由於android4.0之後不允許在主執行緒中進行網路才操作，在學習過程中不知道這點，導致發生了比較蛋疼的事情，本人菜鳥一個，知識水平很有限，利用Handler 傳送訊息傳遞下載的圖片資源，並在UI介面中予以顯示。

package com.example.ko.ok;


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


import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ImageView;


public class MainActivity extends Activity {
Button btn;
String imageUrl = "http://imgstatic.baidu.com/img/image/shouye/qinchunmeinv0808.jpg"; ;
Bitmap bmImg; 
ImageView im;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
 
setContentView(R.layout.activity_main);
im=(ImageView)findViewById(R.id.imageView1);
btn=(Button)findViewById(R.id.button1);
final Handler handler=new Handler(){
public void handleMessage(Message msg)
{
bmImg=(Bitmap)msg.obj;
im.setImageBitmap(bmImg);
}
};
btn.setOnClickListener(new OnClickListener() {

@Override
public void onClick(View v) {
// TODO Auto-generated method stub
btn.setText("徐昕");
imageUrl="http://bbs.dvbbs.net/UploadFile/2012-5/201253120192839760.gif";
new Thread("oo"){
public void run()
{
Message msg=new Message();
msg.obj=returnBitMap(imageUrl); 
handler.sendMessage(msg);
}
}.start();
}
});

new Thread("oo"){
public void run()
{
Message msg=new Message();
msg.obj=returnBitMap(imageUrl); 
handler.sendMessage(msg);
}
}.start();
}
public Bitmap returnBitMap(String url) {  
URL myFileUrl = null;  
Bitmap bitmap = null;  
try {  
myFileUrl = new URL(url);  
} 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();  
}  
return 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;
}


}