Question

我正在尝试实现android jetpack导航组件。该案例与官方文档中的案例几乎相同：https://developer.android.com/guide/navigation/navigation-conditional

但是我的情况是，如果用户尚未登录，那么登录访问将记录在数据库（房间）中，然后系统将强制用户登录。我用https://developer.android.com/guide/navigation/navigation-global-action声明登录片段的目的地

然后依次定义如下

主页片段是startDestination，
如果在数据库中未找到用户数据，请显示登录页面
如果登录成功，则将用户带回家并保存数据登录到数据库。

我使用MVVM体系结构和协程，它们对REST运行请求使用翻新。

以下是我使用的一些代码：

导航（xml）

 <navigation xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:app="http://schemas.android.com/apk/res-auto"
     xmlns:tools="http://schemas.android.com/tools"
     android:id="@+id/nav"
     app:startDestination="@id/homeFragment">

     <fragment
         android:id="@+id/homeFragment"
         android:name="com.depo.trask.ui.home.HomeFragment"
         android:label="@string/app_name"
         tools:layout="@layout/fragment_home">

         <argument android:name="authentication"
             android:defaultValue="none" />

         <action
             android:id="@+id/action_homeFragment_to_settingsFragment"
             app:destination="@id/settingsFragment" />

     </fragment>
     <fragment
         android:id="@+id/settingsFragment"
         android:name="com.depo.trask.ui.settings.SettingsFragment"
         android:label="@string/settings" />

     <fragment
         android:id="@+id/loginFragment"
         android:name="com.depo.trask.ui.login.LoginFragment"
         android:label="fragment_login"
         tools:layout="@layout/fragment_login" />

     <action
         android:id="@+id/action_global_loginFragment"
         app:destination="@id/loginFragment"
         app:launchSingleTop="false"
         app:popUpTo="@+id/nav_host_fragment"
         app:popUpToInclusive="true" />
 </navigation>

MainActivity

 class MainActivity : AppCompatActivity() {

     private lateinit var navController: NavController
     private lateinit var bottomNavigationView: BottomNavigationView
     private lateinit var toolbar: Toolbar
     private val navigationInMainScreen = setOf(
         R.id.loginFragment,
         R.id.homeFragment,
         R.id.containerShippingFragment,
         R.id.locationFragment,
         R.id.historyFragment,
         R.id.aboutFragment
     )

     override fun onCreate(savedInstanceState: Bundle?) {
         setTheme(R.style.Theme_MyTheme)
         super.onCreate(savedInstanceState)
         setContentView(R.layout.activity_main)
         setupNavController()
     }

     override fun onSupportNavigateUp(): Boolean {
         navController.navigateUp()
         return super.onSupportNavigateUp()
     }

     // Nav Controller
     private fun setupNavController() {

         navController = findNavController(R.id.nav_host_fragment)
         setupActionBar()
         setupBottomNavigationBar()

         navController.addOnDestinationChangedListener { _, destination, _ ->

             // Listening toolbar
             when(destination.id){
                 R.id.loginFragment, R.id.aboutFragment -> toolbar.visibility = View.GONE
                 else -> toolbar.visibility = View.VISIBLE
             }

             // Listening bottom navigation bar
             when (destination.id) {
                 R.id.loginFragment, R.id.settingsFragment -> bottomNavigationView.visibility = View.GONE
                 else -> bottomNavigationView.visibility = View.VISIBLE
             }
         }
     }

     // Top Bar OR App Bar
     private fun setupActionBar() {
         toolbar = findViewById(R.id.toolbar)
         setSupportActionBar(toolbar)
         val appBarConfiguration = AppBarConfiguration(
             navigationInMainScreen
         )
         setupActionBarWithNavController(navController, appBarConfiguration)

     }

     // Bottom Navigation Bar
     private fun setupBottomNavigationBar() {
         bottomNavigationView = findViewById(R.id.bottom_navigation_view)
         bottomNavigationView.setupWithNavController(navController)
     }
 }

首页片段

 class HomeFragment : Fragment() {

     ?? Should I usede LoginViewModel ?

     override fun onCreateView(
         inflater: LayoutInflater,
         container: ViewGroup?,
         savedInstanceState: Bundle?
     ): View? {
         return inflater.inflate(R.layout.fragment_home, container, false)
     }

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

     private fun observeAuthenticationState() {
         val navController = findNavController()

         // REDIRECT USER TO LOGIN PAGE ?
         // How To check it
         navController.navigate(R.id.action_global_loginFragment)
     }   
 }

登录片段

 class LoginFragment : Fragment() {

     private lateinit var viewModel: LoginViewModel // How can I shared this to home fragment
     private lateinit var binding: FragmentLoginBinding

     override fun onCreateView(
         inflater: LayoutInflater,
         container: ViewGroup?,
         savedInstanceState: Bundle?
     ): View? {

         // For Retrofit
         val networkConnectionInterceptor = NetworkConnectionInterceptor(requireContext())
         val api = MyApi(networkConnectionInterceptor)

         // For Room
         val db = AppDatabase(context = requireActivity().applicationContext)

         // For ViewModel
         val repository = UserRepository(api, db)
         val factory = LoginViewModelFactory(repository)

         binding = DataBindingUtil.inflate(
             inflater,
             R.layout.fragment_login,
             container,
             false
         )

         viewModel = ViewModelProvider(this, factory).get(LoginViewModel::class.java)
         binding.buttonLogin.setOnClickListener { loginUser() }
         return binding.root
     }

     private fun loginUser() {
         val username = binding.editTextUsername.text.toString().trim()
         val password = binding.editTextPassword.text.toString().trim()

         binding.progressBar.show()
         lifecycleScope.launch {
             try {
                 val loginResponse = viewModel.userLogin(username!!, password!!)

                 if(loginResponse.user != null){
                     viewModel.saveLoggedInUser(loginResponse.user)
                 }

                 binding.progressBar.hide()
                 binding.root.context.toast(loginResponse.message!!)

             } catch (e: ApiException) {
                 binding.progressBar.hide()
                 binding.root.context.toast( e.toString())
             } catch (e: NoInternetException) {
                 binding.progressBar.hide()
                 binding.root.context.toast( e.toString())
             }
         }
     }
 }

我的问题吗？

如何强制用户在家庭碎片上正确登录碎片？
如何在HomeFragment上使用LoginViewModel？

带有协程的Android MVVM Jetpack导航组件

0 个答案: