xcode iphone touch 点画
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xcode iphone touch dotted painting
提问by arvin Arabi
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 :
大家好，我是法国人，所以请教我的英语。我的问题是我想用我的手指在 iphone 上画一个像这样的虚线画-----------，不是一条线而是一条画。我有：
CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound); //kCGLineCapSquare, kCGLineCapButt, kCGLineCapRound
CGContextSetLineWidth(UIGraphicsGetCurrentContext(), 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.
请问“dotted”的代码是什么。
回答by zrzka
CGContextSetLineDash
CGContextSetLineDash
Example:
例子：
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).
或者简单地在 Xcode 中打开 QuartzDemo 示例并查看 QuartzLines.m 文件（QuartzDashView 类）。
You should really read documentation (see already mentioned link).
您应该真正阅读文档（请参阅已经提到的链接）。
回答by fightingshadow
Your problem is you did not reference the context before doing this: CGContextSetLineDash( context, 0.0, dashes, 2 );
您的问题是您在执行此操作之前没有引用上下文： 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.
你需要这样做：CGContextRef context = UIGraphicsGetCurrentContext();然后用上下文替换你所有的 UIGraphicsGetC... 调用，无论如何都要加快速度。
Deitel's iPhone App-Driven Approach book has an example of doing this.
Deitel 的 iPhone App-Driven Approach 一书中有一个这样做的例子。
FightingS
格斗S
回答by alones
See the great page about the roles of line properties! https://horseshoe7.wordpress.com/2014/07/16/core-graphics-line-drawing-explained/
请参阅有关线属性角色的精彩页面！ 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 ( . . . .)
根据上面的页面，这里是“点”线的代码，如 ( . . . . )
// 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);
