AsyncTask--实现从网络下载一张图片的功能

http://tech.it168.com/a2009/0907/675/000000675155_3.shtml
http://blog.sina.com.cn/s/blog_62c194760100ggnu.html~type=v5_one&label=rela_nextarticle
package com.android.AsynctaskTest;

import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;

import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.AsyncTask;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.ProgressBar;

public class AsynctaskTest extends Activity {
String imageUrl = "http://hiphotos.baidu.com/baidu/pic/item/7d8aebfebf3f9e125c6008d8.jpg";
String param="";
ProgressBar mypb;
ImageView mimg;
Button btn;
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        mypb =(ProgressBar)findViewById(R.id.pgb);
        mimg =(ImageView)findViewById(R.id.wallpaper);
        btn=(Button)findViewById(R.id.btn);
        btn.setOnClickListener(new OnClickListener(){

@Override
public void onClick(View v) {
// TODO Auto-generated method stub
new myAsynctask().execute(param);
}
       
        });
       
       
    }
   
   
    Bitmap getImageFromNetwork() {
URL myFileUrl = null;
Bitmap bitmap = null;
try {
myFileUrl = new URL(imageUrl);
} catch (MalformedURLException e) {
e.printStackTrace();
}
try {
HttpURLConnection conn = (HttpURLConnection) myFileUrl
.openConnection();
conn.setDoInput(true);

conn.connect();
InputStream is = conn.getInputStream();

bitmap = BitmapFactory.decodeStream(is);

is.close();
} catch (IOException e) {
e.printStackTrace();
}
System.out.println(bitmap==null);
System.out.println(myFileUrl.toString());

return bitmap;
}
   
    class myAsynctask extends AsyncTask<String ,Integer  ,Bitmap >{

@Override
protected Bitmap doInBackground(String... params) {
// TODO Auto-generated method stub
Bitmap bitmap=getImageFromNetwork();
return bitmap;
}



@Override
protected void onPostExecute(Bitmap result) {
// TODO Auto-generated method stub
if(result!=null){
mimg.setImageBitmap(result);
}
else
mimg.setBackgroundResource(R.drawable.icon);
super.onPostExecute(result);
mypb.setVisibility(View.GONE);

}
@Override
protected void onProgressUpdate(Integer... values) {
// TODO Auto-generated method stub
mypb.setProgress(values[0]);
super.onProgressUpdate(values);
}

   @Override
protected void onPreExecute() {
// TODO Auto-generated method stub

mypb.setVisibility(View.VISIBLE);

mypb.setProgress(0);
super.onPreExecute();
}
   
    }
}

 

 

http://aijiawang-126-com.iteye.com/blog/592643