Activity的工作过程(二)

最新推荐文章于 2024-11-17 14:57:45 发布

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最新推荐文章于 2024-11-17 14:57:45 发布 · 225 阅读

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#Android #Activity #启动过程

Activity启动详细流程(下)

四. 新进程启动ActivityThread

Zygote进程孵化出新的应用进程后，会执行ActivityThread类的main方法。
在该方法里会先准备好Looper和消息队列，然后调用attach方法将应用进程绑定到ActivityManagerService。

然后进入loop循环，不断地读取消息队列里的消息，并分发消息。

//ActivityThread类
public static void main(String[] args) {
    //... 
    Looper.prepareMainLooper();
    ActivityThread thread = new ActivityThread();
    thread.attach(false);
    if (sMainThreadHandler == null) {
        sMainThreadHandler = thread.getHandler();
    }
    AsyncTask.init();
    //...
    Looper.loop();
    //...
}

五. 应用进程绑定到ActivityManagerService

在ActivityThread的main方法里调用thread.attach(false);

attach方法的主要代码如下所示:

//ActivityThread类
private void attach(boolean system) {
    sThreadLocal.set(this);
    mSystemThread = system;
    if (!system) {
        //...
        IActivityManager mgr = ActivityManagerNative.getDefault();
        try {
        //调用ActivityManagerService的attachApplication方法
        //将ApplicationThread对象绑定至ActivityManagerService，
        //这样ActivityManagerService就可以
        //通过ApplicationThread代理对象控制应用进程
            mgr.attachApplication(mAppThread);
        } catch (RemoteException ex) {
            // Ignore
        }
    } else {
        //...
    }
    //... 
}

ActivityManagerService的attachApplication方法执行attachApplicationLocked(thread, callingPid)进行绑定。

//ActivityManagerService类
private final boolean attachApplicationLocked(IApplicationThread thread,
        int pid) { 
    ProcessRecord app;
    //...     
    app.thread = thread; 
    //...  
    try {
        //...
        thread.bindApplication(processName, appInfo, providers,
                app.instrumentationClass, profileFile, profileFd, profileAutoStop,
                app.instrumentationArguments, app.instrumentationWatcher, testMode,
                enableOpenGlTrace, isRestrictedBackupMode || !normalMode, app.persistent,
                new Configuration(mConfiguration), app.compat, getCommonServicesLocked(),
                mCoreSettingsObserver.getCoreSettingsLocked());
        //... 
    } catch (Exception e) {
       //...
    }
    //... 
    ActivityRecord hr = mMainStack.topRunningActivityLocked(null);
    if (hr != null && normalMode) {
        if (hr.app == null && app.uid == hr.info.applicationInfo.uid
                && processName.equals(hr.processName)) {
            try {
                if (mHeadless) {
                    Slog.e(TAG, "Starting activities not supported on headless device: " + hr);
                } else if (mMainStack.realStartActivityLocked(hr, app, true, true)) {
                //mMainStack.realStartActivityLocked真正启动activity
                    didSomething = true;
                }
            } catch (Exception e) {
                //...
            }
        } else {
            //...
        }
    }
    //..