我不明白MVVM上的“实例尚未初始化”

Question

    fun getInstance(): NicePlaceRepository {
        if (instance == null) {
            instance = NicePlaceRepository()
        }
        Log.d("TAG","11111")
        return instance
    }

ViewModel

private lateinit var mNicePlaces :MutableLiveData<List<NicePlace>>
lateinit var mRepository : NicePlaceRepository

fun init(){
    if(mNicePlaces!=null) return
    mRepository =  NicePlaceRepository().getInstance()
    mNicePlaces = mRepository.getNicePlaces()
}

fun getNicePlaces():LiveData<List<NicePlace>>{
    return mNicePlaces
}

储存库

private val dataSet = ArrayList<NicePlace>()
companion object {
    lateinit var instance: NicePlaceRepository
}

fun getInstance(): NicePlaceRepository {
    if (instance == null) {
        instance = NicePlaceRepository()
    }
    Log.d("TAG","11111")
    return instance
}
fun getNicePlaces():MutableLiveData<List<NicePlace>>{
    setNicePlaces()
   var data = MutableLiveData<List<NicePlace>>()
   data.value = dataSet
   return data
}
private fun setNicePlaces(){
    for(i:Int in 0..5){
        dataSet.add(NicePlace("111", "111"))
    }
}

Answer 1

由于您已经声明了lateinit var instance：niceplacerepository，因此该实例不能为null。您的检查if(instance==null)将不会通过，并且instance将不会被启动。

解决的一种方法是检查lateinit实例是否初始化，而不是null检查。或使实例为空：

改变这一点，

lateinit var instance: NicePlaceRepository

 var instance: NicePlaceRepository? = null

fun getInstance(): NicePlaceRepository {
    if (instance == null) {
        instance = NicePlaceRepository()
    }
    Log.d("TAG","11111")
    return instance!!
}