Android含文檔server結束（client UI介面非同步請求的一部分）三

標籤：

在本文中，AsyncTask為了實現非同步請求，詳細代碼如下所示的：

public class downloadActivity extends Activity {private TextView myTextView=null;private Button button=null;private static final String path="http://192.168.0.179:8080/Myweb/download.do";private ProgressDialog progressDialog=null;private URL url=null;   @Override   protected void onCreate(Bundle savedInstanceState) {  super.onCreate(savedInstanceState);  setContentView(R.layout.download);    //擷取傳過來的使用者名稱  Intent intent = getIntent();  String value = intent.getStringExtra("username");  value="hello"+" "+value;   //  myTextView = (TextView) findViewById(R.id.textView1);  myTextView.setText(value);  button=(Button)this.findViewById(R.id.download_btn);  progressDialog=new ProgressDialog(this);  progressDialog.setCancelable(false);  progressDialog.setTitle("提示");  progressDialog.setMessage("請耐心等待，檔案正在下載中....");  try {url=new URL(path);  } catch (MalformedURLException e) {// TODO Auto-generated catch blocke.printStackTrace();  }  button.setOnClickListener(new OnClickListener() {public void onClick(View arg0) {//progressDialog.show(); new DownloadFilesTask().execute(url);}});      }         private class DownloadFilesTask extends AsyncTask<URL, Void, Void> {@Overrideprotected void onPreExecute() {progressDialog.show();super.onPreExecute();}@Overrideprotected Void doInBackground(URL... urls) {httpUtils.sendDownloadPost(urls[0]);return null;}  @Overrideprotected void onPostExecute(Void result) {progressDialog.dismiss();super.onPostExecute(result);}   }}

在注冊時，使用Intent傳遞了username資料。

AsyncTask<URL, Void, Void>

主要有三個參數

1. Params, the type of the parameters sent to the task upon execution.  本文傳遞URL資料
2. Progress, the type of the progress units published during the background computation.//進度條
3. Result, the type of the result of the background computation.  //結果

本文未採用進度條形式，僅僅使用了ProgressDialog，故第二個參數置為空白，第三個參數選取時，本文在httpUtils包類已經寫入檔案到sd卡，故也置為空白。

重寫的方法：

1. onPreExecute(), invoked on the UI thread immediately after the task is executed. This step is normally used to setup the task, for instance by showing a progress bar in the user interface.  UI主線程中，初始化參數
2. doInBackground(Params...), invoked on the background thread immediately after onPreExecute() finishes executing. This step is used to perform background computation that can take a long time. The parameters of the asynchronous task are passed to this step. The result of the computation must be returned by this step and will be passed back to the last step. This step can also use publishProgress(Progress...) to publish one or more units of progress. These values are published on the UI thread, in theonProgressUpdate(Progress...) step.  非主線程。耗時操作
3. onProgressUpdate(Progress...), invoked on the UI thread after a call to publishProgress(Progress...). The timing of the execution is undefined. This method is used to display any form of progress in the user interface while the background computation is still executing. For instance, it can be used to animate a progress bar or show logs in a text field.
4. onPostExecute(Result), invoked on the UI thread after the background computation finishes. The result of the background computation is passed to this step as a parameter.  結果更新

Android含文檔server結束（client UI介面非同步請求的一部分）三