Android开发之使用Handler封装下载图片工具类(源码分享)

假设每下载一张图片，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能够调用。

（1）在清单文件加入权限

<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 stub
dialog = new ProgressDialog(context);
dialog.setTitle("提示");
dialog.setMessage("玩命载入中");

}

@SuppressLint("HandlerLeak")
public void Down(final String path, final DownLoadCallback callback) {
final Handler handler = new Handler() {
@Override
public void handleMessage(Message msg) {
// TODO Auto-generated method stub
super.handleMessage(msg);
byte[] result = (byte[]) msg.obj;

callback.download(result);

if (msg.what == 1) {
dialog.dismiss();
}
}
};
class MyThread implements Runnable {
@Override
public void run() {
// TODO Auto-generated method stub
HttpClient 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 block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.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";
@Override
protected 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() {

@Override
public void onClick(View v) {
// TODO Auto-generated method stub
DownLoad downLoad=new DownLoad(MainActivity.this);
downLoad.Down(path, new DownLoadCallback() {

@Override
public void download(byte[] data) {
// TODO Auto-generated method stub
Bitmap bitmap=BitmapFactory.decodeByteArray(data, 0, data.length);
imageView.setImageBitmap(bitmap);
}
});
}
});
}

@Override
public 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;
}

}