AsyncTask（异步任务）的用法

doInBackground方法和onPostExecute的参数必须对应，这两个参数在AsyncTask声明的泛型参数列表中指定，第一个为doInBackground接受的参数，第二个为显示进度的参数，第第三个为doInBackground返回和onPostExecute传入的参数。

从网上获取一个网页，在一个TextView中将其源代码显示出来

  

   

    

     

    
    

     

      package test.list;
     
    
   

    

     

    
    

     

      import java.io.ByteArrayOutputStream;
     
    
   

    

     

    
    

     

      import java.io.InputStream;
     
    
   

    

     

    
    

     

      import java.util.ArrayList;
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     

      import org.apache.http.HttpEntity;
     
    
   

    

     

    
    

     

      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 android.app.Activity;
     
    
   

    

     

    
    

     

      import android.app.ProgressDialog;
     
    
   

    

     

    
    

     

      import android.content.Context;
     
    
   

    

     

    
    

     

      import android.content.DialogInterface;
     
    
   

    

     

    
    

     

      import android.os.AsyncTask;
     
    
   

    

     

    
    

     

      import android.os.Bundle;
     
    
   

    

     

    
    

     

      import android.os.Handler;
     
    
   

    

     

    
    

     

      import android.os.Message;
     
    
   

    

     

    
    

     

      import android.view.View;
     
    
   

    

     

    
    

     

      import android.widget.Button;
     
    
   

    

     

    
    

     

      import android.widget.EditText;
     
    
   

    

     

    
    

     

      import android.widget.TextView;
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     

      public class NetworkActivity extends Activity{
     
    
   

    

     

    
    

     
    private TextView message;
     
    
   

    

     

    
    

     
    private Button open;
     
    
   

    

     

    
    

     
    private EditText url;
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     
    @Override
     
    
   

    

     

    
    

     
    public void onCreate(Bundle savedInstanceState) {
     
    
   

    

     

    
    

     
       super.onCreate(savedInstanceState);
     
    
   

    

     

    
    

     

             setContentView(R.layout.network);
     
    
   

    

     

    
    

     

             message= (TextView) findViewById(R.id.message);
     
    
   

    

     

    
    

     

             url= (EditText) findViewById(R.id.url);
     
    
   

    

     

    
    

     

             open= (Button) findViewById(R.id.open);
     
    
   

    

     

    
    

     

             open.setOnClickListener(new View.OnClickListener() {
     
    
   

    

     

    
    

     
           public void onClick(View arg0) {
     
    
   

    

     

    
    

     

                    connect();
     
    
   

    

     

    
    

     

                 }
     
    
   

    

     

    
    

     

             });
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     

          }
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     
    private void connect() {
     
    
   

    

     

    
    

     
        PageTask task = new PageTask(this);
     
    
   

    

     

    
    

     

              task.execute(url.getText().toString());
     
    
   

    

     

    
    

     

          }
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     
    class PageTask extends AsyncTask<String, Integer, String> {
     
    
   

    

     

    
    

     
        // 可变长的输入参数，与AsyncTask.exucute()对应
     
    
   

    

     

    
    

     

              ProgressDialog pdialog;
     
    
   

    

     

    
    

     
        public PageTask(Context context){
     
    
   

    

     

    
    

     

                  pdialog = new ProgressDialog(context, 0);   
     
    
   

    

     

    
    

     

                  pdialog.setButton("cancel", new DialogInterface.OnClickListener() {
     
    
   

    

     

    
    

     
             public void onClick(DialogInterface dialog, int i) {
     
    
   

    

     

    
    

     

                    dialog.cancel();
     
    
   

    

     

    
    

     

                   }
     
    
   

    

     

    
    

     

                  });
     
    
   

    

     

    
    

     

                  pdialog.setOnCancelListener(new DialogInterface.OnCancelListener() {
     
    
   

    

     

    
    

     
             public void onCancel(DialogInterface dialog) {
     
    
   

    

     

    
    

     

                    finish();
     
    
   

    

     

    
    

     

