feat: addListener returns removal function for granular listener control

Author: mfazekas

android/src/main/java/com/margelo/nitro/rive/BaseHybridViewModelProperty.kt

@@ -9,12 +9,14 @@ import kotlinx.coroutines.flow.Flow
 @Keep
 @DoNotStrip
 interface BaseHybridViewModelProperty<T> {
-    val scope: CoroutineScope?
-    val job: Job?
-    val listeners: MutableList<(T) -> Unit>
+  val scope: CoroutineScope?
+  val job: Job?
+  val listeners: MutableMap<String, (T) -> Unit>
 
-    fun ensureValueListenerJob(valueFlow: Flow<T>, drop: Int = 0)
-    fun onChanged(value: T)
-    fun removeListeners()
-    fun dispose()
+  fun ensureValueListenerJob(valueFlow: Flow<T>, drop: Int = 0)
+  fun onChanged(value: T)
+  fun addListenerInternal(callback: (T) -> Unit): () -> Unit
+  fun removeListener(id: String)
+  fun removeListeners()
+  fun dispose()
 }

android/src/main/java/com/margelo/nitro/rive/BaseHybridViewModelPropertyImpl.kt

@@ -9,42 +9,61 @@ import kotlinx.coroutines.cancel
 import kotlinx.coroutines.launch
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.drop
+import java.lang.ref.WeakReference
+import java.util.UUID
 
 @Keep
 @DoNotStrip
 class BaseHybridViewModelPropertyImpl<T> : BaseHybridViewModelProperty<T> {
-    override var scope: CoroutineScope? = null
-    override var job: Job? = null
-    override val listeners = mutableListOf<(T) -> Unit>()
+  override var scope: CoroutineScope? = null
+  override var job: Job? = null
+  override val listeners = mutableMapOf<String, (T) -> Unit>()
 
   override fun ensureValueListenerJob(valueFlow: Flow<T>, drop: Int) {
-        if (scope == null) {
-            scope = CoroutineScope(Dispatchers.Default)
-        }
-        if (job == null) {
-            job = scope?.launch {
-                valueFlow.drop(drop).collect { value ->
-                    onChanged(value)
-                }
-            }
+    if (scope == null) {
+      scope = CoroutineScope(Dispatchers.Default)
+    }
+    if (job == null) {
+      job = scope?.launch {
+        valueFlow.drop(drop).collect { value ->
+          onChanged(value)
         }
+      }
     }
+  }
 
-    override fun onChanged(value: T) {
-        listeners.forEach { listener ->
-            listener(value)
-        }
+  override fun onChanged(value: T) {
+    listeners.values.forEach { listener ->
+      listener(value)
     }
+  }
 
-    override fun removeListeners() {
-        listeners.clear()
-        job?.cancel()
-        scope?.cancel()
-        job = null
-        scope = null
+  override fun addListenerInternal(callback: (T) -> Unit): () -> Unit {
+    val id = UUID.randomUUID().toString()
+    listeners[id] = callback
+    val weakSelf = WeakReference(this)
+    return {
+      weakSelf.get()?.removeListener(id)
     }
+  }
 
-    override fun dispose() {
-        removeListeners()
+  override fun removeListener(id: String) {
+    listeners.remove(id)
+    if (listeners.isEmpty()) {
+      job?.cancel()
+      job = null
     }
+  }
+
+  override fun removeListeners() {
+    listeners.clear()
+    job?.cancel()
+    scope?.cancel()
+    job = null
+    scope = null
+  }
+
+  override fun dispose() {
+    removeListeners()
+  }
 }

android/src/main/java/com/margelo/nitro/rive/HybridViewModelBooleanProperty.kt

@@ -15,8 +15,9 @@ class HybridViewModelBooleanProperty(private val viewModelBoolean: ViewModelBool
       viewModelBoolean.value = value
     }
 
