feat(banner): 배너 자동 전환 동작을 추가한다

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

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

@@ -52,6 +52,12 @@ class BannerAdapter(
 
     fun toRealIndex(position: Int): Int = if (items.isEmpty()) 0 else position % items.size
 
+    fun startPosition(realIndex: Int): Int {
+        if (items.size <= 1) return realIndex
+        val center = VIRTUAL_ITEM_COUNT / 2
+        return center - (center % items.size) + realIndex
+    }
+
     inner class BannerViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
         private val imageView: ImageView = itemView.findViewById(R.id.iv_banner)
 

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

@@ -1,6 +1,8 @@
 package kr.co.vividnext.sodalive.v2.widget.banner
 
 import android.content.Context
+import android.os.Handler
+import android.os.Looper
 import android.util.AttributeSet
 import android.view.LayoutInflater
 import android.view.View
@@ -8,6 +10,7 @@ import android.widget.FrameLayout
 import android.widget.ImageView
 import android.widget.TextView
 import androidx.recyclerview.widget.LinearLayoutManager
+import androidx.recyclerview.widget.LinearSmoothScroller
 import androidx.recyclerview.widget.PagerSnapHelper
 import androidx.recyclerview.widget.RecyclerView
 import kr.co.vividnext.sodalive.R
@@ -28,8 +31,23 @@ class BannerView @JvmOverloads constructor(
     private val snapHelper = PagerSnapHelper()
     private var items: List<BannerItem> = emptyList()
     private var currentIndex: Int = 0
+    private var currentAdapterPosition: Int = 0
     private var itemSpacingPx: Int = 0
     private var spacingDecoration: RecyclerView.ItemDecoration? = null
+    private val autoScrollHandler = Handler(Looper.getMainLooper())
+    private val autoScrollRunnable = Runnable { moveToNextBanner() }
+    private var hasWindowAttachmentForAutoScroll = false
+    private val bannerScrollListener = object : RecyclerView.OnScrollListener() {
+        override fun onScrollStateChanged(recyclerView: RecyclerView, newState: Int) {
+            when (newState) {
+                RecyclerView.SCROLL_STATE_DRAGGING -> stopAutoScroll()
+                RecyclerView.SCROLL_STATE_IDLE -> {
+                    updateCurrentIndexFromSnap()
+                    startAutoScrollIfNeeded()
+                }
+            }
+        }
+    }
 
     init {
         clipToPadding = false
@@ -44,6 +62,18 @@ class BannerView @JvmOverloads constructor(
         updateCounter()
     }
 
+    override fun onAttachedToWindow() {
+        super.onAttachedToWindow()
+        hasWindowAttachmentForAutoScroll = true
+        startAutoScrollIfNeeded()
+    }
+
+    override fun onDetachedFromWindow() {
+        stopAutoScroll()
+        hasWindowAttachmentForAutoScroll = false
+        super.onDetachedFromWindow()
+    }
+
     override fun onSizeChanged(w: Int, h: Int, oldw: Int, oldh: Int) {
         super.onSizeChanged(w, h, oldw, oldh)
         if (w > 0) applyLayoutSize(w)
@@ -53,9 +83,12 @@ class BannerView @JvmOverloads constructor(
         this.items = items
         currentIndex = BannerState.from(items.size, currentIndex).currentIndex
         visibility = if (items.isEmpty()) GONE else VISIBLE
+        stopAutoScroll()
         adapter.submitItems(items)
+        scrollToCurrentBanner()
         if (width > 0) applyLayoutSize(width)
         updateCounter()
+        startAutoScrollIfNeeded()
     }
 
     fun setOnBannerClickListener(listener: ((BannerItem) -> Unit)?) {
@@ -73,11 +106,7 @@ class BannerView @JvmOverloads constructor(
             clipToPadding = false
             clipChildren = false
             if (onFlingListener == null) snapHelper.attachToRecyclerView(this)
-            addOnScrollListener(object : RecyclerView.OnScrollListener() {
+            addOnScrollListener(bannerScrollListener)
-                override fun onScrollStateChanged(recyclerView: RecyclerView, newState: Int) {
-                    if (newState == RecyclerView.SCROLL_STATE_IDLE) updateCurrentIndexFromSnap()
-                }
-            })
         }
     }
 
@@ -95,10 +124,44 @@ class BannerView @JvmOverloads constructor(
         }
     }
 
