我正在使用UIView的子类来绘制,这个子类视图用于在视图控制器上获取您的签名.有一个清除按钮,应该清除UIView,除非它不起作用.这是我尝试过的.
subclass.h
@implementation subclassed uiview
{
UIBezierPath *path;
UIImage *incrementalImage; // (1)
}
- (id)initWithCoder:(NSCoder *)aDecoder {
if (self = [super initWithCoder:aDecoder]) {
[self setMultipleTouchEnabled:NO];
[self setBackgroundColor:[UIColor clearColor]];
path = [UIBezierPath bezierPath];
[path setLineWidth:2.0];
}
return self;
}
- (void)drawRect:(CGRect)rect {
[incrementalImage drawInRect:rect]; // (3)
[path stroke];
}
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
UITouch *touch = [touches anyObject];
CGPoint p = [touch locationInView:self];
[path moveToPoint:p];
}
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
UITouch *touch = [touches anyObject];
CGPoint p = [touch locationInView:self];
[path addLineToPoint:p];
[self setNeedsDisplay];
}
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event // (2)
{
UITouch *touch = [touches anyObject];
CGPoint p = [touch locationInView:self];
[path addLineToPoint:p];
[self drawBitmap]; // (3)
[self setNeedsDisplay];
[path removeAllPoints]; //(4)
}
- (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event {
[self touchesEnded:touches withEvent:event];
}
- (void)drawBitmap // (3)
{
UIGraphicsBeginImageContextWithOptions(self.bounds.size,NO,0.0);
//[[UIColor blackColor] setStroke];
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];
[path stroke];
incrementalImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
}
@end
查看controller.m
- (IBAction)clearTapped:(id)sender {
self.subclassedView.backgroundColor = [UIColor clearColor];
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetFillColorWithColor(context,[UIColor clearColor].CGColor);
CGContextFillRect(context,self.subclassedView.bounds);
CGContextClearRect(context,self.subclassedView.bounds);
CGContextFlush(context);
[self.subclassedView setNeedsDisplay];
}
任何人都可以告诉我为什么这不起作用,我应该做什么呢？
解决方法
重新初始化路径变量并强制视图使用此新创建的空路径进行绘制.这给人以擦除先前绘制路径的印象.在你的子类中包含这个函数,
- (void)erase {
path = nil; //Set current path nil
path = [UIBezierPath bezierPath]; //Create new path
[self setNeedsDisplay];
}
在子类的.h文件中声明此方法.从视图控制器类中,您需要在需要擦除视图时调用此方法,
- (IBAction)clearTapped:(id)sender {
[self.subclassedView erase];
}
试试看.
希望有所帮助！
