Android ViewPager - 此设计的平滑过渡

Question

我真的无法计算出为以下设计进行平滑过渡的数学方法。任何帮助将不胜感激:)。

在过渡期间，页面会上下跳动，但我希望它们变得平滑。

设计

过渡

相关ViewPage代码：

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    final ViewPager viewPager = (ViewPager) findViewById(R.id.pager);
    PagerAdapter pagerAdapter = new PagerAdapter(getSupportFragmentManager());
    viewPager.setAdapter(pagerAdapter);
    viewPager.setOffscreenPageLimit(3);
    viewPager.setPageMargin(100);
    viewPager.setPageTransformer(false, new ViewPager.PageTransformer() {
        @Override
        public void transformPage(View page, float position) {
            int pageWidth = viewPager.getMeasuredWidth() - viewPager.getPaddingLeft() - viewPager.getPaddingRight();
            int pageHeight = viewPager.getHeight();
            int paddingLeft = viewPager.getPaddingLeft();
            float transformPos = (float) (page.getLeft() - (viewPager.getScrollX() + paddingLeft)) / pageWidth;

            final float normalizedposition = Math.abs(Math.abs(transformPos) - 1);
            page.setAlpha(normalizedposition + 0.5f);

            if (transformPos < -1) { // [-Infinity,-1)
                // This page is way off-screen to the left.
                page.setTranslationY(0);
            } else if (transformPos <= 1) { // [-1,1]
                page.setTranslationY(-pageHeight / 10);

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


        }
    });

}

注意：'transformPos' 用于解决此错误 - https://code.google.com/p/android/issues/detail?id=64046

我的 ViewPager

<android.support.v4.view.ViewPager
    android:id="@+id/pager"
    android:layout_width="match_parent"
    android:layout_height="260dp"
    android:layout_centerInParent="true"
    android:clipToPadding="false"
    android:paddingLeft="80dp"
    android:paddingRight="80dp"/>

完整来源 - https://github.com/krishnaraj/ViewPagerSample

Answer 1

试试这个

    viewPager.setPageTransformer(false, new ViewPager.PageTransformer() {
        @Override
        public void transformPage(View page, float position) {
            int pageWidth = viewPager.getMeasuredWidth() - viewPager.getPaddingLeft() - viewPager.getPaddingRight();
            int pageHeight = viewPager.getHeight();
            int paddingLeft = viewPager.getPaddingLeft();
            float transformPos = (float) (page.getLeft() - (viewPager.getScrollX() + paddingLeft)) / pageWidth;

            final float normalizedposition = Math.abs(Math.abs(transformPos) - 1);
            page.setAlpha(normalizedposition + 0.5f);

            int max = -pageHeight / 10;

            if (transformPos < -1) { // [-Infinity,-1)
                // This page is way off-screen to the left.
                page.setTranslationY(0);
            } else if (transformPos <= 1) { // [-1,1]
                page.setTranslationY(max * (1-Math.abs(transformPos)));

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


        }
    });

Answer 2

将您的 if 更改为：

float upTranslation = -pageHeight / 10f;
if (transformPos < -1) {// [-Infinity,-1)
    page.setTranslationY(0);
} else if (transformPos < 0) { // [-1,0)
    float translationY = upTranslation * (transformPos + 1f);
    page.setTranslationY(translationY);
} else if (transformPos == 0) { // 0
    page.setTranslationY(upTranslation);
} else if (transformPos <= 1) { // (0,1]
    float translationY = upTranslation * (1f - transformPos);
    page.setTranslationY(translationY);
} else { // (1,+Infinity]
    page.setTranslationY(0);
}

Answer 3

如果你真的不需要pageTransformer，使用下面的代码

    viewPager.setPageTransformer(false, new ViewPager.PageTransformer() {
    @Override
    public void transformPage(View page, float position) {
        if(position==1){

            int pageWidth = viewPager.getMeasuredWidth() - viewPager.getPaddingLeft() - viewPager.getPaddingRight();
            int pageHeight = viewPager.getHeight();
            int paddingLeft = viewPager.getPaddingLeft();
            float transformPos = (float) (page.getLeft() - (viewPager.getScrollX() + paddingLeft)) / pageWidth;

            final float normalizedposition = Math.abs(Math.abs(transformPos) - 1);
            page.setAlpha(normalizedposition + 0.5f);

            if (transformPos < -1) { // [-Infinity,-1)
                // This page is way off-screen to the left.
                page.setTranslationY(0);
            } else if (transformPos <= 1) { // [-1,1]
                page.setTranslationY(-pageHeight / 10);

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

然后再试一次...