add save function of explanation

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

@@ -434,6 +434,7 @@ class MainActivity : Activity() {
             explanationOverlay.show(
                 sentence,
                 controller.currentTrainingItem()?.title.orEmpty(),
+                controller.currentTrainingItem()?.id.orEmpty(),
             )
         }
 

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

@@ -18,11 +18,12 @@ internal class SentenceExplanationOverlay(
     private val activity: Activity,
     private val api: SentenceExplanationApi,
 ) {
+    private val store = SentenceExplanationStore(activity)
     private var currentOverlay: View? = null
     private var currentRequest: CancellableExplanationRequest? = null
     private var requestGeneration = 0
 
-    fun show(sentence: SentenceBoundary, courseTitle: String) {
+    fun show(sentence: SentenceBoundary, courseTitle: String, mediaId: String) {
         close()
         val generation = ++requestGeneration
         val root = FrameLayout(activity).apply {
@@ -51,6 +52,31 @@ internal class SentenceExplanationOverlay(
             setTextColor(SampleTheme.textDark)
             textSize = 19f
             typeface = Typeface.DEFAULT_BOLD
+            layoutParams = LinearLayout.LayoutParams(0, ViewGroup.LayoutParams.WRAP_CONTENT, 1f)
+        }
+        val saveHint = TextView(activity).apply {
+            text = HINT_UNSAVED
+            setTextColor(SampleTheme.textSubtle)
+            textSize = 12f
+            setPadding(6.dp, 0, 0, 0)
+        }
+        val saveButton = TextView(activity).apply {
+            text = "保存"
+            setTextColor(Color.WHITE)
+            textSize = 13f
+            typeface = Typeface.DEFAULT_BOLD
+            gravity = Gravity.CENTER
+            background = rounded(SampleTheme.button, 8f)
+            setPadding(12.dp, 6.dp, 12.dp, 6.dp)
+            isEnabled = false
+            alpha = 0.45f
+        }
+        val titleRow = LinearLayout(activity).apply {
+            orientation = LinearLayout.HORIZONTAL
+            gravity = Gravity.CENTER_VERTICAL
+            addView(title)
+            addView(saveButton)
+            addView(saveHint)
         }
         val subtitle = TextView(activity).apply {
             text = sentence.text?.takeIf { it.isNotBlank() } ?: courseTitle
@@ -86,7 +112,7 @@ internal class SentenceExplanationOverlay(
             ).apply { topMargin = 16.dp }
             setOnClickListener { close() }
         }
-        card.addView(title)
+        card.addView(titleRow)
         card.addView(subtitle)
         card.addView(scroll)
         card.addView(close)
@@ -94,6 +120,22 @@ internal class SentenceExplanationOverlay(
 
         addToWindow(root)
         currentOverlay = root
+
+        val cached = store.load(mediaId, sentence.index)
+        if (!cached.isNullOrBlank()) {
+            message.text = cached
+            message.setTextColor(SampleTheme.textDark)
+            markSaved(saveButton, saveHint)
+            return
+        }
+
+        var loadedExplanation: String? = null
+        saveButton.setOnClickListener {
+            val explanation = loadedExplanation ?: return@setOnClickListener
+            if (store.save(mediaId, sentence.index, explanation)) {
+                markSaved(saveButton, saveHint)
+            }
+        }
         currentRequest = api.explain(
             sentence.text.orEmpty(),
             courseTitle,
@@ -101,14 +143,20 @@ internal class SentenceExplanationOverlay(
             sentence.language,
             object : SentenceExplanationCallback {
                 override fun onSuccess(result: SentenceExplanationResult) {
-                    if (generation == requestGeneration) message.text = result.explanation
+                    if (generation != requestGeneration) return
+                    loadedExplanation = result.explanation
+                    message.text = result.explanation
+                    message.setTextColor(SampleTheme.textDark)
+                    saveButton.isEnabled = true
+                    saveButton.alpha = 1f
                 }
 
                 override fun onError(error: Throwable) {
-                    if (generation == requestGeneration) {
+                    if (generation != requestGeneration) return
                     message.text = "讲解失败：${error.message ?: "请稍后重试"}"
                     message.setTextColor(SampleTheme.danger)
-                    }
+                    saveButton.isEnabled = false
+                    saveButton.alpha = 0.45f
                 }
             },
         )
@@ -128,6 +176,13 @@ internal class SentenceExplanationOverlay(
         api.release()
     }
 
