How to center drawArc using canvas

I'm trying to create a graph using the class RectF and the class Canvas , for this I created a View custom, where I draw drawc.

I also have to insert text in the center of the drawn graph, I am trying to center the text using canvas.getWidth/2 and canvas.getHeight/2 and passing those values within canvas.drawText .

follows the class code

public class Circle extends View {
    private static final int START_ANGLE = 0;
    private Paint paint;
    private RectF rectF;
    private float angle;
    private Paint paintCinza;

    public Circle(Context context, AttributeSet attrs) {
        super(context, attrs);
        paint = new Paint();
        paint.setAntiAlias(true);
        paint.setStyle(Paint.Style.STROKE);
        paint.setStrokeWidth(30);
        paint.setColor(getResources().getColor(R.color.verde));
        paint.setTextAlign(Paint.Align.CENTER);
        rectF = new RectF(40,40, 250, 250);
        angle = 120;
    }

    @Override
    protected void onDraw(Canvas canvas) {
        canvas.drawColor(Color.BLACK);
        Paint p1 = new Paint();
        p1.setColor(getResources().getColor(R.color.cinza));
        p1.setTextSize(80);
        canvas.drawText("72%", (canvas.getWidth() ) / 2, (canvas.getHeight()) / 2, p1);
        canvas.drawArc(rectF, START_ANGLE, angle, false, paint);

    }

    public float getAngle() {
        return angle;
    }

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

xml:

  <br.net.getinfo.treinamentos.view.Circle
    android:id="@+id/circle"
    android:layout_width="250dp"
    android:layout_height="250dp"
    android:layout_gravity="center"
    android:background="@android:color/transparent" />

What do I need to change to get the graph I created to be centered within the space of Canvas (space in the black color of the image)?