AsyncTask 學習 （3）

轉自百度文檔 ：　讀取網頁內容　　更新進度

import java.io.ByteArrayOutputStream;
import java.io.InputStream;

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.os.AsyncTask;

public class PageTask extends AsyncTask<String, Integer, String>{
//可變長的輸入參數 ， 與AsyncTask.exucute()對應
 @Override
 protected String doInBackground(String... params) {
  try {
   HttpClient client  = new DefaultHttpClient();
   //params[0] 表示連接的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[4*32];
    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  相應的長度，調用publishprogress() 更新
      publishProgress((int)((count / (float) length)*100));
      
     }
     Thread.sleep(100);
    }
    
    s = new String(baos.toByteArray());
    //返回結果
    return s;
   }
   
  } catch (Exception e) {
   e.printStackTrace();
  }
  return null;
 }

 @Override
 protected void onCancelled() {
  super.onCancelled();
 }

 @Override
 protected void onPostExecute(String result) {
  //返回HTML 頁面的內容
//  message.setText(result);
 }

 @Override
 protected void onPreExecute() {
  //super.onPreExecute();
  //任務啓動 ， 可以在這裏顯示一個對話框 ， 這裏簡單處理
  //message.setText(R.string.task_started);
 }

 @Override
 protected void onProgressUpdate(Integer... values) {
 // super.onProgressUpdate(values);
  //更新進度
  //message.setText(values[0]);
 }

}

PageTask task = new PageTask();

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