Notify Observer when item is added to List of LiveData

Question

I need to get an Observer event when the item is added to the List of LiveData. But as far as I understand the event receives only when I replace the old list with a new one

Answer 1

LiveData will only notify when its wrapped object reference is changed. When you assign a new List to a LiveData then it will notify because its wrapped object reference is changed but if add/remove items from a LiveData's List it will not notify because it still has the same List reference as wrapped object. So you can overcome this problem by making an extension of MutableLiveData as follows:

fun  MutableLiveData>.addNewItem(item: T) {
    val oldValue = this.value ?: mutableListOf()
    oldValue.add(item)
    this.value = oldValue
}

fun  MutableLiveData>.addNewItemAt(index: Int, item: T) {
    val oldValue = this.value ?: mutableListOf()
    oldValue.add(index, item)
    this.value = oldValue
}

fun  MutableLiveData>.removeItemAt(index: Int) {
    if (!this.value.isNullOrEmpty()) {
        val oldValue = this.value
        oldValue?.removeAt(index)
        this.value = oldValue
    } else {
        this.value = mutableListOf()
    }
}

Then add/remove items from your MutableLiveData like:

// Here is your IssuePost list
var issuePostList = MutableLiveData>()

// Add new item to your list
issuePostList.addNewItem(IssuePost(UserEntity(name, email, photoUrl), issueEntity))

// Delete an item from your list at position i
issuePostList.removeItemAt(i)

// Add new item to your list at position i
issuePostList.addNewItemAt(i, IssuePost(UserEntity(name, email, photoUrl), issueEntity))