Handle Fragment duplication on Screen Rotate (with sample code)

Question

There are some similar answers, but not to this situation. My situation is simple. I have an Activity with two different layouts, one in Portrait, another in Landscape. In Portrait, i use `` and add `Fragment` into it dynamically. In Landscape, i use `` so the `Fragment` is static. (in fact this doesn't matter) It first starts in Portrait, then i added the `Fragment` by simply: ``` ListFrag listFrag = new ListFrag(); getSupportFragmentManager().beginTransaction() .replace(R.id.FragmentContainer, listFrag).commit(); ``` where `ListFrag extends ListFragment`. Then i do a screen rotate. I found the listFrag is re-creating in the Landscape mode. (In which i noticed the `onCreate()` method is called again with a non-null Bundle) i tried to use `setRetainInstance(false)` like @NPike said in this post. But the `getRetainInstance()` is already `false` by default. It does not do what i expected as the docs said. Could anyone please explain? The fragment i am dealing with…

Accepted Answer

I finally come up with a solution to prevent unwanted Fragment re-creating upon the Activity re-creates. It is like what i mentioned in the question:

The only neat way i found is doing `getSupportFragmentManager().beginTransaction().remove(getSupportFragmentManager().findFragmentById(R.id.FragmentContainer)).commit();` in `onSaveInstanceState()`. But it will raise another problems...

... with some improvements.

In `onSaveInstanceState()`:

```
@Override
protected void onSaveInstanceState(Bundle outState) {
    if (isPortrait2Landscape()) {
        remove_fragments();
    }
    super.onSaveInstanceState(outState);
}

private boolean isPortrait2Landscape() {
    return isDevicePortrait() && (getResources().getConfiguration().orientation == Configuration.ORIENTATION_LANDSCAPE);
}
```

and the `isDevicePortrait()` would be like:

```
private boolean isDevicePortrait() {
    return (findViewById(R.id.A_View_Only_In_Portrait) != null);
}
```

*Notice that we cannot use `getResources().getConfiguration().orientation` to determine if the device is currently literally Portrait. It is because the `Resources` object is changed RIGHT AFTER the screen rotates - EVEN BEFORE `onSaveInstanceState()` is called!!

If we do not want to use `findViewById()` to test orientation (for any reasons, and it's not so neat afterall), keep a global variable `private int current_orientation;` and initialise it by `current_orientation = getResources().getConfiguration().orientation;` in `onCreate()`. This seems neater. But we should be aware not to change it anywhere during the Activity lifecycle.

*Be sure we `remove_fragments()` before `super.onSaveInstanceState()`.

(Because in my case, i remove the Fragments from the Layout, and from the Activity. If it is after `super.onSaveInstanceState()`, the Layout will already be saved into the Bundle. Then the Fragments will also be re-created after the Activity re-creates. ###)

### I have proved this phenomenon. But the reason of What to determine a Fragment restore upon Activity re-create? is just by my guess. If you have any ideas about it, please answer my another question.

Handle Fragment duplication on Screen Rotate (with sample code)

Solution

Problem

Related problems