ios - 如何通过 UIPopoverController 更改 UILabel

Question

我有一个简单的代码，其中有两个类: View Controller (这是主要的 rootViewController)和 ProductsViewController (谁是通过 PopoverController 打开的 Controller)。

正在发生的事情如下，在 内 View Controller 类我有一个负责更新 UILabel 的 setter 命令:

IBOutlet UILabel *myLabel;
@property(nonatomic,retain)  NSString *saver;

- (void)viewDidLoad{
    [super viewDidLoad];
    myLabel.text = saver;
}
-(void)setLabel:(NSString*)value{
    saver = value;
    myLabel.text = value;
}

在 ProductsViewController 我的类有负责激活 setter 方法的代码:

ViewController *detailViewController = [[ViewController alloc] init];
[detailViewController setLabel:@"Changes?"];
[detailViewController release];

我相信问题在于弹出窗口打开的时间，因为我相信 UILabel 不知何故处于非事件状态，因为如果我们把 NSLog(@"Exists -> %@",myLabel);在 setter 方法中，我们得到 (空)

有人可以帮我解决这个问题，以及如何解决这个问题？

谢谢。

编辑

我试图以这种方式使用协议(protocol):

ViewController.h

#import <UIKit/UIKit.h>
#import "ProductsViewController.h"

@interface ViewController : UIViewController <ProductsViewControllerDelegate>{

    IBOutlet UILabel *myLabel;
}

-(IBAction)showPopOver:(id)sender;
- (void)productWasSelected:(NSString *)product;
@end

ViewController.m

- (void)presentProductsViewController:(ProductsViewController *)productsViewController {
    productsViewController.delegate = self;
    //present in popover here...
}

- (void)productWasSelected:(NSString *)product{
    myLabel.text = product;
}

ProductsViewController.h

#import <UIKit/UIKit.h>

@protocol ProductsViewControllerDelegate <NSObject>
- (void)productWasSelected:(NSString *)product;
@end

@interface ProductsViewController : UIViewController
@property (nonatomic, retain) id<ProductsViewControllerDelegate> delegate;
@end

ProductsViewController.m

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
    [self.delegate productWasSelected:@"Selected Product"];
    NSLog(@"Called!");
}

我的 ShowPopover 方法如下:

-(IBAction)showPopOver:(id)sender{

    UIButton *btn =sender;
    ProductsViewController *productsView =[[ProductsViewController alloc] initWithNibName:@"ProductsViewController" bundle:nil];
    popOver =[[UIPopoverController alloc] initWithContentViewController:productsView];
    [popOver presentPopoverFromRect:btn.frame inView:self.view permittedArrowDirections:UIPopoverArrowDirectionDown animated:YES];

    [productsView release];

}

Answer 1

共享同一个类的两个对象不会使它们成为同一个对象。您可能想在这里使用委托(delegate)。网上有很多教程。这是一个例子......

@protocol ProductsViewControllerDelegate <NSObject>
- (void)productWasSelected:(NSString *)product;
@end

@interface ProductsViewController : UIViewController
@property (nonatomic, weak) id<ProductsViewControllerDelegate> delegate;
@end


@implementation ProductsViewController

- (void)didSelectProduct {
    [self.delegate productWasSelected:@"Selected Product"];
}

@end

@interface MainViewController : UIViewController <ProductsViewControllerDelegate>
@end


@implementation MainViewController

- (IBAction)showPopOver:(id)sender{
    UIButton *btn =sender;
    ProductsViewController *productsView =[[ProductsViewController alloc] initWithNibName:@"ProductsViewController" bundle:nil];
    productsView.delegate = self;
    popOver =[[UIPopoverController alloc] initWithContentViewController:productsView];
    [popOver presentPopoverFromRect:btn.frame inView:self.view permittedArrowDirections:UIPopoverArrowDirectionDown animated:YES];
}

- (void)productWasSelected:(NSString *)product {
    self.myLabel.text = product;
}

@end