[英]How do I use UIBezierPath to draw a line that follows a touch event?
我從一個類似的問題中選擇了以下代碼,但是我沒有運氣好。
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
NSLog(@"Check #1");
UITouch* touch = [touches anyObject];
self.currentPath = [UIBezierPath bezierPath];
currentPath.lineWidth = 3.0;
[currentPath moveToPoint:[touch locationInView:self.view]];
[paths addObject:self.currentPath];
}
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
UITouch *touch = [touches anyObject];
[self.currentPath addLineToPoint:[touch locationInView:self.view]];
[self.view setNeedsDisplay];
}
- (void)drawRect:(CGRect)rect {
[[UIColor redColor] set];
for (UIBezierPath *path in paths) {
NSLog(@"Check #2?");
[path stroke];
}
}
我從中得到的是我需要使用UIBezierPath
但我不知道如何讓它跟隨我的手指。 我只想繪制一條線,在用戶觸摸時啟動它並在它們拿起手指的地方結束它。
如何使用UIBezierPath實現此線條圖?
#import <UIKit/UIKit.h>
@interface Canvas : UIImageView
@property (nonatomic, assign) CGPoint location;
@end
#import "Canvas.h"
@implementation Canvas
- (void) touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
UITouch *touch = [touches anyObject];
self.location = [touch locationInView:self];
}
- (void) touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
UITouch *touch = [touches anyObject];
CGPoint currentLocation = [touch locationInView:self];
UIGraphicsBeginImageContext(self.frame.size);
CGContextRef ctx = UIGraphicsGetCurrentContext();
[self.image drawInRect:CGRectMake(0, 0, self.frame.size.width, self.frame.size.height)];
CGContextSetLineCap(ctx, kCGLineCapRound);
CGContextSetLineWidth(ctx, 5.0);
CGContextSetRGBStrokeColor(ctx, 1.0, 0.0, 0.0, 1.0);
CGContextBeginPath(ctx);
CGContextMoveToPoint(ctx, self.location.x, self.location.y);
CGContextAddLineToPoint(ctx, currentLocation.x, currentLocation.y);
CGContextStrokePath(ctx);
self.image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
self.location = currentLocation;
}
- (void) touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
UITouch *touch = [touches anyObject];
CGPoint currentLocation = [touch locationInView:self];
UIGraphicsBeginImageContext(self.frame.size);
CGContextRef ctx = UIGraphicsGetCurrentContext();
[self.image drawInRect:CGRectMake(0, 0, self.frame.size.width, self.frame.size.height)];
CGContextSetLineCap(ctx, kCGLineCapRound);
CGContextSetLineWidth(ctx, 5.0);
CGContextSetRGBStrokeColor(ctx, 1.0, 0.0, 0.0, 1.0);
CGContextBeginPath(ctx);
CGContextMoveToPoint(ctx, self.location.x, self.location.y);
CGContextAddLineToPoint(ctx, currentLocation.x, currentLocation.y);
CGContextStrokePath(ctx);
self.image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
self.location = currentLocation;
}
@end
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