feat(banner): 배너 시각 정렬을 보완한다

app/src/main/java/kr/co/vividnext/sodalive/v2/widget/banner/BannerView.kt

@@ -38,6 +38,7 @@ class BannerView @JvmOverloads constructor(
     private var currentAdapterPosition: Int = 0
     private var itemSpacingPx: Int = 0
     private var spacingDecoration: RecyclerView.ItemDecoration? = null
+    private var shouldAlignCurrentPositionAfterLayout = false
     private val autoScrollHandler = Handler(Looper.getMainLooper())
     private val autoScrollRunnable = Runnable { moveToNextBanner() }
     private var hasWindowAttachmentForAutoScroll = false
@@ -116,6 +117,7 @@ class BannerView @JvmOverloads constructor(
     fun setItems(items: List<BannerItem>) {
         this.items = items
         currentIndex = 0
+        shouldAlignCurrentPositionAfterLayout = true
         visibility = if (items.isEmpty()) GONE else VISIBLE
         stopAutoScroll()
         adapter.submitItems(items)
@@ -179,6 +181,15 @@ class BannerView @JvmOverloads constructor(
             spacingDecoration?.let(::removeItemDecoration)
             spacingDecoration = BannerSpacingDecoration(itemSpacingPx).also(::addItemDecoration)
         }
+        counterContainer?.let { counter ->
+            val params = counter.layoutParams as? LayoutParams ?: return@let
+            params.marginEnd = (size.sideInsetDp + COUNTER_ITEM_MARGIN_DP).dpToPx()
+            counter.layoutParams = params
+        }
+        if (shouldAlignCurrentPositionAfterLayout) {
+            scrollToCurrentBanner()
+            shouldAlignCurrentPositionAfterLayout = false
+        }
     }
 
     private fun scrollToCurrentBanner() {
@@ -188,8 +199,16 @@ class BannerView @JvmOverloads constructor(
         } else {
             currentIndex
         }
+        val layoutManager = recyclerView.layoutManager as? LinearLayoutManager
+        if (items.size > 1 && layoutManager != null) {
+            layoutManager.scrollToPositionWithOffset(
+                currentAdapterPosition,
+                -(itemSpacingPx / 2)
+            )
+        } else {
             recyclerView.scrollToPosition(currentAdapterPosition)
         }
+    }
 
     private fun moveToNextBanner() {
         if (BannerState.from(items.size, currentIndex).displayMode != BannerDisplayMode.Carousel) return
@@ -263,6 +282,7 @@ class BannerView @JvmOverloads constructor(
     companion object {
         private const val AUTO_SCROLL_INTERVAL_MS = 5_000L
         private const val SCROLL_ANIMATION_DURATION_MS = 350
+        private const val COUNTER_ITEM_MARGIN_DP = 14
 
         fun scrollAnimationDurationMsForTest(): Int = SCROLL_ANIMATION_DURATION_MS
     }
@@ -280,7 +300,9 @@ class BannerView @JvmOverloads constructor(
             parent: RecyclerView,
             state: RecyclerView.State
         ) {
-            outRect.right = spacingPx
+            val leftSpacing = spacingPx / 2
+            outRect.left = leftSpacing
+            outRect.right = spacingPx - leftSpacing
         }
     }
 }

app/src/test/java/kr/co/vividnext/sodalive/v2/widget/banner/BannerViewTest.kt

@@ -173,11 +173,63 @@ class BannerViewTest {
 
         assertEquals(20.dpToPx(), recyclerView.paddingLeft)
         assertEquals(20.dpToPx(), recyclerView.paddingRight)
-        assertEquals(8.dpToPx(), itemOffset.right)
+        assertEquals(4.dpToPx(), itemOffset.left)
+        assertEquals(4.dpToPx(), itemOffset.right)
+        assertEquals(8.dpToPx(), itemOffset.left + itemOffset.right)
         assertEquals(362.dpToPx(), holder.itemView.layoutParams.width)
         assertEquals(362.dpToPx(), holder.itemView.layoutParams.height)
     }
 
+    @Test
+    fun `배너 view는 carousel item 간격을 좌우 대칭으로 적용한다`() {
+        val view = inflateBannerView()
+        val recyclerView = view.findViewById<RecyclerView>(R.id.rv_banner)
+
+        view.setItems(listOf(sampleItem("1"), sampleItem("2")))
+        view.measure(exactly(402.dpToPx()), exactly(402.dpToPx()))
+        view.layout(0, 0, 402.dpToPx(), 402.dpToPx())
+        val holder = recyclerView.adapter!!.onCreateViewHolder(recyclerView, 0)
+        recyclerView.adapter!!.onBindViewHolder(holder, 0)
+        val itemOffset = Rect()
+        recyclerView.getItemDecorationAt(0).getItemOffsets(itemOffset, holder.itemView, recyclerView, RecyclerView.State())
+
+        assertEquals(4.dpToPx(), itemOffset.left)
+        assertEquals(4.dpToPx(), itemOffset.right)
+        assertEquals(8.dpToPx(), itemOffset.left + itemOffset.right)
+    }
+
+    @Test
+    fun `배너 view counter는 현재 item 내부 우상단 기준 margin을 적용한다`() {
+        val view = inflateBannerView()
+
+        view.setItems(listOf(sampleItem("1"), sampleItem("2")))
+        view.measure(exactly(402.dpToPx()), exactly(402.dpToPx()))
+        view.layout(0, 0, 402.dpToPx(), 402.dpToPx())
+
+        val counter = view.findViewById<View>(R.id.layout_banner_counter)
+        val params = counter.layoutParams as FrameLayout.LayoutParams
+        assertEquals(14.dpToPx(), params.topMargin)
+        assertEquals(34.dpToPx(), params.marginEnd)
+    }
+
+    @Test
+    fun `배너 view는 최초 layout 직후 현재 item 중심을 view 중심에 맞춘다`() {
+        val view = inflateBannerView()
+        val recyclerView = view.findViewById<RecyclerView>(R.id.rv_banner)
+
+        view.setItems(listOf(sampleItem("1"), sampleItem("2"), sampleItem("3")))
+        view.measure(exactly(402.dpToPx()), exactly(402.dpToPx()))
+        view.layout(0, 0, 402.dpToPx(), 402.dpToPx())
+
+        val layoutManager = requireNotNull(recyclerView.layoutManager)
+        val currentItem = requireNotNull(layoutManager.findViewByPosition(view.currentAdapterPositionForTest()))
+        val itemCenter = (currentItem.left + currentItem.right) / 2
+        val viewCenter = view.width / 2
+        assertEquals(viewCenter, itemCenter)
+        assertEquals(20.dpToPx(), currentItem.left)
+        assertEquals(20.dpToPx(), view.width - currentItem.right)
+    }
+
     @Test
     fun `배너 view는 wrap content 높이면 402dp 폭 기준 362dp 높이로 측정된다`() {
         val view = inflateBannerView()
@@ -221,6 +273,7 @@ class BannerViewTest {
         val itemOffset = Rect()
         recyclerView.getItemDecorationAt(0).getItemOffsets(itemOffset, holder.itemView, recyclerView, RecyclerView.State())
 
+        assertEquals(0, itemOffset.left)
         assertEquals(0, itemOffset.right)
     }