在 kotlin 中编译时我得到未解决的参考

Question

我是 kotlin 的新手，编译时我得到了未解决的参考
它无法获得对我的 class 的引用，这里有两个 classes.

这是我的Activityclass

RoomActivity.kt

class RoomActivity : AppCompatActivity() {

val NEW_WORD_ACTIVITY_REQUEST_CODE = 1

//    private var mWordViewModel: WordViewModel? = null
private var mWordViewModel: WordViewModel?=null

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_room)

    val toolbar = findViewById<Toolbar>(R.id.toolbar)
    setSupportActionBar(toolbar)

    val recyclerView = findViewById<RecyclerView>(R.id.recyclerview)
    val adapter = WordListAdapter(this)
    recyclerView.adapter = adapter
    recyclerView.layoutManager = LinearLayoutManager(this)

    // Get a new or existing ViewModel from the ViewModelProvider.
    mWordViewModel = ViewModelProviders.of(this).get(WordViewModel::class.java)

    // Add an observer on the LiveData returned by getAlphabetizedWords.
    // The onChanged() method fires when the observed data changes and the activity is
    // in the foreground.
    mWordViewModel!!.allWords.observe(this, Observer<List<Word>> {
        adapter.setWords(Word)
        TODO("not implemented") //To change body of created functions use File | Settings | File Templates.
    })

    val fab = findViewById<FloatingActionButton>(R.id.fab)
    fab.setOnClickListener(object : View.OnClickListener {
        override fun onClick(view: View) {
            val intent = Intent(this@RoomActivity, NewWordActivity::class.java)
            startActivityForResult(intent, NEW_WORD_ACTIVITY_REQUEST_CODE)
        }
    })
}

public override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
    super.onActivityResult(requestCode, resultCode, data)

    if (requestCode == NEW_WORD_ACTIVITY_REQUEST_CODE && resultCode == Activity.RESULT_OK) {
        val word = Word(data!!.getStringExtra(NewWordActivity.EXTRA_REPLY))
        mWordViewModel!!.insert(word)
    } else {
        Toast.makeText(
                applicationContext,
                R.string.empty_not_saved,
                Toast.LENGTH_LONG).show()
    }
}

}

这是我的ViewModelclass

WordViewModel.kt

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

private var parentJob = Job()
private val coroutineContext: CoroutineContext
    get() = parentJob + Dispatchers.Main
private val scope = CoroutineScope(coroutineContext)

private val repository: WordRepository
val allWords: LiveData<List<Word>>

init {
    val wordsDao = WordRoomDatabase.getDatabase(application)?.wordDao()
    repository = WordRepository(wordsDao!!)
    allWords = repository.allWords
}

fun insert(word: Word) = scope.launch(Dispatchers.IO) {
    repository.insert(word)
}

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

有什么问题请帮帮我。

Answer 1

AndroidViewModel - 当您需要上下文时使用它 class 其他时候使用 ViewModel() class。如果您使用的是 androidviewmodel 或 viewmodel，则以下代码均有效。

class UserViewModel : ViewModel() {

lateinit var userList: LiveData<PagedList<User>>

private val compositeDisposable = CompositeDisposable()

private val pageSize = 10

lateinit var sourceFactory: UsersDataSourceFactory

lateinit var productList:LiveData<PagedList<ProductsItem>>
var tDataSource: LiveData<ProductListSource>? = null

lateinit var productListSource:ProductDataSourceFactory

var networkState: LiveData<NetworkState>? = null
var productData: LiveData<Product>? = null
fun init(apiListener: ApiListener) {
    sourceFactory = UsersDataSourceFactory(compositeDisposable, apiListener)
    val config = PagedList.Config.Builder()
            .setPageSize(pageSize)
            .setEnablePlaceholders(false)
            .build()
    userList = LivePagedListBuilder<Long, User>(sourceFactory, config).build()
}
fun getProductData(apiListener: ApiListener){
    productListSource= ProductDataSourceFactory(apiListener)
    tDataSource = productListSource.mutableLiveData
    networkState = Transformations.switchMap(productListSource.mutableLiveData) { dataSource -> dataSource.networkState }
    productData = Transformations.switchMap(productListSource.mutableLiveData) { dataSource -> dataSource.productList }

    val config=PagedList.Config.Builder()
            .setInitialLoadSizeHint(5)
            .setPageSize(pageSize)
            .setEnablePlaceholders(false)
            .build()
    productList=LivePagedListBuilder<Long,ProductsItem>(productListSource,config).build()
}
override fun onCleared() {
    super.onCleared()
    compositeDisposable.dispose()
}
fun retryGetProduct() {
    productListSource.mutableLiveData.value!!.retry()
}

fun retry() {
    sourceFactory.usersDataSourceLiveData.value!!.retry()
}

fun refresh() {
    sourceFactory.usersDataSourceLiveData.value!!.invalidate()
}

/* 有趣的 getNetworkStateData(): LiveData = Transformations.switchMap( productListSource.mutableLiveData, { it.networkState })

fun getNetworkState(): LiveData<NetworkState> = Transformations.switchMap<UsersDataSource, NetworkState>(
        sourceFactory.usersDataSourceLiveData, { it.networkState })

fun getRefreshState(): LiveData<NetworkState> = Transformations.switchMap<UsersDataSource, NetworkState>(
        sourceFactory.usersDataSourceLiveData, { it.initialLoad })*/

}

这样访问..

 viewModel = ViewModelProviders.of(this).get(UserViewModel::class.java)

Answer 2

如果您从另一个项目复制文件 WordViewModel.kt，请确保将第一行中的包名称更改为您在项目中使用的名称。

package application.hdlakhani.com.myapplication

Answer 3

你的回答已经很晚了，但我认为它会对某人有所帮助。我今天遇到了同样的问题，我通过重建我的项目解决了它。只需转到：Build -> Rebuild Project

在 kotlin 中编译时我得到未解决的参考

I am getting Unresolved Reference when compiling in kotlin

android

kotlin

android-viewmodel