Can't drawRect line
Can't drawRect line
提问于 2013-11-26 08:46:12
我试着在用户每次点击的时候连接线路。用户点击的点被创建，但连接它们的线没有被创建。它给出了以下错误：
CGContextAddLineToPoint: no current point.有人能告诉我为什么吗？我检查过了，但找不到任何相关的东西，因为我的笔划方法在最后。这是我正在尝试的：
- (id)initWithCoder:(NSCoder *)aDecoder {
if (self = [super initWithCoder:aDecoder]) {
[self setMultipleTouchEnabled:NO];
[self setBackgroundColor:[UIColor clearColor]];
o = 0.5 / 1.0;
sW = 5.0;
r = 255.0/255.0;
g = 59.0/255.0;
b = 48.0/255.0;
first = CGPointZero;
second = CGPointZero;
third = CGPointZero;
}
return self;
}
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
UITouch *touch = [touches anyObject];
[self setOpacity:o];
if (CGPointEqualToPoint(first, CGPointZero)) {
first = [touch locationInView:self];
}
else if (!CGPointEqualToPoint(first, CGPointZero) && CGPointEqualToPoint(second, CGPointZero)) {
second = [touch locationInView:self];
}
else if (!CGPointEqualToPoint(first, CGPointZero) && !(CGPointEqualToPoint(second, CGPointZero)) && CGPointEqualToPoint(third, CGPointZero)) {
third = [touch locationInView:self];
}
else {
first = CGPointZero;
second = CGPointZero;
third = CGPointZero;
}
[self setNeedsDisplay];
}
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
UITouch *touch = [touches anyObject];
if (!CGPointEqualToPoint(first, CGPointZero) && CGPointEqualToPoint(second, CGPointZero)) {
first = [touch locationInView:self];
}
else if (!CGPointEqualToPoint(first, CGPointZero) && !(CGPointEqualToPoint(second, CGPointZero)) && CGPointEqualToPoint(third, CGPointZero)) {
second = [touch locationInView:self];
}
else {
third = [touch locationInView:self];
}
[self setNeedsDisplay];
}
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
[self drawBitmap];
}
- (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event {
}
- (void)drawRect:(CGRect)rect {
[incrementalImage drawInRect:rect];
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetLineWidth(context, sW);
CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), r, g, b, o);
NSLog(@"R:%f, G:%f, B:%f",r,g,b);
if (!CGPointEqualToPoint(first, CGPointZero)) {
CGRect rectangle = CGRectMake(first.x, first.y, 20, 20);
CGContextAddEllipseInRect(context, rectangle);
CGContextFillEllipseInRect(context, rectangle);
CGContextMoveToPoint(context, first.x, first.y);
}
if (!CGPointEqualToPoint(second, CGPointZero)) {
CGRect rectangle2 = CGRectMake(second.x, second.y, 20, 20);
CGContextAddEllipseInRect(context, rectangle2);
CGContextFillEllipseInRect(context, rectangle2);
CGContextAddLineToPoint(context, second.x, second.y);
}
if (!CGPointEqualToPoint(third, CGPointZero)) {
CGRect rectangle3 = CGRectMake(third.x, third.y, 20, 20);
CGContextAddEllipseInRect(context, rectangle3);
CGContextFillEllipseInRect(context, rectangle3);
CGContextAddLineToPoint(context, third.x, third.y);
}
CGContextStrokePath(context);
CGContextDrawPath(context, kCGPathFill);
}
- (void)drawBitmap {
UIGraphicsBeginImageContextWithOptions(self.bounds.size, NO, 0.0);
[[UIColor redColor] setStroke];
//CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), 255.0/255.0, 255.0/255.0, 255.0/255.0, 1.0/1.0);
if (!incrementalImage) { // first draw;
UIBezierPath *rectpath = [UIBezierPath bezierPathWithRect:self.bounds]; // enclosing bitmap by a rectangle defined by another UIBezierPath object
[[UIColor clearColor] setFill];
[rectpath fill]; // fill it
}
[incrementalImage drawAtPoint:CGPointZero];
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetLineWidth(context, sW);
CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), r, g, b, o);
if (!CGPointEqualToPoint(first, CGPointZero)) {
CGRect rectangle = CGRectMake(first.x, first.y, 20, 20);
CGContextAddEllipseInRect(context, rectangle);
CGContextFillEllipseInRect(context, rectangle);
CGContextMoveToPoint(context, first.x, first.y);
}
if (!CGPointEqualToPoint(second, CGPointZero)) {
CGRect rectangle2 = CGRectMake(second.x, second.y, 20, 20);
CGContextAddEllipseInRect(context, rectangle2);
CGContextFillEllipseInRect(context, rectangle2);
CGContextAddLineToPoint(context, second.x, second.y);
}
if (!CGPointEqualToPoint(third, CGPointZero)) {
CGRect rectangle3 = CGRectMake(third.x, third.y, 20, 20);
CGContextAddEllipseInRect(context, rectangle3);
CGContextFillEllipseInRect(context, rectangle3);
CGContextAddLineToPoint(context, third.x, third.y);
}
CGContextStrokePath(context);
incrementalImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
}此外，笔触颜色始终为黑色。我把它记入日志，它会显示正确的颜色。关于无当前点错误的不合理之处在于，我在点击时使用相同的参数来创建圆，它工作得很好，唯一不起作用的是直线。
回答 1
Stack Overflow用户
发布于 2013-11-26 08:51:07
在这里，您需要第三点，但它应该是第二点。
if(!CGPointEqualToPoint(third, CGPointZero)){
CGContextAddLineToPoint(context, second.x, second.y);
}
CGContextAddEllipseInRect(context, rectangle3);
CGContextFillEllipseInRect(context, rectangle3);在这里，您再次调用第三点，但在正确的位置
if(!CGPointEqualToPoint(third, CGPointZero)){
CGContextAddLineToPoint(context, third.x, third.y);
}页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/20206493
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