對于LocalBroadcastManager在google官方文檔中也說得很清楚，比較簡短杭煎，也很好看懂恩够，可以去看看。
Helper to register for and send broadcasts of Intents to local objects within your process. This has a number of advantages over sending global broadcasts with sendBroadcast(Intent):
- You know that the data you are broadcasting won't leave your app, so don't need to worry about leaking private data.
- It is not possible for other applications to send these broadcasts to your app, so you don't need to worry about having security holes they can exploit.
- It is more efficient than sending a global broadcast through the system.
大體介紹就是這些羡铲，顧名思義蜂桶，本地廣播(注冊)，數(shù)據(jù)安全也切，其他app也不能給你發(fā)廣播(接收)扑媚。也比系統(tǒng)廣播高效。
使用十分簡單：
注冊(接收)：
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
if(savedInstanceState!=null) {
if(mLocalBroadcastManager!=null && mBoradCast!=null) {
mLocalBroadcastManager.unregisterReceiver(mBoradCast);
mLocalBroadcastManager=null;
mBoradCast=null;
}
}
mLocalBroadcastManager=LocalBroadcastManager.getInstance(this);
mBoradCast = new MyBroadCast(); IntentFilter intentFilter = new IntentFilter();
//重點(diǎn)在這里雷恃，本地注冊疆股，本地接收。
mLocalBroadcastManager.registerReceiver(mBoradCast, intentFilter);
}
@Override
protected void onDestroy() {
super.onDestroy();
if(mLocalBroadcastManager!=null && mBoradCast!=null) {
mLocalBroadcastManager.unregisterReceiver(mBoradCast);
mLocalBroadcastManager=null;
mBoradCast=null;
}
}
發(fā)送：
LocalBroadcastManager lcm=LocalBroadcastManager.getInstance(mContext);
lcm.sendBroadcast(new Intent(ACTION_LOCATION));//發(fā)送
以上則是簡單的使用倒槐。那么來說說為何呢：有興趣去看看LocalBroadcastManager旬痹。
注冊這里可以看到，它其實(shí)是一個(gè)單例讨越，針對本應(yīng)用進(jìn)程的唱凯。：
public static LocalBroadcastManager More ...getInstance(Context context) {
synchronized (mLock) {
if (mInstance == null) {
mInstance = new LocalBroadcastManager(context.getApplicationContext());//應(yīng)用的上下文
}
return mInstance;
}
}
private More ...LocalBroadcastManager(Context context) {
mAppContext = context;
//用主線程注冊
handler mHandler = new Handler(context.getMainLooper()) {
@Override public void More ...handleMessage(Message msg) {
switch (msg.what) {
case MSG_EXEC_PENDING_BROADCASTS:
executePendingBroadcasts();
break;
default:
super.handleMessage(msg);
}
}
};
}```
注冊的代碼：
private final HashMap<BroadcastReceiver, ArrayList<IntentFilter>> mReceivers = new HashMap<BroadcastReceiver, ArrayList<IntentFilter>>();
public void More ...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);
//這里很明顯是用的一個(gè)HashMap來裝的我們注冊的receiver和filter 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);
}
}
}
取消注冊:
public void More ...unregisterReceiver(BroadcastReceiver receiver) {
synchronized (mReceivers) {
ArrayList<IntentFilter> filters = mReceivers.remove(receiver);
if (filters == null) {
return;8
}
for (int i=0; i<filters.size(); i++) {
IntentFilter filter = filters.get(i);
for (int j=0; j<filter.countActions(); j++) {
String action = filter.getAction(j);
ArrayList<ReceiverRecord> receivers = mActions.get(action);
if (receivers != null) {
for (int k=0; k<receivers.size(); k++) {
if (receivers.get(k).receiver == receiver) {
//從Map里移除
receivers.remove(k);
k--;
}
}
if (receivers.size() <= 0) {
mActions.remove(action);
}
}
}
}
}
}```
發(fā)送廣播，截取一部分：
if (receivers != null) {
for (int i=0; i<receivers.size(); i++) {
receivers.get(i).broadcasting = false;
}
mPendingBroadcasts.add(new BroadcastRecord(intent, receivers));
if (!mHandler.hasMessages(MSG_EXEC_PENDING_BROADCASTS)) {
mHandler.sendEmptyMessage(MSG_EXEC_PENDING_BROADCASTS);
}
return true;
}
private void More ...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++) {
//重點(diǎn)在這里谎痢，每個(gè)注冊的都調(diào)用了我們注冊的onReceive方法(讓其自行接收處理)磕昼。
br.receivers.get(j).receiver.onReceive(mAppContext, br.intent);
}
}
}
}
這就大致了解了工作原理了。使用起來是很方便的节猿，單例效率也高票从。所以如果不是非本地注冊本地接收的漫雕，還是使用LocalBroadcastManager更好。如果是更新圖庫等峰鄙，需要系統(tǒng)接收的除外浸间。
