Android开发之使用Handler封装下载图片工具类(源代码分享)

          如果每下载一张图片，就得重写一次Http协议，多线程的启动和handler的信息传递就显得太麻烦了，我们直接来封装一个工具类，便于我们以后在开发时随时可以调用。

 （1）在清单文件添加权限

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

（2）编辑工具类

package com.example.g05_handler;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.annotation.SuppressLint;import android.app.ProgressDialog;import android.content.Context;import android.os.Handler;import android.os.Message;import android.util.Log;public class DownLoad {private ProgressDialog dialog;public DownLoad(Context context) {// TODO Auto-generated constructor stubdialog = new ProgressDialog(context);dialog.setTitle("提示");dialog.setMessage("玩命加载中");}@SuppressLint("HandlerLeak")public void Down(final String path, final DownLoadCallback callback) {final Handler handler = new Handler() {@Overridepublic void handleMessage(Message msg) {// TODO Auto-generated method stubsuper.handleMessage(msg);byte[] result = (byte[]) msg.obj;callback.download(result);if (msg.what == 1) {dialog.dismiss();}}};class MyThread implements Runnable {@Overridepublic void run() {// TODO Auto-generated method stubHttpClient client = new DefaultHttpClient();HttpGet httpGet = new HttpGet(path);try {HttpResponse httpResponse = client.execute(httpGet);Log.i("TAG", "------>"+ httpResponse.getStatusLine().getStatusCode());if (httpResponse.getStatusLine().getStatusCode() == 200) {byte[] result = EntityUtils.toByteArray(httpResponse.getEntity());Message message = Message.obtain();message.obj = result;message.what = 1;handler.sendMessage(message);}} catch (ClientProtocolException e) {// TODO Auto-generated catch blocke.printStackTrace();} catch (IOException e) {// TODO Auto-generated catch blocke.printStackTrace();} finally {if (client != null) {client.getConnectionManager().shutdown();}}};}new Thread(new MyThread()).start();dialog.show();}public interface DownLoadCallback {public void download(byte[] data);}}

    （3）调用该工具类

package com.example.g05_handler;import com.example.g05_handler.DownLoad.DownLoadCallback;import android.os.Bundle;import android.app.Activity;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 Button button;    private ImageView imageView;    private final String path="http://avatar.csdn.net/D/7/5/1_u013900875.jpg";@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);button=(Button)this.findViewById(R.id.button1);imageView=(ImageView)this.findViewById(R.id.imageView1);button.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View v) {// TODO Auto-generated method stubDownLoad downLoad=new DownLoad(MainActivity.this);downLoad.Down(path, new DownLoadCallback() {@Overridepublic void download(byte[] data) {// TODO Auto-generated method stubBitmap bitmap=BitmapFactory.decodeByteArray(data, 0, data.length);imageView.setImageBitmap(bitmap);}});}});}@Overridepublic boolean onCreateOptionsMenu(Menu menu) {// Inflate the menu; this adds items to the action bar if it is present.getMenuInflater().inflate(R.menu.main, menu);return true;}}