Android:非同期タスクAsyncTask、execute、publishProgress、onProgressUpdate

public class MainActivity extends Activity implements OnClickListener 
{ 
        
    private TextView textView; 
    private ProgressBar progressBar; 
        
    class MyAsyncTask extends AsyncTask 
    { 
        /** 
         *     ：AsyncTask 
         * 1.Params:UI        。 
         * 2.Progress:       。 
         * 3.Result:       。    doInBackground                。 
         * 
         *     ： 
         * 1.onPreExecute() 
         * 2.doInBackground()-->onProgressUpdate() 
         * 3.onPostExecute() 
         */
        @Override                      
        protected void onProgressUpdate(Integer... values)//     ，      
        { 
            progressBar.setProgress(values[0]);//        
        } 
        @Override
        protected void onPreExecute()//          UI     
        { 
            progressBar.setVisibility(View.VISIBLE);//    ，      ，        
        } 
            
        @Override
        protected String doInString...  params)//       
        { 
            //          ,         ，      
            //String result = download(); 
            for (int i = 0; i < 10; i++) 
            { 
                try
                { 
                    Thread.sleep(1000); 
                    publishProgress(i * 10);//       10%,          onProgressUpdate() 
                } 
                catch (InterruptedException e) 
                { 
                    e.printStackTrace(); 
                } 
                    
            } 
            return "    !"; 
        } 
            
        @Override
        protected void onPostExecute(String result)//          UI     
        { 
            //      main     
            progressBar.setVisibility(View.GONE);//     ，      
            textView.setText(result); 
        } 
            
    } 
    @Override
    protected void onCreate(Bundle savedInstanceState) 
    { 
        super.onCreate(savedInstanceState); 
        setContentView(R.layout.activity_main); 
            
        findViewById(R.id.button1).setOnClickListener(this); 
        textView = (TextView) findViewById(R.id.textView1); 
        progressBar = (ProgressBar) findViewById(R.id.progressBar1); 
    } 
        
    @Override
    public boolean onCreateOptionsMenu(Menu menu) 
    { 
        getMenuInflater().inflate(R.menu.activity_main, menu); 
        return true; 
    } 
    @Override
    public void onClick(View v) 
    { 
        switch (v.getId()) 
        { 
        case R.id.button1: 
            btnClick(); 
            break; 
            
        default: 
            break; 
        } 
    } 
    private void btnClick()//  AsyncTask  ，     
    { 
        MyAsyncTask asyncTask = new MyAsyncTask(); 
        asyncTask.execute("http://www.google.com");//          AsyncTask,execute     UI      
    } 
    private String download()//  ，     
    { 
        try
        { 
            Thread.sleep(3000); 
        } 
        catch (InterruptedException e) 
        { 
            e.printStackTrace(); 
        } 
        return "    !"; 
    } 
}