android - Firebase 数据的更改不会更新

Question

我正在试验一款下单和送货应用。我的想法是，在我下订单后，直到确认时，订单才会显示在我的应用程序屏幕上。我可能会提出多个订单查询，直到它们被接受时，它们才会显示在我的屏幕上。数据存储在 Firebase 中，屏幕上的订单列表是动态创建的。

问题是，如果在 Firebase 中更改了订单数据，例如，如果我从 Firebase 中删除数据，则屏幕上不会反射(reflect)相同的数据。只有当我从模拟器中删除应用程序并重新安装它时，屏幕上才会出现正确的内容。这意味着问题不在 Firebase 中，而在于从 Firebase 获取它。

这是我从 Firebase 获取数据的代码:

activeordertext.setOnClickListener {
if(isNetworkAvailable()){

    val user = FirebaseAuth.getInstance().currentUser
    val userid = user?.uid

    Ref = FirebaseDatabase.getInstance().reference.child("Orders")

    if(userid != null){

        Ref.addListenerForSingleValueEvent(object: ValueEventListener{
            override fun onCancelled(p0: DatabaseError) {
            }

            override fun onDataChange(p0: DataSnapshot) {
                val activeQuerylayout: LinearLayout = findViewById(R.id.activeQueryeorderlayout)
                activeQuerylayout.removeAllViews()
                for (uniqueKeySnapshot in p0.children) {
                    val querykey = uniqueKeySnapshot.key
                    if(querykey!=null){
                        if((p0.child(querykey).child("Customer ID").getValue(String::class.java)==userid)&&(p0.child(querykey).child("Order Status").getValue(String::class.java)=="Query")){

                            var  param: LinearLayout.LayoutParams = LinearLayout.LayoutParams(RelativeLayout.LayoutParams.MATCH_PARENT,RelativeLayout.LayoutParams.WRAP_CONTENT, 1.0F)
                            param.setMargins(64,16,64,0)
                   var  param2: LinearLayout.LayoutParams = LinearLayout.LayoutParams(RelativeLayout.LayoutParams.WRAP_CONTENT,RelativeLayout.LayoutParams.WRAP_CONTENT, 0.3F)
param2.setMargins(16,0,0,0)



                            var activeQuerysublayout = LinearLayout(this)
                            activeQuerysublayout.layoutParams = param
                            activeQuerysublayout.orientation = LinearLayout.HORIZONTAL
                            activeQuerysublayout.weightSum = 1.0F
                            activeQuerysublayout.setBackgroundResource(R.drawable.queryborder)
                            activeQuerylayout.addView(activeQuerysublayout)

                            var queryTimeView = TextView(this)
                            queryTimeView.layoutParams = param
                            queryTimeView.text = p0.child(querykey).child("Time").getValue(String::class.java)
                            queryTimeView.textSize = 16.0F
                            queryTimeView.setTextColor(Color.parseColor("#3488c3"))
                            queryTimeView.setPadding(32,16,0,16)
                            activeQuerysublayout.addView(queryTimeView)

                            var queryAlertLayout = RelativeLayout(this)
                            queryAlertLayout.layoutParams = param2
                            activeQuerysublayout.addView(queryAlertLayout)

                            var queryAlertSubLayout = RelativeLayout(this)
                            queryAlertSubLayout.layoutParams = param2
                            queryAlertSubLayout.id = View.generateViewId()
                            queryAlertLayout.addView(queryAlertSubLayout)

                            var queryAlert = ImageView(this)
                            queryAlert.layoutParams = param2
                            queryAlert.setImageResource(R.drawable.ic_bell)
                            queryAlert.setPadding(0,16,0,0)
                            queryAlertSubLayout.addView(queryAlert)

                        }
                    }
                }
            }

        })

    }


}else{
    Toast.makeText(this, "Please connect to the internet ", Toast.LENGTH_LONG).show()
}
}

还证明了数据在屏幕上的填充方式的快照。忽略红色标记。这是由其他一些代码处理的

Answer 1

只需将您使用的监听器更改为:

Ref.addValueEventListener(object: ValueEventListener{
        override fun onCancelled(p0: DatabaseError)