+    private fun scrollToCurrentBanner() {
+        val recyclerView = requireNotNull(recyclerView)
+        currentAdapterPosition = if (items.size > 1) {
+            adapter.startPosition(currentIndex)
+        } else {
+            currentIndex
+        }
+        recyclerView.scrollToPosition(currentAdapterPosition)
+    }
+
+    private fun moveToNextBanner() {
+        if (BannerState.from(items.size, currentIndex).displayMode != BannerDisplayMode.Carousel) return
+        val recyclerView = requireNotNull(recyclerView)
+        val layoutManager = recyclerView.layoutManager as? LinearLayoutManager ?: return
+        val nextPosition = currentAdapterPosition + 1
+        currentAdapterPosition = nextPosition
+        currentIndex = adapter.toRealIndex(nextPosition)
+        layoutManager.startSmoothScroll(BannerSmoothScroller(context).apply { targetPosition = nextPosition })
+        updateCounter()
+        startAutoScrollIfNeeded()
+    }
+
+    private fun startAutoScrollIfNeeded() {
+        stopAutoScroll()
+        if (!hasWindowAttachmentForAutoScroll) return
+        if (BannerState.from(items.size, currentIndex).displayMode != BannerDisplayMode.Carousel) return
+        autoScrollHandler.postDelayed(autoScrollRunnable, AUTO_SCROLL_INTERVAL_MS)
+    }
+
+    private fun stopAutoScroll() {
+        autoScrollHandler.removeCallbacks(autoScrollRunnable)
+    }
+
     private fun updateCurrentIndexFromSnap() {
         val layoutManager = requireNotNull(recyclerView).layoutManager ?: return
         val snapView = snapHelper.findSnapView(layoutManager) ?: return
         val position = layoutManager.getPosition(snapView)
+        currentAdapterPosition = position
         currentIndex = adapter.toRealIndex(position)
         updateCounter()
     }
@@ -118,6 +181,17 @@ class BannerView @JvmOverloads constructor(
 
     private fun Int.dpToPx(): Int = (this * resources.displayMetrics.density).roundToInt()
 
+    companion object {
+        private const val AUTO_SCROLL_INTERVAL_MS = 5_000L
+        private const val SCROLL_ANIMATION_DURATION_MS = 350
+
+        fun scrollAnimationDurationMsForTest(): Int = SCROLL_ANIMATION_DURATION_MS
+    }
+
+    private class BannerSmoothScroller(context: Context) : LinearSmoothScroller(context) {
+        override fun calculateTimeForScrolling(dx: Int): Int = SCROLL_ANIMATION_DURATION_MS
+    }
+
     private class BannerSpacingDecoration(
         private val spacingPx: Int
     ) : RecyclerView.ItemDecoration() {

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

@@ -18,7 +18,9 @@ import org.junit.Assert.assertTrue
 import org.junit.Test
 import org.junit.runner.RunWith
 import org.robolectric.RobolectricTestRunner
+import org.robolectric.Shadows.shadowOf
 import org.robolectric.annotation.Config
+import java.time.Duration
 
 @RunWith(RobolectricTestRunner::class)
 @Config(sdk = [28], application = Application::class)
@@ -148,11 +150,152 @@ class BannerViewTest {
         assertNotNull(imageView.outlineProvider)
     }
 
