Android RatingBar Tutorial

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1- Android RatingBar

In AndroidRatingBar is a user interface control used to receive reviews from users. RatingBar is a descendant of ProgressBar,  so it has features inherited from the  ProgressBar. It is also used to display an aggregate rating (average) from all users. In terms of the RatingBar interface, it consists of stars, and users will select a star to give a rating, the first star corresponds to the lowest rating, and the final star corresponds to the highest rating.
Below is the structure of a RatingBar:

android:numStars

The android:numStars attribute allows you to set the number of stars to be displayed on the RatingBar. Its default value is 5.
android:numStars
<!-- numStars default is 5 -->
<RatingBar
    android:id="@+id/ratingBar21"
    android:rating="3.5"
    android:stepSize="0.1" ... />

<!-- numStars = 7 -->
<RatingBar
    android:id="@+id/ratingBar22"
    android:numStars="7"
    android:rating="5.7"
    android:stepSize="0.1" ... />

android:rating, android:stepSize

android:rating: A value indicating the rating of the user, or the average value from all ratings of all users. It is in the range of  (0,numStars].
The default value of the  android:stepSize attribute is 0.5, which means that the RatingBar will only display the ratings (or the user reviews) with the values of  0, 0.5, 1, 1.5, 2, etc. When the value of the  android:stepSite attribute is changed to 0.1, RatingBar can display the ratings with the values of  0, 0.1, 0.2, 0.3, 0.4, 0.5, etc.
android:stepSize
<!-- android.stepSize = "0.5" (Default) -->
<RatingBar
    android:id="@+id/ratingBar31"
    android:rating="2.7" ... />

<!-- android.stepSize = "0.1" -->
<RatingBar
    android:id="@+id/ratingBar32"
    android:rating="2.7"
    android:stepSize="0.1" ... />

android:isIndicator

The android :isIndicator = "true" attribute is used when you do not want users to leave a rating with this RatingBar. For example, you expect to have a RatingBar only to show an aggregate rating (average) from all users. By default the​​​​​​​ value of the attribute is false.
<!-- android:isIndicator = "false" (Default) -->
<RatingBar
    android:id="@+id/ratingBar51"
    android:rating="2" ... />

<!-- android:isIndicator = "true" (Readonly RatingBar) -->
<RatingBar
    android:id="@+id/ratingBar52"
    android:isIndicator="true"
    android:rating="4.5" ... />

2- RatingBar Styles

The style attribute is an option of the RatingBar, which allows you to set the style for RatingBar. There are several styles available in Android library that may be ready to use.
The Android library offers quite a few styles for RatingBar; however, a remarkable number of them look so much alike. Thus, it is hard for you to tell the difference. Here is an example with some nice designs:
  • style="@style/Widget.AppCompat.RatingBar.Indicator"  
  • style="@android:style/Widget.DeviceDefault.Light.RatingBar.Small"
  • style="@android:style/Widget.RatingBar"
  • style="@android:style/Widget.Holo.RatingBar"
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity" >

    <TextView
        android:id="@+id/textView41"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="16dp"
        android:layout_marginEnd="16dp"
        android:layout_marginRight="16dp"
        android:text="(Default)"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <RatingBar
        android:id="@+id/ratingBar41"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="8dp"
        android:rating="2.7"
        android:stepSize="0.1"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView41" />

    <TextView
        android:id="@+id/textView42"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="16dp"
        android:layout_marginEnd="16dp"
        android:layout_marginRight="16dp"
        android:text="AppCompat.RatingBar.Indicator"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/ratingBar41" />

    <RatingBar
        android:id="@+id/ratingBar42"
        style="@style/Widget.AppCompat.RatingBar.Indicator"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="8dp"
        android:rating="4.5"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView42" />

    <TextView
        android:id="@+id/textView43"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="16dp"
        android:layout_marginEnd="16dp"
        android:layout_marginRight="16dp"
        android:text="Widget.DeviceDefault.Light.RatingBar.Small"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/ratingBar42" />

    <RatingBar
        android:id="@+id/ratingBar43"
        style="@android:style/Widget.DeviceDefault.Light.RatingBar.Small"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="8dp"
        android:rating="2.5"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView43" />

    <TextView
        android:id="@+id/textView44"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="16dp"
        android:layout_marginEnd="16dp"
        android:layout_marginRight="16dp"
        android:text="Widget.RatingBar"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/ratingBar43" />

    <RatingBar
        android:id="@+id/ratingBar44"
        style="@android:style/Widget.RatingBar"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="8dp"
        android:rating="3"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView44" />

    <TextView
        android:id="@+id/textView45"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="16dp"
        android:layout_marginEnd="16dp"
        android:layout_marginRight="16dp"
        android:text="Widget.Holo.RatingBar"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/ratingBar44" />

    <RatingBar
        android:id="@+id/ratingBa45"
        style="@android:style/Widget.Holo.RatingBar"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="8dp"
        android:rating="3.5"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView45" />

</androidx.constraintlayout.widget.ConstraintLayout>

3- RatingBar Events

There are quite a few events related to a RatingBar, but the following events are most frequently used:
  • setOnClickListener(View.OnClickListener);
  • setOnRatingBarChangeListener(RatingBar.OnRatingBarChangeListener);

