带有异步任务的进度对话框 [英] progress dialog with asynctask

问题描述

我有 3 个类，名为 WebServiceCleint 的类正在扩展 Asynctask 并且在 doInBackgrnd() 中，我正在传递 url 并从网络服务获取数据.但我是从另一个类的名为 VerifyTeacherId 的方法中调用它的.现在我如何显示进度对话框???我应该在哪里写 pg.show 和 pg.dismiss.???

i have 3 classes and the class called WebServiceCleint class is extending Asynctask and in doInBackgrnd() i m passing url and i m getting data from webservice. but i m calling this from another class's method called VerifyTeacherId. Now how can i show progress dialog??? where should i write the pg.show and pg.dismiss.???

public  class WebServiceClient extends AsyncTask<String, Void, String>
{

 private static final String base_path = "http://www.gdaschools.in/";
 protected static final String SLASH = "/";


 private ProgressDialog dialog;
 private Activity activity;

 public WebServiceClient(Activity activity) {
        this.activity = activity;
        this.dialog = new ProgressDialog(activity);
    }

    @Override
     protected void onPreExecute() {
            this.dialog.setMessage("Progress start");
            this.dialog.show();
        }



@Override
protected String doInBackground(String... params) {

    StringBuffer sb = new StringBuffer();
    sb.append(base_path);
    sb.append(params[0]);
    HttpRetriever retrieveResponse = new HttpRetriever();
    retrieveResponse.retrieve(sb.toString());
    return retrieveResponse.getResponseXml();
}



 @Override
protected void onPostExecute(String result) {
     if (this.dialog.isShowing()) {
           this.dialog.dismiss();
     }
}
}

我调用的方法是在另一个名为 SelectOptionActivity 的类中.方法是

And the method where i m calling is it in another class named SelectOptionActivity. The method is

public void verifyTeacherId(View view)
{
    teacherIdString = TeacherId.getText().toString().trim();

    clientThread = new WebServiceClient(SelectOptionActivity.this);
    clientThread.execute("teacher/" + teacherIdString);     

    try 
    {
        String xml = clientThread.get();

        DocumentBuilderFactory factory1 = DocumentBuilderFactory.newInstance();
        factory1.setNamespaceAware(true);
        try
        {
            DocumentBuilder builder = factory1.newDocumentBuilder();
            Document doc =builder.parse(new InputSource(new StringReader(xml))); 
            Element root = doc.getDocumentElement();
            if (doc != null) 
            {
                    NodeList nl = doc.getElementsByTagName("empId");
                    if (nl.getLength() > 0)
                    {
                        Node node = nl.item(0);
                        responseTeacherId = node.getTextContent();
                    }
                    NodeList n2=doc.getElementsByTagName("empName");
                    if (n2.getLength() > 0)
                    {
                        Node node = n2.item(0);
                        responseTeacherName = node.getTextContent();

                    }
            }

             Toast.makeText(getBaseContext(),""+responseTeacherId,10).show();
        }
        catch(Exception e)
        {
            e.printStackTrace();
        }
    } catch (InterruptedException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (ExecutionException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } 

现在得到像

05-08 12:10:10.834: D/AndroidRuntime(524): Shutting down VM
05-08 12:10:10.834: W/dalvikvm(524): threadid=1: thread exiting with uncaught exception (group=0x40014760)
05-08 12:10:10.872: E/AndroidRuntime(524): FATAL EXCEPTION: main
05-08 12:10:10.872: E/AndroidRuntime(524): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.GDAProj/com.GDAProj.SelectOptionActivity}: java.lang.NullPointerException
05-08 12:10:10.872: E/AndroidRuntime(524):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1739)
05-08 12:10:10.872: E/AndroidRuntime(524):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1831)
05-08 12:10:10.872: E/AndroidRuntime(524):  at android.app.ActivityThread.access$500(ActivityThread.java:122)
05-08 12:10:10.872: E/AndroidRuntime(524):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1024)
05-08 12:10:10.872: E/AndroidRuntime(524):  at android.os.Handler.dispatchMessage(Handler.java:99)
05-08 12:10:10.872: E/AndroidRuntime(524):  at android.os.Looper.loop(Looper.java:132)
05-08 12:10:10.872: E/AndroidRuntime(524):  at android.app.ActivityThread.main(ActivityThread.java:4123)
05-08 12:10:10.872: E/AndroidRuntime(524):  at java.lang.reflect.Method.invokeNative(Native Method)
05-08 12:10:10.872: E/AndroidRuntime(524):  at java.lang.reflect.Method.invoke(Method.java:491)
05-08 12:10:10.872: E/AndroidRuntime(524):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:841)
05-08 12:10:10.872: E/AndroidRuntime(524):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:599)
05-08 12:10:10.872: E/AndroidRuntime(524):  at dalvik.system.NativeStart.main(Native Method)
05-08 12:10:10.872: E/AndroidRuntime(524): Caused by: java.lang.NullPointerException
05-08 12:10:10.872: E/AndroidRuntime(524):  at android.content.ContextWrapper.getApplicationInfo(ContextWrapper.java:132)
05-08 12:10:10.872: E/AndroidRuntime(524):  at android.view.ContextThemeWrapper.getTheme(ContextThemeWrapper.java:65)
05-08 12:10:10.872: E/AndroidRuntime(524):  at android.app.AlertDialog.resolveDialogTheme(AlertDialog.java:120)
05-08 12:10:10.872: E/AndroidRuntime(524):  at android.app.AlertDialog.<init>(AlertDialog.java:80)
05-08 12:10:10.872: E/AndroidRuntime(524):  at android.app.ProgressDialog.<init>(ProgressDialog.java:76)
05-08 12:10:10.872: E/AndroidRuntime(524):  at com.GDAProj.WebServiceClient.<init>(WebServiceClient.java:20)
05-08 12:10:10.872: E/AndroidRuntime(524):  at com.GDAProj.SelectOptionActivity.<init>(SelectOptionActivity.java:70)
05-08 12:10:10.872: E/AndroidRuntime(524):  at java.lang.Class.newInstanceImpl(Native Method)
05-08 12:10:10.872: E/AndroidRuntime(524):  at java.lang.Class.newInstance(Class.java:1301)
05-08 12:10:10.872: E/AndroidRuntime(524):  at android.app.Instrumentation.newActivity(Instrumentation.java:1022)
05-08 12:10:10.872: E/AndroidRuntime(524):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1730)
05-08 12:10:10.872: E/AndroidRuntime(524):  ... 11 more

推荐答案

将当前活动的上下文传递给 AsyncTask 类，并使用该上下文在 onPreExecute() 并关闭它 onPostExecute()

Pass context of your current activity to AsyncTask class and using that context show progress dialog in onPreExecute() and dismiss it onPostExecute()

public  class WebServiceClient extends AsyncTask<String, Void, String>
{
 private static final String base_path = "http://www.gdaschools.in";
 protected static final String SLASH = "/";
 private ProgressDialog dialog;
 private Activity activity;

public WebServiceClient(Activity activity) {
    this.activity = activity;
    this.dialog = new ProgressDialog(activity);
}

@Override
 protected void onPreExecute() {
        this.dialog.setMessage("Progress start");
        this.dialog.show();
    }

@Override
    protected void onPostExecute(final Boolean success) {
        if (this.dialog.isShowing()) {
           this.dialog.dismiss();
        }

.
.
.

代码仅供您理解..

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