Have you tried this?
you can override the back button on activity
@Override
public void onBackPressed() {
super.onBackPressed();
}
UPDATE
@Override
public void onConfigurationChanged(Configuration newConfig) {
super.onConfigurationChanged(newConfig);
// Checks whether a hardware keyboard is available
if (newConfig.hardKeyboardHidden == Configuration.HARDKEYBOARDHIDDEN_NO) {
Toast.makeText(this, "keyboard visible", Toast.LENGTH_SHORT).show();
} else if (newConfig.hardKeyboardHidden == Configuration.HARDKEYBOARDHIDDEN_YES) {
Toast.makeText(this, "keyboard hidden", Toast.LENGTH_SHORT).show();
}
}