ViewModel在java中没有零参数构造函数。朗，同学们。newInstance（本机方法）

Question

由于以下运行时异常，程序无法运行：

无法创建类ViewModel的实例，并且在java.lang.Class.new实例（本机方法）中没有零参数构造函数

我使用了这样的注入构造：

CharactersViewModel@Inject构造函数（private val charactersUseCase:charactersUseCase，private val searchCharacterCase:searchCharacterCase:ViewModel）

有人知道怎么解决吗？非常感谢

    dependencies {

implementation'androidx.room:room-runtime:2.5.0-alpha01'
annotationProcessor'androidx.room:room-compiler:2.5.0-alpha01'
implementation 'androidx.annotation:annotation:1.4.0-alpha02'
implementation 'com.android.support:support-annotations:28.0.0'
implementation 'com.squareup.picasso:picasso:2.71828'
implementation 'com.github.bumptech.glide:glide:4.12.0'
annotationProcessor 'com.github.bumptech.glide:compiler:4.12.0'
implementation 'androidx.fragment:fragment-ktx:1.4.1'
implementation 'androidx.lifecycle:lifecycle-viewmodel-ktx:2.5.0-alpha04'
implementation 'androidx.lifecycle:lifecycle-livedata-ktx:2.5.0-alpha04'
implementation 'androidx.lifecycle:lifecycle-runtime-ktx:2.5.0-alpha04'
implementation 'com.squareup.retrofit2:retrofit:2.9.0'
implementation 'com.squareup.retrofit2:converter-gson:2.5.0'
implementation "com.google.dagger:hilt-android:2.31.2-alpha"
implementation 'com.google.dagger:dagger:2.31.2'
implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-core:1.6.0'
implementation 'com.squareup.retrofit2:retrofit:2.9.0'
implementation 'androidx.core:core-ktx:1.7.0'
implementation 'androidx.appcompat:appcompat:1.4.1'
implementation 'com.google.android.material:material:1.5.0'
implementation 'androidx.constraintlayout:constraintlayout:2.1.3'
testImplementation 'junit:junit:4.13.2'
androidTestImplementation 'androidx.test.ext:junit:1.1.3'
androidTestImplementation 'androidx.test.espresso:espresso-core:3.4.0' 
      

//这是ViewModel类

    import android.util.Log
    import androidx.lifecycle.ViewModel
    import androidx.lifecycle.viewModelScope
  import com.alons.marvel_universe.domain.use_cases.CharactersUseCase
import com.alons.marvel_universe.domain.use_cases.SearchCharacterCase
    import com.alons.marvel_universe.util.States
    import dagger.hilt.android.lifecycle.HiltViewModel
    import kotlinx.coroutines.Dispatchers
    import kotlinx.coroutines.flow.*
    import kotlinx.coroutines.launch
    import javax.inject.Inject


   @ HiltViewModel


    class CharactersViewModel @Inject constructor(

private val charactersUseCase : CharactersUseCase,
private val searchCharacterCase : SearchCharacterCase
) : ViewModel(){

private val marvelValue = MutableStateFlow(MarvelListState())
var _marvelValue : StateFlow<MarvelListState> = marvelValue

fun getSearchedCharacters(search:String)=viewModelScope.launch(Dispatchers.IO){
    searchCharacterCase.invoke(search=search).collect {
        when(it){
            is States.Success ->{
                marvelValue.value = MarvelListState(characterList = it.data?: emptyList())
                Log.d("toCharacter",_marvelValue.value.toString())
            }
            is States.Loading ->{
                marvelValue.value = MarvelListState(isLoading = true)
                Log.d("loading",it.data.toString())
            }
            is States.Error ->{
                marvelValue.value = MarvelListState(error = it.message?:"An Unexpected Error")
                Log.d("Error",it.data.toString())
            }
        }
    }
}
fun getAllCharactersData(offset:Int)=viewModelScope.launch(Dispatchers.IO){
    charactersUseCase(offset).collect {
        when(it){
            is States.Success ->{
                marvelValue.value = MarvelListState(characterList = it.data?: emptyList())
                Log.d("toCharacter",_marvelValue.value.toString())
            }
            is States.Loading ->{
                marvelValue.value = MarvelListState(isLoading = true)
                Log.d("loading",it.data.toString())
            }
            is States.Error ->{
                marvelValue.value = MarvelListState(error = it.message?:"An Unexpected Error")
                Log.d("Error",it.data.toString())
            }
        }
    }
}

}

Answer 1

首先，应该为viewmodel类注释@HiltViewModel。其次，您应该提供@Singleton或@ViewModelScoped for dagger-hilt等用例，以了解向viewmodel注入什么。