PageTransformer转换中的ViewPager边距

Question

我有一个ViewPager,其中每个视图都代表卡片上的卡片.每张卡片使用ViewPager边距在边框上有阴影:

cardsViewPager.setPageMargin(getResources().getDisplayMetrics().widthPixels / 20);
cardsViewPager.setPageMarginDrawable(R.drawable.shadow);

它按预期工作.

但是,如果我添加一个PageTransformer,以便右侧的卡片堆叠在左侧的卡片上:

public class ScalePageTransformer implements PageTransformer {  
    private final ViewPager mViewPager;

    public ScalePageTransformer(ViewPager viewPager) {
        this.mViewPager = viewPager;
    }

    @Override
    public void transformPage(View page, float position) {
        if (position <= 0) {
            int pageWidth = mViewPager.getWidth();
            final float translateValue = position * -pageWidth;
            if (translateValue > -pageWidth) {
                page.setTranslationX(translateValue);
            } else {
                page.setTranslationX(0);
            }
        }
    }
}

我是这样做的:

cardsViewPager.setPageTransformer(false, new ScalePageTransformer(cardsViewPager));

但现在,保证金没有出现.如果我在PageTransformer上有缩小效果,我可以看到当前卡缩小的时间,可绘制的边距低于屏幕上的当前卡.这是一张描述正在发生的事情的图片:

红卡顶部正在从右向左滑动蓝卡.由于红牌有一个比例变换,我们可以看到它背后的黑色可绘制.

有没有办法强制将保证金绘制在红牌之上？这不应该是默认行为吗？

Answer 1

尝试使用此代码进行视图页面的转换阶段：

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);
    }
}

希望这可以帮助...