package com.wasu.cs.anim;

import android.support.v4.view.ViewPager;
import android.view.View;

/**
 * Created by chenming on 2016/8/4.
 *
 * @author chenming
 * @Description: viewpager收缩并褪色切换动画
 * @email chenming@wasu.com
 * @date 2016/8/4 13:27
 */

public class ZoomOutPageTransformer implements ViewPager.PageTransformer {
	private static final float MIN_SCALE = 0.8f;
	private static final float MIN_ALPHA = 0.5f;

	public void transformPage(View view, float position) {
		int pageWidth = view.getWidth();
		int pageHeight = view.getHeight();

		if (position < -1) { // [-Infinity,-1)
			// This page is way off-screen to the left.
			view.setAlpha(0);

		} else if (position <= 1) { // [-1,1]
			// Modify the default slide transition to shrink the page as well
			float scaleFactor = Math.max(MIN_SCALE, 1 - Math.abs(position));
			float vertMargin = pageHeight * (1 - scaleFactor) / 2;
			float horzMargin = pageWidth * (1 - scaleFactor) / 2;
			if (position < 0) {
				view.setTranslationX(horzMargin - vertMargin / 2);
			} else {
				view.setTranslationX(-horzMargin + vertMargin / 2);
			}

			// Scale the page down (between MIN_SCALE and 1)
			view.setScaleX(scaleFactor);
			view.setScaleY(scaleFactor);

			// Fade the page relative to its size.
			view.setAlpha(MIN_ALPHA +
					(scaleFactor - MIN_SCALE) /
							(1 - MIN_SCALE) * (1 - MIN_ALPHA));

		} else { // (1,+Infinity]
			// This page is way off-screen to the right.
			view.setAlpha(0);
		}
	}
}
