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];
- }];
