在Android应用程序框架中,Activity和Service类都继承了ContextWrapper类,因此,我们可以在Activity或者Service的子类中调用registerReceiver函数来注册广播接收器。
下图是在activity中注册广播的过程:
step1~step3,就是一般的调用过程。
step4,registerReceiverInternal()方法如下:
private Intent registerReceiverInternal(BroadcastReceiver receiver, int userId,
IntentFilter filter, String broadcastPermission,
Handler scheduler, Context context) {
IIntentReceiver rd = null;
if (receiver != null) {
if (mPackageInfo != null && context != null) {
if (scheduler == null) {
scheduler = mMainThread.getHandler();
}
rd = mPackageInfo.getReceiverDispatcher(
receiver, context, scheduler,
mMainThread.getInstrumentation(), true);
} else {
if (scheduler == null) {
scheduler = mMainThread.getHandler();
}
rd = new LoadedApk.ReceiverDispatcher(
receiver, context, scheduler, null, true).getIIntentReceiver();
}
}
try {
return ActivityManagerNative.getDefault().registerReceiver(
mMainThread.getApplicationThread(), mBasePackageName,
rd, filter, broadcastPermission, userId);
} catch (RemoteException e) {
return null;
}
}
scheduler传下的是null,scheduler = mMainThread.getHandler();将获得H的对象mH,用于后续broadcast的发送。
step6,先从已有的注册列表mReceivers中查找是否由相同的ReceiverDispatcher,若之前没有注册过,则new一个ReceiverDispatcher,并记录在mReceivers中,ReceiverDispatcher创建过程中,同时生成一个InnerReceiver,InnerReceiver用于接收处理sendBroadcast发过来的广播。
step9~step11,通过binder访问ActivityManagerService的registerReceiver,将广播接收器receiver保存起来。
下图是广播发送(sendBroadcast)的过程:
分析步骤参考:http://blog.csdn.net/luoshengyang/article/details/6744448
右键复制图片地址,在浏览器中打开即可查看大图。
未完待续,有不对的地方,请指正。