+    private fun markSaved(saveButton: TextView, saveHint: TextView) {
+        saveButton.text = "已保存"
+        saveButton.isEnabled = false
+        saveButton.alpha = 0.7f
+        saveHint.text = HINT_SAVED
+    }
+
     private fun addToWindow(view: View) {
         (activity.window?.decorView as? ViewGroup)?.addView(view)
     }
@@ -147,4 +202,9 @@ internal class SentenceExplanationOverlay(
         cornerRadius = radiusDp.dp.toFloat()
         strokeColor?.let { setStroke(1.dp, it) }
     }
+
+    private companion object {
+        const val HINT_UNSAVED = "（下次直接看本地）"
+        const val HINT_SAVED = "（已保存本地）"
+    }
 }

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

@@ -0,0 +1,39 @@
+package cn.learningpad.oraltrainer.sample
+
+import android.content.Context
+import java.io.File
+import java.util.Locale
+
+/** Persists sentence explanations under app filesDir for reuse without another API call. */
+internal class SentenceExplanationStore(context: Context) {
+    private val rootDir = File(context.applicationContext.filesDir, "sentence-explanations")
+
+    fun load(mediaId: String, sentenceIndex: Int): String? {
+        val file = fileFor(mediaId, sentenceIndex) ?: return null
+        if (!file.isFile || file.length() <= 0L) return null
+        return file.readText()
+    }
+
+    fun save(mediaId: String, sentenceIndex: Int, explanation: String): Boolean {
+        val text = explanation.trim()
+        if (text.isEmpty()) return false
+        val file = fileFor(mediaId, sentenceIndex) ?: return false
+        file.parentFile?.mkdirs()
+        file.writeText(text)
+        return file.isFile && file.length() > 0L
+    }
+
+    private fun fileFor(mediaId: String, sentenceIndex: Int): File? {
+        val directoryName = sanitize(mediaId) ?: return null
+        return File(File(rootDir, directoryName), "$sentenceIndex.txt")
+    }
+
+    companion object {
+        fun sanitize(mediaId: String): String? {
+            val filtered = mediaId.trim().lowercase(Locale.US)
+                .replace(Regex("[^a-z0-9._-]"), "_")
+                .trim('_')
+            return filtered.takeIf { it.isNotBlank() && it != "." && it != ".." }
+        }
+    }
+}

