由于 Kotlin 1.8 强制视图绑定，所以我在主要活动和片段中实现了它。但是我在夸大类片段时遇到错误
这里是主要活动课。我认为由于视图绑定，在膨胀主布局时存在错误。我已经初始化了 navContoller，它在 home fragment 中添加代码之前工作正常
class MainActivity : AppCompatActivity() {
private lateinit var binding: ActivityMainBinding
private lateinit var navController: NavController
private lateinit var appBarConfiguration: AppBarConfiguration
lateinit var viewModel: MandirViewModel
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
binding = ActivityMainBinding.inflate(layoutInflater)
setContentView(binding.root)
val mandirRep = (application as MandirApplication).repository
val viewModelFactory = MandirViewModelFactory(mandirRep)
viewModel = ViewModelProvider(this , viewModelFactory).get(MandirViewModel::class.java)
navController = findNavController(R.id.navContainer)
appBarConfiguration = AppBarConfiguration(setOf(R.id.homeFragment , R.id.notificationsFragment , R.id.favouriteFragment , R.id.settingsFragment))
setupActionBarWithNavController(navController , appBarConfiguration)
binding.bottomNavigationView.setupWithNavController(navController)
} }
这里是调用 API 调用存储库的主页片段。我认为这里的错误是夸大了布局。可能是因为viewbinding
class HomeFragment : Fragment() {
private lateinit var mandirViewModel: MandirViewModel
private lateinit var mandirAdapter: MandirAdapter
private lateinit var binding: FragmentHomeBinding
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
// Inflate the layout for this fragment
binding = FragmentHomeBinding.inflate(inflater , container , false)
mandirViewModel = (activity as MainActivity).viewModel
mandirAdapter = MandirAdapter()
binding!!.rvMandir.apply {
adapter = mandirAdapter
layoutManager = LinearLayoutManager(context)
}
mandirViewModel.mAndirs.observe( viewLifecycleOwner , Observer {
it.let { response->
mandirAdapter.differ.submitList(response.data)
}
})
return view
}
}
这是应用类。我已经使用它来使用 Retrofit 类的实例初始化存储库
class MandirApplication : Application() {
lateinit var repository: MandirRepository
override fun onCreate() {
super.onCreate()
initialize()
}
private fun initialize() {
val mandirService = RetrofitHelper.getInstance().create(MandirAPI::class.java)
repository = MandirRepository( mandirService , applicationContext)
}
}
这里是主要活动的 XML 文件。我使用了框架布局，因为我在这里读到片段视图需要框架布局才能跨片段移动
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout 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:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".ui.MainActivity">
<fragment
android:id="@+id/navContainer"
android:name="androidx.navigation.fragment.NavHostFragment"
android:layout_width="match_parent"
android:layout_height="0dp"
app:defaultNavHost="true"
app:layout_constraintBottom_toTopOf="@+id/bottomNavigationView"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:navGraph="@navigation/navgraph" />
<com.google.android.material.bottomnavigation.BottomNavigationView
android:id="@+id/bottomNavigationView"
android:layout_width="match_parent"
android:layout_height="70dp"
android:layout_gravity="bottom"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="1.0"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="0.997"
app:menu="@menu/menu" />
</FrameLayout>
这里是 home Fragment 的 XML 文件。在主页片段中膨胀此布局是一个错误
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".ui.HomeFragment">
<androidx.recyclerview.widget.RecyclerView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/rvMandir"/>
</FrameLayout>
这是错误日志。不知道是不是显示 viewModel 未初始化。它还显示了膨胀布局中的问题 请帮助
2023-05-03 15:38:17.103 1931-1931 AndroidRuntime com.example.mandirapp E 致命异常：main
Process: com.example.mandirapp, PID: 1931
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.mandirapp/com.example.mandirapp.ui.MainActivity}: android.view.InflateException: Binary XML file line #19 in com.example.mandirapp:layout/activity_main: Binary XML file line #19 in com.example.mandirapp:layout/activity_main: Error inflating class fragment
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3635)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3792)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:103)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2210)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loopOnce(Looper.java:201)
at android.os.Looper.loop(Looper.java:288)
