fixed some bugs

android/sample-app/build.gradle.kts

@@ -37,6 +37,7 @@ kotlin {
 dependencies {
     implementation(project(":oral-trainer-sdk"))
     implementation("androidx.core:core-ktx:1.13.1")
+    implementation("androidx.recyclerview:recyclerview:1.3.2")
     implementation("androidx.media3:media3-common:1.11.0")
     implementation("androidx.media3:media3-exoplayer:1.11.0")
 }

android/sample-app/src/main/java/cn/learningpad/oraltrainer/sample/MainActivity.kt

@@ -263,6 +263,9 @@ class MainActivity : Activity() {
         if (screenState.activeModule == Module.MINE) {
             screenFactory.refreshMyContent(sdk.userApi, authSessionStore.session?.token.orEmpty())
         }
+        if (screenState.activeModule == Module.READING) {
+            screenFactory.scrollToReadingCurrentSentence()
+        }
     }
 
     private fun refreshCurrentUi() {
@@ -552,6 +555,17 @@ class MainActivity : Activity() {
             return sentenceFavoriteStore.toggle(favoriteUserKey(), item.id, sentence.index)
         }
 
+        override fun onSentenceDoubleTapped(sentence: SentenceBoundary) {
+            screenState.continuousPlaybackEnabled = false
+            switchModule(Module.TRAIN)
+            controller.setContinuousPlayback(false)
+            controller.seekTo(sentence.startMs)
+            controller.play()
+            if (bindings.hasPlayerChrome) {
+                bindings.statusText.text = "已定位到第 ${sentence.index + 1} 句，单句循环播放中"
+            }
+        }
+
         override fun onExplainCurrentSentence() {
             val sentence = controller.currentSentence() ?: return
             if (sentence.text.isNullOrBlank()) return

android/sample-app/src/main/java/cn/learningpad/oraltrainer/sample/SampleScreenActions.kt

@@ -29,6 +29,7 @@ internal interface ReadingScreenActions {
     fun onReadingTranslationVisible(visible: Boolean)
     fun isSentenceFavorite(sentence: SentenceBoundary): Boolean
     fun toggleSentenceFavorite(sentence: SentenceBoundary): Boolean
+    fun onSentenceDoubleTapped(sentence: SentenceBoundary)
 }
 
 internal interface TestScreenActions :

android/sample-app/src/main/java/cn/learningpad/oraltrainer/sample/SampleScreenFactory.kt

@@ -85,6 +85,12 @@ internal class SampleScreenFactory(
         }
     }
 
+    fun scrollToReadingCurrentSentence() {
+        if (screenState.activeModule == Module.READING) {
+            readingScreen.scrollToCurrentSentence()
+        }
+    }
+
     fun renderCatalog() {
         if (screenState.activeModule == Module.COURSE) {
             courseScreen.renderCatalog()

android/sample-app/src/main/java/cn/learningpad/oraltrainer/sample/SampleTheme.kt

@@ -19,6 +19,7 @@ internal object SampleTheme {
     val textDark = Color.rgb(18, 24, 31)
     val textMuted = Color.rgb(151, 162, 174)
     val textSubtle = Color.rgb(88, 98, 108)
+    val readingTranslation = Color.rgb(147, 197, 253)
     val danger = Color.rgb(220, 38, 38)
     val textOverlay = Color.rgb(163, 172, 182)
 }

android/sample-app/src/main/java/cn/learningpad/oraltrainer/sample/ui/ReadingScreen.kt

@@ -3,14 +3,16 @@ package cn.learningpad.oraltrainer.sample.ui
 import android.app.Activity
 import android.graphics.Color
 import android.graphics.Typeface
+import android.os.SystemClock
 import android.view.Gravity
 import android.view.View
 import android.view.ViewGroup
 import android.widget.Button
 import android.widget.LinearLayout
-import android.widget.ScrollView
 import android.widget.Switch
 import android.widget.TextView
+import androidx.recyclerview.widget.LinearLayoutManager
+import androidx.recyclerview.widget.RecyclerView
 import cn.learningpad.oraltrainer.sample.ReadingScreenActions
 import cn.learningpad.oraltrainer.sample.SampleTheme
 import cn.learningpad.oraltrainer.sample.TrainingScreenState
@@ -18,7 +20,7 @@ import cn.learningpad.oraltrainer.sample.UiStyled
 import cn.learningpad.oraltrainer.sdk.OralTrainerController
 import cn.learningpad.oraltrainer.sdk.SentenceBoundary
 
