使用 AppDelegate 来回传递数据 [英] Passing data back and forth using AppDelegate

问题描述

首先，我正在构建一个应用程序来学习 Objective-C 的基础知识.如果有任何不清楚的地方，请告诉我，我会编辑我的问题.

To start I am building an app to learn the basics of Objective-C. If there is anything unclear please let me know and I will edit my question.

该应用程序应该具有下一个功能.执行应用程序时打开相机预览.在顶部有一个按钮可以转到 TemplateController，用户可以在其中选择要从 UICollectionView 中选择的帧数组.用户选择模板并返回到相机预览.用户拍摄一张照片，并在 PreviewController 中显示所选框架的照片.如果用户不喜欢该框架并希望将其切换为另一个框架.PreviewController 顶部有一个按钮，可以转到 TemplateController，选择框架并再次返回到带有新框架的 PreviewController.

The app is supposed to have the next functionality. Open the camera preview when the app is executed. On the top there is a button to go to a TemplateController where the user can select an array of frames to select from a UICollectionView. User selects the Template and returns to the Camera Preview. User takes a picture and the picture with the frame selected is shown in the PreviewController. If the user doesn't like the frame and wants to switch it for another one. PreviewController has button on top to go to the TemplateController, select the frame and go back again to the PreviewController with the new frame.

我不想每次都为框架创建一个对象.我希望 AppDelegate 保存该对象.保持活力?(对不起，英语不是我的母语).

I do not want to create an object for the frame everytime. I want the AppDelegate to hold that object. To keep it alive per say?(sorry, English is not my mother tongue).

我想使用 NSUserDefaults 但我真的很想使用 AppDelegate.所以此时 NSUserDefaults 不是一个选项.

I was thinking to use NSUserDefaults BUT I really want to do it using the AppDelegate. So at this point NSUserDefaults is not an option.

现在，我使用带有导航控制器的故事板.屏幕截图可在此处获得现在，当我从 TemplateController 传递到 PreviewController 时，我的代码如下所示:

Now, I am using storyboards with a navigation controller. A screenshot is available here Right now when I pass from the TemplateController to my PreviewController my code looks like this:

从 MainController 或 PreviewController 到达 TemplateController

Reaching TemplateController from MainController or PreviewController

- (IBAction)showFrameSelector:(id)sender 
{
    UIStoryboard *storyboard;
    storyboard = [UIStoryboard storyboardWithName:@"MainStoryboard_iPhone" bundle:nil];
    TemplateController *templateController = [storyboard instantiateViewControllerWithIdentifier:@"TemplateController"];
    templateController.frameDelegate = self;
    [self presentViewController:templateController animated:YES completion:nil];
}

将数据从 TemplateController 传递到其控制器的命运(MainController 或 PreviewController)

Passing the data from TemplateController to its controller's destiny (Either MainController or PreviewController)

- (void)collectionView:(UICollectionView *)collectionView didSelectItemAtIndexPath:(NSIndexPath *)indexPath
{
    _selectedLabelStr = [self.frameImages[indexPath.section] objectAtIndex:indexPath.row];
    [self.collectionView deselectItemAtIndexPath:indexPath animated:NO];

    [self dismissViewControllerAnimated:YES completion:^{
    if ([self.frameDelegate respondsToSelector:@selector(templateControllerLoadFrame:)]) 
    {
            [self.frameDelegate performSelector:@selector(templateControllerLoadFrame:) withObject:self];
    }
    }];
}

这会在 PreviewController 中加载选定的帧

This loads the selected frame in PreviewController

- (void)templateControllerLoadFrame:(TemplateController *)sender
{
    UIImage *tmp = [UIImage imageNamed:sender.selectedLabelStr];
    _frameImageView.image = tmp;      
}

我的问题是，我不太清楚我必须对 AppDelegate 进行哪些更改(它现在未受影响).实现这一目标的最佳方法是什么?主要问题是在拍摄静止图像之前选择了模板.如果我在拍照后选择框架，则会显示.

My problem is, I don't have very clear what changes I have to do on the AppDelegate(it is untouched right now). What would be the best approach to accomplish this? Main issue is when Tamplate is chosen before taking the still image. If I select the frame after taking the picture then it displays.

推荐答案

我不确定我是否理解您的问题.将对象填充到应用程序委托解决方案中可能不是最好的前进方式.事实上，我相信您应该看看 Apple 用于在视图控制器之间进行通信的委托模式.请注意，您似乎已经完成了一半的委托模式.例如，您将 PreviewController 设为 TemplateController 的 frameDelegate.

