JNI based show_soft_input

[jancespivo]

Hi,
this PR is trying to solve not showing soft keyboard on Android.

It might solve #44 🤷

I've tested it on Android version 10 and 12 with xilem (main + winit 0.30.4 (with cherrypicked rust-windowing/winit#3993).

rust-windowing/winit#3787 doesn't work for me at all even it can be better approach for some Android versions.

I've intentionally kept hide_soft_input as is, it works.

[podusowski]

I think the main problem with the keyboard not showing up on NativeActivity is its View not being in focus. I have hacked the way through by using something like this:

public class MainActivity extends NativeActivity implements OnApplyWindowInsetsListener {
  View getNativeActivityView() {
    // This is hacky as hell, but NativeActivity does not give any proper way of
    // accessing it.
    ViewGroup parent = (ViewGroup) (getWindow().getDecorView());
    parent = (ViewGroup) parent.getChildAt(0);
    parent = (ViewGroup) parent.getChildAt(1);
    return parent.getChildAt(0);
  }

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    View nativeActivityView = getNativeActivityView();
    nativeActivityView.setFocusable(true);
    nativeActivityView.setFocusableInTouchMode(true);
    nativeActivityView.requestFocus();

    ViewCompat.setOnApplyWindowInsetsListener(nativeActivityView, this);

but ultimately switched to GameActivity anyway because of other issues.