继上一篇Android系统启动流程分析之安装应用文章接着分析系统启动应用的过程.
Android系统的启动流程简要分析里已经介绍了SystemServer在main方法里创建了一个线程ServerThread,并调用initAndLoop方法加载各种服务.
ActivityManagerService（Ams）就是在initAndLoop方法里加载的.那么,看下initAndLoop方法里关于AMS的核心代码.
1.context = ActivityManagerService.main(factoryTest);
2.ActivityManagerService.setSystemProcess();
3.ActivityManagerService.installSystemProviders();
4.ActivityManagerService.self().setWindowManager(wm);
5.ActivityManagerService.self().systemReady
一步一步进行分析.
1.context = ActivityManagerService.main(factoryTest);
这行代码是启动ActivityManagerService,获取上下文context,进入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 {
//线程等待activitymanagerservice初始化完成
thr.wait();
} catch (InterruptedException e) {
}
}
}
ActivityManagerService m = thr.mService;
mSelf = m;
//启动一个主线程
ActivityThread at = ActivityThread.systemMain();
mSystemThread = at;
//获取上下文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());
//新建一个activity堆栈管理辅助类
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启动完成
thr.notifyAll();
}
m.startRunning(null, null, null, null);
return context;
}1.1
在mian方法里会创建一个线程AThread,AThread用来初始化Looper,AThread等待ActivityManagerService初始化完成后把自己的成员变量mService赋值给ActivityManagerService自身.
1.2
启动一个主线程ActivityThread，ActivityThread是所有Application运行的主线程，
1.3
获取上下文context,最终是调用ContextImpl的createSystemContext方法返回的,context本质是ContextImpl的实例
1.4
等ActivityManagerService启动完成,调用m.startRunning()方法运行，在startRunning方法内部调用systemReady()方法.做系统准备工作.
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;
//如果传入的action为空那么赋值Intent.ACTION_MAIN给mTopAction
mTopAction = action != null ? action : Intent.ACTION_MAIN;
mTopData = data;
if (!mSystemReady) {
return;
}
}
systemReady(null);
}这个mTopAction就是后面要启动第一个Activity,也就是Launcher的Action.
1.4.1
在systemReady方法调用mStackSupervisor.resumeTopActivitiesLocked方法.
public void systemReady(final Runnable goingCallback){
......
......
mStackSupervisor.resumeTopActivitiesLocked();
......
} 1.4.2
最终经过层层跳转会回到ActivityManagerService的startHomeActivityLocked方法.
boolean startHomeActivityLocked(int userId) {
......
......
//获取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);
//启动主程序,也就是Laucnher
mStackSupervisor.startHomeActivity(intent, aInfo);
}
}
return true;
}1.4.3
通过getHomeIntent方法获取Intent信息,看下代码
Intent getHomeIntent() {
Intent intent = new Intent(mTopAction, mTopData != null ? Uri.parse(mTopData) : null);
intent.setComponent(mTopComponent);
if (mFactoryTest != SystemServer.FACTORY_TEST_LOW_LEVEL) {
//设置Category
intent.addCategory(Intent.CATEGORY_HOME);
}
return intent;
}给intent设置了Category,这个mTopAction就是前面设置的.
那么在这里Intent指定Action为action.MAIN,category为category.HOME.这正是启动Launcher的配置
1.4.4
回到1.4.2,调用如下代码启动Launcher
//启动主程序,也就是Laucnher
mStackSupervisor.startHomeActivity(intent, aInfo);2.ActivityManagerService.setSystemProcess()
这个方法是用来注册一些服务和获取、绑定进程信息的.
public static void setSystemProcess() {
try {
ActivityManagerService m = mSelf;
//注册ActivityManagerService
ServiceManager.addService(Context.ACTIVITY_SERVICE, m, true);
//注册进程统计服务
ServiceManager.addService(ProcessStats.SERVICE_NAME, m.mProcessStats);
//注册内存服务
ServiceManager.addService("meminfo", new MemBinder(m));
//注册图像处理服务
ServiceManager.addService("gfxinfo", new GraphicsBinder(m));
//注册数据库服务
ServiceManager.addService("dbinfo", new DbBinder(m));
//注册cpu服务
if (MONITOR_CPU_USAGE) {
ServiceManager.addService("cpuinfo", new CpuBinder(m));
}
//注册权限服务
ServiceManager.addService("permission", new PermissionController(m));
//获取应用信息
ApplicationInfo info = mSelf.mContext.getPackageManager().getApplicationInfo("android", STOCK_PM_FLAGS);
//绑定系统应用信息,
mSystemThread.installSystemApplicationInfo(info);
synchronized (mSelf) {
//获取ProcessRecord实例,ProcessRecord是描述进程信息的
ProcessRecord app = mSelf.newProcessRecordLocked(info, info.processName, false);
app.persistent = true;
app.pid = MY_PID;
app.maxAdj = ProcessList.SYSTEM_ADJ;
//调用ProcessStatsService开始记录process的状态
app.makeActive(mSystemThread.getApplicationThread(), mSelf.mProcessStats);
//把进程名,uid,ProcessRecord实例存到mProcessNames数组中
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里注册一些服务,AMS、进程统计服务、内存服务、图像处理服务、数据库服务、CPU服务、权限服务
2.2
通过PackageManager获取应用信息
//获取应用信息
ApplicationInfo info = mSelf.mContext.getPackageManager().getApplicationInfo("android", STOCK_PM_FLAGS);获取包名为android的apk的信息,对应的就是framework-res.apk.
2.3
调用以下代码将获取到的应用信息绑定到mSystemThread的context上.
mSystemThread.installSystemApplicationInfo(info);2.4
ActivityManagerService调用newProcessRecordLocked方法创建一个ProcessRecord对象，ProcessRecord纪录了一个进程的信息，这里是指systemServer进程
3.ActivityManagerService.installSystemProviders();
这个方法是启动SettingsProvider的.SettingsProvider相当于系统的一个数据库.
4.ActivityManagerService.self().setWindowManager(wm);
这个方法是用来设置窗口管理器的.
5.ActivityManagerService.self().systemReady
这个方法是用来做系统准备工作的.
ActivityManagerService.self().systemReady(new Runnable() {
public void run() {
Slog.i(TAG, "Making services ready");
try {
// 开始监视native是否crash
ActivityManagerService.self().startObservingNativeCrashes();
} catch (Throwable e) {
reportWtf("observing native crashes", e);
}
if (!headless) {
//启动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
开始监视native是否crash
5.2
启动SystemUi
5.3
做各种服务的准备工作,比如挂载管理服务、电脑管理服务、网络连接管理服务.
结束语:按照上述5大步来就可以慢慢理清启动应用的流程了.具体细节你们可以自己去探索.