I am not certain that I understand your question. Stuffing an object into the app delegate solution may not be the best way forward. In fact I believe you ought to look at the delegation pattern that is used by Apple to communicate between view controllers. Please note that you appear to be doing half of the delegate pattern already. For example you make your PreviewController a frameDelegate of the TemplateController.

因此，我认为您应该使用以下内容将信息从 TemplateController 传输回 PreviewController.请注意，我已经包含了准备转场，因为这是向前推动数据对象的常见模式(如果您将转场从 PreviewController 连接到 TemplateController 并在您的操作方法中调用 performSegueWithIdentifier:@"SegueTitle"，它将被调用).使用templateControllerDidFinish"委托方法是一种常用模式，用于在 TemplateController 关闭时将信息从 TemplateController 推回.

So I would think you'd have something like the following to transfer information from TemplateController back to the PreviewController. Note that I've included prepare for segue as that is a common pattern to push a data object forward (it will be called if you connect a segue from the PreviewController to the TemplateController and in your action method call performSegueWithIdentifier:@"SegueTitle"). Use of the "templateControllerDidFinish" delegation method is a common pattern used to push information back from TemplateController when it closes.

TemplateController.h

@class TemplateController;
@protocol TemplateControllerDelegate <NSObject>
-(void) templateControllerDidFinish :(TemplateController*)controller;
@end

@interface TemplateController : UIViewController 
@property (nonatomic, weak) id <TemplateControllerDelegate>delegate;
...
@end

TemplateController.m
 //! The internals for this method can also be called from wherever in your code you need to dismiss the TemplateController by copying the internal 
-(IBAction)doneButtonAction:(id)sender
{

    __weak TemplateController*weakSelf = self;
    [self dismissViewControllerAnimated:YES completion:^{
        [self.delegate templateControllerDidFinish:weakSelf];
    }];
}

PreviewController.h

#import "TemplateController.h"

@interface PreviewController<TemplateControllerDelegate>
...
@end

PreviewController.m

@implementation
...
-(void) templateControllerDidFinish :(TemplateController*)controller
{
    self.dataProperty = controller.someImportantData;
    ...
}

...

-(void)prepareForSegue:(UIStoryboardSegue*)segue sender:(id)sender
{
    if ( [[segue identifier]isEqualToString:@""] ) 
    {
         TemplateController *tc = [segue destinationViewController];
         tc.delegate = self;
         tc.data = [someDataObjectFromPreviewController];
    }
}

进一步解决这种情况:

1. 从 PreviewController 添加一个 segue 到 TemplateController(按住 Ctrl 键从预览视图控制器拖动到模板控制器在文档大纲模式下)
2. 在身份检查器中命名 segue 标识符

3. 更改显示视图控制器的代码:

1. Add a segue from the PreviewController to the TemplateController (Ctrl-drag from Preview view controller to the Template Controller in the document outline mode)
2. Name the segue identifier in the identity inspector

3. Change your code that presents the view controller from:

• (IBAction)showFrameSelector:(id)sender{UIStoryboard *故事板；storyboard = [UIStoryboard storyboardWithName:@"MainStoryboard_iPhone" bundle:nil];TemplateController *templateController = [storyboard instantiateViewControllerWithIdentifier:@"TemplateController"];templateController.frameDelegate = self;[self presentViewController:templateController 动画:YES 完成:nil];}

到

- (IBAction)showFrameSelector:(id)sender 
{
    [self performSegueWithIdentifier:@"SegueTitle"];
}

如 prepareForSegue 中所述，将您的数据对象添加到目标视图控制器，您将处于良好状态.然后使用委托方法来捕获从您的模板返回的任何数据(只需将数据作为属性添加到控制器中，您就应该是金子了)

Add your data object to the target view controller as noted in prepareForSegue and you will be in good shape. Then use the delegate method to catch any data returned from your template (just add the data as properties to the controller and you should be golden)

您可以在 Xcode 的实用程序项目模板中看到这种委托的更好示例(我刚刚将其键入...)我希望这些信息对您有所帮助.您可以在这些资源中获取更多信息，也可以通过在 Google 和 SO 中搜索 iOS 委托来获取更多信息:

You can see a better example of this delegation in a utility project template from Xcode (I just keyed this in..) I hope this information helps. You can get more information at these resources and also by searching Google and SO for iOS delegation :

Objective C 中的概念(委托和数据源)

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