feat: notification listener service and media source hardening

app/src/main/java/top/yeij/hearth/media/HearthNotificationListenerService.kt

@@ -0,0 +1,13 @@
+package top.yeij.hearth.media
+
+import android.service.notification.NotificationListenerService
+
+// 通知监听服务：空实现，仅作为「通知使用权」授权凭据，
+// 让 MediaSessionManager.addOnActiveSessionsChangedListener(cb, listenerComponent)
+// 能拿到活跃媒体会话（否则普通 APK 拿不到 MEDIA_CONTENT_CONTROL 系统权限）。
+// Notification listener service: empty implementation, only serves as the
+// "notification access" authorization credential so that
+// MediaSessionManager.addOnActiveSessionsChangedListener(cb, listenerComponent)
+// can receive active media sessions (a normal APK cannot hold the
+// MEDIA_CONTENT_CONTROL system permission).
+class HearthNotificationListenerService : NotificationListenerService()

app/src/main/java/top/yeij/hearth/media/MediaSessionSource.kt

@@ -1,5 +1,6 @@
 package top.yeij.hearth.media
 
+import android.content.ComponentName
 import android.content.Context
 import android.media.MediaMetadata
 import android.media.session.MediaController
@@ -11,16 +12,26 @@ import android.util.Log
 // Watch active media sessions; build MediaInfo from the first controller's metadata + playbackState
 class MediaSessionSource(context: Context) {
     private val msm = context.getSystemService(Context.MEDIA_SESSION_SERVICE) as MediaSessionManager
-    private var listener: ((MediaInfo?) -> Unit)? = null
 
-    fun start(cb: (MediaInfo?) -> Unit) {
-        listener = cb
-        msm.addOnActiveSessionsChangedListener({ controllers ->
+    // 通知监听组件作为授权凭据传入 addOnActiveSessionsChangedListener，
+    // 取代依赖 MEDIA_CONTENT_CONTROL 系统权限的 null 方案。
+    // The notification listener component is passed as the authorization credential,
+    // replacing the null-based approach that relied on the MEDIA_CONTENT_CONTROL permission.
+    private val listenerComponent = ComponentName(context, HearthNotificationListenerService::class.java)
+
+    private var callback: ((MediaInfo?) -> Unit)? = null
+    private var registered = false
+
+    // 具名监听器字段：回调通过 callback 字段转发，便于 start/stop 幂等管理
+    // Named listener field: forwards via callback, enabling idempotent start/stop
+    private val activeSessionsListener =
+        MediaSessionManager.OnActiveSessionsChangedListener { controllers ->
+            val cb = callback ?: return@OnActiveSessionsChangedListener
             val c = controllers?.firstOrNull()
             if (c == null) {
-                Log.d("HearthMedia", "no active media session")
+                Log.d(TAG, "no active media session")
                 cb(null)
-                return@addOnActiveSessionsChangedListener
+                return@OnActiveSessionsChangedListener
             }
             val meta = c.metadata
             val state = c.playbackState
@@ -35,7 +46,32 @@ class MediaSessionSource(context: Context) {
                     c.packageName,
                 )
             )
-            Log.d("HearthMedia", "media: ${c.packageName}")
-        }, null)
+            Log.d(TAG, "media: ${c.packageName}")
+        }
+
+    // 注册监听：幂等——先移除旧监听再注册，避免重复 start 累积监听器
+    // Register the listener: idempotent — remove the old listener first, avoiding
+    // listener accumulation from repeated start() calls
+    fun start(cb: (MediaInfo?) -> Unit) {
+        stop()
+        callback = cb
+        msm.addOnActiveSessionsChangedListener(activeSessionsListener, listenerComponent)
+        registered = true
+        Log.d(TAG, "start: media session listener registered")
+    }
+
+    // 注销监听：释放回调引用，供 Activity onDestroy 调用
+    // Unregister the listener: release the callback, call from Activity onDestroy
+    fun stop() {
+        if (registered) {
+            msm.removeOnActiveSessionsChangedListener(activeSessionsListener)
+            registered = false
+            Log.d(TAG, "stop: media session listener removed")
+        }
+        callback = null
+    }
+
+    companion object {
+        private const val TAG = "HearthMedia"
     }
 }