我想用触摸事件模拟橡皮擦效果,以显示顶部阻挡物后面的图像,例如灰色;
类似的东西:
我已经找到了很长时间的解决方案,但我做得不好。
以下是我的自定义视图代码: CustomView.m:
-(id)initWithCoder:(NSCoder *)aDecoder
{
if (self = [super initWithCoder:aDecoder]) {
[self setup];
}
return self;
}
-(id)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
if (self) {
[self setup];
}
return self;
}
-(void)setup
{
[self setMultipleTouchEnabled:NO];
[self setBackgroundColor:[UIColor darkGrayColor]];
self.drawingPath = [UIBezierPath bezierPath];
[self.drawingPath moveToPoint:CGPointZero];
[self.drawingPath setLineWidth:5.0];
self.image = [UIImage imageNamed:@"transformers.jpg"];
self.shapeLayer = [CAShapeLayer layer];
self.caLayer = [CALayer layer];
self.caLayer.frame = self.bounds;
self.caLayer.contents = (id)(self.image.CGImage);
[self.layer addSublayer:self.caLayer];
}
- (void)drawRect:(CGRect)rect
{
self.shapeLayer.path = [self.drawingPath CGPath];
self.caLayer.mask = self.shapeLayer;
self.shapeLayer.lineWidth = 5.0;
}
-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
UITouch *touch = [touches anyObject];
CGPoint location = [touch locationInView:self];
[self.drawingPath moveToPoint:location];
lastPt = location;
[self setNeedsDisplay];
NSLog(@"Touch Began");
}
-(void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
UITouch *touch = [touches anyObject];
CGPoint location = [touch locationInView:self];
[self.drawingPath addLineToPoint:location];
[self setNeedsDisplay];
}
-(void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
[self touchesMoved:touches withEvent:event];
}
-(void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event
{
[self touchesMoved:touches withEvent:event];
}
然而,它只是模拟路径中的后方图像填充。 我想像照片一样成为橡皮擦效果。 请帮忙。
答案 0 :(得分:6)
您的代码很接近,但您需要的是具有灰色背景的自定义图层类,并将路径绘制为透明。你可以用这样的代码
来做到这一点<强> RevealLayer.h 强>
@interface RevealLayer : CALayer
@property (strong, nonatomic) UIBezierPath *drawingPath;
@end
<强> RevealLayer.m 强>
@implementation RevealLayer
- (UIBezierPath *)drawingPath
{
if ( !_drawingPath )
{
_drawingPath = [UIBezierPath new];
[_drawingPath moveToPoint:CGPointZero];
[_drawingPath setLineWidth:20.0];
[_drawingPath setLineCapStyle:kCGLineCapRound];
}
return( _drawingPath );
}
- (void)drawInContext:(CGContextRef)context
{
UIGraphicsPushContext( context );
[[UIColor darkGrayColor] set];
CGContextFillRect( context, self.bounds );
CGContextSetBlendMode( context, kCGBlendModeClear );
[self.drawingPath stroke];
UIGraphicsPopContext();
}
@end
然后,自定义视图类的代码与您已有的类似。但是,设置稍有不同,您无需实现drawRect:
方法。
<强> CustomView.m 强>
@interface CustomView()
@property (strong, nonatomic) RevealLayer *revealLayer;
@end
@implementation CustomView
- (void)setup
{
self.userInteractionEnabled = YES;
[self setMultipleTouchEnabled:NO];
self.image = [UIImage imageNamed:@"transformers.jpg"];
self.revealLayer = [RevealLayer new];
self.revealLayer.frame = self.bounds;
self.revealLayer.backgroundColor = [[UIColor clearColor] CGColor];
[self.revealLayer setNeedsDisplay];
[self.layer addSublayer:self.revealLayer];
}
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
UITouch *touch = [touches anyObject];
CGPoint location = [touch locationInView:self];
[self.revealLayer.drawingPath moveToPoint:location];
[self.revealLayer setNeedsDisplay];
}
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
UITouch *touch = [touches anyObject];
CGPoint location = [touch locationInView:self];
[self.revealLayer.drawingPath addLineToPoint:location];
[self.revealLayer setNeedsDisplay];
}