-/** Scrollable full-text reading view for the selected course. */
+/** Lazy-loading full-text reading view for the selected course. */
 internal class ReadingScreen(
     private val activity: Activity,
     private val screenState: TrainingScreenState,
@@ -28,90 +30,81 @@ internal class ReadingScreen(
 ) : UiStyled {
     override val uiContext get() = activity
 
-    private data class SentenceRow(
+    private var readingAdapter: ReadingSentenceAdapter? = null
-        val translation: TextView,
-        val favoriteButton: Button,
-    )
-
-    private val sentenceRows = mutableMapOf<Int, SentenceRow>()
-    private var sentenceList: LinearLayout? = null
     private var titleText: TextView? = null
+    private var sentenceListView: RecyclerView? = null
+    private var lastClickedSentenceIndex = Int.MIN_VALUE
+    private var lastClickedAtMs = 0L
 
     fun createSection(): View {
-        val content = LinearLayout(activity).apply {
+        val root = LinearLayout(activity).apply {
             orientation = LinearLayout.VERTICAL
             setPadding(16.dp, 12.dp, 16.dp, 16.dp)
         }
-        val list = LinearLayout(activity).apply {
+        val adapter = ReadingSentenceAdapter()
-            orientation = LinearLayout.VERTICAL
+        readingAdapter = adapter
-        }
+        val list = RecyclerView(activity).apply {
-        sentenceList = list
+            layoutManager = LinearLayoutManager(activity)
-
+            this.adapter = adapter
-        val title = TextView(activity).apply {
+            itemAnimator = null
-            setTextColor(Color.WHITE)
+            setItemViewCacheSize(12)
-            textSize = 24f
+            clipToPadding = false
-            typeface = Typeface.DEFAULT_BOLD
+            setPadding(0, 0, 0, 16.dp)
-            setPadding(0, 0, 0, 6.dp)
-        }
-        titleText = title
-        content.addView(title)
-
-        content.addView(createTranslationToggle())
-        content.addView(list)
-        renderSentences()
-
-        return ScrollView(activity).apply {
             layoutParams = LinearLayout.LayoutParams(
                 ViewGroup.LayoutParams.MATCH_PARENT,
                 0,
                 1f,
             )
-            addView(content)
         }
+        sentenceListView = list
+
+        val title = TextView(activity).apply {
+            setTextColor(Color.WHITE)
+            textSize = 15f
+            typeface = Typeface.DEFAULT_BOLD
+            setPadding(0, 0, 0, 6.dp)
+        }
+        titleText = title
+        root.addView(title)
+        root.addView(createTranslationToggle())
+        root.addView(list)
+        renderSentences()
+
+        return root
     }
 
     fun renderSentences() {
-        val list = sentenceList ?: return
         val item = controller.currentTrainingItem()
-        titleText?.text = screenState.currentCourse?.title.orEmpty()
+        val baseTitle = screenState.currentCourse?.title.orEmpty()
             .ifBlank { item?.title ?: "阅读模式" }
-        sentenceRows.clear()
+        val sentences = item?.sentences.orEmpty()
-        list.removeAllViews()
+        titleText?.text = if (sentences.isEmpty()) {
-        if (item == null || item.sentences.isEmpty()) {
+            baseTitle
-            list.addView(widgets.infoCard("当前课程还没有可阅读的句子文本"))
+        } else {
-            return
+            "$baseTitle · ${sentences.size} 句"
-        }
-        val currentTitle = titleText?.text?.toString().orEmpty()
-        titleText?.text = "$currentTitle · ${item.sentences.size} 句"
-        item.sentences.forEach { sentence ->
-            list.addView(sentenceRow(sentence))
         }
+        readingAdapter?.submitSentences(sentences)
     }
 
     fun refreshTranslations() {
-        val item = controller.currentTrainingItem() ?: return
+        readingAdapter?.notifyDataSetChanged()
-        item.sentences.forEach { sentence ->
-            val row = sentenceRows[sentence.index] ?: return@forEach
-            row.translation.visibility = if (screenState.readingTranslationVisible) {
-                View.VISIBLE
-            } else {
-                View.GONE
-            }
-            row.translation.text = translationText(sentence)
-        }
     }
 
     fun refreshFavorites() {
-        val item = controller.currentTrainingItem() ?: return
+        readingAdapter?.notifyDataSetChanged()
-        item.sentences.forEach { sentence ->
-            sentenceRows[sentence.index]?.favoriteButton?.apply {
-                val isFavorite = actions.isSentenceFavorite(sentence)
-                setText(if (isFavorite) "已收藏" else "收藏")
-                background = rounded(
-                    if (isFavorite) SampleTheme.accent else SampleTheme.button,
-                    8f,
-                )
     }
+
+    fun scrollToCurrentSentence() {
+        val list = sentenceListView ?: return
+        val currentSentence = controller.currentSentence() ?: return
+        val item = controller.currentTrainingItem() ?: return
+        val position = item.sentences.indexOfFirst { it.index == currentSentence.index }
+        if (position < 0) return
+        list.post {
+            if (sentenceListView !== list) return@post
+            val layoutManager = list.layoutManager as? LinearLayoutManager ?: return@post
+            val offset = (list.height * 0.25f).toInt().coerceAtLeast(0)
+            layoutManager.scrollToPositionWithOffset(position, offset)
         }
     }
 
