Android AsyncTask異步處理抓取網頁

Android AsyncTask異步處理抓取網頁

/*
 


@author yanggang
@see http://blog.csdn.net/sunboy_2050
*/
public class MainActivity extends Activity {
 private EditText metURL;
 private TextView mtvPage;
 private Button mbtnConn;
@Override
 public void onCreate(Bundle savedInstanceState) {

 super.onCreate(savedInstanceState);
 setContentView(R.layout.activity_main);

 metURL = (EditText)findViewById(R.id.etURL);        // 輸入網址
 mbtnConn = (Button)findViewById(R.id.btnConn);      // 連接網站
 mtvPage = (TextView)findViewById(R.id.tvPage);      // 顯示網頁

 mbtnConn.setOnClickListener(new View.OnClickListener() {
     @Override
     public void onClick(View v) {
         connURL();
     }
 });

}
private void connURL(){

 URLTask urlTask = new URLTask(this);    // 實例化抽象AsyncTask
 urlTask.execute(metURL.getText().toString().trim());    // 調用AsyncTask，傳入url參數

}
/* 繼承AsyncTask的子類，下載url網頁內容 /
 class URLTask extends AsyncTask<String, Integer, String> {

 ProgressDialog proDialog;

 public URLTask(Context context) {
     proDialog = new ProgressDialog(context, 0);
     proDialog.setButton("cancel", new DialogInterface.OnClickListener() {
         @Override
         public void onClick(DialogInterface dialog, int which) {
             dialog.cancel();
         }
     });
     proDialog.setOnCancelListener(new DialogInterface.OnCancelListener() {
         @Override
         public void onCancel(DialogInterface dialog) {
             finish();
         }
     });
     proDialog.setCancelable(true);
     proDialog.setMax(100);
     proDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
     proDialog.show();
 }

 @Override
 protected void onPreExecute(){
     mtvPage.setText(R.string.hello_world);      // 可以與UI控件交互
 }

 @Override
 protected String doInBackground(String... params) {     // 在后臺，下載url網頁內容
     try {
         HttpGet get = new HttpGet(params[0]);           // url
         HttpResponse response = new DefaultHttpClient().execute(get);

         if(response.getStatusLine().getStatusCode() == 200) {       // 判斷網絡連接是否成功

//                  String result = EntityUtils.toString(response.getEntity(), "gb2312");   // 獲取網頁內容
//                  return result;

             HttpEntity entity = response.getEntity();
             long len = entity.getContentLength();       // 獲取url網頁內容總大小
             InputStream is = entity.getContent();

             ByteArrayOutputStream bos = new ByteArrayOutputStream();
             byte[] buffer = new byte[1024];
             int ch = -1;
             int count = 0;      // 統計已下載的url網頁內容大小
             while(is != null && (ch = is.read(buffer)) != -1 ) {
                 bos.write(buffer, 0, ch);
                 count += ch;
                 if(len > 0) {
                     float ratio = count/(float)len * 100;   // 計算下載url網頁內容百分比
                     publishProgress((int)ratio);    // android.os.AsyncTask.publishProgress(Integer... values)
                 }
                 Thread.sleep(100);
             }
             String result = new String(bos.toString("gb2312"));
             return result;
         }
     } catch (Exception e) {
         e.printStackTrace();
     }

     return null;
 }

 @Override
 protected void onProgressUpdate(Integer... values) {    // 可以與UI控件交互
     mtvPage.setText("" + values[0]);    // 獲取 publishProgress((int)ratio)的values
     proDialog.setProgress(values[0]);
 }

 @Override
 protected void onPostExecute(String result) {   // 可以與UI控件交互
     mtvPage.setText(result);
     proDialog.dismiss();
 }

}
}</pre>