Android中实现多线程的例子

我觉得例子还不错：
http://blog.csdn.net/sirnuo/article/details/21097599

package com.example.android_th_sendrunnable;

import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;


public class MainActivity extends Activity {
    private Button bt1;
    private Button bt2;
    private TextView tv;
    private static Handler handler=new Handler();
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        bt1=(Button)findViewById(R.id.bt1);
        bt2=(Button)findViewById(R.id.bt2);
        tv=(TextView)findViewById(R.id.tv);
        bt1.setOnClickListener(new View.OnClickListener() {
            
            @Override
            public void onClick(View arg0) {
                // TODO Auto-generated method stub
                new Thread(new Runnable(){
                    public void run(){
                        handler.post(new Runnable(){
                            public void run(){
                                tv.setText("使用handler.post在工作线程中发送一段执行到消息队列中,在主线程中执行。");
                            }
                        });
                    }
                }).start();
            }
        });
        bt2.setOnClickListener(new View.OnClickListener() {
        
            @Override
            public void onClick(View arg0) {
                // TODO Auto-generated method stub
                new Thread(new Runnable(){
                    public void run(){
                        handler.postDelayed(new Runnable(){
                                public void run(){
                                    tv.setText("使用handler.postDelayed在工作线程中发送一段执行到消息队列中,在主线程中延迟3s执行。");
                                }
                        },3000);
                    }
                }).start();
            }
        });
        
    }

}

上边的例子是使用Handler.post(Runnable)，下边的例子是Handler.sendMessage(Message)发送图片信息。主要是看一下两者的区别。

当发送Runnable的时候

到Runnable从消息队列中取出来更新UI的时候，主线程会自动调用它的Run()函数处理的。

如果发送的是Message就要，就要使用HandleMessage来判断消息的类型，然后在觉得如何更新UI的操作。

发送Message的方式比较灵活，处理方式灵活

下边下载图片的例子,我也试过了。

不过要加一个权限，不然会异常。

    </application>
<uses-permission android:name="android.permission.INTERNET" />
</manifest>

package com.example.android_th_sendrunnable_demo;

import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.util.EntityUtils;

import android.app.Activity;
import android.app.ProgressDialog;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;


public class MainActivity extends Activity {
    private Button bt_down;
    private ImageView viewShow;
    private static String image_path="http://c1.mifile.cn/f/i/bbs/forum/errormitu.jpg";
    private ProgressDialog dialog;
    private static int IS_FINISH=1;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        bt_down=(Button)findViewById(R.id.bt_down);
        viewShow=(ImageView)findViewById(R.id.viewShow);
        //进度条对话框
        dialog=new ProgressDialog(this);
        dialog.setTitle("提示信息");
        dialog.setMessage("正在下载，请稍后。。。。。");
        dialog.setCancelable(false);
        
        bt_down.setOnClickListener(new View.OnClickListener() {
            
            @Override
            public void onClick(View arg0) {
                // TODO Auto-generated method stub
                    new Thread(new MyThread()).start();
                    dialog.show();
        }
    });
    }
    
    private Handler handler=new Handler(){
        public void handleMessage(Message msg){
            if(msg.what==IS_FINISH){
                byte[] data= (byte[])msg.obj;
                Bitmap bmp=BitmapFactory.decodeByteArray(data,0,data.length);
                viewShow.setImageBitmap(bmp);
                dialog.dismiss();
        }
    }};
    
        public class MyThread implements Runnable{
            public void run(){
                HttpClient httpclient=new DefaultHttpClient();
                HttpGet httpGet=new HttpGet(image_path);
                HttpResponse  httpResponse=null;
                try{
                    httpResponse = httpclient.execute(httpGet);
                    if(httpResponse.getStatusLine().getStatusCode()==200){
                        byte[] data=EntityUtils.toByteArray(httpResponse.getEntity());
                        Message msg=Message.obtain();
                        msg.obj=data;
                        msg.what=IS_FINISH;
                        handler.sendMessage(msg);
                    }
                    }catch(Exception e){
                        e.printStackTrace();
                }
            }
        }
    }