Android多线程——Handler （一） 实现图片下载

在ＵＩ线程中创建子线程——》在子线程中获取网络图片－－》在线程中通过Ｍｅｓｓａｇｅ　传递二进制图片给Ｈａｎｄｌｅｒ，－－》Ｈａｎｄｌｅｒ在ｈａｎｄｌｅＭｅｓｓａｇｅ（）中处理消息

package com.example.android_handler_message;
import java.io.IOException;
import org.apache.http.HttpResponse;
import org.apache.http.client.ClientProtocolException;
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.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.app.Activity;
import android.app.ProgressDialog;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.view.Menu;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;
public class MainActivity extends Activity {
    private static int IS_FINISHED = 1;
    private Button button = null;
    private ImageView imageView = null;
    private String image_path = "http://i1.juyouqu.com/uploads/content//2014/04/1396611698344.jpg!w598";
    private ProgressDialog dialog = null;
    private Handler handle = new Handler(){
        public void handleMessage(android.os.Message msg)
        {
            Bitmap bitmap = null;
            byte[] data = (byte[])msg.obj;
            bitmap = BitmapFactory.decodeByteArray(data, 0, data.length);
            if(msg.what == IS_FINISHED)
            {
                dialog.dismiss();
                imageView.setImageBitmap(bitmap);
            }
        }
          
    };
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
          
        button = (Button)findViewById(R.id.button1);
        imageView = (ImageView)findViewById(R.id.imageView1);
        dialog = new ProgressDialog(this);
        dialog.setTitle("提示");
        dialog.setMessage("正在下载..........");
          
          
        button.setOnClickListener(new View.OnClickListener() {
              
            @Override
            public void onClick(View arg0) {
                // TODO Auto-generated method stub
                new Thread(new MyTask()).start();
                dialog.show();
            }
        });
    }
    public class MyTask implements Runnable
    {
        @Override
        public void run() {
            // TODO Auto-generated method stub
            HttpClient httpClient = new DefaultHttpClient();
            HttpGet httpGet = new HttpGet(image_path);
            try {
                HttpResponse httpResponse = httpClient.execute(httpGet);
                if(httpResponse.getStatusLine().getStatusCode() == 200)
                {
                    byte[] data = EntityUtils.toByteArray(httpResponse.getEntity());
                    Message message = Message.obtain();
                    message.obj = data;
                    message.what = IS_FINISHED;
                    handle.sendMessage(message);
                }
            } catch (ClientProtocolException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
          
    }
}

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