if (viewPager == null)
{
// Initializing view pager
viewPager = (ViewPager) findViewById(R.id.vpLookBook);
// Disable clip to padding
viewPager.setClipToPadding(false);
// set padding manually, the more you set the padding the more you see of prev & next page
viewPager.setPadding(40, 0, 40, 0);
// sets a margin b/w individual pages to ensure that there is a gap b/w them
viewPager.setPageMargin(20);
}
mPager.setClipToPadding(false);
DisplayMetrics displayMetrics = new DisplayMetrics();
self.getWindowManager().getDefaultDisplay().getMetrics(displayMetrics);
int width = displayMetrics.widthPixels;
int paddingToSet = width/4; //set this ratio according to how much of the next and previos screen you want to show.
mPager.setPadding(paddingToSet,0,paddingToSet,0);
// 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)
/**
* 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
}
}
newsHomeViewPager.apply {
clipToPadding = false // allow full width shown with padding
clipChildren = false // allow left/right item is not clipped
offscreenPageLimit = 2 // make sure left/right item is rendered
}
//increase this offset to show more of left/right
val offsetPx =
resources.getDimension(R.dimen.dp_30).toInt().dpToPx(resources.displayMetrics)
newsHomeViewPager.setPadding(0, 0, offsetPx, 0)
//increase this offset to increase distance between 2 items
val pageMarginPx =
resources.getDimension(R.dimen.dp_5).toInt().dpToPx(resources.displayMetrics)
val marginTransformer = MarginPageTransformer(pageMarginPx)
newsHomeViewPager.setPageTransformer(marginTransformer)
Dp 到像素函数:
Fun Int.dpToPx (displayMetrics: DisplayMetrics) : Int = (this * displayMetrics.password) . toInt ()
fun ViewPager2.showHorizontalPreview(offsetDpLeft : Int, offsetDpRight : Int, marginBtwItems : Int){
this.apply {
clipToPadding = false // allow full width shown with padding
clipChildren = false // allow left/right item is not clipped
offscreenPageLimit = 2 // make sure left/right item is rendered
}
// increase this offset to show more of left/right
val offsetPxLeft = offsetDpLeft.toPx()
val offsetPxRight = offsetDpRight.toPx()
this.setPadding(offsetPxLeft, 0, offsetPxRight, 0)
// increase this offset to increase distance between 2 items
val pageMarginPx = marginBtwItems.toPx()
val marginTransformer = MarginPageTransformer(pageMarginPx)
this.setPageTransformer(marginTransformer)
}