Question

好的，当用户第一次启动我的应用程序时，我想要一个警报视图，它会弹出2个选项。我正在使用以下方法：

- (void) displayWelcomeScreen
{
    NSUserDefaults *prefs = [NSUserDefaults standardUserDefaults];
    NSString *alreadyRun = @"already-run";
    if ([prefs boolForKey:alreadyRun])
        return;
    [prefs setBool:YES forKey:alreadyRun];
    UIAlertView *alert = [[UIAlertView alloc]
        initWithTitle:@"…"
        message:@"…"
        delegate:nil cancelButtonTitle:nil otherButtonTitles:@"OK", nil];
    [alert show];
    [alert release];
}

首次启动应用时，不会弹出警报视图。难道我做错了什么？顺便说一句，我希望它只在应用程序的首次启动时显示。它不能显示任何其他时间。提前致谢。

Answer 1

试试这个：

(void)viewDidLoad{

NSLog(@"In viewDidLoad");
[self displayWelcomeScreen];

}

在displayWelcomeScreen中编写代码：

- (void) displayWelcomeScreen
{
    NSLog(@"In displayWelcomeScreen");
    NSUserDefaults *prefs = [NSUserDefaults standardUserDefaults];
    NSString *alreadyRun = @"already-run";
    if ([prefs boolForKey:alreadyRun])
        return;
    [prefs setBool:YES forKey:alreadyRun];
    UIAlertView *alert = [[UIAlertView alloc]
        initWithTitle:@"…"
        message:@"…"
        delegate:nil cancelButtonTitle:nil otherButtonTitles:@"OK", nil];
    [alert show];
    [alert release];
}

并检查控制台是否显示在displayWelcomeScreen。

Answer 2

尝试使用这些。我刚刚对你的代码进行了一些修改。

- (void) displayWelcomeScreen
{
    NSUserDefaults *prefs = [NSUserDefaults standardUserDefaults];

    if ([prefs objectForKey:@"alreadyRun"])
    {
        return;
    }
    else
    {
        [prefs setObject:@"YES" forKey:@"alreadyRun"];
        [prefs synchronize];
        UIAlertView *alert = [[UIAlertView alloc]
        initWithTitle:@"…"
        message:@"…"
        delegate:nil cancelButtonTitle:nil otherButtonTitles:@"OK", nil];
        [alert show];
        [alert release];
    }
}

Answer 3

在appDelegate didFinishLaunchingWithOptions中，添加这样的内容

NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
if (![defaults boolForKey:@"everLaunched"]) {
    [defaults setBool:YES forKey:@"everLaunched"];
    [defaults setBool:YES forKey:@"firstLaunch"];
}
else{
    [defaults setBool:NO forKey:@"firstLaunch"];
}

检查是否需要显示欢迎信息：

 - (void) displayWelcomeScreen
 {
  if ([[NSUserDefaults standardUserDefaults] boolForKey:@"firstLaunch"]) 
         {
          NSLog(@"I should display alert view now with two selections");
          //what to you want to to here now? show alert view? with two choices?
          //you might want to remember the selected choice from user
         }
   else  {
         NSLog(@"the user already made his choice, this is not a first launch");
         //what do you want to do here now? show home screen? let the user use the app? 
         //the user has already made his choice
         }
}

我需要有关动作的自动警报视图的帮助

3 个答案: