使用自定义线程来更新组件中的数据

 

在Android系统中，Activtiy,Service和BroadercastReceiver都是工作在主线程上，因此任何耗时的处理过程都会降低用户界面的响应速度，甚至导致用户界面失去响应。当用户界面失去响应超过5秒， Andorid系统会允许用户强行关闭应用程序。  因此，较好的解决方案是将耗时的处理过程转移到转移到子线程上，这样可以避免负责界面更新的主线程无法处理界面事件，从而避免用户界面长时间失去响应。   下面就举《Android应用程序开发》中的一个示例：

 

该示例的要点是通过Handler将产生的随机数显示在用户界面上。

 

package my.yaner.service;

 

import android.app.Activity;

import android.content.Intent;

import android.os.Bundle;

import android.os.Handler;

import android.view.View;

import android.view.View.OnClickListener;

import android.widget.Button;

import android.widget.LinearLayout;

import android.widget.TextView;

 

/**使用自定义线程来控制service将数据传递给UI控件*/

public class ThreadServiceActivity extends Activity {

   

    private static Handler handler = new Handler();

    private static TextView lableView =null;

    private static double randomDouble;

   

    Button startservice, stopservice;

   

    protected void onCreate(Bundle savedInstaceState){

       super.onCreate(savedInstaceState);

      

       LinearLayout linearlayout = new LinearLayout(this);

      

       lableView = new TextView(this);

       startservice = new Button(this);

       stopservice = new Button(this);

       startservice.setText("启动service");

       stopservice.setText("停止service");

       lableView.setText("此处显示随机数");

      

       linearlayout.addView(lableView);

       linearlayout.addView(startservice);

       linearlayout.addView(stopservice);

      

       setContentView(linearlayout);

      

       final Intent servieIntent = new Intent(this, RandomService.class);

       startservice.setOnClickListener(new OnClickListener(){

           @Override

           public void onClick(View v) {

              startService(servieIntent);

           }

          

       });

      

       stopservice.setOnClickListener(new OnClickListener() {

           @Override

           public void onClick(View v) {

              stopService(servieIntent);

           }

       });

    }

   

    public static void UpdateGUI(double refreshDouble){

       randomDouble = refreshDouble;

       handler.post(refreshLable);

    }

   

    private static Runnable refreshLable  =new Runnable(){

       public void run(){

           lableView.setText(String.valueOf(randomDouble));

       }

    };

}

 

 

package my.yaner.service;

 

import android.app.Service;

import android.content.Intent;

import android.os.IBinder;

import android.widget.Toast;

 

public class RandomService extends Service {

    private Thread workThread;

 

    @Override

    public IBinder onBind(Intent intent) {

       return null;

    }

 

    public void onCreate() {

       super.onCreate();

       Toast.makeText(this, "(1)调用onCreate()", Toast.LENGTH_LONG).show();

 

       workThread = new Thread(null, backgroundWork, "WorkThread");

    }

 

    public void onDestroy() {

       super.onDestroy();

       Toast.makeText(this, "(3)调用onDestory()", Toast.LENGTH_SHORT).show();

       workThread.interrupt();

    }

 

    public void onStart(Intent intent, int startId) {

       super.onStart(intent, startId);

       Toast.makeText(this, "(2)调用onStart()", Toast.LENGTH_SHORT).show();

       if (!workThread.isAlive()) {

           workThread.start();

       }

    }

 

    private Runnable backgroundWork = new Runnable() {

       @Override

       public void run() {

           try {

              while (!Thread.interrupted()) {

                  double randomDouble = Math.random();

                  ThreadServiceActivity.UpdateGUI(randomDouble);

                  Thread.sleep(1000);

              }

           } catch (InterruptedException e) {

              e.printStackTrace();

           }

       }

    };

}

 

 

 

<service android:name=".service.RandomService"></service>