Draw arc with 2 points and center of the circle

Question

I have two points of circle and center of this circle. I want to draw an arc between these points. Method drawArc is to simple and doesn't fit my purpose. Anybody help?

Liguria

Is this homework? If so please tag it as such. – Lieu

I know that exists meny functions to draw Arc, but I can't fint suitable – Liguria

Answer 1

You can use Canvas.drawArc, but you must compute the arguments it needs:

Lets say that the center of the circle is (x0, y0) and that the arc contains your two points (x1, y1) and (x2, y2). Then the radius is: r=sqrt((x1-x0)(x1-x0) + (y1-y0)(y1-y0)). So:

int r = (int)Math.sqrt((x1-x0)*(x1-x0) + (y1-y0)*(y1-y0));
int x = x0-r;
int y = y0-r;
int width = 2*r;
int height = 2*r;
int startAngle = (int) (180/Math.PI*atan2(y1-y0, x1-x0));
int endAngle = (int) (180/Math.PI*atan2(y2-y0, x2-x0));
canvas.drawArc(x, y, width, height, startAngle, endAngle);

Good luck!

Thurston

FYI: This code would work a bit better if you used float instead of int variables. PI=3.14, Square Roots, etc. You could be creating a lot of zeros if you stick with int types. – Anoxemia

in theory yes. however, drawArc() has int parameters. – Thurston

Note that r = Math.hypot(x1-x0, y1 - 0) – Bengt

Currently this canvas.drawArc() has 2 parameters more and is designed for API 21. Use overriden version if you need < 21. – Narine

Answer 2

Graphics.drawArc expects the following parameters:

• x
• y
• width
• height
• startAngle
• arcAngle

Given your arc start and end points it is possible to compute a bounding box where the arc will be drawn. This gives you enough information to provide parameters: x, y, width and height.

You haven't specified the desired angle so I guess you could choose one arbitrarily.

Lammergeier