chore: 清理订阅请求死代码 + RTSP 自动重连指数退避

- ControlCommands.kt: 删除 subscribeStatus() 及 SUB_* 常量
- ProtocolClient.kt: 删除 sendSubscriptionRequests() 方法及调用
- RtspVideoPlayer.kt: 播放失败后自动重试，指数退避（1s~30s，倍率2），覆盖层显示重试次数和倒计时

Generated by Mistral Vibe.
Co-Authored-By: Mistral Vibe <vibe@mistral.ai>

app/src/main/java/com/example/m20_gamepad/network/ProtocolClient.kt

@@ -130,9 +130,6 @@ class ProtocolClient(
                 }
             }
 
-            // 发送订阅请求（触发服务端 UDP 推送）
-            sendSubscriptionRequests()
-
             // 启动断线检测（立即开始，覆盖 CONNECTING 和 CONNECTED 状态）
             timeoutJob = scope.launch {
                 timeoutCheckLoop()
@@ -195,25 +192,6 @@ class ProtocolClient(
         socket = null
     }
 
-    /** 发送订阅请求 */
-    private fun sendSubscriptionRequests() {
-        val subscriptions: List<Pair<Int, Int>> = listOf(
-            ControlCommands.SUB_BASIC,
-            ControlCommands.SUB_MOTION_CONTROL,
-            ControlCommands.SUB_DEVICE,
-            ControlCommands.SUB_ERROR
-        )
-        val sock = socket ?: return
-        val addr = remoteAddress ?: return
-        for ((type, cmd) in subscriptions) {
-            try {
-                val json = ControlCommands.subscribeStatus(type, cmd)
-                val packet = encoder.encode(json)
-                sock.send(DatagramPacket(packet, packet.size, addr, port))
-            } catch (_: Exception) { }
-        }
-    }
-
     /** 接收循环 */
     private fun CoroutineScope.receiveLoop(sock: DatagramSocket) {
         val buffer = ByteArray(65535)

app/src/main/java/com/example/m20_gamepad/network/models/ControlCommands.kt

@@ -122,10 +122,6 @@ object ControlCommands {
     // ---- 2.10 休眠状态查询 ----
     fun querySleepStatus(time: String = now()): String = buildAsdu(type = 1101, command = 7, time = time)
 
-    // ---- 订阅状态上报 ----
-    fun subscribeStatus(type: Int, command: Int, time: String = now()): String =
-        buildAsdu(type = type, command = command, time = time)
-
     // ========== 常量 ==========
 
     // 运动状态常量
@@ -147,9 +143,4 @@ object ControlCommands {
     const val MODE_NAVIGATION = 1
     const val MODE_ASSIST = 2
 
-    // 订阅 Type/Command — 用于 subscribeStatus()
-    val SUB_ERROR = Pair(1002, 3)
-    val SUB_MOTION_CONTROL = Pair(1002, 4)
-    val SUB_DEVICE = Pair(1002, 5)
-    val SUB_BASIC = Pair(1002, 6)
 }

app/src/main/java/com/example/m20_gamepad/video/RtspVideoPlayer.kt

@@ -1,12 +1,15 @@
 package com.example.m20_gamepad.video
 
 import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.Column
 import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.foundation.layout.padding
 import androidx.compose.material3.Text
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.DisposableEffect
 import androidx.compose.runtime.LaunchedEffect
 import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableIntStateOf
 import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.remember
 import androidx.compose.runtime.setValue
@@ -14,6 +17,9 @@ import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.graphics.Color
 import androidx.compose.ui.platform.LocalContext
+import androidx.compose.ui.text.font.FontWeight
+import androidx.compose.ui.unit.dp
+import androidx.compose.ui.unit.sp
 import androidx.compose.ui.viewinterop.AndroidView
 import androidx.media3.common.MediaItem
 import androidx.media3.common.PlaybackException
@@ -26,6 +32,7 @@ import androidx.media3.exoplayer.mediacodec.MediaCodecSelector
 import androidx.media3.ui.AspectRatioFrameLayout
 import androidx.media3.ui.PlayerView
 import com.example.m20_gamepad.data.VideoResizeMode
+import kotlinx.coroutines.delay
 
 /**
  * 视频解码器选择策略。
@@ -44,13 +51,18 @@ enum class VideoCodec {
 /** RTSP 播放状态 */
 sealed class RtspState {
     /** 连接中 */
-    object Connecting : RtspState()
+    data class Connecting(val retryCount: Int = 0) : RtspState()
     /** 播放中 */
     object Playing : RtspState()
-    /** 连接失败 */
+    /** 连接失败（自动重试中） */
-    data class Error(val message: String) : RtspState()
+    data class Error(val message: String, val retryCount: Int = 0, val nextRetryMs: Long = 0) : RtspState()
 }
 
