使用
- 自定义 BroadcastReveicer 子类
public class LocalBroadcastReceiver extends BroadcastReceiver {
@Override
public void onReceive(Context arg0, Intent intent) {
Bitmap bitmap = intent.getParcelableExtra("bitmap");
image.setImageBitmap(bitmap);
}
}
- 注册接收器
localReceiver = new LocalBroadcastReceiver();
LocalBroadcastManager.getInstance(this).registerReceiver(localReceiver, new IntentFilter(ACTION_LOCAL_SEND));
- 发送广播
网络请求成功
LocalBroadcastManager.getInstance(TestHttpURLConnection.this)
.sendBroadcast(new Intent(ACTION_LOCAL_SEND)
.putExtra("bitmap", bitmap));
- 取消注册
@Override
protected void onDestroy() {
super.onDestroy();
LocalBroadcastManager.getInstance(this).unregisterReceiver(localReceiver);
}
实现
public static LocalBroadcastManager getInstance(Context context) {
synchronized (mLock) {
if (mInstance == null) {
mInstance = new LocalBroadcastManager(context.getApplicationContext());
}
return mInstance;
}
}
private LocalBroadcastManager(Context context) {
mAppContext = context;
mHandler = new Handler(context.getMainLooper()) {
@Override
public void handleMessage(Message msg) {
switch (msg.what) {
case MSG_EXEC_PENDING_BROADCASTS:
executePendingBroadcasts();
break;
default:
super.handleMessage(msg);
}
}
};
}
单例实现因而私有化构造函数，基于主线程的 Looper 新建了一个 Handler，handleMessage
中会调用接收器对广播的消息进行处理
注册接收器
HashMap<BroadcastReceiver, ArrayList<IntentFilter>> mReceivers
= new HashMap<BroadcastReceiver, ArrayList<IntentFilter>>();
HashMap<String, ArrayList<ReceiverRecord>> mActions
= new HashMap<String, ArrayList<ReceiverRecord>>();
public void registerReceiver(BroadcastReceiver receiver, IntentFilter filter) {
synchronized (mReceivers) {
ReceiverRecord entry = new ReceiverRecord(filter, receiver);
ArrayList<IntentFilter> filters = mReceivers.get(receiver);
if (filters == null) {
filters = new ArrayList<IntentFilter>(1);
mReceivers.put(receiver, filters);
}
filters.add(filter);
for (int i=0; i<filter.countActions(); i++) {
String action = filter.getAction(i);
ArrayList<ReceiverRecord> entries = mActions.get(action);
if (entries == null) {
entries = new ArrayList<ReceiverRecord>(1);
mActions.put(action, entries);
}
entries.add(entry);
}
}
}
mReceivers 存储广播和过滤器信息，以BroadcastReceiver作为 key，IntentFilter链表作为 value。
mReceivers 是接收器和IntentFilter的对应表，主要作用是方便在unregisterReceiver(…)取消注册，同时作为对象锁限制注册接收器、发送广播、取消接收器注册等几个过程的并发访问。
mActions 以Action为 key，注册这个Action的BroadcastReceiver链表为 value。mActions 的主要作用是方便在广播发送后快速得到可以接收它的BroadcastReceiver。
发送广播
先根据Action从mActions中取出ReceiverRecord列表，循环每个ReceiverRecord判断 filter 和 intent 中的action、type、scheme、data、categoried 是否 match，是的话则保存到receivers列表中，发送 what 为MSG_EXEC_PENDING_BROADCASTS的消息，通过 Handler 去处理。
消息处理
private void executePendingBroadcasts() {
while (true) {
BroadcastRecord[] brs = null;
synchronized (mReceivers) {
final int N = mPendingBroadcasts.size();
if (N <= 0) {
return;
}
brs = new BroadcastRecord[N];
mPendingBroadcasts.toArray(brs);
mPendingBroadcasts.clear();
}
for (int i=0; i<brs.length; i++) {
BroadcastRecord br = brs[i];
for (int j=0; j<br.receivers.size(); j++) {
br.receivers.get(j).receiver.onReceive(mAppContext, br.intent);
}
}
}
}
mPendingBroadcasts转换为数组BroadcastRecord，循环每个receiver，调用其onReceive函数
取消注册
从mReceivers及mActions中移除相应元素。