-  override fun addListener(onChanged: (value: Boolean) -> Unit) {
-    listeners.add(onChanged)
+  override fun addListener(onChanged: (value: Boolean) -> Unit): () -> Unit {
+    val remover = addListenerInternal(onChanged)
     ensureValueListenerJob(viewModelBoolean.valueFlow)
+    return remover
   }
 }

android/src/main/java/com/margelo/nitro/rive/HybridViewModelColorProperty.kt

@@ -15,8 +15,9 @@ class HybridViewModelColorProperty(private val viewModelColor: ViewModelColorPro
       viewModelColor.value = value.toInt()
     }
 
-  override fun addListener(onChanged: (value: Double) -> Unit) {
-    listeners.add { intValue: Int -> onChanged(intValue.toDouble()) }
+  override fun addListener(onChanged: (value: Double) -> Unit): () -> Unit {
+    val remover = addListenerInternal { intValue: Int -> onChanged(intValue.toDouble()) }
     ensureValueListenerJob(viewModelColor.valueFlow)
+    return remover
   }
 }

android/src/main/java/com/margelo/nitro/rive/HybridViewModelEnumProperty.kt

@@ -15,8 +15,9 @@ class HybridViewModelEnumProperty(private val viewModelEnum: ViewModelEnumProper
       viewModelEnum.value = value
     }
 
-  override fun addListener(onChanged: (value: String) -> Unit) {
-    listeners.add(onChanged)
+  override fun addListener(onChanged: (value: String) -> Unit): () -> Unit {
+    val remover = addListenerInternal(onChanged)
     ensureValueListenerJob(viewModelEnum.valueFlow)
+    return remover
   }
 }

android/src/main/java/com/margelo/nitro/rive/HybridViewModelImageProperty.kt

@@ -14,8 +14,9 @@ class HybridViewModelImageProperty(private val viewModelImage: ViewModelImagePro
     viewModelImage.set((image as? HybridRiveImage)?.renderImage)
   }
 
-  override fun addListener(onChanged: () -> Unit) {
-    listeners.add(onChanged)
+  override fun addListener(onChanged: () -> Unit): () -> Unit {
+    val remover = addListenerInternal { _ -> onChanged() }
     ensureValueListenerJob(viewModelImage.valueFlow.map { })
+    return remover
   }
 }

android/src/main/java/com/margelo/nitro/rive/HybridViewModelNumberProperty.kt

@@ -16,8 +16,9 @@ class HybridViewModelNumberProperty(private val viewModelNumber: ViewModelNumber
       viewModelNumber.value = value.toFloat()
     }
 
-  override fun addListener(onChanged: (value: Double) -> Unit) {
-    listeners.add(onChanged)
+  override fun addListener(onChanged: (value: Double) -> Unit): () -> Unit {
+    val remover = addListenerInternal(onChanged)
     ensureValueListenerJob(viewModelNumber.valueFlow.map { it.toDouble() })
+    return remover
   }
 }

android/src/main/java/com/margelo/nitro/rive/HybridViewModelStringProperty.kt

@@ -15,8 +15,9 @@ class HybridViewModelStringProperty(private val viewModelString: ViewModelString
       viewModelString.value = value
     }
 
-  override fun addListener(onChanged: (value: String) -> Unit) {
-    listeners.add(onChanged)
+  override fun addListener(onChanged: (value: String) -> Unit): () -> Unit {
+    val remover = addListenerInternal(onChanged)
     ensureValueListenerJob(viewModelString.valueFlow)
+    return remover
   }
 }

android/src/main/java/com/margelo/nitro/rive/HybridViewModelTriggerProperty.kt

@@ -13,9 +13,10 @@ class HybridViewModelTriggerProperty(private val viewModelTrigger: ViewModelTrig
     viewModelTrigger.trigger()
   }
 
-  override fun addListener(onChanged: () -> Unit) {
-    listeners.add { _ -> onChanged() }
+  override fun addListener(onChanged: () -> Unit): () -> Unit {
+    val remover = addListenerInternal { _ -> onChanged() }
     // We drop the first value as a trigger has no initial value
     ensureValueListenerJob(viewModelTrigger.valueFlow, 1)
+    return remover
   }
 }