                   }
     
    
   

    

     

    
    

     

                  });
     
    
   

    

     

    
    

     

                  pdialog.setCancelable(true);
     
    
   

    

     

    
    

     

                  pdialog.setMax(100);
     
    
   

    

     

    
    

     

                  pdialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
     
    
   

    

     

    
    

     

                  pdialog.show();
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     

              }
     
    
   

    

     

    
    

     
        @Override
     
    
   

    

     

    
    

     
        protected String doInBackground(String... params) {
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     
            try{
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     
               HttpClient client = new DefaultHttpClient();
     
    
   

    

     

    
    

     
               // params[0]代表连接的url
     
    
   

    

     

    
    

     
               HttpGet get = new HttpGet(params[0]);
     
    
   

    

     

    
    

     
               HttpResponse response = client.execute(get);
     
    
   

    

     

    
    

     
               HttpEntity entity = response.getEntity();
     
    
   

    

     

    
    

     
               long length = entity.getContentLength();
     
    
   

    

     

    
    

     
               InputStream is = entity.getContent();
     
    
   

    

     

    
    

     
               String s = null;
     
    
   

    

     

    
    

     
               if(is != null) {
     
    
   

    

     

    
    

     
                   ByteArrayOutputStream baos = new ByteArrayOutputStream();
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     
                   byte[] buf = new byte[128];
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     
                   int ch = -1;
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     
                   int count = 0;
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     
                   while((ch = is.read(buf)) != -1) {
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     

                            baos.write(buf, 0, ch);
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     

                            count += ch;
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     
                      if(length > 0) {
     
    
   

    

     

    
    

     
                          // 如果知道响应的长度，调用publishProgress（）更新进度
     
    
   

    

     

    
    

     

                                publishProgress((int) ((count / (float) length) * 100));
     
    
   

    

     

    
    

     

                            }
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     
                      // 让线程休眠100ms
     
    
   

    

     

    
    

     

                            Thread.sleep(100);
     
    
   

    

     

    
    

     

                         }
     
    
   

    

     

    
    

     

                         s = new String(baos.toByteArray());              }
     
    
   

    

     

    
    

     
               // 返回结果
     
    
   

    

     

    
    

     
               return s;
     
    
   

    

     

    
    

     

                  } catch(Exception e) {
     
    
   

    

     

    
    

     

                     e.printStackTrace();
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     

                  }
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     
            return null;
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     

              }
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     
        @Override
     
    
   

    

     

    
    

     
        protected void onCancelled() {
     
    
   

    

     

    
    

     
            super.onCancelled();
     
    
   

    

     

    
    

     

              }
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     
        @Override
     
    
   

    

     

    
    

     
        protected void onPostExecute(String result) {
     
    
   

    

     

    
    

     
            // 返回HTML页面的内容
     
    
   

    

     

    
    

     

                  message.setText(result);
     
    
   

    

     

    
    

     

                  pdialog.dismiss(); 
     
    
   

    

     

    
    

     

              }
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     
        @Override
     
    
   

    

     

    
    

     
        protected void onPreExecute() {
     
    
   

    

     

    
    

     
            // 任务启动，可以在这里显示一个对话框，这里简单处理
     
    
   

    

     

    
    

     

                  message.setText(R.string.task_started);
     
    
   

    

     

    
    

     

              }
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     
        @Override
     
    
   

    

     

    
    

     
        protected void onProgressUpdate(Integer... values) {
     
    
   

    

     

    
    

     
            // 更新进度
     
    
   

    

     

    
    

     

                    System.out.println(""+values[0]);
     
    
   

    

     

    
    

     

                    message.setText(""+values[0]);
     
    
   

    

     

    
    

     

                    pdialog.setProgress(values[0]);
     
    
   

    

     

    
    

     

              }
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     

           }
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     

      }
     
    
  
 

文章来源: panda1234lee.blog.csdn.net，作者：panda1234lee，版权归原作者所有，如需转载，请联系作者。

原文链接：panda1234lee.blog.csdn.net/article/details/8673783