当我有这行代码
UILongPressGestureRecognizer *downwardGesture = [[UILongPressGestureRecognizer alloc] initWithTarget:self action:@selector(dragGestureChanged:)];
还有这个
- (void)dragGestureChanged:(UILongPressGestureRecognizer*)gesture{
...
}
我想在“@selector(dragGestureChanged :)”中添加一个参数即“(UIScrollView *)scrollView”,我该怎么办？
解决方法
你不能直接–UIGestureRecognizers知道如何发出一个只接受一个参数的选择器的调用.要完全一般,你可能希望能够传递一个块.苹果公司还没有这样做,但它很容易添加,至少如果你愿意将手势识别器子类化,你想要解决添加新属性和正确清理的问题,而不深入研究运行时.
所以,例如(我去的时候写的,未经检查)
typedef void (^ recogniserBlock)(UIGestureRecognizer *recogniser);
@interface UILongPressGestureRecognizerWithBlock : UILongPressGestureRecognizer
@property (nonatomic,copy) recogniserBlock block;
- (id)initWithBlock:(recogniserBlock)block;
@end
@implementation UILongPressGestureRecognizerWithBlock
@synthesize block;
- (id)initWithBlock:(recogniserBlock)aBlock
{
self = [super initWithTarget:self action:@selector(dispatchBlock:)];
if(self)
{
self.block = aBlock;
}
return self;
}
- (void)dispatchBlock:(UIGestureRecognizer *)recogniser
{
block(recogniser);
}
- (void)dealloc
{
self.block = nil;
[super dealloc];
}
@end
然后你就可以这样做：
UILongPressGestureRecognizer = [[UILongPressGestureRecognizerWithBlock alloc]
initWithBlock:^(UIGestureRecognizer *recogniser)
{
[someObject relevantSelectorWithRecogniser:recogniser
scrollView:relevantScrollView];
}];
