给UIButton 建立一个Category
--UIButton+EnlargeEdge.h
#import <objc/runtime.h>
@interface UIButton (EnlargeEdge)
- (void)setEnlargeEdge:(CGFloat) size;
- (void)setEnlargeEdgeWithTop:(CGFloat) top right:(CGFloat) right bottom:(CGFloat) bottom left:(CGFloat) left;
@end
--UIButton+EnlargeEdge.m
#import "UIButton+EnlargeEdge.h"
@implementation UIButton (EnlargeEdge)
static char topNameKey;
static char rightNameKey;
static char bottomNameKey;
static char leftNameKey;
- (void)setEnlargeEdge:(CGFloat) size
{
objc_setAssociatedObject(self, &topNameKey, [NSNumber numberWithFloat:size], OBJC_ASSOCIATION_COPY_NONATOMIC);
objc_setAssociatedObject(self, &rightNameKey, [NSNumber numberWithFloat:size], OBJC_ASSOCIATION_COPY_NONATOMIC);
objc_setAssociatedObject(self, &bottomNameKey, [NSNumber numberWithFloat:size], OBJC_ASSOCIATION_COPY_NONATOMIC);
objc_setAssociatedObject(self, &leftNameKey, [NSNumber numberWithFloat:size], OBJC_ASSOCIATION_COPY_NONATOMIC);
}
- (void)setEnlargeEdgeWithTop:(CGFloat) top right:(CGFloat) right bottom:(CGFloat) bottom left:(CGFloat) left
{
objc_setAssociatedObject(self, &topNameKey, [NSNumber numberWithFloat:top], OBJC_ASSOCIATION_COPY_NONATOMIC);
objc_setAssociatedObject(self, &rightNameKey, [NSNumber numberWithFloat:right], OBJC_ASSOCIATION_COPY_NONATOMIC);
objc_setAssociatedObject(self, &bottomNameKey, [NSNumber numberWithFloat:bottom], OBJC_ASSOCIATION_COPY_NONATOMIC);
objc_setAssociatedObject(self, &leftNameKey, [NSNumber numberWithFloat:left], OBJC_ASSOCIATION_COPY_NONATOMIC);
}
- (CGRect)enlargedRect
{
NSNumber* topEdge = objc_getAssociatedObject(self, &topNameKey);
NSNumber* rightEdge = objc_getAssociatedObject(self, &rightNameKey);
NSNumber* bottomEdge = objc_getAssociatedObject(self, &bottomNameKey);
NSNumber* leftEdge = objc_getAssociatedObject(self, &leftNameKey);
if (topEdge && rightEdge && bottomEdge && leftEdge)
{
return CGRectMake(self.bounds.origin.x - leftEdge.floatValue,
self.bounds.origin.y - topEdge.floatValue,
self.bounds.size.width + leftEdge.floatValue + rightEdge.floatValue,
self.bounds.size.height + topEdge.floatValue + bottomEdge.floatValue);
}
else
{
return self.bounds;
}
}
- (BOOL)pointInside:(CGPoint)point withEvent:(UIEvent *)event
{
CGRect rect = [self enlargedRect];
if (CGRectEqualToRect(rect, self.bounds))
{
return [super pointInside:point withEvent:event];
}
return CGRectContainsPoint(rect, point) ? YES : NO;
}
/*
- (UIView*)hitTest:(CGPoint) point withEvent:(UIEvent*) event
{
CGRect rect = [self enlargedRect];
if (CGRectEqualToRect(rect, self.bounds))
{
return [super hitTest:point withEvent:event];
}
return CGRectContainsPoint(rect, point) ? self : nil;
}*/
@end
原理
利用 objective-c 中的 objc_setAssociatedObject 來記錄要變大的範圍。
objc_setAssociatedObject 是 objective-c runtime library 裡面的 function。
需要#import <objc/runtime.h>
最后，最重要的是去 override - (UIView) hitTest:(CGPoint) point withEvent:(UIEvent) event
用新设定的 Rect 来当着点击范围。
使用
[enlargeButton setEnlargeEdge:20.0];
或者[enlargeButton setEnlargeEdgeWithTop:20 right:20 bottom:20 left:10];
