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());
