ViewPager的切换动画

自android3.0之后，google提供了viewPager的切换动画。
官方示例地址：http://developer.android.com/training/animation/screen-slide.html

实现方式都已经讲明了

mViewPager.setPageTransformer(true,new ZoomOutPageTransformer());

这里的ZoomOutPageTransformer()是google提供的一种动画，google一共提供了2种动画，DepthPageTransformer() 和ZoomOutPageTransformer()同时也提供了这2中方法的源码

1、DepthPageTransformer()

public class DepthPageTransformer implements ViewPager.PageTransformer {    private static final float MIN_SCALE = 0.75f;    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);        }    }}

对应的效果如图

2、ZoomOutPageTransformer()

public class ZoomOutPageTransformer implements ViewPager.PageTransformer {    private static final float MIN_SCALE = 0.85f;    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);        }    }}

对应效果如下：

3、自定义动画
看了上面2个动画，相信大家也想试试手，入手实现一个自定义的动画呢？
分析一下上面两个代码：
当我们滑动时：打印出ViewPager中存活的每个View以及它们的position的变化~~
position的可能性的值有，其实从官方示例的注释就能看出：

[-Infinity,-1) 已经看不到了

(1,+Infinity] 已经看不到了

[-1,1]

重点看[-1,1]这个区间，其他两个的View都已经看不到了~~

假设现在ViewPager在A页现在滑出B页，则:

A页的position变化就是( 0, -1]

B页的position变化就是[ 1 , 0 ]

知道了我们滑动时position的变化~~那么就开始设计我们的个性的切换效果；

我们设置View的旋转中心为：

ViewHelper.setPivotX(view, view.getMeasuredWidth() * 0.5f);
ViewHelper.setPivotY(view, view.getMeasuredHeight());

依然是ViewPager在A页现在滑出B页

那么A页应当在滑动过程中0度到-20度的偏移，B页应当在滑动过程中+20度到0度的偏移

结合

A页的position变化就是( 0, -1]

B页的position变化就是[ 1 , 0 ]

那么旋转的角度即：mRot = (20 * position); A页 mRot :0 ,~ -20 ; B页 mRot :20 ~ 0 ;

完整代码如下：

public class RotateDownPageTransformer implements ViewPager.PageTransformer {    private static final float ROT_MAX = 20.0f;    private float mRot;    public void transformPage(View view, float position) {        if (position < -1) { // [-Infinity,-1)            // This page is way off-screen to the left.            view.setRotation(0);        } else if (position <= 1){ // a页滑动至b页 ； a页从 0.0 ~ -1 ；b页从1 ~ 0.0            // Modify the default slide transition to shrink the page as well            if (position < 0){//a页从 0.0 ~ -1                mRot = (ROT_MAX * position);                view.setPivotX(view.getMeasuredWidth() * 0.5f);                view.setPivotY(view.getMeasuredHeight());                view.setRotation(mRot);            } else{//b页从1 ~ 0.0                mRot = (ROT_MAX * position);                view.setPivotX(view.getMeasuredWidth() * 0.5f);                view.setPivotY(view.getMeasuredHeight());                view.setRotation(mRot);            }            // Scale the page down (between MIN_SCALE and 1)            // Fade the page relative to its size.        } else { // (1,+Infinity]            // This page is way off-screen to the right.            view.setRotation(0);        }    }

以上参考
http://developer.android.com/training/animation/screen-slide.html
【张鸿洋的博客】

更多相关文章

随机推荐