使用新 ViewPager2 的解决方案
现在您应该考虑使用ViewPager2，它“取代了 ViewPager，解决了其前身的大部分痛点”：
- 基于 RecyclerView
- 支持 RTL（从右到左）布局
- 垂直方向支持
- 可靠的 Fragment 支持（包括处理对底层 Fragment 集合的更改）
- 数据集更改动画（包括
DiffUtil 支持）
结果
代码
在您的 Activity/Fragment 中，设置 ViewPager2：
// MyRecyclerViewAdapter is an standard RecyclerView.Adapter :)
viewPager2.adapter = MyRecyclerViewAdapter()
// You need to retain one page on each side so that the next and previous items are visible
viewPager2.offscreenPageLimit = 1
// Add a PageTransformer that translates the next and previous items horizontally
// towards the center of the screen, which makes them visible
val nextItemVisiblePx = resources.getDimension(R.dimen.viewpager_next_item_visible)
val currentItemHorizontalMarginPx = resources.getDimension(R.dimen.viewpager_current_item_horizontal_margin)
val pageTranslationX = nextItemVisiblePx + currentItemHorizontalMarginPx
val pageTransformer = ViewPager2.PageTransformer { page: View, position: Float ->
page.translationX = -pageTranslationX * position
// Next line scales the item's height. You can remove it if you don't want this effect
page.scaleY = 1 - (0.25f * abs(position))
// If you want a fading effect uncomment the next line:
// page.alpha = 0.25f + (1 - abs(position))
}
viewPager2.setPageTransformer(pageTransformer)
// The ItemDecoration gives the current (centered) item horizontal margin so that
// it doesn't occupy the whole screen width. Without it the items overlap
val itemDecoration = HorizontalMarginItemDecoration(
context,
R.dimen.viewpager_current_item_horizontal_margin
)
viewPager2.addItemDecoration(itemDecoration)
添加HorizontalMarginItemDecoration，这是一个微不足道的ItemDecoration：
/**
* Adds margin to the left and right sides of the RecyclerView item.
* Adapted from https://stackoverflow.com/a/27664023/4034572
* @param horizontalMarginInDp the margin resource, in dp.
*/
class HorizontalMarginItemDecoration(context: Context, @DimenRes horizontalMarginInDp: Int) :
RecyclerView.ItemDecoration() {
private val horizontalMarginInPx: Int =
context.resources.getDimension(horizontalMarginInDp).toInt()
override fun getItemOffsets(
outRect: Rect, view: View, parent: RecyclerView, state: RecyclerView.State
) {
outRect.right = horizontalMarginInPx
outRect.left = horizontalMarginInPx
}
}
添加控制上一个/下一个项目的可见程度以及当前项目水平边距的尺寸：
<dimen name="viewpager_next_item_visible">26dp</dimen>
<dimen name="viewpager_current_item_horizontal_margin">42dp</dimen>
最后将ViewPager2 添加到您的布局中：
<androidx.viewpager2.widget.ViewPager2
android:id="@+id/viewPager"
android:layout_width="match_parent"
android:layout_height="wrap_content" />
一件重要的事情：ViewPager2 项目必须有 layout_height="match_parent"（否则它会引发 IllegalStateException），因此您应该执行以下操作：
<androidx.cardview.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent" <-- this!
app:cardCornerRadius="8dp"
app:cardUseCompatPadding="true">
<androidx.constraintlayout.widget.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="280dp">
<!-- ... -->
</androidx.constraintlayout.widget.ConstraintLayout>
</androidx.cardview.widget.CardView>
PageTransformer 示例
Google 在 ViewPager2 上添加了一个指南，其中包含 2 个 PageTransformer 实现，您可以将其用作灵感：https://developer.android.com/training/animation/screen-slide-2
关于新的 ViewPager2