Service联合Broadcase更新UI

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();
        }
}