添加到可变列表 (NPE) Kotlin 时出错 Android

Question

---数据Class---

正在尝试将对象添加到 meals MutableList------------------------------------ ---------------------------------------------- ---------------------------------------------- ---------------------------------------------- ----------------------

data class YelpRestaurant(

val name: String,
val rating: Double,
val price: String,
@SerializedName("review_count") val numReviews: Int,
@SerializedName("image_url") val imageUrl: String,
val categories: List<YelpCategory>,
val location: YelpLocation,
val meals: MutableList<UserMeals>

)

----已编辑ACTIVITY----

class ThoughtsActivity : AppCompatActivity() {

lateinit var mealName: String
lateinit var mealPrice: String
lateinit var mealThought: String

lateinit var selected_Restaurant : YelpRestaurant

val meals = mutableListOf<UserMeals>()

@Subscribe(sticky = true)
fun getRest(selectedRestaurant : YelpRestaurant)  {
    selected_Restaurant = selectedRestaurant

}

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


    thoughtBtn.setOnClickListener() {

        mealName = m_name.text.toString()
        mealPrice = m_price.text.toString()
        mealThought = m_thought.text.toString()

        var addedMeal = UserMeals(mealName, mealPrice.toDouble(), mealThought)

        if (mealName.isNotEmpty()) {
            selected_Restaurant.meals.add(addedMeal)
        }

    }
}



override fun onStart() {
    super.onStart()
    EventBus.getDefault().register(this)
}

override fun onStop() {
    super.onStop()
    EventBus.getDefault().unregister(this)
}

}

Answer 1

访问selected_Restaurant.meals时出现空指针异常以防止NPE将meals更改为val并在selected_Restaurant中这样声明时实例化它：

val meals = mutableListOf<UserMeals>()

添加到可变列表 (NPE) Kotlin 时出错 Android

Error adding to mutable list (NPE) Kotlin Android

android

kotlin

androidx