android - 如何创建具有上一页和下一页预览的 ViewPager，并从预览中缩放居中

Question

viewPager.setClipToPadding(false);
viewPagerMusicCategory.setPadding(width/3, 0, width /3, 0);
viewPagerMusicCategory.setPageMargin(40));

我通过上面的代码得到了下一个和上一个预览。但现在我需要居中页面的缩放效果。

提前致谢

Answer 1

viewPagerMusicCategory.setPageTransformer(false, new ViewPager.PageTransformer() {
        @Override
        public void transformPage(View page, float position) {
            Log.e("pos",new Gson().toJson(position));
            if (position < -1) {
                page.setScaleY(0.7f);
                page.setAlpha(1);
            } else if (position <= 1) {
                float scaleFactor = Math.max(0.7f, 1 - Math.abs(position - 0.14285715f));
                page.setScaleX(scaleFactor);
                Log.e("scale",new Gson().toJson(scaleFactor));
                page.setScaleY(scaleFactor);
                page.setAlpha(scaleFactor);
            } else {
                page.setScaleY(0.7f);
                page.setAlpha(1);
            }
        }
    }
);

……

Answer 2

使用它recyclerview并使用 snap helper

public class CenterZoomLayoutManager extends LinearLayoutManager {

    private final float mShrinkAmount = 0.15f;
    private final float mShrinkDistance = 0.9f;

    public CenterZoomLayoutManager(Context context) {
        super(context);
    }

    public CenterZoomLayoutManager(Context context, int orientation, boolean reverseLayout) {
        super(context, orientation, reverseLayout);
    }


    @Override
    public int scrollVerticallyBy(int dy, RecyclerView.Recycler recycler, RecyclerView.State state) {
        int orientation = getOrientation();
        if (orientation == VERTICAL) {
            int scrolled = super.scrollVerticallyBy(dy, recycler, state);
            float midpoint = getHeight() / 2.f;
            float d0 = 0.f;
            float d1 = mShrinkDistance * midpoint;
            float s0 = 1.f;
            float s1 = 1.f - mShrinkAmount;
            for (int i = 0; i < getChildCount(); i++) {
                View child = getChildAt(i);
                float childMidpoint =
                        (getDecoratedBottom(child) + getDecoratedTop(child)) / 2.f;
                float d = Math.min(d1, Math.abs(midpoint - childMidpoint));
                float scale = s0 + (s1 - s0) * (d - d0) / (d1 - d0);
                child.setScaleX(scale);
                child.setScaleY(scale);
            }
            return scrolled;
        } else {
            return 0;
        }
    }

    @Override
    public int scrollHorizontallyBy(int dx, RecyclerView.Recycler recycler, RecyclerView.State state) {
        int orientation = getOrientation();
        if (orientation == HORIZONTAL) {
            int scrolled = super.scrollHorizontallyBy(dx, recycler, state);

            float midpoint = getWidth() / 2.f;
            float d0 = 0.f;
            float d1 = mShrinkDistance * midpoint;
            float s0 = 1.f;
            float s1 = 1.f - mShrinkAmount;
            for (int i = 0; i < getChildCount(); i++) {
                View child = getChildAt(i);
                float childMidpoint =
                        (getDecoratedRight(child) + getDecoratedLeft(child)) / 2.f;
                float d = Math.min(d1, Math.abs(midpoint - childMidpoint));
                float scale = s0 + (s1 - s0) * (d - d0) / (d1 - d0);
                child.setScaleX(scale);
                child.setScaleY(scale);
            }
            return scrolled;
        } else {
            return 0;
        }

    }
}

使用它recyclerview并使用 snap helper

recyclerView.setAdapter(mAdapter);
CenterZoomLayoutManager layoutManager = new CenterZoomLayoutManager(getContext(), LinearLayoutManager.HORIZONTAL, false);

recyclerView.setLayoutManager(layoutManager);
        new LinearSnapHelper().attachToRecyclerView(recyclerView);

recyclerView.setScrollingTouchSlop(  recyclerView.TOUCH_SLOP_PAGING);