package com.cnn.asynctask;import android.app.Activity;import android.content.Intent;import android.os.Bundle;import android.view.Menu;import android.view.MenuItem;import android.view.View;import android.view.View.OnClickListener;import android.widget.Button;public class MainActivity extends Activity {	private Button btnButton;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);                btnButton=(Button) findViewById(R.id.button1);        btnButton.setOnClickListener(new OnClickListener() {						@Override			public void onClick(View v) {				// TODO 自动生成的方法存根				Intent intent = new Intent(MainActivity.this, ImageTest.class);				startActivity(intent);			}		});    }    @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;    }    @Override    public boolean onOptionsItemSelected(MenuItem item) {        // Handle action bar item clicks here. The action bar will        // automatically handle clicks on the Home/Up button, so long        // as you specify a parent activity in AndroidManifest.xml.        int id = item.getItemId();        if (id == R.id.action_settings) {            return true;        }        return super.onOptionsItemSelected(item);    }}

　　

package com.cnn.asynctask;import java.io.BufferedInputStream;import java.io.IOException;import java.io.InputStream;import java.net.MalformedURLException;import java.net.URL;import java.net.URLConnection;import android.app.Activity;import android.graphics.Bitmap;import android.graphics.BitmapFactory;import android.opengl.Visibility;import android.os.AsyncTask;import android.os.Bundle;import android.view.View;import android.widget.ImageView;import android.widget.ProgressBar;public class ImageTest extends Activity {	private ImageView imageView;	private ProgressBar bar;	private String urlString="http://pic2.ooopic.com/01/03/51/25b1OOOPIC19.jpg";	@Override	protected void onCreate(Bundle savedInstanceState) {		// TODO 自动生成的方法存根		super.onCreate(savedInstanceState);		setContentView(R.layout.image);				imageView=(ImageView) findViewById(R.id.image);		bar=(ProgressBar) findViewById(R.id.bar);				new ImageAsync().execute(urlString);	}		class ImageAsync extends AsyncTask
     
       {		@Override		protected Bitmap doInBackground(String... params) {			// TODO 自动生成的方法存根			//获取传递进来的参数			String urlString=params[0];			Bitmap bitmap=null;			URLConnection connection;			InputStream inputStream;			try {				connection=new URL(urlString).openConnection();				inputStream=connection.getInputStream();				BufferedInputStream bisBufferedInputStream= new BufferedInputStream(inputStream);				//通过decodeStream方法解析输入流 转化为bitmap 				bitmap=BitmapFactory.decodeStream(bisBufferedInputStream);				inputStream.close();				bisBufferedInputStream.close();			} catch (MalformedURLException e) {				// TODO 自动生成的 catch 块				e.printStackTrace();			} catch (IOException e) {				// TODO 自动生成的 catch 块				e.printStackTrace();			}			//bitmap作为返回值返回给后面调用的方法			return bitmap;		}				@Override		protected void onPreExecute() {			// TODO 自动生成的方法存根			super.onPreExecute();			bar.setVisibility(View.VISIBLE);		}				@Override		protected void onPostExecute(Bitmap result) {			// TODO 自动生成的方法存根			super.onPostExecute(result);			bar.setVisibility(View.GONE);			imageView.setImageBitmap(result);		}	}}