How to Create Custom Shapes of Data Points in GraphView in Android?

If you are looking for a view to represent some statistical data or looking for a UI for displaying a graph in your app then in this article we will take a look at creating a line graph view and showing custom shape to the data points in our Android App.  

What we are going to build in this article?  

We will be building a simple Line Graph View in our Android app and we will be displaying some sample data with custom shapes in our application. Note that we are going to implement this project using the Java language. 

Step by Step Implementation

Step 1: Create a New Project

To create a new project in Android Studio please refer to How to Create/Start a New Project in Android Studio. Note that select Java as the programming language.

Step 2: Add dependency

Navigate to the Gradle Scripts > build.gradle(Module:app) and add the below dependency in the dependencies section.   

implementation ‘com.jjoe64:graphview:4.2.2’

Step 3: Working with the activity_main.xml file

Navigate to the app > res > layout > activity_main.xml and add the below code to that file. Below is the code for the activity_main.xml file. 

XML

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    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"
    tools:context=".MainActivity">

    <com.jjoe64.graphview.GraphView
        android:id="@+id/graphview"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

</RelativeLayout>

Step 4: Working with the MainActivity.java file

Go to the MainActivity.java file and refer to the following code. Below is the code for the MainActivity.java file. Comments are added inside the code to understand the code in more detail.

Java

import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.os.Bundle;

import androidx.appcompat.app.AppCompatActivity;

import com.jjoe64.graphview.GraphView;
import com.jjoe64.graphview.series.DataPoint;
import com.jjoe64.graphview.series.DataPointInterface;
import com.jjoe64.graphview.series.PointsGraphSeries;

public class MainActivity extends AppCompatActivity {

    GraphView graphView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        graphView = findViewById(R.id.graphview);

        // For creating Point Graph Series We use PointGraphSeries
        PointsGraphSeries<DataPoint> series = new PointsGraphSeries<>(getDataPoint());

        graphView.addSeries(series);

        // we use this method to define the shape that
        // will be used for data points
        // series.setShape(PointsGraphSeries.Shape.TRIANGLE);
        // we use this method to define the size of the shape
        series.setSize(50);

        // we use this method to set the color
        series.setColor(Color.RED);

        // we use this method to define the custom shape,
        // we create our own shape
        series.setCustomShape(new PointsGraphSeries.CustomShape() {
            @Override
            public void draw(Canvas canvas, Paint paint, float x, float y, DataPointInterface dataPoint) {
                paint.setStrokeWidth(5);
                // we are initialising the shape structure of data points
                canvas.drawLine(x - 20, y, x, y - 20, paint);
                canvas.drawLine(x, y - 20, x + 20, y, paint);
                canvas.drawLine(x + 20, y, x, y + 20, paint);
                canvas.drawLine(x - 20, y, x, y + 20, paint);
            }
        });
    }

    // initialising the data points
    private DataPoint[] getDataPoint() {
        DataPoint[] dp = new DataPoint[]{
                new DataPoint(0, 1),
                new DataPoint(2, 1),
                new DataPoint(3, 5),
                new DataPoint(6, 2),
                new DataPoint(7, 8),
        };
        return dp;
    }
}

Output: