Android Keyboard Open or Close helper

Keyboardhelper.java

import android.annotation.TargetApi;
import android.content.Context;
import android.graphics.Rect;
import android.os.Build;
import android.util.DisplayMetrics;
import android.view.View;
import android.view.ViewTreeObserver;
import android.view.WindowManager;

import static android.os.Build.VERSION.SDK_INT;
import static android.os.Build.VERSION_CODES.JELLY_BEAN;

public class Keyboardhelper {

    private final int MIN_KEYBOARD_HEIGHT = 100;
    private int keyboardHeight = 0;
    private KeyBoardListener mKeyBoardListener;
    private View refView;
    private Context mContext;


    public Keyboardhelper(View rootView , KeyBoardListener l){
        this.refView = rootView;
        this.mContext = rootView.getContext();
        this.mKeyBoardListener = l;
        this.refView.getViewTreeObserver().addOnGlobalLayoutListener(onGlobalLayoutListener);
    }

    public void dismiss(){
        AppLog.d("dismiss removeOnGlobalLayoutListener " + refView + " ," + onGlobalLayoutListener);
        if(refView != null && onGlobalLayoutListener != null) {
            removeOnGlobalLayoutListener(refView, onGlobalLayoutListener);
        }
    }

    public interface KeyBoardListener{
        void onClosed();
        void onOpened();
    }

    @TargetApi(JELLY_BEAN)
    void removeOnGlobalLayoutListener(final View v, final ViewTreeObserver.OnGlobalLayoutListener listener) {
        if (SDK_INT < JELLY_BEAN) {
            //noinspection deprecation
            v.getViewTreeObserver().removeGlobalOnLayoutListener(listener);
        } else {
            v.getViewTreeObserver().removeOnGlobalLayoutListener(listener);
        }
    }

    int getUsableScreenHeight() {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR1) {
            final DisplayMetrics metrics = new DisplayMetrics();

            final WindowManager windowManager = (WindowManager) mContext.getSystemService(Context.WINDOW_SERVICE);
            windowManager.getDefaultDisplay().getMetrics(metrics);

            return metrics.heightPixels;
        } else {
            return refView.getRootView().getHeight();
        }
    }

    private final ViewTreeObserver.OnGlobalLayoutListener onGlobalLayoutListener =
            new ViewTreeObserver.OnGlobalLayoutListener() {

                private final Rect rect = new Rect();
                private boolean isKeyboardOpen;

                @Override public void onGlobalLayout() {

                    refView.getWindowVisibleDisplayFrame(rect);

                    int keyboardHeight = getUsableScreenHeight() - (rect.bottom - rect.top);

                    boolean isOpen = keyboardHeight > MIN_KEYBOARD_HEIGHT;

                    if (isOpen == isKeyboardOpen) {
                        return;
                    }

                    isKeyboardOpen = isOpen;

                    if(mKeyBoardListener != null){
                        if(isKeyboardOpen)
                            mKeyBoardListener.onOpened();
                        else
                            mKeyBoardListener.onClosed();
                    }

                }
            };
}