在Android中，异步更新UI，通常我们会选用Handler启动线程，或者sendMessage的方式，那么利用Service和广播也可以更新UI的，例子如下：
我们建立一个Service：
package com.andy
import android.app.Service;//引入相关包
import android.content.BroadcastReceiver;//引入相关包
import android.content.Context;//引入相关包
import android.content.Intent;//引入相关包
import android.content.IntentFilter;//引入相关包
import android.os.IBinder;//引入相关包
//继承自Service的子类
public class MyService extends Service{
CommandReceiver cmdReceiver;
boolean flag;
@Override
public void onCreate() {//重写onCreate方法
flag = true;
cmdReceiver = new CommandReceiver();
super.onCreate();
}
@Override
public IBinder onBind(Intent intent) {//重写onBind方法
// TODO Auto-generated method stub
return null;
}
@Override
public int onStartCommand(Intent intent, int flags, int startId) {//重写onStartCommand方法
IntentFilter filter = new IntentFilter();//创建IntentFilter对象
filter.addAction("wyf.wpf.MyService");
registerReceiver(cmdReceiver, filter);//注册Broadcast Receiver
doJob();//调用方法启动线程
return super.onStartCommand(intent, flags, startId);
}
//方法：
public void doJob(){
new Thread(){
public void run(){
while(flag){
try{//睡眠一段时间
Thread.sleep(1000);
}
catch(Exception e){
e.printStackTrace();
}
Intent intent = new Intent();//创建Intent对象
intent.setAction("wyf.wpf.Sample_3_6");
intent.putExtra("data", Math.random());
sendBroadcast(intent);//发送广播
}
}
}.start();
}
private class CommandReceiver extends BroadcastReceiver{//继承自BroadcastReceiver的子类
@Override
public void onReceive(Context context, Intent intent) {//重写onReceive方法
int cmd = intent.getIntExtra("cmd", -1);//获取Extra信息
if(cmd == Sample_3_6.CMD_STOP_SERVICE){//如果发来的消息是停止服务
flag = false;//停止线程
stopSelf();//停止服务
}
}
}
@Override
public void onDestroy() {//重写onDestroy方法
this.unregisterReceiver(cmdReceiver);//取消注册的CommandReceiver
super.onDestroy();
}
}
建立一个activity
package com.andy;//声明包语句
import android.app.Activity;//引入相关包
import android.content.BroadcastReceiver;//引入相关包
import android.content.Context;//引入相关包
import android.content.Intent;//引入相关包
import android.content.IntentFilter;//引入相关包
import android.os.Bundle;//引入相关包
import android.view.View;//引入相关包
import android.view.View.OnClickListener;//引入相关包
import android.widget.Button;//引入相关包
import android.widget.TextView;//引入相关包
//继承自Activity的子类
public class Sample_3_6 extends Activity {
public static final int CMD_STOP_SERVICE = 0;
Button btnStart;//开始服务Button对象应用
Button btnStop;//停止服务Button对象应用
TextView tv;//TextView对象应用
DataReceiver dataReceiver;//BroadcastReceiver对象
@Override
public void onCreate(Bundle savedInstanceState) {//重写onCreate方法
super.onCreate(savedInstanceState);
setContentView(R.layout.main);//设置显示的屏幕
btnStart = (Button)findViewById(R.id.btnStart);
btnStop = (Button)findViewById(R.id.btnStop);
tv = (TextView)findViewById(R.id.tv);
btnStart.setOnClickListener(new OnClickListener() {//为按钮添加点击事件监听
@Override
public void onClick(View v) {//重写onClick方法
Intent myIntent = new Intent(Sample_3_6.this, wyf.wpf.MyService.class);
Sample_3_6.this.startService(myIntent);//发送Intent启动Service
}
});
btnStop.setOnClickListener(new OnClickListener() {//为按钮添加点击事件监听
@Override
public void onClick(View v) {//重写onClick方法
Intent myIntent = new Intent();//创建Intent对象
myIntent.setAction("wyf.wpf.MyService");
myIntent.putExtra("cmd", CMD_STOP_SERVICE);
sendBroadcast(myIntent);//发送广播
}
});
}
private class DataReceiver extends BroadcastReceiver{//继承自BroadcastReceiver的子类
@Override
public void onReceive(Context context, Intent intent) {//重写onReceive方法
double data = intent.getDoubleExtra("data", 0);
tv.setText("Service的数据为:"+data);
}
}
@Override
protected void onStart() {//重写onStart方法
dataReceiver = new DataReceiver();
IntentFilter filter = new IntentFilter();//创建IntentFilter对象
filter.addAction("wyf.wpf.Sample_3_6");
registerReceiver(dataReceiver, filter);//注册Broadcast Receiver
super.onStart();
}
@Override
protected void onStop() {//重写onStop方法
unregisterReceiver(dataReceiver);//取消注册Broadcast Receiver
super.onStop();
}
}