从StatusFragment返回后HomeFragment数据绑定失效问题排查

我的应用包含HomeFragment和StatusFragment两个碎片，HomeFragment通过广播接收器获取连接信息并绑定至UI。初始状态下数据绑定正常，但当用户进入StatusFragment再返回HomeFragment后，信息无法完成绑定。

更新：返回HomeFragment后，onCreateView()被调用，但HomeFragmentViewModelFactory未执行！我需要通过它向ViewModel传入新的repo对象。

已尝试的操作 #

• 在onResume()中调用registerReceiver()
• 为binding.lifecycleOwner设置viewLifecycleOwner替代this
• 在StatusFragment中按下返回键时调用popBackStack()

相关代码 #

HomeFragment #

class HomeFragment : Fragment() {

    private var binding: FragmentHomeBinding? = null
    private var connectionStatus: String? = "Offline"
    private var connectionType: String? = ""

    private lateinit var mReceiver: ConnectivityChangeBroadcastReceiver
    lateinit var homeFragmentViewModel: HomeFragmentViewModel
    lateinit var repo: Repository

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
    }

    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        binding = FragmentHomeBinding.inflate(inflater, container, false)
        binding?.lifecycleOwner = viewLifecycleOwner
        
        repo = Repository().getInstance()!!
        val viewModelFactory = HomeFragmentViewModelFactory(repo)
        homeFragmentViewModel =
            ViewModelProvider(this, viewModelFactory)[HomeFragmentViewModel::class.java]

        binding?.homeFragmentViewModel = homeFragmentViewModel
        this.mReceiver = ConnectivityChangeBroadcastReceiver()

        mReceiver.mData.observe(this, Observer {
            repo.setInfo(mReceiver.getData())
            homeFragmentViewModel.getConnectionInfo()
        })

        homeFragmentViewModel.navToStatusFragment.observe(this, Observer {
            if (it==true){
                this.findNavController().navigate(R.id.action_homeFragment_to_statusFragment)
                homeFragmentViewModel.doneNavigateToStatusFragment()
            }
        })

        return binding?.root
    }


    override fun onStart() {
        super.onStart()

        requireActivity().registerReceiver(
            mReceiver, IntentFilter(ConnectivityManager.CONNECTIVITY_ACTION)
        )
        repo.setInfo(mReceiver.getData())
    }

    override fun onStop() {
        super.onStop()
        requireActivity().unregisterReceiver(mReceiver)
    }

}

StatusFragment #

class StatusFragment : Fragment() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
    }

    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        requireActivity().onBackPressedDispatcher.addCallback(this){
            requireActivity().supportFragmentManager.popBackStack()
        }
        return inflater.inflate(R.layout.fragment_status, container, false)
    }

}

HomeFragmentViewModel #

class HomeFragmentViewModel(private val repo: Repository?) : ViewModel() {

    private val viewModelJob = Job()

    private val _navToStatusFragment = MutableLiveData<Boolean?>()
    val navToStatusFragment: LiveData<Boolean?>
        get() = _navToStatusFragment

    private val _connected = MutableLiveData<String?>()
    val connected: LiveData<String?>
        get() = _connected

    private val _connectionType = MutableLiveData<String?>()
    val connectionType: LiveData<String?>
        get() = _connectionType

    init {
        _navToStatusFragment.value = false
    }

    var isConnected: LiveData<Boolean> = connected.map {
        when (it) {
            "Online" -> true
            else -> false
        }
    }

    fun doneNavigateToStatusFragment(){
        _navToStatusFragment.value = false
    }

    fun navigateToStatusFragment(){
        _navToStatusFragment.value = true
    }

    fun getConnectionInfo() {

        when (repo?.getInfo()?.value) {
            0 -> {
                _connected.value = "Offline"
                _connectionType.value = "Check Your Connection"
                _connectionDetails.value = null
            }
            1 -> {
                _connected.value = "Online"
                _connectionType.value = "Cellular"
                _connectionDetails.value = null
            }
            2 -> {
                _connected.value = "Online"
                _connectionType.value = "WIFI"
                _connectionDetails.value = null
            }
            3 -> {
                _connected.value = "Online"
                _connectionType.value = "VPN"
                _connectionDetails.value = null
            }
        }
        Log.d("LOGGED", "Info Checked ...")
    }


    override fun onCleared() {
        super.onCleared()
        viewModelJob.cancel()
    }
}

内容的提问来源于stack exchange，提问作者Reza Asadian