Android Jetpack compose：使用谷歌地图在地图创建时崩溃

Question

我试图在 google compose 示例项目调用 Crane 的帮助下实现 google map： https://github.com/android/compose-samples/tree/main/Crane

我使用相同的实现并使用 MapViewUtils 来实现 map 的 lifeCycler 并防止重新组合内容等等...我把所有的 android 地图键和权限在清单上， 但是我的代码在地图开始时崩溃了：

这就是我想展示地图的地方：

@Composable
fun MapScreen(latitude: String, longitude: String) {
    // The MapView lifecycle is handled by this composable. As the MapView also needs to be updated
    // with input from Compose UI, those updates are encapsulated into the MapViewContainer
    // composable. In this way, when an update to the MapView happens, this composable won't
    // recompose and the MapView won't need to be recreated.
    val mapView = rememberMapViewWithLifecycle()
    MapViewContainer(mapView, latitude, longitude)
}

@Composable
private fun MapViewContainer(
    map: MapView,
    latitude: String,
    longitude: String
) {
//    var zoom by savedInstanceState { InitialZoom }

    AndroidView({ map }) { mapView ->
        // Reading zoom so that AndroidView recomposes when it changes. The getMapAsync lambda
        mapView.getMapAsync {
            val position = LatLng(latitude.toDouble(), longitude.toDouble())
            it.addMarker(
                MarkerOptions().position(position)
            )
            it.moveCamera(CameraUpdateFactory.newLatLng(position))
        }
    }
}

这是在 Util 类中：

@Composable
fun rememberMapViewWithLifecycle(): MapView {
    val context = ContextAmbient.current
    val mapView = remember {
        MapView(context).apply {
            id = R.id.map
        }
    }

//     Makes MapView follow the lifecycle of this composable
    val lifecycleObserver = rememberMapLifecycleObserver(mapView)
    val lifecycle = LifecycleOwnerAmbient.current.lifecycle
    onCommit(lifecycle) {
        lifecycle.addObserver(lifecycleObserver)
        onDispose {
            lifecycle.removeObserver(lifecycleObserver)
        }
    }

    return mapView
}

@Composable
private fun rememberMapLifecycleObserver(mapView: MapView): LifecycleEventObserver =
    remember(mapView) {
        LifecycleEventObserver { _, event ->
            when (event) {
                Lifecycle.Event.ON_CREATE -> mapView.onCreate(Bundle()) //Crashes here
                Lifecycle.Event.ON_START -> mapView.onStart()
                Lifecycle.Event.ON_RESUME -> mapView.onResume()
                Lifecycle.Event.ON_PAUSE -> mapView.onPause()
                Lifecycle.Event.ON_STOP -> mapView.onStop()
                Lifecycle.Event.ON_DESTROY -> mapView.onDestroy()
                else -> throw IllegalStateException()
            }
        }
    }

我遇到了这个崩溃：

2020-11-05 12:16:09.282 2665-3383/com.google.android.gms.persistent E/ModuleIdSetter: exception when setting module id
    java.lang.IllegalStateException: Unable to get current module info in ModuleManager created with non-module Context
        at com.google.android.chimera.config.ModuleManager.getCurrentModule(:com.google.android.gms@202414022@20.24.14 (040700-319035315):2)
        at aewd.a(:com.google.android.gms@202414022@20.24.14 (040700-319035315):4)
        at aewg.b(:com.google.android.gms@202414022@20.24.14 (040700-319035315):9)
        at aeso.a(Unknown Source:0)
        at rpm.a(:com.google.android.gms@202414022@20.24.14 (040700-319035315):0)
        at rlv.c(:com.google.android.gms@202414022@20.24.14 (040700-319035315):1)
        at rlt.b(:com.google.android.gms@202414022@20.24.14 (040700-319035315):1)
        at rok.b(:com.google.android.gms@202414022@20.24.14 (040700-319035315):6)
        at rok.c(:com.google.android.gms@202414022@20.24.14 (040700-319035315):6)
        at rok.b(:com.google.android.gms@202414022@20.24.14 (040700-319035315):10)
        at rok.a(:com.google.android.gms@202414022@20.24.14 (040700-319035315):17)
        at rok.g(:com.google.android.gms@202414022@20.24.14 (040700-319035315):3)
        at sdr.a(:com.google.android.gms@202414022@20.24.14 (040700-319035315):2)
        at scr.a(:com.google.android.gms@202414022@20.24.14 (040700-319035315):10)
        at sci.a(:com.google.android.gms@202414022@20.24.14 (040700-319035315):0)
        at scl.handleMessage(:com.google.android.gms@202414022@20.24.14 (040700-319035315):28)
        at android.os.Handler.dispatchMessage(Handler.java:107)
        at aekz.a(:com.google.android.gms@202414022@20.24.14 (040700-319035315):2)
        at aekz.dispatchMessage(:com.google.android.gms@202414022@20.24.14 (040700-319035315):14)
        at android.os.Looper.loop(Looper.java:214)
        at android.os.HandlerThread.run(HandlerThread.java:67)

Answer 1

您需要获得访问用户位置的权限，并在显示地图之前确保您拥有该权限。您可以使用带有 LiveData 和 ViewModel 的变量，该变量在授予权限时更新，这是示例的一部分：

class MainViewModel : ViewModel() {
    private val _permissionGranted = MutableLiveData(false)
    val permissionGranted = _permissionGranted
    
    fun onPermissionGranted() = _permissionGranted.postValue(true)
    
    // ...
}

class MainActivity : AppCompatActivity() {
    private val mainViewModel by viewModels<MainViewModel>
    
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContent {
            val permissionGranted = mainViewModel.permissionGranted.observeAsState()
            if (permissionGranted) {
                // logic to show your map
            } else {
                // logic to ask for permission
            }
        }
    }
    
    override fun onRequestPermissionsResult(requestCode: Int,
        permissions: Array<String>, grantResults: IntArray) {
        // check if it's your request
        mainViewModel.onPremissionGranted()
    }
    
    // ...
}

您可以在此处获取有关请求权限的更多信息：https://developer.android.com/training/permissions/requesting

Answer 2

去掉从“fun rememberMapViewWithLifecycle(): MapView”到“fun rememberMapViewWithLifecycle()”的返回类型

很明显，您的可组合函数正在返回一个 MapView，但它不应该返回一个类型才能被视为可组合函数。 我引用“https://developer.android.com/jetpack/compose/mental-model"

""" 该函数不返回任何内容。发出 UI 的 Compose 函数不需要返回任何内容，因为它们描述了所需的屏幕状态，而不是构造 UI 小部件。

"""