ZoomOutPageTransformer.java

package com.fanxin.huangfangyi.main.widget.custom;

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

/**
 * Created by Mr_immortalZ on 2016/5/2.
 * email : mr_immortalz@qq.com
 */
public class ZoomOutPageTransformer implements ViewPager.PageTransformer {
    private static final float MIN_SCALE = 0.70f;
    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(MIN_ALPHA);
            view.setScaleX(MIN_SCALE);
            view.setScaleY(MIN_SCALE);
        } 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);
                view.setScaleX(1 + 0.3f * position);
                view.setScaleY(1 + 0.3f * position);
            } else {
                view.setTranslationX(-horzMargin + vertMargin / 2);

                view.setScaleX(1 - 0.3f * position);
                view.setScaleY(1 - 0.3f * position);
            }

            // Scale the page down (between MIN_SCALE and 1)

            // 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.setScaleX(MIN_SCALE);
            view.setScaleY(MIN_SCALE);
            view.setAlpha(MIN_ALPHA);
        }
    }
}