Yes. I am pretty sorry for my carelessness when extracting the related code
snippets.
new MyAsyncTask.execute() should be new MyAsyncTask(this).execute().
As for the MyAsyncTask:
public class MyAsyncTask extends AsyncTask<Void,Void,Void>{ //do network
operation
private Fragment*A* fragment;
public MyAsyncTask(Fragment*A* fragmentA){
fragment = fragmentA;
}
If there is any mistake, please feel free to correct me.
Piren於 2013年9月15日星期日UTC+8下午8時08分31秒寫道：
> and did you use that constructor? because the code snippet shows you've
> used the default constructor
>
> On Sunday, September 15, 2013 1:52:22 PM UTC+3, Greenhand wrote:
>>
>> Thanks for pointing out the mistakes. The whole code is too long to post
>> and maintain readability so I just put some snippet. The "MyAsyncTask
>> having a constructor named GetTokenAsyncTask" is a typo, the constructor
>> should named MyAsyncTask.
>> As for ProgressFragment, I use its toString() method to check using
>> Log.d(). They are the same across rotation.
>>
>>
>>
>> 2013/9/15 Piren <[email protected]>
>>
>>> It's hard to follow your code since it seems some of it is incorrect
>>> (like MyAsyncTask having a constructor named GetTokenAsyncTask) and some
>>> of it is missing...
>>> Either way you should verify you actually used that constructor (in the
>>> current code you don't, so the member "fragment" is null).Either case, you
>>> should also verify that the proper ProgressFragment is being set during
>>> onAttach of FragmentA since i assume a new one will be created after
>>> rotation (though i'm not sure about that).
>>>
>>> Since this isn't that much code, you should probably just find a
>>> tutorial on how to do that (there's a lot of those online) and start from
>>> scratch (just so you wouldn't miss something)
>>>
>>> On Sunday, September 15, 2013 1:30:20 PM UTC+3, Greenhand wrote:
>>>>
>>>> I use appcompat library to host some fragments for tabs. In a specific
>>>> fragment A, I need to do network operation. In order not to block the UI
>>>> thread, I use an AsyncTask and do the network operation in
>>>> doInBackGround().
>>>>
>>>> To prevent messing around keep AsyncTask to survive rotation in the
>>>> fragment, I call setRetainInstance(true) in the fragment A oncreate().
>>>>
>>>> It works fine but I need to prompt user something when the network
>>>> operation is in progress. Therefore, I use DialogFragment. In the
>>>> DialogFragment onCreateView(), it instantiates a ProgressDialog and
>>>> returns.
>>>>
>>>> To be concrete, the following is the code snippets of FragmentA,
>>>> MyDialogFragment and AsyncTask :
>>>> public class FragmentA extends Fragment{ //as tab for actionbar
>>>> (appcompat)
>>>> private boolean isNetworkOperationCalled;
>>>> private MyDialogFragment myDialogFragment;
>>>> ...
>>>> public void showProgressDialog(){ //for MyAsyncTask#onPreExecute()
>>>> myDialogFragment = new MyDialogFragment();
>>>> myDialogFragment.show(**getFragmentManager(), "mydialog");
>>>> }
>>>> public void showProgressDialog(){ //for MyAsyncTask#onPostExecute()
>>>> myDialogFragment.dismiss();
>>>> }
>>>> public void onResume() {
>>>> if(!**isNetworkOperationCalled){
>>>> isNetworkOperationCalled=true;
>>>> new MyAsyncTask.execute();//do the network operation
>>>> }
>>>> }
>>>> ...
>>>> }
>>>>
>>>>
>>>> public class MyDialogFragment extends DialogFragment{ //ProgressDialog
>>>> for FragmentA
>>>> ...
>>>> public Dialog onCreateDialog(Bundle savedInstanceState) {
>>>> ProgressDialog progressDialog = new ProgressDialog(getActivity(),**
>>>> ProgressDialog.STYLE_SPINNER);
>>>> ... //set the dialog attributes
>>>> return progressDialog;
>>>> }
>>>> ...