ios/OralTrainer.xcodeproj/project.pbxproj

@@ -10,6 +10,7 @@
 		AA0000000000000000000090 /* AuthAPI.swift in Sources */ = {isa = PBXBuildFile; fileRef = AA0000000000000000000091 /* AuthAPI.swift */; };
 		AA00000000000000000000A1 /* UserHistory.swift in Sources */ = {isa = PBXBuildFile; fileRef = AA00000000000000000000A2 /* UserHistory.swift */; };
 		AA00000000000000000000A3 /* TrainingHistoryStore.swift in Sources */ = {isa = PBXBuildFile; fileRef = AA00000000000000000000A4 /* TrainingHistoryStore.swift */; };
+		AA00000000000000000000B0 /* SentenceExplanationStore.swift in Sources */ = {isa = PBXBuildFile; fileRef = AA00000000000000000000B1 /* SentenceExplanationStore.swift */; };
 		AA0000000000000000000092 /* AuthView.swift in Sources */ = {isa = PBXBuildFile; fileRef = AA0000000000000000000093 /* AuthView.swift */; };
 		AA0000000000000000000040 /* Assets.xcassets in Resources */ = {isa = PBXBuildFile; fileRef = AA0000000000000000000020 /* Assets.xcassets */; };
 		AA0000000000000000000042 /* OralTrainerApp.swift in Sources */ = {isa = PBXBuildFile; fileRef = AA0000000000000000000022 /* OralTrainerApp.swift */; };
@@ -41,6 +42,7 @@
 		AA0000000000000000000091 /* AuthAPI.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = AuthAPI.swift; sourceTree = "<group>"; };
 		AA00000000000000000000A2 /* UserHistory.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = UserHistory.swift; sourceTree = "<group>"; };
 		AA00000000000000000000A4 /* TrainingHistoryStore.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = TrainingHistoryStore.swift; sourceTree = "<group>"; };
+		AA00000000000000000000B1 /* SentenceExplanationStore.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = SentenceExplanationStore.swift; sourceTree = "<group>"; };
 		AA0000000000000000000093 /* AuthView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = AuthView.swift; sourceTree = "<group>"; };
 		AA000000000000000000000A /* OralTrainer.app */ = {isa = PBXFileReference; explicitFileType = wrapper.application; includeInIndex = 0; path = OralTrainer.app; sourceTree = BUILT_PRODUCTS_DIR; };
 		AA000000000000000000001F /* Info.plist */ = {isa = PBXFileReference; lastKnownFileType = text.plist.xml; path = Info.plist; sourceTree = "<group>"; };
@@ -131,6 +133,7 @@
 				AA000000000000000000002A /* SentenceBoundaryAPI.swift */,
 				AA000000000000000000002B /* ImitationAssessor.swift */,
 				AA00000000000000000000A4 /* TrainingHistoryStore.swift */,
+				AA00000000000000000000B1 /* SentenceExplanationStore.swift */,
 				AA00000000000000000000A2 /* UserHistory.swift */,
 				AA000000000000000000007E /* DubbingCompositor.swift */,
 				AA0000000000000000000081 /* AudioRecorderSession.swift */,
@@ -267,6 +270,7 @@
 				AA0000000000000000000090 /* AuthAPI.swift in Sources */,
 				AA00000000000000000000A1 /* UserHistory.swift in Sources */,
 				AA00000000000000000000A3 /* TrainingHistoryStore.swift in Sources */,
+				AA00000000000000000000B0 /* SentenceExplanationStore.swift in Sources */,
 				AA0000000000000000000092 /* AuthView.swift in Sources */,
 				AA0000000000000000000053 /* TestView.swift in Sources */,
 				AA0000000000000000000054 /* FullscreenPlayerView.swift in Sources */,

ios/OralTrainer.xcodeproj/project.xcworkspace/xcuserdata/liushuming.xcuserdatad/IDEFindNavigatorScopes.plist

@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<array/>
+</plist>

ios/OralTrainer/Services/SentenceExplanationStore.swift

@@ -0,0 +1,47 @@
+import Foundation
+
+final class SentenceExplanationStore {
+    static let shared = SentenceExplanationStore()
+
+    private let root: URL
+
+    init() {
+        let documents = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)[0]
+        root = documents.appendingPathComponent("SentenceExplanations", isDirectory: true)
+        try? FileManager.default.createDirectory(at: root, withIntermediateDirectories: true)
+    }
+
+    func load(mediaId: String, sentenceIndex: Int) -> String? {
+        let url = fileURL(mediaId: mediaId, sentenceIndex: sentenceIndex)
+        guard FileManager.default.fileExists(atPath: url.path) else { return nil }
+        let text = try? String(contentsOf: url, encoding: .utf8)
+        let trimmed = text?.trimmingCharacters(in: .whitespacesAndNewlines) ?? ""
+        return trimmed.isEmpty ? nil : trimmed
+    }
+
+    @discardableResult
+    func save(mediaId: String, sentenceIndex: Int, explanation: String) -> Bool {
+        let trimmed = explanation.trimmingCharacters(in: .whitespacesAndNewlines)
+        guard !trimmed.isEmpty else { return false }
+        let url = fileURL(mediaId: mediaId, sentenceIndex: sentenceIndex)
+        try? FileManager.default.createDirectory(at: url.deletingLastPathComponent(), withIntermediateDirectories: true)
+        do {
+            try trimmed.write(to: url, atomically: true, encoding: .utf8)
+            return true
+        } catch {
+            return false
+        }
+    }
+
+    private func fileURL(mediaId: String, sentenceIndex: Int) -> URL {
+        let directory = root.appendingPathComponent(Self.sanitize(mediaId), isDirectory: true)
+        return directory.appendingPathComponent("\(sentenceIndex).txt")
+    }
+
+    static func sanitize(_ mediaId: String) -> String {
+        let allowed = CharacterSet.alphanumerics.union(CharacterSet(charactersIn: "._-"))
+        let filtered = mediaId.lowercased().unicodeScalars.map { allowed.contains($0) ? Character($0) : "_" }
+        let value = String(filtered).trimmingCharacters(in: CharacterSet(charactersIn: "_"))
+        return value.isEmpty || value == "." || value == ".." ? "unknown" : value
+    }
+}

