LiveData Observer 只捕获第一个值

Question

我从 Firebase 数据库和 return LiveData 获取问题列表。

fun getAllIssues(): MutableLiveData<IssueEntity> {
    val issues: MutableLiveData<IssueEntity> = MutableLiveData()
    val issuesReference = FirebaseDatabase.getInstance().reference.child("issues")
    issuesReference.addValueEventListener(object : ValueEventListener {
        override fun onCancelled(p0: DatabaseError?) {

        }

        override fun onDataChange(snapshot: DataSnapshot?) {
            if (snapshot == null) {
                return
            }
            snapshot.children.forEach({
                val issueMessage = it.child("message").value.toString()
                val issueTitle = it.child("title").value.toString()
                val issueOwner = it.child("owner").value.toString()

                issues.postValue(IssueEntity(issueTitle, issueMessage, issueOwner))
            })
        }
    })
    return issues
}

我的代码 Activity:

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_all_issues)
    val issues: MutableList<IssueEntity> = mutableListOf()
    issuesList.adapter = IssuesAdapter(issues)
    IssueRepository().getAllIssues().observe(this, Observer {
        if (it != null) {
            issues.add(it)
            val issuesAdapter = issuesList.adapter as IssuesAdapter
            issuesAdapter.notifyDataSetChanged()
        }
    })
}

但是 Observer 只得到第一个值。你能告诉我为什么吗？

Answer 1

抱歉造成混淆。我只需要 return 而不仅仅是 MutableLiveData 和 MutableLiveData>