将对象添加到可变的实时数据列表

Question

我正在尝试将两家商店添加到可变列表中，如下所示：

private var _shopList =  MutableLiveData<List<Shop>>()
    var shopList: LiveData<List<Shop>> = ()
        get() = _shopList


    // This function will get the arrayList items
    fun getArrayList(): MutableLiveData<List<Shop>>
    {


        // Here we need to get the data
        val shop1 = Shop("AOB", "Lat and Long","LA")
        val shop2 = Shop("Peach", "Lat and Long","Vegas")



        _shopList.add(shop1)
        _shopList.add(shop2)



        return _shopList
    }

但是它说没有引用添加函数？

Answer 1

来自文档：

List：元素的通用有序集合。此接口中的方法仅支持 read-only 访问列表； read/write 通过 MutableList 接口支持访问。

MutableList: 支持添加和删除元素的通用有序元素集合。

您可以修改 MutableList：更改、删除、添加...它的元素。在列表中你只能阅读它们。

解决方案-

 private var _shopList = MutableLiveData<List<Shop>>() // List is fine here as read only
val shopList: LiveData<List<Shop>>  // List is fine here as read only
    get() = _shopList


// This function will get the arrayList items
fun getArrayList(): MutableLiveData<List<Shop>> {
    // Here we need to get the data
    val shop1 = Shop("AOB", "Lat and Long", "LA")  //  var to val
    val shop2 = Shop("Peach", "Lat and Long", "Vegas") //var to val

    _shopList.value = mutableListOf(shop1, shop2) // assigns a mutable list as value to the live data which can be observed in the view

    return _shopList
}

Answer 2

解决方法如下：

private var _shopList =  MutableLiveData<MutableList<Shop>>()
val shopList: LiveData<MutableList<Shop>> 
    get() = _shopList


// This function will get the arrayList items
fun getArrayList(): MutableLiveData<MutableList<Shop>>
{


    // Here we need to get the data
    var shop1 = Shop("AOB", "Lat and Long","LA")
    var shop2 = Shop("Peach", "Lat and Long","Vegas")


    _shopList.value = mutableListOf(shop1,shop2)

    return _shopList
}

将对象添加到可变的实时数据列表

Adding an object to a mutable live data list

android

kotlin

mutablelivedata