【问题标题】：How to show something when an android app is not active/focused?如何在 Android 应用程序未激活/未聚焦时显示内容？
【发布时间】：2022-11-15 18:06:03
【问题描述】：

我想打开我的应用程序并从中查看随处可用的内容（例如小部件），而不仅仅是在打开应用程序时
例子：

请注意，我在桌面页面上，应用程序未打开，但在后台处于活动状态，并在各处显示带有 Hello 文本的“小部件”

【问题讨论】：

标签： android kotlin android-jetpack-compose android-view

【解决方案1】：

为AndroidManifest.xml添加android.permission.SYSTEM_ALERT_WINDOW权限

// AndroidManifest.xml
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    package="com.freephoenix888.savemylife"> 
    // Something else

    <uses-permission android:name="android.permission.SYSTEM_ALERT_WINDOW"/>
    // Something else
</manifest>

注意：不要忘记向用户请求此权限 Documentation

创建一个实现 SavedStateRegistryOwner 的类

internal class MyLifecycleOwner : SavedStateRegistryOwner {

    private var mLifecycleRegistry: LifecycleRegistry = LifecycleRegistry(this)
    private var mSavedStateRegistryController: SavedStateRegistryController = SavedStateRegistryController.create(this)

    val isInitialized: Boolean
        get() = true
    override val savedStateRegistry: SavedStateRegistry
        get() = mSavedStateRegistryController.savedStateRegistry

    override fun getLifecycle(): Lifecycle {
        return mLifecycleRegistry
    }

    fun setCurrentState(state: Lifecycle.State) {
        mLifecycleRegistry.currentState = state
    }

    fun handleLifecycleEvent(event: Lifecycle.Event) {
        mLifecycleRegistry.handleLifecycleEvent(event)
    }

    fun performRestore(savedState: Bundle?) {
        mSavedStateRegistryController.performRestore(savedState)
    }

    fun performSave(outBundle: Bundle) {
        mSavedStateRegistryController.performSave(outBundle)
    }
}

在活动或服务中添加您的视图

val layoutFlag: Int = if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
    WindowManager.LayoutParams.TYPE_APPLICATION_OVERLAY
} else {
    WindowManager.LayoutParams.TYPE_PHONE
}

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

/* For views (not compose views)
val floatView = (getSystemService(Context.LAYOUT_INFLATER_SERVICE) as LayoutInflater).inflate(R.layout.view_service_float, null)
*/

val composeView = ComposeView(this)
composeView.setContent {
    Text(
        text = "Hello",
        color = Color.Black,
        fontSize = 50.sp,
        modifier = Modifier
            .wrapContentSize()
            .background(Color.Green)
    )
}

val viewModelStore = ViewModelStore()
val lifecycleOwner = MyLifecycleOwner()
lifecycleOwner.performRestore(null)
lifecycleOwner.handleLifecycleEvent(Lifecycle.Event.ON_CREATE)
ViewTreeLifecycleOwner.set(composeView, lifecycleOwner)
ViewTreeViewModelStoreOwner.set(composeView) { viewModelStore }
composeView.setViewTreeSavedStateRegistryOwner(lifecycleOwner)

windowManager.addView(composeView, params)

【讨论】：