Draw line in Cocoa? - objective-c

Question

How i can draw a line in a specific window after a button click?
i'm using this:
NSBezierPath * path = [NSBezierPath bezierPath];
[path setLineWidth: 4];
NSPoint startPoint = { 21, 21 };
NSPoint endPoint = { 128,128 };
[path moveToPoint: startPoint];
[path lineToPoint:endPoint];
[[NSColor redColor] set];
[path stroke];
but it work only if i put it in the:
- (void)applicationDidFinishLaunching:(NSNotification *)aNotification
how i can solve this?
my goal is to create an application that can draw lines , according to the details(coordinate) received
thank you.

Answer 1

You should not be drawing outside of a view or layer's drawing method (e.g. drawRect:). What you want to do, in broad strokes, is have a view there that draws the line when a flag is set, and when you click the button, set the flag and tell the view to redraw.

Answer 2

When you click the mouse event. This code will create line, curve and draw.
#import <Cocoa/Cocoa.h>
#interface BezierView : NSView {
NSPoint points[4];
NSUInteger pointCount;
}
#end
#import "BezierView.h"
#implementation BezierView
- (id)initWithFrame:(NSRect)frame {
self = [super initWithFrame:frame];
if (self) {
// Initialization code here.
}
return self;
}
- (void)drawRect:(NSRect)rect
{
NSBezierPath *control1 = [NSBezierPath bezierPath];
[control1 moveToPoint: points[0]];
[control1 lineToPoint: points[1]];
[[NSColor redColor] setStroke];
[control1 setLineWidth: 2];
[control1 stroke];
NSBezierPath *control2 = [NSBezierPath bezierPath];
[control2 moveToPoint: points[2]];
[control2 lineToPoint: points[3]];
[[NSColor greenColor] setStroke];
[control2 setLineWidth: 2];
[control2 stroke];
NSBezierPath *curve = [NSBezierPath bezierPath];
[curve moveToPoint: points[0]];
[curve curveToPoint: points[3]
controlPoint1: points[1]
controlPoint2: points[2]];
[[NSColor blackColor] setStroke];
CGFloat pattern[] = {4, 2, 1, 2};
[curve setLineDash: pattern
count: 4
phase: 1];
[[NSColor grayColor] setFill];
[curve fill];
[curve stroke];
}
- (void)mouseDown: (NSEvent*)theEvent
{
NSPoint click = [self convertPoint: [theEvent locationInWindow]
fromView: nil];
points[pointCount++ % 4] = click;
if (pointCount % 4 == 0)
{
[self setNeedsDisplay: YES];
}
}
#end