关于AsyncTask异步执行任务Demo

public class MainActivity extends Activity {
private String url = "http://wenwen.soso.com/p/20100322/20100322095024-1008716746.jpg";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
testTask();
}
public void testTask(){
DownloadPicTask task = new DownloadPicTask();
task.imgPath = url;
task.img = (ImageView) findViewById(R.id.imageView1);
task.execute(url);
}
}

package com.example.task;
import org.apache.http.HttpResponse;
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.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.AsyncTask;
import android.util.Log;
import android.widget.ImageView;
public  class DownloadPicTask extends AsyncTask<String, Integer, String>{
public String imgPath;
private byte[] data;
public ImageView img;
protected void onPrepareExecute(){
Log.v("task", "onPrepareExecute");
super.onPreExecute();
}
// doInBackground方法内部执行后台任务,不可在此方法内修改UI
@Override
protected String doInBackground(String... arg0) {
// TODO Auto-generated method stub
Log.v("task", "doInBackground " + arg0);
HttpClient httpClient = new DefaultHttpClient();
HttpGet httpGet = new HttpGet(imgPath);
HttpResponse httpResponse = null;
try {
httpResponse = httpClient.execute(httpGet);
if (httpResponse.getStatusLine().getStatusCode() == 200) {
data = EntityUtils.toByteArray(httpResponse
.getEntity());
}
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
// onProgressUpdate方法用于更新进度信息
@Override
protected void onProgressUpdate(Integer... progresses) {
Log.v("task", "onProgressUpdate");
super.onProgressUpdate(progresses);
}
// onPostExecute方法用于在执行完后台任务后更新UI,显示结果
@Override
protected void onPostExecute(String result) {
// progressDialog.dismiss();
Log.v("task", "onPostExecute");
Bitmap bmp=BitmapFactory.decodeByteArray(data, 0, data.length);
img.setImageBitmap(bmp);
}
// onCancelled方法用于在取消执行中的任务时更改UI
@Override
protected void onCancelled() {
Log.v("task", "onCancelled");
}
}