ViewPager2 在屏幕第一页和最后一页中查看下一页和居中的一部分

Question

我有一个配置了各种扩展函数的回收器视图，以居中并查看下一项：

fun RecyclerView.pageSnap() = this.post {
    if (this.onFlingListener == null) PagerSnapHelper().attachToRecyclerView(this)
}
fun RecyclerView.snapCenterWithMargin(left: Int, top: Int, right: Int, bottom: Int) {
    val offsetItemDecoration = SnapCenterWithMargin(left, top, right, bottom)
    this.addItemDecoration(offsetItemDecoration)
}
private class SnapCenterWithMargin(
    private val left: Int,
    private val top: Int,
    private val right: Int,
    private val bottom: Int
) : RecyclerView.ItemDecoration() {
    override fun getItemOffsets(outRect: Rect, view: View, parent: RecyclerView, state: RecyclerView.State) {
        view.measure(LinearLayout.LayoutParams.WRAP_CONTENT, LinearLayout.LayoutParams.WRAP_CONTENT)
        val position = parent.getChildAdapterPosition(view)
        val firstItem = 0
        val lastItem = state.itemCount - 1
        when (position) {
            firstItem -> {
                val firstPadding = (parent.width) / 2 - view.measuredWidth / 2
                outRect.set(firstPadding, 0, 0, 0)
            }
            lastItem -> {
                val lastPadding = (parent.width) / 2 - view.measuredWidth / 2
                outRect.set(0, 0, lastPadding, 0)
            }
            else -> {
                outRect.set(left, top, right, bottom)
            }
        }
    }
}

问题是 ListAdapter 动画在这种方法中很糟糕。然后我尝试移动到 ViewPager2，但我无法获得此行为(请参阅下一个屏幕并保持项目居中(。

Answer 1

页面项目的布局：

android:paddingStart="24dp"
android:paddingEnd="24dp"

代码中的查看页面r2：

viewPager2.setClipToPadding(false);
viewPager2.setOffscreenPageLimit(2);
viewPager2.setPageTransformer(new ViewPager2.PageTransformer()
{
    @Override
    public void transformPage(@NonNull View page, float position)
    {
        float offset = (int)ScreenUtils.dpToPx(48) * position;
        page.setTranslationX(-offset);
    }
});