ios/OralTrainer/Views/FullscreenPlayerView.swift

@@ -97,6 +97,7 @@ struct FullscreenPlayerView: View {
         }
         .sheet(item: $explanationSentence) { sentence in
             SentenceExplanationSheet(
+                mediaId: controller.currentItem?.id ?? "",
                 courseTitle: controller.currentItem?.title ?? "口语训练课程",
                 sentence: sentence
             )

ios/OralTrainer/Views/PlayerSectionView.swift

@@ -22,6 +22,7 @@ struct PlayerSectionView: View {
         .padding(.horizontal, 16)
         .sheet(item: $explanationSentence) { sentence in
             SentenceExplanationSheet(
+                mediaId: controller.currentItem?.id ?? "",
                 courseTitle: controller.currentItem?.title ?? "口语训练课程",
                 sentence: sentence
             )
@@ -96,7 +97,7 @@ struct PlayerSectionView: View {
                 Text(sentenceTextText)
                 .font(.system(size: 15))
                     .foregroundColor(.white)
-                    .lineLimit(2)
+                    .lineLimit(4)
                 Spacer()
                 Button {
                     guard let sentence = controller.currentSentence, !(sentence.text ?? "").isEmpty else {
@@ -230,12 +231,14 @@ struct PlayerSectionView: View {
 }
 
 struct SentenceExplanationSheet: View {
+    let mediaId: String
     let courseTitle: String
     let sentence: SentenceBoundary
 
     @Environment(\.dismiss) private var dismiss
     @State private var explanation = ""
     @State private var errorMessage: String?
+    @State private var saved = false
 
     var body: some View {
         NavigationView {
@@ -267,6 +270,14 @@ struct SentenceExplanationSheet: View {
             .navigationBarTitleDisplayMode(.inline)
             .toolbar {
                 ToolbarItem(placement: .navigationBarTrailing) {
+                    HStack(spacing: 6) {
+                        Button(saved ? "已保存" : "保存") {
+                            saveExplanation()
+                        }
+                        .disabled(saved || explanation.isEmpty || errorMessage != nil)
+                        Text(saved ? "（已保存本地）" : "（下次直接看本地）")
+                            .font(.system(size: 12))
+                            .foregroundColor(Theme.textMuted)
                         Button {
                             dismiss()
                         } label: {
@@ -278,7 +289,16 @@ struct SentenceExplanationSheet: View {
                     }
                 }
             }
+        }
         .task {
+            if let cached = SentenceExplanationStore.shared.load(
+                mediaId: mediaId,
+                sentenceIndex: sentence.index
+            ) {
+                explanation = cached
+                saved = true
+                return
+            }
             guard explanation.isEmpty, errorMessage == nil else { return }
             do {
                 explanation = try await SentenceBoundaryAPI.explain(
@@ -290,4 +310,13 @@ struct SentenceExplanationSheet: View {
             }
         }
     }
+
+    private func saveExplanation() {
+        guard !saved, !explanation.isEmpty, errorMessage == nil else { return }
+        saved = SentenceExplanationStore.shared.save(
+            mediaId: mediaId,
+            sentenceIndex: sentence.index,
+            explanation: explanation
+        )
+    }
 }