ios - 在 UICollectionView 中复制标注

Question

我在每个单元格中都有一个带有 UIImageView 的 UICollectionView，现在我想添加 Copy Callout，就像在 Photos.app 中一样:

我在 UICollectionViewDelegate 中看到了这个方法:

- (BOOL)collectionView:(UICollectionView *)collectionView shouldShowMenuForItemAtIndexPath:(NSIndexPath *)indexPath {
    return YES;
}

经过额外几分钟的研究，我发现了 UIMenuController 类，据我所知，我必须使用它来获取菜单，但无论如何，我认为必须有比创建 UIGestureRecognizer、创建、定位更简单的方法等我的 UIMenu。

我走在正确的轨道上吗？您如何实现此功能？

Answer 1

是的，您走在正确的轨道上。您还可以使用此技术实现剪切、复制和粘贴之外的自定义操作。

Custom actions for the UICollectionView

// ViewController.h
@interface ViewController : UICollectionViewController

// ViewController.m
-(void)viewDidLoad
{
    [super viewDidLoad];
    self.collectionView.delegate = self;

    UIMenuItem *menuItem = [[UIMenuItem alloc] initWithTitle:@"Custom Action"
                                                      action:@selector(customAction:)];
    [[UIMenuController sharedMenuController] setMenuItems:[NSArray arrayWithObject:menuItem]];

}

#pragma mark - UICollectionViewDelegate methods
- (BOOL)collectionView:(UICollectionView *)collectionView
      canPerformAction:(SEL)action
    forItemAtIndexPath:(NSIndexPath *)indexPath
            withSender:(id)sender {
    return YES;  // YES for the Cut, copy, paste actions
}

- (BOOL)collectionView:(UICollectionView *)collectionView
shouldShowMenuForItemAtIndexPath:(NSIndexPath *)indexPath {
    return YES;
}

- (void)collectionView:(UICollectionView *)collectionView
         performAction:(SEL)action
    forItemAtIndexPath:(NSIndexPath *)indexPath
            withSender:(id)sender {
    NSLog(@"performAction");
}

#pragma mark - UIMenuController required methods
- (BOOL)canBecomeFirstResponder {
    // NOTE: The menu item will on iOS 6.0 without YES (May be optional on iOS 7.0)
    return YES;
}

- (BOOL)canPerformAction:(SEL)action withSender:(id)sender {
    NSLog(@"canPerformAction");
     // The selector(s) should match your UIMenuItem selector
    if (action == @selector(customAction:)) {
        return YES;
    }
    return NO;
}

#pragma mark - Custom Action(s)
- (void)customAction:(id)sender {
    NSLog(@"custom action! %@", sender);
}

注意:iOS 7.0 改变了行为

1. 在您的 UICollectionViewCell 子类中，您需要添加自定义操作方法，否则什么也不会出现。

   // Cell.m
   #import "Cell.h"
   
   @implementation Cell
   
   - (id)initWithFrame:(CGRect)frame {
       self = [super initWithFrame:frame];
       if (self) {
           // custom logic
       }
       return self;
   }
   
   - (void)customAction:(id)sender {
       NSLog(@"Hello");
   
       if([self.delegate respondsToSelector:@selector(customAction:forCell:)]) {
           [self.delegate customAction:sender forCell:self];
       }
   }
   @end
   

2. 您需要创建一个委托(delegate)协议(protocol)并将其设置在每个单元格上以回调维护您的 UICollectionView 的 UIController。这是因为单元格不应该与您的模型有关，因为它只涉及显示内容。

   // Cell.h
   #import <UIKit/UIKit.h>
   
   @class Cell; // Forward declare Custom Cell for the property
   
   @protocol MyMenuDelegate <NSObject>
   @optional
   - (void)customAction:(id)sender forCell:(Cell *)cell;
   @end
   
   @interface Cell : UICollectionViewCell
   
   @property (strong, nonatomic) UILabel* label;
   @property (weak, nonatomic) id<MyMenuDelegate> delegate;
   @end
   

3. 在您的 ViewController 或 UICollectionViewController 的子类中，您需要遵守协议(protocol)并实现新方法。

   // ViewController.m
   @interface ViewController () <MyMenuDelegate>
   @end
   
   // @implementation ViewController  ...
   
   - (UICollectionViewCell *)collectionView:(UICollectionView *)cv cellForItemAtIndexPath:(NSIndexPath *)indexPath;
   {
       Cell *cell = [cv dequeueReusableCellWithReuseIdentifier:@"MY_CELL" forIndexPath:indexPath];
       cell.delegate = self;
       return cell;
   }
   // ...
   
   // Delegate method for iOS 7.0 to get action from UICollectionViewCell
   - (void)customAction:(id)sender forCell:(Cell *)cell {
       NSLog(@"custom action! %@", sender);
   }
   

   

4. 可选:在您的 UIView 子类中，如果您在此处而不是在 UIViewController 中实现 canPerformAction 方法，则可以覆盖默认的剪切、复制和粘贴。否则，该行为将在您的自定义方法之前显示默认方法。

   // Cell.m
   - (BOOL)canPerformAction:(SEL)action withSender:(id)sender {
       NSLog(@"canPerformAction");
       // The selector(s) should match your UIMenuItem selector
   
       NSLog(@"Sender: %@", sender);
       if (action == @selector(customAction:)) {
           return YES;
       }
       return NO;
   }