如何使UIAlertView只出现一次，在iPhone应用程序的第一次启动？ [英] How do I make a UIAlertView appear only once, at the first start-up of an iPhone app?

问题描述

我使用 UIAlertView 在应用程式启动后发出弹出式视窗。它工作正常，但我只想让弹出窗口出现在应用程序的第一次启动。目前我已经在 AppDelegate 类中的 applicationDidFinishLaunching 中找到 UIAlertView code>方法。这是我的代码：

I'm using the UIAlertView to make a pop-up happen once the app has started up. It works fine but I only want the pop up to appear on the first start-up of the app. At the moment I've got the UIAlertView in the AppDelegate class, in applicationDidFinishLaunching method. Here is my code:

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {    
sleep(4);
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Welcome!" message:@"SAMPLE!!!" delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil];
[alert show];
[alert release];

我是新开发的应用程式开发，如果这很简单，很抱歉。

I'm new to app development so sorry if this is simple.

推荐答案

要确定应用程序是否是第一次运行，您需要有一个持久变量来存储此信息。 NSUser默认是这是存储这些简单配置值的最佳方式。

To determine whether the app is run the first time, you need to have a persistent variable to store this info. NSUserDefaults is the best way to store these simple configuration values.

例如，

-(BOOL)application:(UIApplication *)application … {
    NSUserDefaults* defaults = [NSUserDefaults standardUserDefaults];
    if (! [defaults boolForKey:@"notFirstRun"]) {
      // display alert...
      [defaults setBool:YES forKey:@"notFirstRun"];
    }
    // rest of initialization ...
}

这里， [defaults boolForKey：@notFirstRun] 从配置中读取一个名为 notFirstRun 的布尔值。这些值初始化为NO。所以如果这个值是NO，我们执行 if 分支并显示警报。

Here, [defaults boolForKey:@"notFirstRun"] reads a boolean value named notFirstRun from the config. These values are initialized to NO. So if this value is NO, we execute the if branch and display the alert.

使用 [defaults setBool：YES forKey：@notFirstRun] 将此布尔值更改为YES，因此 if 分支将永远不会再次执行（假设用户不删除应用程序）。

After it's done, we use [defaults setBool:YES forKey:@"notFirstRun"] to change this boolean value to YES, so the if branch will never be executed again (assume the user doesn't delete the app).

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