iOS为什么不能从UITapGestureRecognizer中调用方式UITapGestureRecognizer:didSelectItemAtIndexPath: be？

Question

我在UITapGestureRecognizer中为UIScrollView设置了一个UICollectionView。我已经将它配置为正确地检测点击并触发我编写的方法，但是如果我试图将选择器设置为collectionView:didSelectItemAtIndexPath:程序在单元格被点击时崩溃。

知道为什么会这样吗？

这工作：

UITapGestureRecognizer *singleTap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(tapped:)];

- (void) tapped:(UIGestureRecognizer *)gesture{
//some code
}

--这不起作用：

UITapGestureRecognizer *singleTap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(collectionView:didSelectItemAtIndexPath:)];

- (void) collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath
{
//some code
}

Answer 1

你写的代码，

UITapGestureRecognizer *singleTap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(collectionView:didSelectItemAtIndexPath:)];

选择器通常只是一个singleFunction，其中有一个输入参数，即UITapGestureRecogniser对象。

应该是这样，

-(void)clicked:(UIGestureRecogniser *)ges{

}

但是您使用的选择器不正确，因为它需要两个不能与gestureRecogniser.Hence一起提供的输入--崩溃。

将上述代码更改为1以下，

UITapGestureRecognizer *singleTap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(clicked:)];
-(void)clicked:(UIgestureRecogniser *)ges{
    //use gesture to get get the indexPath, using CGPoint (locationInView). 
    NSIndexPath *indexPath = ...;
    [self collectionView:self.collectionView didSelectItemAtIndexPath:indexPath];

}

Answer 2

手势识别器的操作必须符合下列签名之一：

- (void)handleGesture;
- (void)handleGesture:(UIGestureRecognizer *)gestureRecognizer;

您需要使用这些动作签名之一，并在该方法中执行所需的任何操作，包括为手势确定正确的indexPath。

见docs：ref/occ/instm/UIGestureRecognizer/initWithTarget:action

Answer 3

我们必须从正确的引用对象调用didSelectItemAtIndexPath。

UITapGestureRecognizer *singleTap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(tapped:)];

- (void) tapped:(UIGestureRecognizer *)gesture{

      NSIndexPath *indexPath =    //create your custom index path here

      [self.collectionViewObject didSelectItemAtIndexPath:indexPath];

}