http://blog.csdn.net/zhaokaiqiang1992/article/details/49428287
It’s right time to learn Android’s Framework ！
- 前言
- 学习目标
- 写作方式
- 主要对象功能介绍
- SystemServer是什么有什么作用它与zygote的关系是什么
- ActivityManagerService是什么什么时候初始化的有什么作用
- Launcher是什么什么时候启动的
- Instrumentation是什么和ActivityThread是什么关系
- 如何理解AMS和ActivityThread之间的Binder通信
- 一个App的程序入口到底是什么
- 整个App的主线程的消息循环是在哪里创建的
- zygote
- ActivityThreadInstrumentationAMS
不要使用 startActivityForResult(intent,RESULT_OK)
这是因为startActivity()是这样实现的
public void startActivity(Intent intent, @Nullable Bundle options) {
if (options != null) {
startActivityForResult(intent, -1, options);
} else {
// Note we want to go through this call for compatibility with
// applications that may have overridden the method.
startActivityForResult(intent, -1);
}
}
而
public static final int RESULT_OK = -1;
所以
startActivityForResult(intent,RESULT_OK) = startActivity()
你不可能从onActivityResult()里面收到任何回调。而这个问题是相当难以被发现的，就是因为这个坑，我工作一年多来第一次加班到9点 (ˇˍˇ）
一个App的程序入口到底是什么？
是ActivityThread.main()。
整个App的主线程的消息循环是在哪里创建的？
是在ActivityThread初始化的时候，就已经创建消息循环了，所以在主线程里面创建Handler不需要指定Looper，而如果在其他线程使用Handler，则需要单独使用Looper.prepare()和Looper.loop()创建消息循环。
public static void main(String[] args) {
...ignore some code...
Looper.prepareMainLooper();
ActivityThread thread = new ActivityThread();
thread.attach(false);
if (sMainThreadHandler == null) {
sMainThreadHandler = thread.getHandler();
}
AsyncTask.init();
if (false) {
Looper.myLooper().setMessageLogging(new
LogPrinter(Log.DEBUG, "ActivityThread"));
}
Looper.loop();
...ignore some code...
}
Application是在什么时候创建的？onCreate()什么时候调用的？
也是在ActivityThread.main()的时候，再具体点呢，就是在thread.attach(false)的时候。
看你的表情，不信是吧！凯子哥带你溜溜~
我们先看一下ActivityThread.attach()
private void attach(boolean system) {
sCurrentActivityThread = this;
mSystemThread = system;
//普通App进这里
if (!system) {
...ignore some code...
RuntimeInit.setApplicationObject(mAppThread.asBinder());
final IActivityManager mgr = ActivityManagerNative.getDefault();
try {
mgr.attachApplication(mAppThread);
} catch (RemoteException ex) {
// Ignore
}
} else {
//这个分支在SystemServer加载的时候会进入，通过调用
// private void createSystemContext() {
// ActivityThread activityThread = ActivityThread.systemMain()；
//}
// public static ActivityThread systemMain() {
// if (!ActivityManager.isHighEndGfx()) {
// HardwareRenderer.disable(true);
// } else {
// HardwareRenderer.enableForegroundTrimming();
// }
// ActivityThread thread = new ActivityThread();
// thread.attach(true);
// return thread;
// }
}
}
这里需要关注的就是mgr.attachApplication(mAppThread)，这个就会通过Binder调用到AMS里面对应的方法
@Override
public final void attachApplication(IApplicationThread thread) {
synchronized (this) {
int callingPid = Binder.getCallingPid();
final long origId = Binder.clearCallingIdentity();
attachApplicationLocked(thread, callingPid);
Binder.restoreCallingIdentity(origId);
}
}
然后就是
private final boolean attachApplicationLocked(IApplicationThread thread,
int pid) {
thread.bindApplication(processName, appInfo, providers, app.instrumentationClass,
profilerInfo, app.instrumentationArguments, app.instrumentationWatcher,
app.instrumentationUiAutomationConnection, testMode, enableOpenGlTrace,
isRestrictedBackupMode || !normalMode, app.persistent,
new Configuration(mConfiguration), app.compat, getCommonServicesLocked(),
mCoreSettingsObserver.getCoreSettingsLocked());
}
thread是IApplicationThread，实际上就是ApplicationThread在服务端的代理类ApplicationThreadProxy，然后又通过IPC就会调用到
ApplicationThread的对应方法
private class ApplicationThread extends ApplicationThreadNative {
public final void bindApplication(String processName, ApplicationInfo appInfo,
List<ProviderInfo> providers, ComponentName instrumentationName,
ProfilerInfo profilerInfo, Bundle instrumentationArgs,
IInstrumentationWatcher instrumentationWatcher,
IUiAutomationConnection instrumentationUiConnection, int debugMode,
boolean enableOpenGlTrace, boolean isRestrictedBackupMode, boolean persistent,
Configuration config, CompatibilityInfo compatInfo, Map<String, IBinder> services,
Bundle coreSettings) {
...ignore some code...
AppBindData data = new AppBindData();
data.processName = processName;
data.appInfo = appInfo;
data.providers = providers;
data.instrumentationName = instrumentationName;
data.instrumentationArgs = instrumentationArgs;
data.instrumentationWatcher = instrumentationWatcher;
data.instrumentationUiAutomationConnection = instrumentationUiConnection;
data.debugMode = debugMode;
data.enableOpenGlTrace = enableOpenGlTrace;
data.restrictedBackupMode = isRestrictedBackupMode;
data.persistent = persistent;
data.config = config;
data.compatInfo = compatInfo;
data.initProfilerInfo = profilerInfo;
sendMessage(H.BIND_APPLICATION, data);
}
}
我们需要关注的其实就是最后的sendMessage()，里面有函数的编号H.BIND_APPLICATION，然后这个Messge会被H这个Handler处理
private class H extends Handler {
...ignore some code...
public static final int BIND_APPLICATION = 110;
...ignore some code...
public void handleMessage(Message msg) {
switch (msg.what) {
...ignore some code...
case BIND_APPLICATION:
Trace.traceBegin(Trace.TRACE_TAG_ACTIVITY_MANAGER, "bindApplication");
AppBindData data = (AppBindData)msg.obj;
handleBindApplication(data);
Trace.traceEnd(Trace.TRACE_TAG_ACTIVITY_MANAGER);
break;
...ignore some code...
}
}
最后就在下面这个方法中，完成了实例化，拨那个企鹅通过mInstrumentation.callApplicationOnCreate实现了onCreate()的调用。
private void handleBindApplication(AppBindData data) {
try {
...ignore some code...
Application app = data.info.makeApplication(data.restrictedBackupMode, null);
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