Android Compose悬浮窗按返回按钮无法关闭问题求助

问题背景 #

在使用Jetpack Compose开发Android的Overlay Service悬浮窗时，按下返回按钮关闭悬浮窗的需求遇到两个问题：

• 使用BackHandler组件时，报错：No OnBackPressedDispatcherOwner was provided via LocalOnBackPressedDispatcherOwner
• 尝试为ComposeView设置OnKeyListener监听返回键，未收到任何回调

用户原Overlay Service核心代码：

class OverlayService : Service() {

val windowManager get() = getSystemService(WINDOW_SERVICE) as WindowManager

override fun onCreate() {
    super.onCreate()
    this.updateAppLanguage()
}

override fun onStartCommand(intent: Intent?, flags: Int, startId: Int): Int {
    handleIntent(intent)
    return super.onStartCommand(intent, flags, startId)
}

private fun handleIntent(intent: Intent?) {
    intent?.let {
        val number = it.getStringExtra("number")
        val dateEnd = it.getLongExtra("date", 0)
        if (number != null) {
            showOverlay(number, dateEnd)
        }
    }
}

private fun showOverlay(number: String, date: Long) {
    val layoutFlag: Int = WindowManager.LayoutParams.TYPE_APPLICATION_OVERLAY

    val params = WindowManager.LayoutParams(
        WindowManager.LayoutParams.MATCH_PARENT,
        WindowManager.LayoutParams.MATCH_PARENT,
        layoutFlag,
        WindowManager.LayoutParams.FLAG_LAYOUT_IN_SCREEN or WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE,
        PixelFormat.TRANSLUCENT
    )

    val composeView = ComposeView(this)
    composeView.setContent {
        // 原有Compose内容
        val context = LocalContext.current
        val rememberAds by remember {
            mutableStateOf(PreviousCallCard.showAd(context))
        }
        val animVisibleState = remember {
            MutableTransitionState(false)
                .apply { targetState = true }
        }
        if (!animVisibleState.targetState &&
            !animVisibleState.currentState
        ) {
            PreviousCallCard.finishedShowingCard(this)
            windowManager.removeView(composeView)
            this@OverlayService.stopSelf()
        }

        AnimatedVisibility(
            modifier = Modifier,
            visibleState = animVisibleState,
            enter = fadeIn(),
            exit = fadeOut()
        ) {
            // 原有布局内容
        }
    }

    // 原有生命周期相关设置
    val viewModelStore = ViewModelStore()
    val viewModelStoreOwner = object : ViewModelStoreOwner {
        override val viewModelStore: ViewModelStore
            get() = viewModelStore
    }
    val lifecycleOwner = MyLifecycleOwner()
    lifecycleOwner.performRestore(null)
    lifecycleOwner.handleLifecycleEvent(Lifecycle.Event.ON_CREATE)
    lifecycleOwner.handleLifecycleEvent(Lifecycle.Event.ON_START)
    lifecycleOwner.handleLifecycleEvent(Lifecycle.Event.ON_RESUME)
    composeView.setViewTreeLifecycleOwner(lifecycleOwner)
    composeView.setViewTreeSavedStateRegistryOwner(lifecycleOwner)
    composeView.setViewTreeViewModelStoreOwner(viewModelStoreOwner)

    windowManager.addView(composeView, params)
}

override fun onBind(intent: Intent): IBinder? {
    return null
}

用户尝试的OnKeyListener代码（未生效）：

composeView.requestFocus()
composeView.setFocusableInTouchMode(true)
composeView.setOnKeyListener(View.OnKeyListener { v, keyCode, event ->
    if (keyCode == KeyEvent.KEYCODE_BACK) {
        stopSelf()
        return@OnKeyListener true
    }
    false
})

核心问题分析 #

OnKeyListener未生效的根本原因是WindowManager.LayoutParams设置了FLAG_NOT_FOCUSABLE，该标记会让悬浮窗无法获取焦点，自然收不到任何按键事件。同时BackHandler报错是因为Compose的LocalOnBackPressedDispatcherOwner未被正确提供。

有效解决方案 #

方案一：修改LayoutParams后使用OnKeyListener #

1. 修改WindowManager.LayoutParams的flags
   将原有flags中的FLAG_NOT_FOCUSABLE替换为FLAG_NOT_TOUCH_MODAL，确保悬浮窗可以获取焦点：

   val params = WindowManager.LayoutParams(
       WindowManager.LayoutParams.MATCH_PARENT,
       WindowManager.LayoutParams.MATCH_PARENT,
       layoutFlag,
       WindowManager.LayoutParams.FLAG_LAYOUT_IN_SCREEN or WindowManager.LayoutParams.FLAG_NOT_TOUCH_MODAL,
       PixelFormat.TRANSLUCENT
   )
   

   FLAG_NOT_TOUCH_MODAL的作用是允许其他View接收触摸事件，同时当前悬浮窗仍能获取焦点和按键事件。

2. 正确设置ComposeView的焦点和OnKeyListener
   在添加到WindowManager之前，设置ComposeView的焦点属性并绑定监听器：

   composeView.apply {
       isFocusable = true
       isFocusableInTouchMode = true
       setOnKeyListener { _, keyCode, event ->
           // 只处理按下事件，避免重复触发
           if (event.action == KeyEvent.ACTION_DOWN && keyCode == KeyEvent.KEYCODE_BACK) {
               // 执行关闭逻辑：先移除View再停止Service
               windowManager.removeView(this)
               this@OverlayService.stopSelf()
               true
           } else {
               false
           }
       }
   }
   

方案二：自定义OnBackPressedDispatcherOwner，使用Compose BackHandler #

如果你更倾向于使用Compose的BackHandler组件，可以按以下步骤实现：

1. 同样先修改LayoutParams的flags（同方案一第一步，去掉FLAG_NOT_FOCUSABLE）

2. 实现自定义OnBackPressedDispatcherOwner
   在showOverlay方法中，添加自定义的OnBackPressedDispatcherOwner实现，并绑定到ComposeView的ViewTree：

   // 自定义OnBackPressedDispatcherOwner
   val backPressedDispatcherOwner = object : OnBackPressedDispatcherOwner {
       private val dispatcher = OnBackPressedDispatcher()
       override val onBackPressedDispatcher: OnBackPressedDispatcher
           get() = dispatcher
   
       override val lifecycle: Lifecycle
           get() = lifecycleOwner.lifecycle
   }
   
   // 绑定到ComposeView的ViewTree
   composeView.setViewTreeOnBackPressedDispatcherOwner(backPressedDispatcherOwner)
   

3. 在Compose内容中使用BackHandler
   在composeView.setContent内部添加BackHandler：

   composeView.setContent {
       // ... 原有代码
       BackHandler {
           // 触发关闭动画
           animVisibleState.targetState = false
           // 动画结束后执行销毁逻辑
           LaunchedEffect(animVisibleState.currentState) {
               if (!animVisibleState.currentState) {
                   windowManager.removeView(composeView)
                   this@OverlayService.stopSelf()
               }
           }
       }
       // ... 原有AnimatedVisibility等内容
   }
   

内容的提问来源于stack exchange，提问作者hema ezzat