Kotlin Firebase Realtime Database – Get List of Data example | Android

Kotlin

104

firebase

39

android

87

loveprogramming viết ngày 24/04/2021

https://grokonez.com/android/kotlin-firebase-realtime-database-get-list-data-example-android

Kotlin Firebase Realtime Database – Get List of Data example | Android

In previous post, we had known how to read/write single data object. Today, we're gonna look at way to get List of Data in an Android App.

Related Article:
Kotlin Firebase Realtime Database – Read/Write Data example | Android

More Practice:
Kotlin Firebase Realtime Database – Display List of Data with FirebaseRecyclerAdapter | Android

I. Way to get List of Data

0. Add Firebase to Android App

Please visit Kotlin - Add_Firebase_to_Android_App for details.

1. Write to specific child of a node

Before retrieving all data item from a list, we need a node that contains child nodes as data items. So we should write data to each node at first.

Assume that we have a class like this:

@IgnoreExtraProperties
class Message {

    var author: String? = ""
    var body: String? = ""
    var time: String? = ""

    constructor() {
        // Default constructor required for calls to DataSnapshot.getValue(Message.class)
    }

    // ...

    @Exclude
    fun toMap(): Map {
        val result = HashMap()
        result.put("author", author!!)
        result.put("body", body!!)
        result.put("time", time!!)

        return result
    }
}

Use the updateChildren() method, we can write data to specific child node without overwriting other child nodes (by specifying a path for the key):

More at:

https://grokonez.com/android/kotlin-firebase-realtime-database-get-list-data-example-android

Kotlin Firebase Realtime Database – Get List of Data example | Android