objective-c - iOS:简单的 NSMutableArray 调用

Question

我需要在我的一种方法中调用 removeObject，但我不知道如何正确执行此操作。我是 Objective-C 的新手，仍在学习基础知识。我有一个应用程序，其行为有点像照片库，并显示 UIImageViews。我正在实现让用户从他们的图库中删除照片的选项。为此，我决定在每张图片上放置一个不可见的按钮。当用户点击“编辑”按钮时，每张图片上的隐藏删除按钮将变为事件状态(为简单起见，我在每个隐藏按钮上使用相同的 IBOutlet)。当用户点击图片上的按钮时，会出现一个警告 View ，询问他们是否真的要删除它。如果他们点击是，deleteAlertView 开始发挥作用:

- (void)deleteAlertView:(UIAlertView *)deleteButtonPressed
       didDismissWithButtonIndex:(NSInteger)buttonIndex {
    if (buttonIndex != [deleteButtonPressed cancelButtonIndex]) {
        [array removeObject:@"%@", deleteButtonPressed];
    }

这里的问题是 [array removeObject:@"%@", deleteButtonPressed];，我做了 %@ 以便这将自动确定数组中的哪个对象被点击，而不是手动为每个 UIImageView 添加一个新的方法和按钮(我可能不得不这样做)。我收到有关“array”和“deleteButtonPressed”(使用未声明的标识符)的错误，我终究无法弄清楚应该放什么。我仍在学习基础知识以及这种语言的继承方式。任何帮助或建议都会很棒!我可能应该发布整个 View Controller 文件以显示相关的继承:

 - (IBAction)grabImage {
    self.imgPicker = [[UIImagePickerController alloc] init];
    self.imgPicker.delegate = self;
    self.imgPicker.sourceType = UIImagePickerControllerSourceTypePhotoLibrary;

    if ([[UIDevice currentDevice] userInterfaceIdiom] == UIUserInterfaceIdiomPad) {
        _popover = [[UIPopoverController alloc] initWithContentViewController:imgPicker];
        [_popover presentPopoverFromRect:self.imageView.bounds inView:self.imageView permittedArrowDirections:UIPopoverArrowDirectionAny animated:YES];
    } 

    else {
        [self presentModalViewController:imgPicker animated:YES];
    }
    [self.imgPicker resignFirstResponder];
}
// Sets the image in the UIImageView
- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingImage:(UIImage *)img editingInfo:(NSDictionary *)editInfo {
    if (imageView.image == nil) {
        imageView.image = img;
        [picker dismissModalViewControllerAnimated:YES];
        [self.popover dismissPopoverAnimated:YES];
        return;

    }

    if (imageView2.image == nil) {
        imageView2.image = img;
        [picker dismissModalViewControllerAnimated:YES];
        [self.popover dismissPopoverAnimated:YES];
        return;
    }
    if (imageView3.image == nil) {
        imageView3.image = img;
        [picker dismissModalViewControllerAnimated:YES];
        [self.popover dismissPopoverAnimated:YES];
        return;
    }
}

- (void)viewWillAppear:(BOOL)animated
{

    self.user = [NSUserDefaults standardUserDefaults];

    NSMutableArray* array = [[self.user objectForKey:@"images"]mutableCopy];
    while(array == nil)
    {
        [self.user setObject:[NSMutableArray arrayWithObject:@""] forKey:@"images"];
        array = [[self.user objectForKey:@"images"]mutableCopy];
        NSLog(@"%@",@"attempting to create an array to store the images in");
    }

}

- (void)applicationDidEnterBackground:(UIApplication*)application {
    NSLog(@"Image on didenterbackground: %@", imageView);
    NSMutableArray* array = [NSMutableArray arrayWithObject:[NSData dataWithData:UIImagePNGRepresentation(imageView.image)]];

    [array addObject:[NSData dataWithData:UIImagePNGRepresentation(imageView2.image)]];
     [array addObject:[NSData dataWithData:UIImagePNGRepresentation(imageView3.image)]];

            [self.user setObject:array forKey:@"images"];
    [user synchronize];

            }

- (void)viewDidLoad
    {
        self.user = [NSUserDefaults standardUserDefaults];
        NSLog(@"It is %@", self.user);
        NSMutableArray* array = [[self.user objectForKey:@"images"]mutableCopy];
        imageView.image = [[UIImage alloc] initWithData:[array objectAtIndex:0]];
        imageView2.image = [[UIImage alloc] initWithData:[array objectAtIndex:1]];
        imageView3.image = [[UIImage alloc] initWithData:[array objectAtIndex:2]];


        UIApplication *app = [UIApplication sharedApplication];
        [[NSNotificationCenter defaultCenter] addObserver:self
                                                 selector:@selector(applicationDidEnterBackground:)
                                                     name:UIApplicationDidEnterBackgroundNotification
                                                   object:app];

        backToGalleryButton.hidden = YES;
        tapToDeleteLabel.hidden = YES;
        deleteButton1.hidden = YES;
        [super viewDidLoad];

    }

     - (IBAction)deleteButtonPressed:(id)sender {
    UIAlertView *deleteAlertView = [[UIAlertView alloc] initWithTitle:@"Delete"
                                                              message:@"Are you sure you want to delete this photo?"
                                                             delegate:self
                                                    cancelButtonTitle:@"Yes"
                                                    otherButtonTitles:@"No", nil];
    [deleteAlertView show];

}

- (void)deleteAlertView:(UIAlertView *)deleteButtonPressed
       didDismissWithButtonIndex:(NSInteger)buttonIndex {
    if (buttonIndex != [deleteButtonPressed cancelButtonIndex]) {
        [array removeObject:@"%@", deleteButtonPressed];
    }       

}

Answer 1

这里有一个问题，但首先是一个相对次要的问题:

 - (void)deleteAlertView:(UIAlertView *)deleteButtonPressed didDismissWithButtonIndex:(NSInteger)buttonIndex

短语“deleteButtonPressed”暗示偶数，因为它以动词结尾。它实际上指的是一个对象，具体指的是一个UIAlertView类型的参数。您应该将其命名为更像是 AlertView 的名称。

其次，这一行是完全错误的:

[array removeObject:@"%@", deleteButtonPressed];

您正试图删除一个字符串。如果该方法接受一个参数列表(您在其中传递以逗号分隔的多个对象)，您将删除字面上的“deleteButtonPressed”。您想要删除 deleteButtonPressed 变量指向的对象。所以你所要做的就是:

 [array removeObject:deleteButtonPressed];