How to draw a circle with animation in android with circle size based on a value

Question

I want to develop a custom component which draws part of the circle based on different values. e.g draw 1/4 cirle, 1/2 circle etc. The component needs to be animated to disp

Answer 1

You have to draw the circle view, and after that you should create an animation to it.

Creating the circle view:

public class Circle extends View {

    private static final int START_ANGLE_POINT = 90;

    private final Paint paint;
    private final RectF rect;

    private float angle;

    public Circle(Context context, AttributeSet attrs) {
        super(context, attrs);

        final int strokeWidth = 40;

        paint = new Paint();
        paint.setAntiAlias(true);
        paint.setStyle(Paint.Style.STROKE);
        paint.setStrokeWidth(strokeWidth);
        //Circle color
        paint.setColor(Color.RED);

        //size 200x200 example
        rect = new RectF(strokeWidth, strokeWidth, 200 + strokeWidth, 200 + strokeWidth);

        //Initial Angle (optional, it can be zero)
        angle = 120;
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        canvas.drawArc(rect, START_ANGLE_POINT, angle, false, paint);
    }

    public float getAngle() {
        return angle;
    }

    public void setAngle(float angle) {
        this.angle = angle;
    }
}

Creating the animation class to set the new angle:

public class CircleAngleAnimation extends Animation {

    private Circle circle;

    private float oldAngle;
    private float newAngle;

    public CircleAngleAnimation(Circle circle, int newAngle) {
        this.oldAngle = circle.getAngle();
        this.newAngle = newAngle;
        this.circle = circle;
    }

    @Override
    protected void applyTransformation(float interpolatedTime, Transformation transformation) {
        float angle = oldAngle + ((newAngle - oldAngle) * interpolatedTime);

        circle.setAngle(angle);
        circle.requestLayout();
    }
}

Put circle into your layout:

And finally starting the animation:

Circle circle = (Circle) findViewById(R.id.circle);

CircleAngleAnimation animation = new CircleAngleAnimation(circle, 240);
animation.setDuration(1000);
circle.startAnimation(animation);

The result is: