Question

我有一个AsyncTask，它将在onCreate方法中执行。但是，我的ProgressDialog并没有出现。从调试开始，确认正在执行AsyncTask。

@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_lifestyle);
        context = getApplicationContext();

        new testAsync().execute();
}

private class testAsync extends AsyncTask<Void,Void,Void> {
        private ProgressDialog pDialog;

        @Override
        protected  void onPreExecute() {
            super.onPreExecute();
            pDialog = new ProgressDialog(MainActivity.this); // tried with context, no difference
            pDialog.setTitle("Inserting sample data");
            pDialog.setMessage("Please wait. This dialog will be dismissed upon completion.");
            pDialog.setIndeterminate(false);
            pDialog.setCancelable(false);
            pDialog.show();
        }

        @Override
        protected Void doInBackground(Void... params) {
          //  TableControllerReadings TCR = new TableControllerReadings(context);
          //  TCR.insertSampleData(getApplicationContext());

            new Timer().schedule(new TimerTask() {
                @Override
                public void run() {
                 //delay for 5 seconds
                }
            }, 5000);

            return null;
        }

        @Override
        protected void onPostExecute(Void v) {
            pDialog.dismiss();
        }
    }

Answer 1

在调用onResume方法之前，活动不会显示任何视图。如果AsyncTask执行在onResume之前完成，那么您将永远不会看到ProgressDialog。

最好在new testAsync().execute();

中致电onResume

Answer 2

将pDialog.dismiss();带入您的计时器帖子。

原因： onPostExecute()立即致电，因为后台任务已经完成。

它的seprate线程处于延迟状态，因此光标移动到onPostExecute()

 private class testAsync extends AsyncTask<Void, Void, Void> {
        private ProgressDialog pDialog;

        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            pDialog = new ProgressDialog(MainActivity.this); // tried with context, no difference
            pDialog.setTitle("Inserting sample data");
            pDialog.setMessage("Please wait. This dialog will be dismissed upon completion.");
            pDialog.setIndeterminate(false);
            pDialog.setCancelable(false);
            pDialog.show();
        }

        @Override
        protected Void doInBackground(Void... params) {
            //  TableControllerReadings TCR = new TableControllerReadings(context);
            //  TCR.insertSampleData(getApplicationContext());

            new Timer().schedule(new TimerTask() {
                @Override
                public void run() {
                    //delay for 5 seconds
                    pDialog.dismiss();
                }
            }, 5000);

            return null;
        }

        @Override
        protected void onPostExecute(Void v) {
         // pDialog.dismiss();
        }
    }

Answer 3

在doInBackground中添加pDialog.show();并在onResume中添加new testAsync().execute();

Answer 4

您的代码在Thread.sleep（5000）中正常运行;如果你想添加延迟，那么使用Thread.Sleep（/ time in milisec /）而不是Timer.Schedule。由于Timer.Schedule异步任务在显示任何对话框之前执行得如此之快。

Android：在onCreate（）中调用的AsyncTask中没有显示ProgressDialog

4 个答案: