServerThread,並調用initAndLoop方法加載各種服務.
ActivityManagerService(Ams)就是在initAndLoop方法裏加載的.那麼,看下initAndLoop方法裏關於AMS的核心代碼.
1.context = ActivityManagerService.main(factoryTest);
2.ActivityManagerService.setSystemProcess();
3.ActivityManagerService.installSystemProviders();
4.ActivityManagerService.self().setWindowManager(wm);
5.ActivityManagerService.self().systemReady
一步一步進行分析.
1.context = ActivityManagerService.main(factoryTest);
這行代碼是啓動ActivityManagerService,獲取上下文context,進入AMS的main方法看一下
public static final Context main(int factoryTest) {
AThread thr = new AThread();
thr.start();
synchronized (thr) {
while (thr.mService == null) {
try {
//線程等待activitymanagerservice初始化完成
thr.wait();
} catch (InterruptedException e) {
}
}
}
ActivityManagerService m = thr.mService;
mSelf = m;
//啓動一個主線程
ActivityThread at = ActivityThread.systemMain();
mSystemThread = at;
//獲取上下文context
Context context = at.getSystemContext();
context.setTheme(android.R.style.Theme_Holo);
m.mContext = context;
m.mFactoryTest = factoryTest;
m.mIntentFirewall = new IntentFirewall(m.new IntentFirewallInterface());
//新建一個activity堆棧管理輔助類
m.mStackSupervisor = new ActivityStackSupervisor(m, context, thr.mLooper);
m.mBatteryStatsService.publish(context);
m.mUsageStatsService.publish(context);
m.mAppOpsService.publish(context);
synchronized (thr) {
thr.mReady = true;
//activitymanagerservice啓動完成
thr.notifyAll();
}
m.startRunning(null, null, null, null);
return context;
}
1.1
在mian方法裏會創建一個線程AThread,AThread用來初始化Looper,AThread等待ActivityManagerService初始化完成後把自己的成員變量mService賦值給ActivityManagerService自身.
1.2
啓動一個主線程ActivityThread,ActivityThread是所有Application運行的主線程,1.3
獲取上下文context,最終是調用ContextImpl的createSystemContext方法返回的,context本質是ContextImpl的實例
1.4
等ActivityManagerService啓動完成,調用m.startRunning()方法運行,在startRunning方法內部調用systemReady()方法.做系統準備工作.
public final void startRunning(String pkg, String cls, String action, String data) {
synchronized (this) {
if (mStartRunning) {
return;
}
mStartRunning = true;
mTopComponent = pkg != null && cls != null ? new ComponentName(pkg, cls) : null;
//如果傳入的action爲空那麼賦值Intent.ACTION_MAIN給mTopAction
mTopAction = action != null ? action : Intent.ACTION_MAIN;
mTopData = data;
if (!mSystemReady) {
return;
}
}
systemReady(null);
}
這個mTopAction就是後面要啓動第一個Activity,也就是Launcher的Action.
1.4.1
在systemReady方法調用mStackSupervisor.resumeTopActivitiesLocked方法.
public void systemReady(final Runnable goingCallback){
......
......
mStackSupervisor.resumeTopActivitiesLocked();
......
}
1.4.2
最終經過層層跳轉會回到ActivityManagerService的startHomeActivityLocked方法.
boolean startHomeActivityLocked(int userId) {
......
......
//獲取intent信息
Intent intent = getHomeIntent();
ActivityInfo aInfo = resolveActivityInfo(intent, STOCK_PM_FLAGS, userId);
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);
if (app == null || app.instrumentationClass == null) {
intent.setFlags(intent.getFlags() | Intent.FLAG_ACTIVITY_NEW_TASK);
//啓動主程序,也就是Laucnher
mStackSupervisor.startHomeActivity(intent, aInfo);
}
}
return true;
}
1.4.3
通過getHomeIntent方法獲取Intent信息,看下代碼
Intent getHomeIntent() {
Intent intent = new Intent(mTopAction, mTopData != null ? Uri.parse(mTopData) : null);
intent.setComponent(mTopComponent);
if (mFactoryTest != SystemServer.FACTORY_TEST_LOW_LEVEL) {
//設置Category
intent.addCategory(Intent.CATEGORY_HOME);
}
return intent;
}
給intent設置了Category,這個mTopAction就是前面設置的.
那麼在這裏Intent指定Action爲action.MAIN,category爲category.HOME.這正是啓動Launcher的配置
<intent-filter >
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.HOME" />
</intent-filter>
1.4.4
回到1.4.2,調用如下代碼啓動Launcher
//啓動主程序,也就是Laucnher
mStackSupervisor.startHomeActivity(intent, aInfo);
這個方法是用來註冊一些服務和獲取、綁定進程信息的.
public static void setSystemProcess() {
try {
ActivityManagerService m = mSelf;
//註冊ActivityManagerService
ServiceManager.addService(Context.ACTIVITY_SERVICE, m, true);
//註冊進程統計服務
ServiceManager.addService(ProcessStats.SERVICE_NAME, m.mProcessStats);
//註冊內存服務
ServiceManager.addService("meminfo", new MemBinder(m));
//註冊圖像處理服務
ServiceManager.addService("gfxinfo", new GraphicsBinder(m));
//註冊數據庫服務
ServiceManager.addService("dbinfo", new DbBinder(m));
//註冊cpu服務
if (MONITOR_CPU_USAGE) {
ServiceManager.addService("cpuinfo", new CpuBinder(m));
}
//註冊權限服務
ServiceManager.addService("permission", new PermissionController(m));
//獲取應用信息
ApplicationInfo info = mSelf.mContext.getPackageManager().getApplicationInfo("android", STOCK_PM_FLAGS);
//綁定系統應用信息,
mSystemThread.installSystemApplicationInfo(info);
synchronized (mSelf) {
//獲取ProcessRecord實例,ProcessRecord是描述進程信息的
ProcessRecord app = mSelf.newProcessRecordLocked(info, info.processName, false);
app.persistent = true;
app.pid = MY_PID;
app.maxAdj = ProcessList.SYSTEM_ADJ;
//調用ProcessStatsService開始記錄process的狀態
app.makeActive(mSystemThread.getApplicationThread(), mSelf.mProcessStats);
//把進程名,uid,ProcessRecord實例存到mProcessNames數組中
mSelf.mProcessNames.put(app.processName, app.uid, app);
synchronized (mSelf.mPidsSelfLocked) {
mSelf.mPidsSelfLocked.put(app.pid, app);
}
mSelf.updateLruProcessLocked(app, false, null);
mSelf.updateOomAdjLocked();
}
} catch (PackageManager.NameNotFoundException e) {
throw new RuntimeException("Unable to find android system package", e);
}
}
2.1
在ServiceManager裏註冊一些服務,AMS、進程統計服務、內存服務、圖像處理服務、數據庫服務、CPU服務、權限服務
2.2
通過PackageManager獲取應用信息
//獲取應用信息
ApplicationInfo info = mSelf.mContext.getPackageManager().getApplicationInfo("android", STOCK_PM_FLAGS);
獲取包名爲android的apk的信息,對應的就是framework-res.apk.
2.3
調用以下代碼將獲取到的應用信息綁定到mSystemThread的context上.
mSystemThread.installSystemApplicationInfo(info);
2.4
ActivityManagerService調用newProcessRecordLocked方法創建一個ProcessRecord對象,ProcessRecord紀錄了一個進程的信息,這裏是指systemServer進程
3.ActivityManagerService.installSystemProviders();
這個方法是啓動SettingsProvider的.SettingsProvider相當於系統的一個數據庫.
4.ActivityManagerService.self().setWindowManager(wm);
這個方法是用來設置窗口管理器的.
5.ActivityManagerService.self().systemReady
這個方法是用來做系統準備工作的.
ActivityManagerService.self().systemReady(new Runnable() {
public void run() {
Slog.i(TAG, "Making services ready");
try {
// 開始監視native是否crash
ActivityManagerService.self().startObservingNativeCrashes();
} catch (Throwable e) {
reportWtf("observing native crashes", e);
}
if (!headless) {
//啓動SystemUi
startSystemUi(contextF);
}
try {
if (mountServiceF != null)
mountServiceF.systemReady();
} catch (Throwable e) {
reportWtf("making Mount Service ready", e);
}
try {
if (batteryF != null)
batteryF.systemReady();
} catch (Throwable e) {
reportWtf("making Battery Service ready", e);
}
try {
if (networkManagementF != null)
networkManagementF.systemReady();
} catch (Throwable e) {
reportWtf("making Network Managment Service ready", e);
}
......
......
5.1
開始監視native是否crash
5.2
啓動SystemUi
5.3
做各種服務的準備工作,比如掛載管理服務、電腦管理服務、網絡連接管理服務.
結束語:按照上述5大步來就可以慢慢理清啓動應用的流程了.具體細節你們可以自己去探索.