On Click Event:

The event happens when the user clicks the RatingBar. It is the same as the action of the user clicking a Button.
ratingBar.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {
         RatingBar rb = (RatingBar) v;
         float rating = rb.getRating();
         
         // Your code ...
    }
});

On RatingBar Changed Event

The event happens when the rating changes due to the user's action or the effect of calling the ratingBar.setRating(newRating) method, etc.
ratingBar.setOnRatingBarChangeListener(new RatingBar.OnRatingBarChangeListener() {
    @Override
    public void onRatingChanged(RatingBar ratingBar, float newRating, boolean fromUser) {
         // Your code
    }
});

4- Example of RatingBar

OK, now we are going to set a simple example using RatingBar. In this example, the first RatingBar receives user reviews. The second RatingBar displays an aggregate rating (average) from all users.
On  Android Studio, create a project:
  • File > New > New Project > Empty Activity
    • Name: RatingBarExample
    • Package name: org.o7planning.ratingbarexample
    • Language: Java
Here is the application interface:
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity" >

    <TextView
        android:id="@+id/textView"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="8dp"
        android:layout_marginEnd="16dp"
        android:layout_marginRight="16dp"
        android:text="Give your Rating:"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <RatingBar
        android:id="@+id/ratingBar_yours"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="8dp"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView" />

    <TextView
        android:id="@+id/textView_yourCurrentRating"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="8dp"
        android:layout_marginEnd="16dp"
        android:layout_marginRight="16dp"
        android:text="Your current Rating:"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.0"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/ratingBar_yours" />

    <Button
        android:id="@+id/button_submit"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="8dp"
        android:text="Submit"
        android:textAllCaps="false"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.52"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView_yourCurrentRating" />

    <TextView
        android:id="@+id/textView_ratingCount"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="8dp"
        android:layout_marginEnd="16dp"
        android:layout_marginRight="16dp"
        android:text="Rating Count: 0"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/button_submit" />

    <TextView
        android:id="@+id/textView_sumAllRating"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="8dp"
        android:layout_marginEnd="16dp"
        android:layout_marginRight="16dp"
        android:text="Sum of all Rating: 0"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView_ratingCount" />

    <TextView
        android:id="@+id/textView_averageAllRating"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="8dp"
        android:layout_marginEnd="16dp"
        android:layout_marginRight="16dp"
        android:text="Average value of all Rating: 0"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView_sumAllRating" />

    <RatingBar
        android:id="@+id/ratingBar_all"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="8dp"
        android:isIndicator="true"
        android:stepSize="0.1"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView_averageAllRating" />

</androidx.constraintlayout.widget.ConstraintLayout>
MainActivity.java
package com.example.ratingbarexample;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.RatingBar;
import android.widget.TextView;

import java.util.ArrayList;
import java.util.List;

public class MainActivity extends AppCompatActivity {

    private RatingBar ratingBarYours;
    private RatingBar ratingBarAll;

    private Button buttonSubmit;

    private TextView textViewYourCurrentRating;
    private TextView textViewRatingCount;
    private TextView textViewSumAllRating;
    private TextView textViewAverageAllRating;

    private List<Float> allRatings = new ArrayList<Float>();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        //
        this.buttonSubmit = (Button) this.findViewById(R.id.button_submit);
        this.ratingBarYours = (RatingBar) this.findViewById(R.id.ratingBar_yours);
        this.ratingBarAll = (RatingBar) this.findViewById(R.id.ratingBar_all);

        this.textViewYourCurrentRating = (TextView) this.findViewById(R.id.textView_yourCurrentRating);
        this.textViewRatingCount= (TextView) this.findViewById(R.id.textView_ratingCount);
        this.textViewSumAllRating= (TextView) this.findViewById(R.id.textView_sumAllRating);
        this.textViewAverageAllRating= (TextView) this.findViewById(R.id.textView_averageAllRating);

        this.ratingBarYours.setOnRatingBarChangeListener(new RatingBar.OnRatingBarChangeListener() {
            @Override
            public void onRatingChanged(RatingBar ratingBar, float rating, boolean fromUser) {
                textViewYourCurrentRating.setText("Your current Rating: " + rating);
            }
        });
        this.buttonSubmit.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                doSubmit();
            }
        });
    }

    private void doSubmit()  {
        float rating = this.ratingBarYours.getRating();
        this.allRatings.add(rating);

        int ratingCount = this.allRatings.size();
        float ratingSum = 0f;
        for(Float r: this.allRatings)  {
            ratingSum += r;
        }
        float averageRating = ratingSum / ratingCount;


        this.textViewRatingCount.setText("Rating Count: " + ratingCount);
        this.textViewSumAllRating.setText("Sum off all Rating: " + ratingSum);
        this.textViewAverageAllRating.setText("Average value off all Rating: " + averageRating);

        float ratingAll = this.ratingBarAll.getNumStars() * averageRating / this.ratingBarYours.getNumStars() ;
        this.ratingBarAll.setRating(ratingAll);
    }

}

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