Question

我在UICollectionView中为UIScrollView设置了一个UITapGestureRecognizer。我已将其配置为正确检测点击并触发我编写的方法，但如果我尝试将选择器设置为collectionView：didSelectItemAtIndexPath：程序在点击单元格时崩溃。

知道为什么会这样吗？

这有效：

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带有一个输入参数的singleFunction，它是UITapGestureRecogniser object。

应该是这样的，

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

}

但你使用它的选择器不合适，因为它需要两个输入，不能提供gestureRecogniser.Hence崩溃。

将上述代码更改为低于1，

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以下签名之一：

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

您需要使用其中一个操作签名，并在该方法中执行您需要的任何操作，包括为手势确定正确的indexPath。

查看文档： https://developer.apple.com/library/ios/documentation/uikit/reference/UIGestureRecognizer_Class/Reference/Reference.html#//apple_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];

}

iOS为什么不能从UITapGestureRecognizer调用方法collectionView：didSelectItemAtIndexPath？

3 个答案: