android handler和message的常用方法

private class AsyncServiceHandler extends Handler {

AsyncServiceHandler(android.os.Looper looper) {
super(looper);
}

@Override
public void handleMessage(Message msg) {
...........................................
case WifiManager.ENABLE_TRAFFIC_STATS_POLL: {
...........................................

}

private AsyncServiceHandler mAsyncServiceHandler;

mAsyncServiceHandler = new AsyncServiceHandler(wifiThread.getLooper());

Message msg;

msg = Message.obtain(mAsyncServiceHandler,WifiManager.ENABLE_TRAFFIC_STATS_POLL, 0, 0);

msg.sendToTarget();

这里Message.obtain表示obtain Message object from the global pool, 第一个参数表示发送的handler目标，第二个为what, 第三个为arg1, 第四个为arg2,看函数原型就知道了：

public static Message obtain(Handler h, int what, int arg1, int arg2) {
Message m = obtain();
m.target = h;
m.what = what;
m.arg1 = arg1;
m.arg2 = arg2;

return m;
}
最后调用msg.sendToTarget()将消息发送到AsyncServiceHandler中，AsyncServiceHandler继承并重写handleMessage方法，在handleMessage中根据switch处理接收到的消息

Handler mhandler = new Handler(){
@Override
public void handleMessage(Message msg) {
super.handleMessage(msg);
int what = msg.what;

switch(what){

case 2:

String shortFileNames = msg.getData().getString("packagename");

........................自己的处理方法............................

}

};

Message msg = mhandler.obtainMessage();
Bundle b = new Bundle();// 存放数据
msg.what = 2;
b.putString("packagename", shortfileNames.get(i));
msg.setData(b);
mhandler.sendMessage(msg); // 向Handler发送消息,更新UI

原理和上面1其实是一样的，也是从消息池中获取message,这样不用新new一个，可以节省资源，new Bundle()用来存放数据，然后mhandler.sendMessage将消息发送到Handler中

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