错误:java.lang.IllegalArgumentException:指定为非null的参数为空Firebase事务Kotlin

问题描述

我正在尝试在Firebase数据库中增加一个整数，但是该应用程序崩溃了.

I am trying to increment an integer in Firebase database but, the app crashes.

abstract class BrowserActivity : ThemableBrowserActivity(),OnClickListener {

        private var mAuth: FirebaseAuth? = null

        override fun onCreate(savedInstanceState: Bundle?) {
            super.onCreate(savedInstanceState)
            BrowserApp.appComponent.inject(this)
            setContentView(R.layout.activity_main)

            incrementId() //calling the function increment id
        }

        protected fun incrementId() {
                 val cUser = mAuth?.currentUser
                 val uid: String = cUser!!.uid
                 var databaseReference = FirebaseDatabase.getInstance().getReference("users").child(uid).child("id")


                 databaseReference!!.runTransaction(object : Transaction.Handler {
                        override fun doTransaction(mutableData: MutableData): Transaction.Result {
                            var count = mutableData.getValue(Int::class.java)
                            if (count == null) {
                                mutableData.setValue(1)
                            } else {
                                mutableData.setValue(count+1)
                            }
                            return Transaction.success(mutableData)
                        }

                        override fun onComplete(databaseError: DatabaseError, b: Boolean, dataSnapshot: DataSnapshot) {}
                    })
                }
        }

Logcat:

数据库结构:

my-firebase-app-name-9c826
   |__-users
         |_-FZTuHfNiXoSWOLiNlSv9w1vVZj03  //uid: user id of current user
                 |__id: 1

数据库屏幕截图

我的Firebase规则:`我的Firebase规则:

My Firebase rules:`My Firebase rules:

{ "rules": { ".read": true, ".write": true }}

{ "rules": { ".read": true, ".write": true }}

推荐答案

参考帖子，我将databaseError作为null传递给了onComplete.默认情况下，kotlin中的所有变量都不为null.因此，如果我想传递null参数，我必须在参数中添加?，在我的情况下应为DatabaseError?.因此onComplete函数应如下所示:

With reference to this post, I am passing databaseError as null to onComplete.By default all variables in kotlin are non null. So, if I want to pass a null parameter,I have to add a ? to the parameter, which in my case should be DatabaseError?. So the onComplete function should look like:

override fun onComplete(databaseError: DatabaseError?, b: Boolean, dataSnapshot: DataSnapshot) {}

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