LinearLayout which identifies whether soft keyboard is visible or hidden

DetectSoftKeyboardLinearLayout.java

import android.app.Activity;
import android.content.Context;
import android.graphics.Rect;
import android.util.AttributeSet;
import android.widget.LinearLayout;

/**
 * Created by suraj on 15/6/2016.
 *
 * This linear layout is used to listen to visibility of the soft keyboard.
 * In the onMeasure, based on the height difference between the original rootView and
 * the current rootView, it decides whether keyboard is open or not.
 *
 * This boolean is then sent as a callback to the KeyboardVisibilityListener.
 *
 * The current height difference threshold is kept as 128.
 *
 */
public class DetectSoftKeyboardLinearLayout extends LinearLayout {

    public DetectSoftKeyboardLinearLayout(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public interface KeyboardVisibilityListener {
        void onKeyBoardVisibilityChanged(boolean isVisible);
    }

    private KeyboardVisibilityListener mListener;

    public void addKeyboardVisibilityListener(KeyboardVisibilityListener listener) {
        mListener = listener;
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        int height = MeasureSpec.getSize(heightMeasureSpec);
        Activity activity = (Activity)getContext();
        Rect rect = new Rect();

        activity.getWindow().getDecorView().getWindowVisibleDisplayFrame(rect);

        int statusBarHeight = rect.top;
        int screenHeight = activity.getWindowManager().getDefaultDisplay().getHeight();
        int diff = (screenHeight - statusBarHeight) - height;

        if (mListener != null) {
            mListener.onKeyBoardVisibilityChanged(diff>128); // assume all soft keyboards are at least 128 pixels high
        }
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
    }

    public boolean isKeyboardVisibilityListenerAdded() {
        return mListener != null;
    }
}