@@ -136,16 +129,84 @@ internal class ReadingScreen(
             })
         }
 
-    private fun sentenceRow(sentence: SentenceBoundary): View {
+    private fun translationText(sentence: SentenceBoundary): String = when {
+        !sentence.zhText.isNullOrBlank() -> sentence.zhText.orEmpty()
+        screenState.chineseTranslationLoading -> "正在翻译中文…"
+        screenState.chineseTranslationError.isNotBlank() -> screenState.chineseTranslationError
+        else -> "暂无中文翻译"
+    }
+
+    private inner class ReadingSentenceAdapter :
+        RecyclerView.Adapter<RecyclerView.ViewHolder>() {
+
+        private var sentences: List<SentenceBoundary> = emptyList()
+
+        init {
+            setHasStableIds(true)
+        }
+
+        override fun getItemId(position: Int): Long {
+            return if (sentences.isEmpty()) EMPTY_ID else sentences[position].index.toLong()
+        }
+
+        override fun getItemViewType(position: Int): Int {
+            return if (sentences.isEmpty()) TYPE_EMPTY else TYPE_SENTENCE
+        }
+
+        override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RecyclerView.ViewHolder {
+            return if (viewType == TYPE_EMPTY) {
+                val empty = TextView(activity).apply {
+                    text = "当前课程还没有可阅读的句子文本"
+                    setTextColor(SampleTheme.textDark)
+                    textSize = 13f
+                    background = rounded(SampleTheme.selected, 8f)
+                    setPadding(12.dp, 10.dp, 12.dp, 10.dp)
+                    layoutParams = RecyclerView.LayoutParams(
+                        ViewGroup.LayoutParams.MATCH_PARENT,
+                        ViewGroup.LayoutParams.WRAP_CONTENT,
+                    )
+                }
+                EmptyViewHolder(empty)
+            } else {
+                SentenceViewHolder(createSentenceView())
+            }
+        }
+
+        override fun onBindViewHolder(holder: RecyclerView.ViewHolder, position: Int) {
+            if (holder !is SentenceViewHolder || sentences.isEmpty()) return
+            val sentence = sentences[position]
+            attachDoubleTap(holder.itemView, sentence)
+            holder.text.text =
+                "${sentence.index + 1}. ${sentence.text?.takeIf { it.isNotBlank() } ?: "未提供文本"}"
+            holder.translation.visibility = if (screenState.readingTranslationVisible) {
+                View.VISIBLE
+            } else {
+                View.GONE
+            }
+            holder.translation.text = translationText(sentence)
+            bindFavoriteButton(holder.favoriteButton, sentence)
+        }
+
+        override fun getItemCount(): Int {
+            return if (sentences.isEmpty()) 1 else sentences.size
+        }
+
+        fun submitSentences(updated: List<SentenceBoundary>) {
+            sentences = updated
+            notifyDataSetChanged()
+        }
+
+        private fun createSentenceView(): View {
+            val text = TextView(activity).apply {
+                setTextColor(Color.WHITE)
+                textSize = 16f
+            }
             val translation = TextView(activity).apply {
-            text = translationText(sentence)
+                setTextColor(SampleTheme.readingTranslation)
-            setTextColor(SampleTheme.textSubtle)
                 textSize = 14f
                 setPadding(0, 6.dp, 0, 0)
-            visibility = if (screenState.readingTranslationVisible) View.VISIBLE else View.GONE
             }
             val favoriteButton = Button(activity).apply {
-            setText("收藏")
                 isAllCaps = false
                 setTextColor(Color.WHITE)
                 textSize = 12f
@@ -155,56 +216,91 @@ internal class ReadingScreen(
                 minimumWidth = 0
                 minimumHeight = 0
                 setPadding(12.dp, 0, 12.dp, 0)
-            background = rounded(SampleTheme.button, 8f)
                 layoutParams = LinearLayout.LayoutParams(
                     ViewGroup.LayoutParams.WRAP_CONTENT,
                     32.dp,
                 ).withMargins(10.dp, 0, 0, 0)
-            setOnClickListener {
-                val isFavorite = actions.toggleSentenceFavorite(sentence)
-                setText(if (isFavorite) "已收藏" else "收藏")
-                background = rounded(
-                    if (isFavorite) SampleTheme.accent else SampleTheme.button,
-                    8f,
-                )
             }
-        }
-
-        val isFavorite = actions.isSentenceFavorite(sentence)
-        favoriteButton.setText(if (isFavorite) "已收藏" else "收藏")
-        favoriteButton.background = rounded(
-            if (isFavorite) SampleTheme.accent else SampleTheme.button,
-            8f,
-        )
             val textColumn = LinearLayout(activity).apply {
                 orientation = LinearLayout.VERTICAL
                 layoutParams = LinearLayout.LayoutParams(0, ViewGroup.LayoutParams.WRAP_CONTENT, 1f)
-            addView(TextView(activity).apply {
+                addView(text)
-                text = "${sentence.index + 1}. ${sentence.text?.takeIf { it.isNotBlank() } ?: "未提供文本"}"
-                setTextColor(Color.WHITE)
-                textSize = 16f
-            })
                 addView(translation)
             }
-
             return LinearLayout(activity).apply {
                 orientation = LinearLayout.HORIZONTAL
                 gravity = Gravity.CENTER_VERTICAL
                 background = rounded(SampleTheme.surface, 10f, SampleTheme.border)
                 setPadding(14.dp, 12.dp, 10.dp, 12.dp)
-            layoutParams = LinearLayout.LayoutParams(
+                layoutParams = RecyclerView.LayoutParams(
                     ViewGroup.LayoutParams.MATCH_PARENT,
                     ViewGroup.LayoutParams.WRAP_CONTENT,
-            ).withMargins(0, 0, 0, 10.dp)
+                ).apply {
+                    bottomMargin = 10.dp
+                }
                 addView(textColumn)
                 addView(favoriteButton)
             }
         }
 
-    private fun translationText(sentence: SentenceBoundary): String = when {
+        private fun bindFavoriteButton(button: Button, sentence: SentenceBoundary) {
-        !sentence.zhText.isNullOrBlank() -> sentence.zhText.orEmpty()
+            val isFavorite = actions.isSentenceFavorite(sentence)
-        screenState.chineseTranslationLoading -> "正在翻译中文…"
+            button.setText(if (isFavorite) "已收藏" else "收藏")
-        screenState.chineseTranslationError.isNotBlank() -> screenState.chineseTranslationError
+            button.background = rounded(
-        else -> "暂无中文翻译"
+                if (isFavorite) SampleTheme.accent else SampleTheme.button,
+                8f,
+            )
+            button.setOnClickListener {
+                val favorite = actions.toggleSentenceFavorite(sentence)
+                button.setText(if (favorite) "已收藏" else "收藏")
+                button.background = rounded(
+                    if (favorite) SampleTheme.accent else SampleTheme.button,
+                    8f,
+                )
+            }
+        }
+
+        private fun attachDoubleTap(view: View, sentence: SentenceBoundary) {
+            view.isClickable = true
+            view.setOnClickListener {
+                val now = SystemClock.elapsedRealtime()
+                val isDoubleTap = lastClickedSentenceIndex == sentence.index &&
+                    now - lastClickedAtMs <= DOUBLE_TAP_INTERVAL_MS
+                if (isDoubleTap) {
+                    lastClickedSentenceIndex = Int.MIN_VALUE
+                    lastClickedAtMs = 0L
+                    actions.onSentenceDoubleTapped(sentence)
+                } else {
+                    lastClickedSentenceIndex = sentence.index
+                    lastClickedAtMs = now
+                }
+            }
+        }
+
+        private inner class EmptyViewHolder(root: View) : RecyclerView.ViewHolder(root)
+
+        private inner class SentenceViewHolder(
+            root: View,
+        ) : RecyclerView.ViewHolder(root) {
+            val text: TextView
+            val translation: TextView
+            val favoriteButton: Button
+
+            init {
+                val textColumn = root as ViewGroup
+                val content = textColumn.getChildAt(0) as ViewGroup
+                text = content.getChildAt(0) as TextView
+                translation = content.getChildAt(1) as TextView
+                favoriteButton = textColumn.getChildAt(1) as Button
+            }
+        }
+
+    }
+
+    private companion object {
+        private const val TYPE_EMPTY = 0
+        private const val TYPE_SENTENCE = 1
+        private const val EMPTY_ID = Long.MIN_VALUE
+        private const val DOUBLE_TAP_INTERVAL_MS = 300L
     }
 }