+/** 指数退避参数 */
+private const val RETRY_DELAY_INITIAL_MS = 1000L
+private const val RETRY_DELAY_MAX_MS = 30_000L
+private const val RETRY_DELAY_MULTIPLIER = 2
+
 /**
  * RTSP 视频流播放 Composable。
  *
@@ -72,7 +84,10 @@ fun RtspVideoPlayer(
 ) {
     val context = LocalContext.current
 
-    var state by remember { mutableStateOf<RtspState>(RtspState.Connecting) }
+    var state by remember { mutableStateOf<RtspState>(RtspState.Connecting()) }
+    var retryCount by remember { mutableIntStateOf(0) }
+    var retryDelayMs by remember { mutableStateOf(RETRY_DELAY_INITIAL_MS) }
+    var retrySignal by remember { mutableIntStateOf(0) }
 
     // codec 变化时重建 ExoPlayer，新的 selector 在 RenderersFactory 中注入，
     // 同时使用最小缓冲策略降低延迟
@@ -99,24 +114,42 @@ fun RtspVideoPlayer(
                 addListener(object : Player.Listener {
                     override fun onPlaybackStateChanged(playbackState: Int) {
                         state = when (playbackState) {
-                            Player.STATE_BUFFERING -> RtspState.Connecting
+                            Player.STATE_BUFFERING -> RtspState.Connecting(retryCount)
                             Player.STATE_READY -> RtspState.Playing
-                            Player.STATE_IDLE -> RtspState.Connecting
+                            Player.STATE_IDLE -> RtspState.Connecting(retryCount)
                             else -> state
                         }
                     }
 
                     override fun onPlayerError(error: PlaybackException) {
-                        state = RtspState.Error(error.message ?: "连接失败")
+                        state = RtspState.Error(
+                            message = error.message ?: "连接失败",
+                            retryCount = retryCount,
+                            nextRetryMs = retryDelayMs
+                        )
+                        // 递增 retrySignal 触发 LaunchedEffect 自动重试
+                        retrySignal++
                     }
                 })
             }
     }
 
-    // URL 或 codec 变化时重新加载媒体源
+    // 初始连接 + 自动重试：key 包含 url/codec 变化时自动取消旧重试
-    LaunchedEffect(url, codec) {
+    LaunchedEffect(url, codec, retrySignal) {
         if (url.isNotBlank()) {
-            state = RtspState.Connecting
+            if (retrySignal == 0) {
+                // 首次连接 / URL 或 codec 变更：重置退避
+                retryCount = 0
+                retryDelayMs = RETRY_DELAY_INITIAL_MS
+            } else {
+                // 重试：指数退避等待
+                delay(retryDelayMs)
+                retryDelayMs = (retryDelayMs * RETRY_DELAY_MULTIPLIER).coerceAtMost(RETRY_DELAY_MAX_MS)
+                retryCount++
+            }
+            state = RtspState.Connecting(retryCount)
+            player.stop()
+            player.clearMediaItems()
             val mediaItem = MediaItem.fromUri(url)
             player.setMediaItem(mediaItem)
             player.prepare()
@@ -152,23 +185,50 @@ fun RtspVideoPlayer(
 
         // 连接中 / 错误时的提示覆盖层
         when (val s = state) {
-            is RtspState.Connecting -> StatusOverlay("连接 RTSP 流中...")
+            is RtspState.Connecting -> {
-            is RtspState.Error -> StatusOverlay("RTSP 连接失败: ${s.message}")
+                val msg = if (s.retryCount > 0) {
+                    "RTSP 重连中... (第 ${s.retryCount} 次)"
+                } else {
+                    "连接 RTSP 流中..."
+                }
+                StatusOverlay(msg)
+            }
+            is RtspState.Error -> {
+                val retryHint = if (s.nextRetryMs > 0) {
+                    "${s.nextRetryMs / 1000}s 后自动重试"
+                } else ""
+                StatusOverlay(
+                    text = "RTSP 连接失败: ${s.message}",
+                    subtitle = retryHint
+                )
+            }
             is RtspState.Playing -> { /* 正常播放，不显示覆盖层 */ }
         }
     }
 }
 
 @Composable
-private fun StatusOverlay(text: String) {
+private fun StatusOverlay(text: String, subtitle: String = "") {
     Box(
         modifier = Modifier.fillMaxSize(),
         contentAlignment = Alignment.Center
     ) {
+        Column(horizontalAlignment = Alignment.CenterHorizontally) {
             Text(
                 text = text,
-            color = Color.White
+                color = Color.White,
+                fontSize = 16.sp
             )
+            if (subtitle.isNotBlank()) {
+                Text(
+                    text = subtitle,
+                    color = Color.White.copy(alpha = 0.7f),
+                    fontSize = 13.sp,
+                    fontWeight = FontWeight.Light,
+                    modifier = Modifier.padding(top = 4.dp)
+                )
+            }
+        }
     }
 }