Auto-Hide Behaviour for the Design Support Library FloatingActionButton

FloatingActionButtonBehavior.java

import android.content.Context;
import android.support.annotation.NonNull;
import android.support.design.widget.FloatingActionButton;
import android.util.DisplayMetrics;
import android.view.MotionEvent;
import android.view.WindowManager;
import android.view.animation.AccelerateInterpolator;
import android.view.animation.DecelerateInterpolator;

public class FloatingActionButtonBehavior {

    private static final int TOUCH_SLOP = 50;

    private FloatingActionButton mFloatingActionButton;

    private int startY, finalY;
    private int eventY;

    public FloatingActionButtonBehavior(@NonNull FloatingActionButton floatingActionButton) {
        mFloatingActionButton = floatingActionButton;
        init();
    }

    private void init() {

        WindowManager wm = (WindowManager) mFloatingActionButton.getContext()
                .getSystemService(Context.WINDOW_SERVICE);
        DisplayMetrics metrics = new DisplayMetrics();
        wm.getDefaultDisplay().getMetrics(metrics);

        startY = (int) mFloatingActionButton.getY();
        finalY = metrics.heightPixels;

    }

    public void animate(MotionEvent event) {
        switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                eventY = (int)event.getY();
                break;
            case MotionEvent.ACTION_MOVE:
                if (event.getY() - eventY > TOUCH_SLOP) {
                    animateOff();
                } else if (event.getY() + TOUCH_SLOP < eventY) {
                    animateOn();
                }
                break;
        }
    }

    //Could add option to start immediately for API > 14?
    private void animateOn() {
        mFloatingActionButton
                .animate()
                .translationY(finalY)
                .setInterpolator(new AccelerateInterpolator());
    }

    //Could add option to start immediately for API > 14?
    private void animateOff() {
        mFloatingActionButton
                .animate()
                .translationY(startY)
                .setInterpolator(new DecelerateInterpolator());
    }

}

MainActivity.java

/**
 * Sample implementation in Activity class
 */

public class MainActivity extends AppCompatActivity {
  
    private FloatingActionButton mFloatingActionButton;
    private FloatingActionButtonBehavior mFloatingActionButtonBehavior;
    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
      
      mFloatingActionButton = (FloatingActionButton) findViewById(R.id.fab);  
      mFloatingActionButtonBehavior = new FloatingActionButtonBehavior(mFloatingActionButton);
      
    }
    
    @Override
    public boolean dispatchTouchEvent(MotionEvent ev) {
        mFloatingActionButtonBehavior.animate(ev);
        return super.dispatchTouchEvent(ev);
    }
  
}