Android多線程——Handler （一） 實現圖片下載

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在ＵＩ線程中建立子線程——》在子線程中擷取網狀圖片－－》線上程中通過Ｍｅｓｓａｇｅ　傳遞二進位圖片給Ｈａｎｄｌｅｒ，－－》Ｈａｎｄｌｅｒ在ｈａｎｄｌｅＭｅｓｓａｇｅ（）中處理訊息

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("正在下載..........");                            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();            }        }              }}