我正在做一个绘图项目,我想支持多点触控,我浏览了在线文档,建议跟踪触摸点,我做到了,但我没有得到想要的行为。我没有得到直线。
下面是我的代码
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
red = 0.0/255.0;
green = 0.0/255.0;
blue = 0.0/255.0;
brush = 10.0;
opacity = 1.0;
self.view.multipleTouchEnabled = YES;
touchPaths = [NSMutableDictionary dictionary];
}
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
for (UITouch *touch in touches)
{
NSString *key = [NSString stringWithFormat:@"%d", (int) touch];
lastPoint = [touch locationInView:self.view];
[touchPaths setObject:[NSValue valueWithCGPoint:lastPoint] forKey:key];
}
}
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
for (UITouch *touch in touches)
{
NSString *key = [NSString stringWithFormat:@"%d", (int) touch];
lastPoint = [[touchPaths objectForKey:key] CGPointValue];
CGPoint currentPoint1 = [touch locationInView:self.view];
UIGraphicsBeginImageContext(self.view.frame.size);
[self.tempDrawImage.image drawInRect:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height)];
CGContextMoveToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);
CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), currentPoint1.x, currentPoint1.y);
CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound);
CGContextSetLineWidth(UIGraphicsGetCurrentContext(), brush );
CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), red, green, blue, 1.0);
CGContextSetBlendMode(UIGraphicsGetCurrentContext(),kCGBlendModeNormal);
CGContextStrokePath(UIGraphicsGetCurrentContext());
self.tempDrawImage.image = UIGraphicsGetImageFromCurrentImageContext();
[self.tempDrawImage setAlpha:opacity];
UIGraphicsEndImageContext();
lastPoint = currentPoint1;
}
}
但是当我使用这段代码绘图时,我明白了。
所以 friend 们,请帮帮我,我做错了什么。
问候 兰 git
最佳答案
您没有正确填充 touchPaths
。尝试在每次绘图后设置它,像这样:
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
for (UITouch *touch in touches)
{
NSString *key = [NSString stringWithFormat:@"%d", (int) touch];
CGPoint lastPoint = [[touchPaths objectForKey:key] CGPointValue];
CGPoint currentPoint1 = [touch locationInView:self.view];
UIGraphicsBeginImageContext(self.view.frame.size);
[self.tempDrawImage.image drawInRect:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height)];
CGContextMoveToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);
CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), currentPoint1.x, currentPoint1.y);
CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound);
CGContextSetLineWidth(UIGraphicsGetCurrentContext(), brush );
CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), red, green, blue, 1.0);
CGContextSetBlendMode(UIGraphicsGetCurrentContext(),kCGBlendModeNormal);
CGContextStrokePath(UIGraphicsGetCurrentContext());
self.tempDrawImage.image = UIGraphicsGetImageFromCurrentImageContext();
[self.tempDrawImage setAlpha:opacity];
UIGraphicsEndImageContext();
// I changed your code here
[touchPaths setObject:[NSValue valueWithCGPoint:currentPoint1] forKey:key];
}
}
您当前正在此处设置 lastPoint
,但您似乎没有使用它(而且它只能通过一次触摸工作)。也不需要将 lastPoint
作为字段。
关于ios - 在多点触控中跟踪触摸点,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/20761686/