>>>> }
>>>> public class MyAsyncTask extends AsyncTask<Void,Void,Void>{ //do
>>>> network operation
>>>> private Fragment fragment;
>>>>
>>>> public GetTokenAsyncTask(Fragment fragmentA){
>>>> fragment = fragmentA;
>>>> }
>>>> protected void onPreExecute() {
>>>> fragment.showProgressDialog(**); //show progess dialog for users
>>>> }
>>>> protected String doInBackground(Void... arg0) {
>>>> ...
>>>> }
>>>> protected void onPostExecute() { //dismiss the dialog
>>>> fragment.**dismissProgressDialog();
>>>> }
>>>> }
>>>> In a nutshell, fragment A triggers AsyncTask and AsyncTask call methods
>>>> of FragmentA to show/dismiss dialog. Fragment A use MyDialogFragment to
>>>> show the progress dialog.
>>>>
>>>> The code (method) above works if there is no rotataion occurs while
>>>> doInBackground() is executing. Nevertheless, if the rotation happens
>>>> before
>>>> onPostExecute() is called,
>>>> the rotation is fine and the progress dialog is retained. Sadly, it
>>>> crashes when onPostExecute() finally be called when dismissing the dialog.
>>>>
>>>> E/AndroidRuntime(27493): FATAL EXCEPTION: main
>>>> E/AndroidRuntime(27493): java.lang.NullPointerException
>>>> E/AndroidRuntime(27493): at android.support.v4.app.**DialogFragment.**
>>>> dismissInternal(**DialogFragment.java:184)
>>>> E/AndroidRuntime(27493): at android.support.v4.app.**
>>>> DialogFragment.dismiss(**DialogFragment.java:155)
>>>> E/AndroidRuntime(27493): at com.example.FragmentA.**
>>>> dismissProgressDialog(**FragmentA.java:105)
>>>> E/AndroidRuntime(27493): at com.example.FragmentA.access$**
>>>> 1(FragmentA.java:103)
>>>> E/AndroidRuntime(27493): at com.example.FragmentA$**GetTokenAsyncTask.
>>>> **onPostExecute(FragmentA.java:**40)
>>>> E/AndroidRuntime(27493): at com.example.FragmentA$**GetTokenAsyncTask.
>>>> **onPostExecute(FragmentA.java:**1)
>>>> E/AndroidRuntime(27493): at android.os.AsyncTask.finish(**
>>>> AsyncTask.java:631)
>>>> E/AndroidRuntime(27493): at android.os.AsyncTask.access$**
>>>> 600(AsyncTask.java:177)
>>>> E/AndroidRuntime(27493): at android.os.AsyncTask$**
>>>> InternalHandler.handleMessage(**AsyncTask.java:644)
>>>> E/AndroidRuntime(27493): at android.os.Handler.**
>>>> dispatchMessage(Handler.java:**99)
>>>> E/AndroidRuntime(27493): at android.os.Looper.loop(Looper.**java:137)
>>>> E/AndroidRuntime(27493): at android.app.ActivityThread.**
>>>> main(ActivityThread.java:4875)
>>>> E/AndroidRuntime(27493): at
>>>> java.lang.reflect.Method.**invokeNative(Native
>>>> Method)
>>>> E/AndroidRuntime(27493): at java.lang.reflect.Method.**
>>>> invoke(Method.java:511)
>>>> E/AndroidRuntime(27493): at com.android.internal.os.**ZygoteInit$**
>>>> MethodAndArgsCaller.run(**ZygoteInit.java:804)
>>>> E/AndroidRuntime(27493): at com.android.internal.os.**
>>>> ZygoteInit.main(ZygoteInit.**java:571)
>>>> E/AndroidRuntime(27493): at dalvik.system.NativeStart.**main(Native
>>>> Method)
>>>>
>>>> How can I solve the problem so that the dialog can dismiss correctly
>>>> after rotation?
>>>>
>>>
>>>
>>>
>>
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