at android.app.ActivityThread.main(ActivityThread.java:7839)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:548)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1003)
Caused by: android.view.InflateException: Binary XML file line #19 in com.example.mandirapp:layout/activity_main: Binary XML file line #19 in com.example.mandirapp:layout/activity_main: Error inflating class fragment
Caused by: android.view.InflateException: Binary XML file line #19 in com.example.mandirapp:layout/activity_main: Error inflating class fragment
Caused by: kotlin.UninitializedPropertyAccessException: lateinit property viewModel has not been initialized
at com.example.mandirapp.ui.MainActivity.getViewModel(MainActivity.kt:25)
at com.example.mandirapp.ui.HomeFragment.onCreateView(HomeFragment.kt:34)
at androidx.fragment.app.Fragment.performCreateView(Fragment.java:3104)
at androidx.fragment.app.FragmentStateManager.createView(FragmentStateManager.java:524)
at androidx.fragment.app.FragmentStateManager.moveToExpectedState(FragmentStateManager.java:261)
at androidx.fragment.app.FragmentStore.moveToExpectedState(FragmentStore.java:113)
at androidx.fragment.app.FragmentManager.moveToState(FragmentManager.java:1433)
at androidx.fragment.app.FragmentManager.dispatchStateChange(FragmentManager.java:2977)
at androidx.fragment.app.FragmentManager.dispatchViewCreated(FragmentManager.java:2888)
at androidx.fragment.app.Fragment.performViewCreated(Fragment.java:3129)
at androidx.fragment.app.FragmentStateManager.ensureInflatedView(FragmentStateManager.java:394)
at androidx.fragment.app.FragmentStateManager.moveToExpectedState(FragmentStateManager.java:260)
at androidx.fragment.app.FragmentLayoutInflaterFactory.onCreateView(FragmentLayoutInflaterFactory.java:142)
at androidx.fragment.app.FragmentController.onCreateView(FragmentController.java:136)
at androidx.fragment.app.FragmentActivity.dispatchFragmentsOnCreateView(FragmentActivity.java:248)
at androidx.fragment.app.FragmentActivity.onCreateView(FragmentActivity.java:227)
at android.view.LayoutInflater.tryCreateView(LayoutInflater.java:1073)
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:1001)
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:965)
at android.view.LayoutInflater.rInflate(LayoutInflater.java:1127)
at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:1088)
at android.view.LayoutInflater.inflate(LayoutInflater.java:686)
at android.view.LayoutInflater.inflate(LayoutInflater.java:538)
at com.example.mandirapp.databinding.ActivityMainBinding.inflate(ActivityMainBinding.java:45)
at com.example.mandirapp.databinding.ActivityMainBinding.inflate(ActivityMainBinding.java:39)
at com.example.mandirapp.ui.MainActivity.onCreate(MainActivity.kt:30)
at android.app.Activity.performCreate(Activity.java:8051)
2023-05-03 15:38:17.104 1931-1931 AndroidRuntime com.example.mandirapp E at android.app.Activity.performCreate(Activity.java:8031)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1329)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3608)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3792)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:103)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2210)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loopOnce(Looper.java:201)
at android.os.Looper.loop(Looper.java:288)
at android.app.ActivityThread.main(ActivityThread.java:7839)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:548)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1003)
发生这种情况是因为您必须在 onCreateView() 方法中返回膨胀的视图。在你的情况下是
binding.rootclass HomeFragment : Fragment() {
private lateinit var mandirViewModel: MandirViewModel
private lateinit var mandirAdapter: MandirAdapter
private lateinit var binding: FragmentHomeBinding
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
// Inflate the layout for this fragment
binding = FragmentHomeBinding.inflate(inflater , container , false)
mandirViewModel = (activity as MainActivity).viewModel
mandirAdapter = MandirAdapter()
binding!!.rvMandir.apply {
adapter = mandirAdapter
layoutManager = LinearLayoutManager(context)
}
mandirViewModel.mAndirs.observe( viewLifecycleOwner , Observer {
it.let { response->
mandirAdapter.differ.submitList(response.data)
}
})
return binding.root
}
}