+    @Test
+    fun `배너 view는 attach 후 5초가 지나면 다음 배너로 자동 이동한다`() {
+        val view = inflateBannerView()
+
+        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())
+        view.dispatchAttachedForTest()
+
+        shadowOf(android.os.Looper.getMainLooper()).idleFor(Duration.ofMillis(5_000))
+
+        assertEquals("02", view.findViewById<TextView>(R.id.tv_banner_current_index).text.toString())
+    }
+
+    @Test
+    fun `배너 view는 사용자 drag 중에는 자동 이동 timer를 다시 시작하지 않는다`() {
+        val view = inflateBannerView()
+
+        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())
+        view.dispatchAttachedForTest()
+        view.dispatchScrollStateForTest(RecyclerView.SCROLL_STATE_DRAGGING)
+        shadowOf(android.os.Looper.getMainLooper()).idleFor(Duration.ofMillis(5_000))
+
+        assertEquals("01", view.findViewById<TextView>(R.id.tv_banner_current_index).text.toString())
+
+        view.dispatchScrollStateForTest(RecyclerView.SCROLL_STATE_IDLE)
+        shadowOf(android.os.Looper.getMainLooper()).idleFor(Duration.ofMillis(4_999))
+        assertEquals("01", view.findViewById<TextView>(R.id.tv_banner_current_index).text.toString())
+
+        shadowOf(android.os.Looper.getMainLooper()).idleFor(Duration.ofMillis(1))
+        assertEquals("02", view.findViewById<TextView>(R.id.tv_banner_current_index).text.toString())
+    }
+
+    @Test
+    fun `배너 view는 detach 되면 자동 이동 callback을 제거한다`() {
+        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())
+        view.dispatchAttachedForTest()
+        view.dispatchDetachedForTest()
+        shadowOf(android.os.Looper.getMainLooper()).idleFor(Duration.ofMillis(5_000))
+
+        assertEquals("01", view.findViewById<TextView>(R.id.tv_banner_current_index).text.toString())
+    }
+
+    @Test
+    fun `배너 view는 단일 item이면 attach 후 5초가 지나도 자동 이동하지 않는다`() {
+        val view = inflateBannerView()
+
+        view.setItems(listOf(sampleItem("1")))
+        view.measure(exactly(402.dpToPx()), exactly(402.dpToPx()))
+        view.layout(0, 0, 402.dpToPx(), 402.dpToPx())
+        view.dispatchAttachedForTest()
+        shadowOf(android.os.Looper.getMainLooper()).idleFor(Duration.ofMillis(5_000))
+
+        assertEquals(View.GONE, view.findViewById<View>(R.id.layout_banner_counter).visibility)
+    }
+
+    @Test
+    fun `배너 view는 마지막 배너 다음에 첫 번째 counter로 순환한다`() {
+        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())
+        view.dispatchAttachedForTest()
+        shadowOf(android.os.Looper.getMainLooper()).idleFor(Duration.ofMillis(5_000))
+        assertEquals("02", view.findViewById<TextView>(R.id.tv_banner_current_index).text.toString())
+
+        shadowOf(android.os.Looper.getMainLooper()).idleFor(Duration.ofMillis(5_000))
+
+        assertEquals("01", view.findViewById<TextView>(R.id.tv_banner_current_index).text.toString())
+    }
+
+    @Test
+    fun `배너 view는 자동 전환 animation duration을 350ms로 사용한다`() {
+        assertEquals(350, BannerView.scrollAnimationDurationMsForTest())
+    }
+
+    @Test
+    fun `배너 view는 현재 virtual position 기준으로 다음 배너로 이동한다`() {
+        val view = inflateBannerView()
+        val recyclerView = view.findViewById<RecyclerView>(R.id.rv_banner)
+
+        view.setItems(listOf(sampleItem("1"), sampleItem("2"), sampleItem("3")))
+        val adapter = requireNotNull(recyclerView.adapter as? BannerAdapter)
+        val previousVirtualPosition = adapter.startPosition(0) - 1
+        view.measure(exactly(402.dpToPx()), exactly(402.dpToPx()))
+        view.layout(0, 0, 402.dpToPx(), 402.dpToPx())
+        view.setCurrentPositionForTest(previousVirtualPosition)
+        view.dispatchAttachedForTest()
+
+        shadowOf(android.os.Looper.getMainLooper()).idleFor(Duration.ofMillis(5_000))
+
+        assertEquals(previousVirtualPosition + 1, view.currentAdapterPositionForTest())
+        assertEquals("01", view.findViewById<TextView>(R.id.tv_banner_current_index).text.toString())
+    }
+
     private fun inflateBannerView(): BannerView {
         val context = ApplicationProvider.getApplicationContext<Context>()
         return BannerView(context)
     }
 
+    private fun BannerView.dispatchAttachedForTest() {
+        BannerView::class.java.getDeclaredMethod("onAttachedToWindow").apply {
+            isAccessible = true
+            invoke(this@dispatchAttachedForTest)
+        }
+    }
+
+    private fun BannerView.dispatchDetachedForTest() {
+        BannerView::class.java.getDeclaredMethod("onDetachedFromWindow").apply {
+            isAccessible = true
+            invoke(this@dispatchDetachedForTest)
+        }
+    }
+
+    private fun BannerView.dispatchScrollStateForTest(state: Int) {
+        val listenerField = BannerView::class.java.getDeclaredField("bannerScrollListener").apply { isAccessible = true }
+        val listener = listenerField.get(this) as RecyclerView.OnScrollListener
+        listener.onScrollStateChanged(findViewById(R.id.rv_banner), state)
+    }
+
+
+    private fun BannerView.setCurrentPositionForTest(position: Int) {
+        BannerView::class.java.getDeclaredField("currentAdapterPosition").apply {
+            isAccessible = true
+            setInt(this@setCurrentPositionForTest, position)
+        }
+        BannerView::class.java.getDeclaredField("currentIndex").apply {
+            isAccessible = true
+            setInt(this@setCurrentPositionForTest, requireNotNull(findViewById<RecyclerView>(R.id.rv_banner).adapter as? BannerAdapter).toRealIndex(position))
+        }
+    }
+
+    private fun BannerView.currentAdapterPositionForTest(): Int {
+        return BannerView::class.java.getDeclaredField("currentAdapterPosition").run {
+            isAccessible = true
+            getInt(this@currentAdapterPositionForTest)
+        }
+    }
+
     private fun sampleItem(id: String) = BannerItem(
         bannerId = id,
         imageUrl = "https://example.com/banner-$id.png"