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  • Android -- ViewPager切换动画,PageTransformer

    transformPage(View view, float position)                                         

    view就是滑动中的那个view,position这里是float类型,是当前滑动状态的一个表示,比如当滑动到正全屏时,position是0,如果前一页和下一页基本各在屏幕占一半时,前一页的position是-0.5,后一页的posiotn是0.5(是-0.5还是0.5要看当前的view是前面那一页的view还是后面那一页的),所以根据position的值我们就可以自行设置需要的alpha,x/y信息,就是可以用setAlpha()、setTranslationX()或setSaleY()来自定义切换动画。

    Google官方提供动画效果                                                            

    public class DepthPageTransformer implements PageTransformer {
        private static float MIN_SCALE = 0.75f;
     
        @SuppressLint("NewApi")
        @Override
        public void transformPage(View view, float position) {
            int pageWidth = view.getWidth();
            if (position < -1) { // [-Infinity,-1)
                                    // This page is way off-screen to the left.
                view.setAlpha(0);
            } else if (position <= 0) { // [-1,0]
                                        // Use the default slide transition when
                                        // moving to the left page
                view.setAlpha(1);
                view.setTranslationX(0);
                view.setScaleX(1);
                view.setScaleY(1);
            } else if (position <= 1) { // (0,1]
                                        // Fade the page out.
                view.setAlpha(1 - position);
                // Counteract the default slide transition
                view.setTranslationX(pageWidth * -position);
                // Scale the page down (between MIN_SCALE and 1)
                float scaleFactor = MIN_SCALE + (1 - MIN_SCALE)
                        * (1 - Math.abs(position));
                view.setScaleX(scaleFactor);
                view.setScaleY(scaleFactor);
            } else { // (1,+Infinity]
                        // This page is way off-screen to the right.
                view.setAlpha(0);
             }
        }
    }
    public class ZoomOutPageTransformer implements PageTransformer {
        private static float MIN_SCALE = 0.85f;
     
        private static float MIN_ALPHA = 0.5f;
     
        @Override
        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);
            }
        }

    使用                                                                                   

    ViewPager mPager = (ViewPager) findViewById(R.id.pager);  
    mPager.setPageTransformer(true, new DepthPageTransformer());

    我是天王盖地虎的分割线                                                             

    viewpager系列:

    viewpager背景图渐变效果:Android -- ViewPager滑动背景渐变

    viewpager+fragment:Android -- ViewPager、Fragment、状态保存、通信

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  • 原文地址:https://www.cnblogs.com/yydcdut/p/4179217.html
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