Question

我试图在AsyncTask（）中显示ProgressDialog。在我的代码我使用handler.postdelayed运行AsyncTask。没有handler.postdelayed它显示progressdialog。

final Handler handler = new Handler();

handler.postDelayed(new Runnable() {

    public void run() {
        new AsyncTask<Void, Void, Void>() {

            @Override
            protected void onPreExecute() {
                progress = ProgressDialog.show(getActivity(), "Updating Profile", "Please Wait", true);
                progress.show();
                try {
                    File file = new File(Environment.getExternalStorageDirectory().getPath(), "/myProfileData.txt");
                    if (file.exists()) {
                        try {
                            profileDatabase.updateProfileFromDB();
                            profile = new StructConfigParameters();
                            isUseAutoConfigProfileChecked = true;
                            profileDatabase.updateProfileFromDB();
                            File myFile = new File(Environment.getExternalStorageDirectory().getPath() + "/myProfileData.txt");
                            FileInputStream fIn = new FileInputStream(myFile);
                            BufferedReader myReader = new BufferedReader(
                            new InputStreamReader(fIn));
                            String aDataRow = "";
                            String aBuffer = "";
                            while ((aDataRow = myReader.readLine()) != null) {
                                aBuffer += aDataRow + "\n";
                            }
                            myReader.close();
                        } catch (Exception e) {
                            System.out.println("Exception In updateProfileFromDB 133 " + e);
                        }
                    }
                } catch (Exception e) {
                    System.out.println("Exception In updateProfileFromDB 22 " + e);
                }
            }

            @Override
            protected Void doInBackground(Void... params) {
                return null;
            }

            @Override
            protected void onPostExecute(Void res) {
                progress.dismiss();
            }
        }.execute();
    }
});

Answer 1

当您使用AsyncTask来呼叫网络服务时，您应该遵循这些内容。

由于您已经在使用AsyncTask，因此无需在处理程序中调用它，您可以在AsyncTask的{{3}}方法中显示进度。

public class myAsyncTask extends AsyncTask<Void, Void, Void> {

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        // Show your progress dialog here
    }

    @Override
    protected Void doInBackground(Void... params) {
        // this method should only have code to call web service 
        // or background work which should not be related to UI
        // UI operations should avoid in this method
        return null;
    }

    @Override
    protected void onPostExecute(Void result) {
        super.onPostExecute(result);
        // you can do UI work in this method
        // Dismiss your progress dialog at the end of all operaions.
    }

}

虽然你的情况应该是

new AsyncTask<Void, Void, Void>() {

    @Override
    protected void onPreExecute() {
        progress = ProgressDialog.show(getActivity(), "Updating Profile", "Please Wait", true);
        progress.show();
    }

    @Override
    protected Void doInBackground(Void... params) {
        try {
            File file = new File(Environment.getExternalStorageDirectory().getPath(), "/myProfileData.txt");
            if (file.exists()) {
                try {
                    profileDatabase.updateProfileFromDB();
                    profile = new StructConfigParameters();
                    isUseAutoConfigProfileChecked = true;
                    profileDatabase.updateProfileFromDB();
                    File myFile = new File(Environment.getExternalStorageDirectory().getPath() + "/myProfileData.txt");
                    FileInputStream fIn = new FileInputStream(myFile);
                    BufferedReader myReader = new BufferedReader(new InputStreamReader(fIn));
                    String aDataRow = "";
                    String aBuffer = "";
                    while ((aDataRow = myReader.readLine()) != null) {
                        aBuffer += aDataRow + "\n";
                    }
                    myReader.close();
                } catch (Exception e) {
                    System.out.println("Exception In updateProfileFromDB 133 " + e);
                }
            }
        } catch (Exception e) {
            System.out.println("Exception In updateProfileFromDB 22 " + e);
        }
        return null;
    }

    @Override
    protected void onPostExecute(Void res) {
        progress.dismiss();
    }
}.execute();

Answer 2

 Try the followoing 

            ProgressDialog progressDialog = new ProgressDialog(mainActivity);
            progressDialog.setProgressStyle(ProgressDialog.STYLE_SPINNER);
            progressDialog.setCancelable(false);
            progressDialog.setMessage("Loading Please Wait");
            progressDialog.show();

Answer 3

    class LoadData extends AsyncTask<Void, Void, Void> 
    {
      private ProgressDialog prgDialog;

      @Override
     protected void onPreExecute() 
      {
        prgDialog = new ProgressDialog(DataActivity.this);
        prgDialog.setMessage("Please wait...");
        prgDialog.setCancelable(false);
        prgDialog.show();
        super.onPreExecute();
      }

      @Override
      protected Void doInBackground(Void... params) 
       {
         // do some work like loading data
        return null;
       }

      @Override
      protected void onPostExecute(Void result)
      {
        super.onPostExecute(result);
        prgDialog.cancel();
       // do some work when loading finish
      }

}

Answer 4

变化

 progress = ProgressDialog.show(getActivity(), "Updating Profile",
                                "Please Wait", true);
                        progress.show();

到这个

 progress = ProgressDialog.show(YourActivityName.this, "Updating Profile",
                                "Please Wait", true);
                        progress.show();

无法在AsyncTask中显示ProgressDialog

4 个答案: