Swipe Dismiss

gistfile1.java

import android.animation.ObjectAnimator;
import android.graphics.Rect;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.MotionEvent;
import android.view.View;


public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        // Swipe Image must be a child of parent
        View swipeImage = findViewById(R.id.swipe_image);
        // Swipe parent should be a view that fills the screen giving swipeImage room to animate
        View swipeParent = findViewById(R.id.swipe_parent);
        swipeParent.setOnTouchListener(new SwipeImageTouchListener(swipeImage));
    }

    public static class SwipeImageTouchListener implements View.OnTouchListener{
        private final View swipeView;

        public SwipeImageTouchListener(View swipeView) {
            this.swipeView = swipeView;
        }

        // Allows us to know if we should use MotionEvent.ACTION_MOVE
        private boolean tracking = false;
        // The Position where our touch event started
        private float startY;

        @Override
        public boolean onTouch(View v, MotionEvent event) {
            switch (event.getAction()) {
                case MotionEvent.ACTION_DOWN:
                    Rect hitRect = new Rect();
                    swipeView.getHitRect(hitRect);
                    if (hitRect.contains((int) event.getX(), (int) event.getY())) {
                        tracking = true;
                    }
                    startY = event.getY();
                    return true;
                case MotionEvent.ACTION_UP:
                case MotionEvent.ACTION_CANCEL:
                    tracking = false;
                    animateSwipeView(v.getHeight());
                    return true;
                case MotionEvent.ACTION_MOVE:
                    if (tracking) {
                        swipeView.setTranslationY(event.getY() - startY);
                    }
                    return true;
            }
            return false;
        }

        /**
         * Using the current translation of swipeView decide if it has moved
         * to the point where we want to remove it.
         */
        private void animateSwipeView(int parentHeight) {
            int quarterHeight = parentHeight / 4;
            float currentPosition = swipeView.getTranslationY();
            float animateTo = 0.0f;
            if (currentPosition < -quarterHeight) {
                animateTo = -parentHeight;
            } else if (currentPosition > quarterHeight) {
                animateTo = parentHeight;
            }
            ObjectAnimator.ofFloat(swipeView, "translationY", currentPosition, animateTo)
                    .setDuration(200)
                    .start();
        }
    }
}