如何在Fragment中获取Activity的权限申请结果？

你的问题本质是权限申请结果无法从Activity传递到Fragment，导致用户授权后Fragment没法触发显示地图的逻辑。下面给你三种实用的解决方案，按推荐程度排序：

方案1：让Fragment直接处理权限请求（最推荐） #

其实Fragment本身就自带权限申请和结果回调的能力，完全不需要通过Activity中转。这样逻辑更内聚，也避免了跨组件通信的麻烦。

修改你的MapFragment代码：

override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
    super.onViewCreated(view, savedInstanceState)
    
    if (ContextCompat.checkSelfPermission(requireContext(), android.Manifest.permission.ACCESS_FINE_LOCATION) 
        == PackageManager.PERMISSION_GRANTED) {
        // 权限已授予，显示地图
        permission_button.visibility = View.GONE
        val mapFragment = childFragmentManager.findFragmentById(R.id.map) as SupportMapFragment?
        mapFragment?.getMapAsync(callback)
    } else {
        // 权限未授予，自己申请
        requestPermissions(
            arrayOf(android.Manifest.permission.ACCESS_FINE_LOCATION),
            Constants.LOCATION_PREMMISION_CODE
        )
    }
}

// 重写Fragment的权限结果回调
override fun onRequestPermissionsResult(
    requestCode: Int,
    permissions: Array<out String>,
    grantResults: IntArray
) {
    super.onRequestPermissionsResult(requestCode, permissions, grantResults)
    if (requestCode == Constants.LOCATION_PREMMISION_CODE) {
        if (grantResults.isNotEmpty() && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
            // 用户授予权限，显示地图
            permission_button.visibility = View.GONE
            val mapFragment = childFragmentManager.findFragmentById(R.id.map) as SupportMapFragment?
            mapFragment?.getMapAsync(callback)
        } else {
            // 用户拒绝权限，隐藏地图
            permission_button.visibility = View.VISIBLE
            // 可以在这里提示用户需要权限才能使用地图
        }
    }
}

这样Fragment完全自主处理权限逻辑，不用依赖Activity的uiCommunicationListener，代码更清晰。

方案2：扩展接口回调，让Activity通知Fragment结果 #

如果一定要保留Activity的权限检查逻辑，可以扩展你的uiCommunicationListener接口，增加一个权限结果回调方法，让Activity在收到权限结果后通知Fragment。

第一步：修改接口定义 #

interface UiCommunicationListener {
    fun isLocationPermissionGranted(): Boolean
    // 新增权限结果回调方法
    fun onLocationPermissionResult(granted: Boolean)
}

第二步：修改MainActivity的权限处理 #

override fun isLocationPermissionGranted(): Boolean {
    if (ContextCompat.checkSelfPermission(
            this,
            android.Manifest.permission.ACCESS_FINE_LOCATION
        ) != PackageManager.PERMISSION_GRANTED) {
        ActivityCompat.requestPermissions(
            this,
            arrayOf(android.Manifest.permission.ACCESS_FINE_LOCATION),
            Constants.LOCATION_PREMMISION_CODE
        )
        return false
    } else {
        return true
    }
}

override fun onRequestPermissionsResult(
    requestCode: Int,
    permissions: Array<out String>,
    grantResults: IntArray
) {
    super.onRequestPermissionsResult(requestCode, permissions, grantResults)
    if (requestCode == Constants.LOCATION_PREMMISION_CODE) {
        val granted = grantResults.isNotEmpty() && grantResults[0] == PackageManager.PERMISSION_GRANTED
        // 通知所有实现了接口的Fragment，或者指定你的MapFragment
        supportFragmentManager.fragments.forEach { fragment ->
            if (fragment is UiCommunicationListener) {
                fragment.onLocationPermissionResult(granted)
            }
        }
    }
}

第三步：在MapFragment中实现回调 #

class MapFragment : Fragment(), UiCommunicationListener {
    // ... 其他代码 ...

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
        checkLocationPermission()
    }

    private fun checkLocationPermission() {
        if (uiCommunicationListener.isLocationPermissionGranted()) {
            showMap()
        } else {
            hideMap()
        }
    }

    private fun showMap() {
        permission_button.visibility = View.GONE
        val mapFragment = childFragmentManager.findFragmentById(R.id.map) as SupportMapFragment?
        mapFragment?.getMapAsync(callback)
    }

    private fun hideMap() {
        permission_button.visibility = View.VISIBLE
        // 隐藏地图的逻辑
    }

    override fun onLocationPermissionResult(granted: Boolean) {
        if (granted) {
            showMap()
        } else {
            hideMap()
        }
    }
}

方案3：用ViewModel共享权限状态（适合复杂场景） #

如果你的项目用了Jetpack组件，可以用ViewModel来共享权限状态，Activity更新状态，Fragment观察状态变化。

第一步：创建PermissionViewModel #

class PermissionViewModel : ViewModel() {
    val locationPermissionGranted = MutableLiveData<Boolean>()
}

第二步：在MainActivity中更新状态 #

class MainActivity : AppCompatActivity(), UiCommunicationListener {
    private val permissionViewModel: PermissionViewModel by viewModels()

    override fun isLocationPermissionGranted(): Boolean {
        val granted = ContextCompat.checkSelfPermission(
            this,
            android.Manifest.permission.ACCESS_FINE_LOCATION
        ) == PackageManager.PERMISSION_GRANTED
        permissionViewModel.locationPermissionGranted.value = granted
        if (!granted) {
            ActivityCompat.requestPermissions(
                this,
                arrayOf(android.Manifest.permission.ACCESS_FINE_LOCATION),
                Constants.LOCATION_PREMMISION_CODE
            )
        }
        return granted
    }

    override fun onRequestPermissionsResult(
        requestCode: Int,
        permissions: Array<out String>,
        grantResults: IntArray
    ) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults)
        if (requestCode == Constants.LOCATION_PREMMISION_CODE) {
            permissionViewModel.locationPermissionGranted.value = 
                grantResults.isNotEmpty() && grantResults[0] == PackageManager.PERMISSION_GRANTED
        }
    }
}

第三步：在MapFragment中观察状态 #

class MapFragment : Fragment() {
    private val permissionViewModel: PermissionViewModel by activityViewModels()

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
        
        // 观察权限状态变化
        permissionViewModel.locationPermissionGranted.observe(viewLifecycleOwner) { granted ->
            if (granted) {
                showMap()
            } else {
                hideMap()
            }
        }

        // 初始检查权限
        (activity as? UiCommunicationListener)?.isLocationPermissionGranted()
    }

    private fun showMap() {
        permission_button.visibility = View.GONE
        val mapFragment = childFragmentManager.findFragmentById(R.id.map) as SupportMapFragment?
        mapFragment?.getMapAsync(callback)
    }

    private fun hideMap() {
        permission_button.visibility = View.VISIBLE
        // 隐藏地图的逻辑
    }
}

个人最推荐方案1，因为它让Fragment的逻辑更独立，减少了和Activity的耦合。如果你的项目有统一的权限管理需求，方案2或3会更合适。

内容的提问来源于stack exchange，提问作者ScrapeW