How to retrieve data from firebase in RecyclerView android
AndroidManifest.xml
<!-- adding Internet permissions-->
<uses-permission android:name="android.permission.INTERNET"/>
gradle.build (project)
// Top-level build file where you can add configuration options common to all sub-projects/modules.
buildscript {
repositories {
google()
jcenter()
}
dependencies {
// always use latest version of dependencies
classpath "com.android.tools.build:gradle:4.1.3"
classpath 'com.google.gms:google-services:4.3.10'
// NOTE: Do not place your application dependencies here; they belong
// in the individual module build.gradle files
}
}
allprojects {
repositories {
google()
jcenter()
}
}
task clean(type: Delete) {
delete rootProject.buildDir
}
gradle.build (app)
plugins {
id 'com.android.application'
id 'com.google.gms.google-services'
}
android {
compileSdkVersion 32
buildToolsVersion "30.0.3"
defaultConfig {
applicationId "com.learnoset.firebasetutorials"
minSdkVersion 19
targetSdkVersion 32
versionCode 1
versionName "1.0"
testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
}
buildTypes {
release {
minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
}
}
compileOptions {
sourceCompatibility JavaVersion.VERSION_1_8
targetCompatibility JavaVersion.VERSION_1_8
}
}
dependencies {
implementation 'androidx.appcompat:appcompat:1.4.0'
implementation 'com.google.android.material:material:1.4.0'
implementation 'androidx.constraintlayout:constraintlayout:2.1.2'
testImplementation 'junit:junit:4.+'
// Firebase Bom Dependency
implementation platform('com.google.firebase:firebase-bom:29.0.3')
// Firebase Realtime Dependency
implementation 'com.google.firebase:firebase-database'
androidTestImplementation 'androidx.test.ext:junit:1.1.3'
androidTestImplementation 'androidx.test.espresso:espresso-core:3.4.0'
}
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:gravity="center"
android:orientation="vertical"
tools:context=".MainActivity">
<androidx.recyclerview.widget.RecyclerView
android:id="@+id/recyclerView"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</LinearLayout>
MainActivity.java
import android.os.Bundle;
import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.ValueEventListener;
import java.util.ArrayList;
import java.util.List;
public class MainActivity extends AppCompatActivity {
// getting Firebase Database reference to communicate with firebase database
private final DatabaseReference databaseReference = FirebaseDatabase.getInstance().getReference();
// creating List of MyItems to store user details
private final List<MyItems> myItemsList = new ArrayList<>();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// getting RecyclerView from xml file
final RecyclerView recyclerView = findViewById(R.id.recyclerView);
// setting recyclerview size fixed for every item in the recyclerview
recyclerView.setHasFixedSize(true);
// setting layout manager to the recyclerview. Ex. LinearLayoutManager (vertical mode)
recyclerView.setLayoutManager(new LinearLayoutManager(MainActivity.this));
databaseReference.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot snapshot) {
// clear old items / users from list to add new data/ users
myItemsList.clear();
// getting all children from users root
for (DataSnapshot users : snapshot.child("users").getChildren()) {
// to prevent app crash check if the user has all the details in Firebase Database
if (users.hasChild("fullname") && users.hasChild("mobile") && users.hasChild("email")) {
// getting users details from Firebase Database and store into the List one by one
final String getFullname = users.child("fullname").getValue(String.class);
final String getMobile = users.child("mobile").getValue(String.class);
final String getEmail = users.child("email").getValue(String.class);
// creating user item with user details
MyItems myItems = new MyItems(getFullname, getMobile, getEmail);
// adding this user item to List
myItemsList.add(myItems);
}
}
// after all the users has added to list.
// now set adapter to RecyclerView
recyclerView.setAdapter(new MyAdapter(myItemsList, MainActivity.this));
}
@Override
public void onCancelled(@NonNull DatabaseError error) {
}
});
}
}
MyAdapter.java
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;
import java.util.List;
public class MyAdapter extends RecyclerView.Adapter<MyAdapter.MyViewHolder> {
private final List<MyItems> items; // items array list
private final Context context; // context
// constructor
public MyAdapter(List<MyItems> items, Context context) {
this.items = items;
this.context = context;
}
@NonNull
@Override
public MyAdapter.MyViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
return new MyViewHolder(LayoutInflater.from(parent.getContext()).inflate(R.layout.recyclerview_adapter_layout, null));
}
@Override
public void onBindViewHolder(@NonNull MyAdapter.MyViewHolder holder, int position) {
// getting single item / user details from List
MyItems myItems = items.get(position);
// setting user details to TextViews
holder.fullname.setText(myItems.getFullname());
holder.mobile.setText(myItems.getMobile());
holder.email.setText(myItems.getEmail());
}
@Override
public int getItemCount() {
return items.size();
}
// MyViewHolder class to hold view reference for every item in the RecyclerView
// We will learn more about this in RecyclerView tutorials series
static class MyViewHolder extends RecyclerView.ViewHolder {
// declaring 3 TextViews
private final TextView fullname, email, mobile;
public MyViewHolder(@NonNull View itemView) {
super(itemView);
// getting TextViews from recyclerview_adapter_layout.xml file
fullname = itemView.findViewById(R.id.fullnameTV);
email = itemView.findViewById(R.id.emailTV);
mobile = itemView.findViewById(R.id.mobileTV);
}
}
}
MyItems.java
public class MyItems {
private final String fullname, mobile, email;
public MyItems(String fullname, String mobile, String email) {
this.fullname = fullname;
this.mobile = mobile;
this.email = email;
}
public String getFullname() {
return fullname;
}
public String getMobile() {
return mobile;
}
public String getEmail() {
return email;
}
}
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