public class NetService {
public static InputStream getInputStreamByUrl(String address){
URL url = null;
HttpURLConnection urlConnection = null;
try {
url = new URL(address);
urlConnection = (HttpURLConnection) url.openConnection();
urlConnection.setConnectTimeout(2 * 1000);
urlConnection.setRequestMethod("GET");
return urlConnection.getInputStream();
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
}

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.AsyncTask;
import java.io.BufferedInputStream;
import java.io.InputStream;
public class NetServiceTask extends AsyncTask
public NetServiceTask(String address, URLPostHandler urlPostHandler) {
 this.address=address;
 this.urlPostHandler=urlPostHandler;
}
/**
 * 表示任务执行之前的操作
 */
@Override
protected void onPreExecute() {
 // TODO Auto-generated method stub
 super.onPreExecute();
}
/**
 * 主要是完成耗时的操作
 */
@Override
protected Bitmap doInBackground(String... arg0) {
 InputStream inputStream=NetService.getInputStreamByUrl(arg0[0]);
 if(inputStream!=null){
  return BitmapFactory.decodeStream(new BufferedInputStream(inputStream));
 }
 return null;
}
/**
 * 主要是更新UI的操作
 */
@Override
protected void onPostExecute(Bitmap result) {
 // TODO Auto-generated method stub
 super.onPostExecute(result);
 if(this.urlPostHandler!=null&&result!=null){
  this.urlPostHandler.PostHandler(result);
 }
}
@Override
public void run() {
 execute(this.address);
}
}

public interface URLPostHandler {
void PostHandler(Bitmap bitmap);
}

public class MainActivity extends AppCompatActivity {
Button buttonDownload;
ImageView imageViewImg;
@Override
protected void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.activity_main);
 buttonDownload = (Button) findViewById(R.id.buttonDownload);
 imageViewImg = (ImageView) findViewById(R.id.imageViewImg);
 buttonDownload.setOnClickListener(new View.OnClickListener() {
 @Override
 public void onClick(View v) {
  String address = "https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1490783056273&di=6160d101d31dcf5f44b443ad9c5b2648&imgtype=0&src=http%3A%2F%2Fimg.sc115.com%2Fuploads%2Fallimg%2F110626%2F2011062622383898.jpg";
  NetServiceTask netServerTask= new NetServiceTask(address,new URLPostHandler() {
  @Override
  public void PostHandler(Bitmap bitmap) {
   imageViewImg.setImageBitmap(bitmap);
  }
  });
  Thread thread=new Thread(netServerTask);
  thread.start();
 }
 });
}
}