用2点和圆心绘制圆弧

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?

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!

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.