Android: registerReceiver代码实现

1. 用户接口registerReceiver

frameworks/base/core/java/android/content/ContextWrapper.java

public Intent registerReceiver(BroadcastReceiver receiver, IntentFilter filter) {
return mBase.registerReceiver(receiver, filter);
}

frameworks/base/core/java/android/app/ContextImpl.java
@Override
public Intent registerReceiver(BroadcastReceiver receiver, IntentFilter filter) {
return registerReceiver(receiver, filter, null, null);
}

@Override
public Intent registerReceiver(BroadcastReceiver receiver, IntentFilter filter,
String broadcastPermission, Handler scheduler) {
return registerReceiverInternal(receiver, getUserId(),
filter, broadcastPermission, scheduler, getOuterContext(), 0);
}

@Override
public Intent registerReceiver(BroadcastReceiver receiver, IntentFilter filter,
String broadcastPermission, Handler scheduler, int flags) {
return registerReceiverInternal(receiver, getUserId(),
filter, broadcastPermission, scheduler, getOuterContext(), flags);
}

class ContextImpl extends Context {
......

@Override
public Intent registerReceiver(BroadcastReceiver receiver, IntentFilter filter) {
return registerReceiver(receiver, filter, null, null);
}

@Override
public Intent registerReceiver(BroadcastReceiver receiver, IntentFilter filter,
String broadcastPermission, Handler scheduler) {
return registerReceiverInternal(receiver, filter, broadcastPermission,
scheduler, getOuterContext());
}

private Intent registerReceiverInternal(BroadcastReceiver receiver,
IntentFilter filter, String broadcastPermission,
Handler scheduler, Context context) {
IIntentReceiver rd = null;
if (receiver != null) {
// mPackageInfo是一个LoadedApk实例，它是用来负责处理广播的接收的
// context 是通过调用函数getOuterContext得到的
if (mPackageInfo != null && context != null) {
if (scheduler == null) {

// mMainThread.getHandler来获得一个Handler了，

//这个Hanlder是后面用来分发ActivityManagerService发送过的广播用的。

// 这里的成员变量mMainThread是一个ActivityThread实例
scheduler = mMainThread.getHandler();
}
rd = mPackageInfo.getReceiverDispatcher(
receiver, context, scheduler,
mMainThread.getInstrumentation(), true);
} else {
......
}
}
try {
final Intent intent = ActivityManager.getService().registerReceiver(
mMainThread.getApplicationThread(), mBasePackageName, rd, filter,
broadcastPermission, userId, flags);
if (intent != null) {
intent.setExtrasClassLoader(getClassLoader());
intent.prepareToEnterProcess();
}
return intent;
} catch (RemoteException e) {
return null;
}
}

......

}
// BroadcastReceiver
frameworks/base/core/java/android/content/BroadcastReceiver.java

// getHandler()
public final class ActivityThread {
......
final H mH = new H();

private final class H extends Handler {
......

public void handleMessage(Message msg) {
......

switch (msg.what) {
......
}

......
}

......

}
......

final Handler getHandler() {
return mH;
}
......
}

//
frameworks/base/core/java/android/app/LoadedApk.java
public IIntentReceiver getReceiverDispatcher(BroadcastReceiver r,
Context context, Handler handler,
Instrumentation instrumentation, boolean registered) {

synchronized (mReceivers) {
LoadedApk.ReceiverDispatcher rd = null;
ArrayMap<BroadcastReceiver, LoadedApk.ReceiverDispatcher> map = null;
if (registered) {
// ArrayMap<Context, ArrayMap<BroadcastReceiver, ReceiverDispatcher>> mReceivers = new ArrayMap<>();
//由context获得ArrayMap<BroadcastReceiver, ReceiverDispatcher>>
//由BroadcastReceiver获得ReceiverDispatcher
map = mReceivers.get(context);
if (map != null) {
rd = map.get(r);
}
}
if (rd == null) {
rd = new ReceiverDispatcher(r, context, handler, instrumentation, registered);
if (registered) {
if (map == null) {
map = new ArrayMap<BroadcastReceiver, LoadedApk.ReceiverDispatcher>();
mReceivers.put(context, map);
}
map.put(r, rd);
}
} else {
rd.validate(context, handler);
}
rd.mForgotten = false;
//获得后就会把它传给ActivityManagerService，以便接收广播
return rd.getIIntentReceiver();
}
}

static final class ReceiverDispatcher {
//InnerReceiver实例，这是一个Binder对象，实现了IIntentReceiver接口，

//可以通过ReceiverDispatcher.getIIntentReceiver函数来获得，

//获得后就会把它传给ActivityManagerService，以便接收广播。

final static class InnerReceiver extends IIntentReceiver.Stub {
final WeakReference<LoadedApk.ReceiverDispatcher> mDispatcher;
......
InnerReceiver(LoadedApk.ReceiverDispatcher rd, boolean strong) {
mDispatcher = new WeakReference<LoadedApk.ReceiverDispatcher>(rd);
......
}
......
}

......

final IIntentReceiver.Stub mIIntentReceiver;
final Handler mActivityThread;
......
ReceiverDispatcher(BroadcastReceiver receiver, Context context,
Handler activityThread, Instrumentation instrumentation,
boolean registered) {
......

mIIntentReceiver = new InnerReceiver(this, !registered);
mActivityThread = activityThread;

......
}
......

IIntentReceiver getIIntentReceiver() {
return mIIntentReceiver;
}

}

public class ActivityManagerService extends IActivityManager.Stub
implements Watchdog.Monitor, BatteryStatsImpl.BatteryCallback {
......

public Intent registerReceiver(IApplicationThread caller, IIntentReceiver receiver, IntentFilter filter, String permission) {
synchronized(this) {
// 函数首先是获得调用registerReceiver函数的应用程序进程记录块
ProcessRecord callerApp = null;
if (caller != null) {
callerApp = getRecordForAppLocked(caller);
if (callerApp == null) {
......
}
}

List allSticky = null;

// Look for any matching sticky broadcasts...
Iterator actions = filter.actionsIterator();
if (actions != null) {
while (actions.hasNext()) {
String action = (String)actions.next();
allSticky = getStickiesLocked(action, filter, allSticky);
}
} else {
......
}

//广播接收器receiver保存一个ReceiverList列表中，这个列表的宿主进程是rl.app，这里就是MainActivity所在的进程了，
//在ActivityManagerService中，用一个进程记录块来表示这个应用程序进程，它里面有一个列表receivers，

//专门用来保存这个进程注册的广播接收器。接着，又把这个ReceiverList列表以receiver为Key值保存在

//ActivityManagerService的成员变量mRegisteredReceivers中，这些都是为了方便在收到广播时，快速找到对应的广播接收器的

ReceiverList rl
= (ReceiverList)mRegisteredReceivers.get(receiver.asBinder());
if (rl == null) {
rl = new ReceiverList(this, callerApp,
Binder.getCallingPid(),
Binder.getCallingUid(), receiver);

if (rl.app != null) {
rl.app.receivers.add(rl);
} else {
......
}
mRegisteredReceivers.put(receiver.asBinder(), rl);
}
//创建一个BroadcastFilter来把广播接收器列表rl和filter关联起来，
//然后保存在ActivityManagerService中的成员变量mReceiverResolver中去
BroadcastFilter bf = new BroadcastFilter(filter, rl, permission);
rl.add(bf);
......
mReceiverResolver.addFilter(bf);

}
}

......

}

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Android: registerReceiver代码实现

1. 用户接口registerReceiver

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