xcode iphone touch dotted painting

HI every body I'm french so scuse me for my english. My problem is that I want to draw with my finger on the iphone a dotted drawing like that -----------, not a line but a draw.I have :

CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound); //kCGLineCapSquare, kCGLineCapButt, kCGLineCapRound
CGContextSetLineWidth(UIGraphics开发者_运维知识库GetCurrentContext(), 10.0); // for size
CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), 0.0, 1.0, 0.0, 1.0); //values for R, G, B, and Alpha
CGContextBeginPath(UIGraphicsGetCurrentContext());
CGContextMoveToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);
CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), currentPoint.x, currentPoint.y);
CGContextStrokePath(UIGraphicsGetCurrentContext());
drawImage.image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

What is the code for "dotted" please.

CGContextSetLineDash

http://developer.apple.com/library/mac/#documentation/GraphicsImaging/Reference/CGContext/Reference/reference.html%23//apple_ref/c/func/CGContextSetLineDash

Example:

CGFloat dashes[] = { 1, 1 };
CGContextSetLineDash( context, 0.0, dashes, 2 );

Or simply open QuartzDemo sample in Xcode and look at QuartzLines.m file (QuartzDashView class).

You should really read documentation (see already mentioned link).

Your problem is you did not reference the context before doing this: CGContextSetLineDash( context, 0.0, dashes, 2 );

You need to do this: CGContextRef context = UIGraphicsGetCurrentContext(); then replace all your UIGraphicsGetC... calls with context, to speed it up anyway.

Deitel's iPhone App-Driven Approach book has an example of doing this.

FightingS

See the great page about the roles of line properties! https://horseshoe7.wordpress.com/2014/07/16/core-graphics-line-drawing-explained/

According to the above page, here is the code for the 'dot' line like ( . . . .)

// should
CGContextSetLineCap(context, kCGLineCapRound);

// please see the role of line properties why the first should be 0 and the second should be the doulbe of the given line width
CGFloat dash[] = {0, lineWidth*2};

// the second value (0) means the span between sets of dot patterns defined by dash array
CGContextSetLineDash(context, 0, dash, 2);