Detect Hide Keyboard Event on Android

So I need to keep the immersive mode of an app. The app has a fullscreen webview on immersive mode but the problem is the webview content has a textbox. When the user touch on the textbox, it will trigger the softkeyboard which will disable the immersive mode. I solved the problem when textbox lost its focus, it will trigger a javascriptinterface to reactivated immersive mode again. But the problem is the hide/back button when the softkeyboard is shown.

here is the image

I tried onKeyDown, dispatchKeyEvent and onBackPressed but none of them was triggering when debugging.

For getting visibility of soft keyboard, you have to do this :

contentView.getViewTreeObserver().addOnGlobalLayoutListener(new 
ViewTreeObserver.OnGlobalLayoutListener() {
@Override
public void onGlobalLayout() {

Rect r = new Rect();
contentView.getWindowVisibleDisplayFrame(r);
int screenHeight = contentView.getRootView().getHeight();

int keypadHeight = screenHeight - r.bottom;
if (keypadHeight > screenHeight * 0.15) {
    // keyboard is opened
}
else {
    // keyboard is closed
    }
}
});

Happy coding!!