ios - 第一次点击后停止创建标签

Question

每次单击随机按钮并根据随机选择的情况设置文本时，我都会创建一个选取框标签。这是我的代码示例:

- (IBAction)randomWatch:(id)sender {
    MarqueeLabel *watchTitle = [[MarqueeLabel alloc] initWithFrame:CGRectMake(0, 77, self.view.frame.size.width-20, 44) rate:50.0f andFadeLength:10.0f];
    watchTitle.numberOfLines = 1;
    watchTitle.shadowOffset = CGSizeMake(0.0, -1.0);
    watchTitle.textAlignment = NSTextAlignmentRight;
    watchTitle.textColor = [UIColor colorWithRed:0.234 green:0.234 blue:0.234 alpha:1.000];
    watchTitle.backgroundColor = [UIColor clearColor];
    watchTitle.font = [UIFont fontWithName:@"Helvetica-Neue-Light" size:25.000];
    watchTitle.marqueeType = MLRightLeft;
    [self.view addSubview:watchTitle];
    watchTut1.hidden = YES;
    watchTut2.hidden = YES;
    watchTut3.hidden = YES;
    watchTut4.hidden = YES;
    int i = rand() % 25;
    switch (i) {
        case 0:
            watchTitle.text = @"";
            watchTitle.text = @" How To Catch a Pokemon";
            [[self watchPlaceholder]loadHTMLString:@"<iframe width=\"300\" height=\"225\" src=\"http://www.youtube.com/embed/NyGv8XtKJc4\" frameborder=\"0\" allowfullscreen></iframe>" baseURL:nil];
            break;
        case 1:
            watchTitle.text = @"";
            watchTitle.text = @" Full Turn ECAL/Benjamin Muzzin";
            [[self watchPlaceholder]loadHTMLString:@"<iframe width=\"300\" height=\"225\" src=\"http://player.vimeo.com/video/74735651\" frameborder=\"0\" allowfullscreen></iframe>" baseURL:nil];
            break;
        ........

我有 25 个案例(代码片段中没有全部显示)，每次我按下随机按钮时，代码都会再次执行，创建一个新的 Marquee 标签(这不太好)并更改新标签在这种情况下，文本和视频对应于所选的新案例(这是正常工作的)。我的问题是如何防止再次创建标签？如果我在 IBAction 的 -(void)viewDidLoad 中设置标签，则标签未定义，因此在提到 watchTitle 的任何地方我都会收到错误。我不知道如何处理，非常欢迎任何可以让我走上正轨的反馈和解释。

Answer 1

按照您的尝试将创建代码移动到您的 viewDidLoad(仅将选取框放在属性中并将其隐藏)。然后在按下按钮时，您只需显示它即可。

//Define the property somewhere in your interface
@property (nonatomic, strong) MarqueeLabel* watchTitle;
//...

- (void)viewDidLoad
{
    [super viewDidLoad];

    self.watchTitle = [[MarqueeLabel alloc] initWithFrame:CGRectMake(0, 77, self.view.frame.size.width-20, 44) rate:50.0f andFadeLength:10.0f];
    self.watchTitle.numberOfLines = 1;
    self.watchTitle.shadowOffset = CGSizeMake(0.0, -1.0);
    self.watchTitle.textAlignment = NSTextAlignmentRight;
    self.watchTitle.textColor = [UIColor colorWithRed:0.234 green:0.234 blue:0.234 alpha:1.000];
    self.watchTitle.backgroundColor = [UIColor clearColor];
    self.watchTitle.font = [UIFont fontWithName:@"Helvetica-Neue-Light" size:25.000];
    self.watchTitle.marqueeType = MLRightLeft;
    self.watchTitle.hidden = YES;
    [self.view addSubview:self.watchTitle];
}

- (IBAction)randomWatch:(id)sender {
    self.watchTitle.hidden = NO;

    watchTut1.hidden = YES;
    watchTut2.hidden = YES;
    watchTut3.hidden = YES;
    watchTut4.hidden = YES;
    int i = rand() % 25;
    switch (i) {
        case 0:
            self.watchTitle.text = @"";
            self.watchTitle.text = @" How To Catch a Pokemon";
            [[self watchPlaceholder]loadHTMLString:@"<iframe width=\"300\" height=\"225\" src=\"http://www.youtube.com/embed/NyGv8XtKJc4\" frameborder=\"0\" allowfullscreen></iframe>" baseURL:nil];
            break;
        case 1:
            self.watchTitle.text = @"";
            self.watchTitle.text = @" Full Turn ECAL/Benjamin Muzzin";
            [[self watchPlaceholder]loadHTMLString:@"<iframe width=\"300\" height=\"225\" src=\"http://player.vimeo.com/video/74735651\" frameborder=\"0\" allowfullscreen></iframe>" baseURL:nil];
            break;
        ........