Android异步任务AsyncTask

package com.example.asynctask;

import java.net.MalformedURLException;
import java.net.URL;

import android.app.Activity;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.TextView;
/**
 * 异步任务实现，可以实现直接修改UI线程的控件。
 * @author shb
 *
 */
public class MainActivity extends Activity {
    private TextView tView;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        tView = (TextView) this.findViewById(R.id.textView1);
        TestAsyn testAsyn = new TestAsyn();
        try {
            testAsyn.execute(new URL("https://www.baidu.com/img/bd_logo1.png"));
        } catch (MalformedURLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
    public class TestAsyn extends AsyncTask<URL,Integer,String> {

        @Override
        protected String doInBackground(URL... arg0) {
            // TODO Auto-generated method stub
            return arg0[0].toString();
        }
        @Override
        protected void onPostExecute(String result) {
            // TODO Auto-generated method stub
            super.onPostExecute(result);
            MainActivity.this.tView.setText(result);
        }
        @Override
        protected void onPreExecute() {
            // TODO Auto-generated method stub
            super.onPreExecute();
            Log.d("msg","onPreex");
        }
    }
}