片段无法还原旋转时正确的视图

Question

I'm using a fragment with two primary views that have setVisibility() to show or hide based on the results of an AsyncTask used to search for data online.

For example, here is the method to switch between Views:

private void switchView()
{
    Log.d(LOG_TAG, "switchView(): show = " + show);
    mListView.setVisibility(show ? View.VISIBLE : View.GONE);
    searchView.setVisibility(show ? View.GONE : View.VISIBLE);
    mCompanyArrayAdapter.notifyDataSetChanged();
}

I'm taking this approach so that when the AsyncTask is complete it can parse the data into wrapper classes and create an ArrayList of these objects for use in the ListView adapter. (If there is another way to pass custom classes to another fragment, I would be open to using that.)

Once result == true from Async it hides the searchView and shows the mListView. However on rotate, the screen returns back to the searchView instead of continuing to display the mListView results.

I'm confused by the Log output that shows what I believe to two calls to onCreateView from the same fragment (DiscoverFragment), seen here:

10-17 10:29:21.872    6603-6603/nz.co.exium.panther D/DiscoverFragment﹕ onCreateView: savedinstancestate is null = false
10-17 10:29:21.877    6603-6603/nz.co.exium.panther D/AbsListView﹕ Get MotionRecognitionManager
10-17 10:29:21.882    6603-6603/nz.co.exium.panther D/DiscoverFragment﹕ onCreateView: savedinstancestate is null = true

So the first shows that the savedInstanceState is found != null and sets the boolean value appropriately but then another onCreateView() is called where savedInstanceState is null and sets it back to false. Why the double onCreateView() after rotate?

Thanks for the help.

As requested, code that replaces the fragments in the MainActivity (using a FrameLayout for the content_frame and position == DrawerLayout position item).:

getFragmentManager().beginTransaction()
                    .replace(R.id.content_frame, Fragment.instantiate(
                            getApplicationContext(), mClasses[position]))
                    .commit();

From my MainActivity.onCreate():

if (savedInstanceState == null) {
        selectItem(0);
    } else if (placeID == null || placeID.isEmpty()) {
        selectItem(savedInstanceState.getInt(SELECTED_KEY));
    }   else    {
        selectItem(2);
    }

I already perform a check for a previous savedInstanceState, if null set the default Fragment. If the variable placeID (from a BroadcastReceiver) is null/empty then restore previous state. Else, go to the Fragment that will display the Notifications data.

Answer 1

Fragments are automatically recreated on rotation as part of restoring the state. Therefore you should only call selectItem() when savedInstanceState == null - otherwise you'll get your restored fragment (with its restored state), then immediately replace it with a brand new instance (without the restored state).

Answer 2

So, what happens here is this:

• Your activity is created, and one fragment is added to it
• You rotate your device
• Your activity gets recreated (along with the fragment previously added), and in onCreate, you add a new fragment, which means you have two fragments added in your activity

the easiest way to deal with this is to perform a check in your activity:

if (savedInstanceState == null){    // add fragment }

the other method is to prevent activity recreation by specifying config changes in your AndroidManifest.xml