How to draw Bezier Curve in Android

Introduction

Bezier curves are smooth, mathematically defined curves used in computer graphics and design. They are essential for creating various shapes and effects, from rounded corners to complex animations. In this article, we will explore how to draw Bezier curves in Android using Canvas and Path.

Understanding Bezier Curves

Types of Bezier Curves

• Quadratic Bezier Curve: Defined by three control points: a starting point, a control point, and an ending point.
• Cubic Bezier Curve: Defined by four control points: a starting point, two control points, and an ending point.

Control Points

Control points determine the curve’s shape. Moving a control point alters the curve’s curvature and direction.

Drawing Bezier Curves in Android

Setting Up the Canvas

import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Path;

// ...

// Inside your View's onDraw method:
@Override
protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);

    // Create a Paint object for drawing the curve.
    Paint paint = new Paint();
    paint.setColor(Color.BLACK);
    paint.setStrokeWidth(5f);

    // Create a Path object to define the curve.
    Path path = new Path();

    // ... (Add curve points to the Path)

    // Draw the path on the canvas.
    canvas.drawPath(path, paint);
}

Drawing a Quadratic Bezier Curve

// ... (Inside the onDraw method)

// Starting point.
path.moveTo(100f, 100f);

// Control point.
path.quadTo(200f, 50f, 300f, 100f);

// ... (Draw the path)

Drawing a Cubic Bezier Curve

// ... (Inside the onDraw method)

// Starting point.
path.moveTo(100f, 100f);

// Control points.
path.cubicTo(150f, 50f, 250f, 150f, 300f, 100f);

// ... (Draw the path)

Example: Drawing a Curved Line

// ... (Inside the onDraw method)

// Starting point.
path.moveTo(50f, 200f);

// Control point for the first curve.
path.quadTo(150f, 50f, 250f, 200f);

// Control point for the second curve.
path.quadTo(350f, 350f, 450f, 200f);

// Draw the path.
canvas.drawPath(path, paint);

Conclusion

Bezier curves provide a powerful tool for creating smooth and visually appealing graphics in Android. By understanding the basics and using the Canvas and Path classes, you can implement various curve-based designs and effects.