android - Kotin lateinit Var 未初始化 - Android Studio

Question

我正在开发一个简单的联系人应用程序，用于存储联系人的姓名、电子邮件和号码。
语言: Kotlin
架构:MVVM
但我收到一个错误:lateinit property addContactViewModel has not been initialized

Activity:

class AddContact : AppCompatActivity() {

private lateinit var addContactViewModel : AddContactViewModel

companion object{
    const val EXTRA_REPLY = "com.room.contacts.REPLY"
}

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    val binding  = DataBindingUtil.setContentView<ActivityAddContactBinding>(
        this,R.layout.activity_add_contact
    )

    binding.btnSave.setOnClickListener {
        val replyIntent = Intent()
        val fname= binding.fnameEdit.text.toString()
        val lname= binding.lnameEdit.text.toString()
        val email = binding.emailAddressEdit.text.toString()
        val contactno = binding.contactNumberEdit.text.toString()
        val contact = Contact(fname, lname,email,contactno)
        addContactViewModel.insert(contact)
        val intent = Intent(this, ContactList::class.java)
        // start your next activity
        startActivity(intent)
    }

}}

ViewModel:

class AddContactViewModel (application: Application) : AndroidViewModel(application){

private val repository: ContactRepository

init {
    val contactsDao= ContactRoomDatabase.getDatabase(application).contactDao()
    repository = ContactRepository(contactsDao)
}

fun insert(contact: Contact) = viewModelScope.launch {
    repository.insert(contact)
}}

Error:

E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.room.contacts, PID: 29383
kotlin.UninitializedPropertyAccessException: lateinit property addContactViewModel has not been initialized
    at com.room.contacts.screens.addContact.AddContact.access$getAddContactViewModel$p(AddContact.kt:15)
    at com.room.contacts.screens.addContact.AddContact$onCreate$1.onClick(AddContact.kt:36)
    at android.view.View.performClick(View.java:4781)
    at android.view.View$PerformClick.run(View.java:19907)
    at android.os.Handler.handleCallback(Handler.java:739)
    at android.os.Handler.dispatchMessage(Handler.java:95)
    at android.os.Looper.loop(Looper.java:160)
    at android.app.ActivityThread.main(ActivityThread.java:5541)
    at java.lang.reflect.Method.invoke(Native Method)
    at java.lang.reflect.Method.invoke(Method.java:372)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:964)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:759)

Answer 1

而不是拥有您的 addContactViewModel作为 lateinit您可以将其设为 lazy属性，以便在您第一次尝试在某处使用它时对其进行初始化:

class AddContact : AppCompatActivity() {
    private val addContactViewModel : AddContactViewModel by lazy {
        ViewModelProvider(this).get(AddContactViewModel::class.java)
    }