如何基于Kotlin中的键值从Firebase读取数据 [英] How to read data from firebase based on a key value in Kotlin
问题描述
我想使用Kotlin和android studio从firebase检索数据. 这是我的数据类,用于将数据上传到Firebase:
I want to retrieve data from firebase using Kotlin and android studio. This is my data class which is used to upload data into firebase:
class Data(var id : String,
var productname : String ,
var username : String,
var phonenumber : String,
var address: String,
var status: String)
要向Firebase添加数据,我使用以下格式:
To add data to firebase, I used the following format:
val ref = FirebaseDatabase.getInstance().getReference("orders")
val orderId :String = ref.push().key.toString()
val formdata = Data(orderId,
productname,
username,
phonenumber,
useraddress,
status)
ref.child(orderId).setValue(formdata).addOnCompleteListener {
Toast.makeText(applicationContext,"Order placed sucessfully", Toast.LENGTH_SHORT).show()
}
现在,我想从Firebase检索数据,其中电话号码的值与给定的字符串匹配.
Now I want to retrieve data from firebase where the value of phone number matches the given string.
推荐答案
现在,我想从Firebase检索数据,其中电话号码的值与给定的字符串匹配.
Now I want to retrieve data from firebase where the value of phone number matches the given string.
要解决此问题,您需要使用查询,例如以下代码行:
To solve this, you need to use a query, like in the following lines of code:
val rootRef = FirebaseDatabase.getInstance().reference
val ordersRef = rootRef.child("orders").orderByChild("phonenumber").equalTo(givenString)
val valueEventListener = object : ValueEventListener {
override fun onDataChange(dataSnapshot: DataSnapshot) {
for (ds in dataSnapshot.children) {
val username = ds.child("username").getValue(String::class.java)
Log.d(TAG, username)
}
}
override fun onCancelled(databaseError: DatabaseError) {
Log.d(TAG, databaseError.getMessage()) //Don't ignore errors!
}
}
ordersRef.addListenerForSingleValueEvent(valueEventListener)
logcat中的结果将是电话号码等于给定字符串的订单中存在的用户名.
The result in your logcat, will be the user name that exist in the orders where the phone number is equal to a given string.
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