iPhone 突然发现,setting配置文件中的DefaultValue可能拿不了值

最新推荐文章于 2022-03-23 19:35:12 发布

原创最新推荐文章于 2022-03-23 19:35:12 发布 · 158 阅读

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本文探讨了在用户未设置偏好值时如何正确加载默认值的问题。通过分析AppPrefs代码实现，展示了当用户没有设置任何值时如何从Settings.bundle中读取默认配置并将其注册到应用的默认设置中。

按照我的想法,如果用户没有在setting设置值且有default-value,那么应该获取的是default-value,因为打开setting也能看见这些值.但是今天突然发现好像不是那么会事.获取的是null.看了AppPrefs的代码,它也进行了判断.如下:

- (void)applicationDidFinishLaunching:(UIApplication *)application
{
	[window addSubview:[navigationController view]];
	
	NSString *testValue = [[NSUserDefaults standardUserDefaults] stringForKey:kFirstNameKey];
	if (testValue == nil)
	{
		// no default values have been set, create them here based on what's in our Settings bundle info
		//
		NSString *pathStr = [[NSBundle mainBundle] bundlePath];
		NSString *settingsBundlePath = [pathStr stringByAppendingPathComponent:@"Settings.bundle"];
		NSString *finalPath = [settingsBundlePath stringByAppendingPathComponent:@"Root.plist"];

		NSDictionary *settingsDict = [NSDictionary dictionaryWithContentsOfFile:finalPath];
		NSArray *prefSpecifierArray = [settingsDict objectForKey:@"PreferenceSpecifiers"];

		NSString *firstNameDefault;
		NSString *lastNameDefault;
		NSNumber *nameColorDefault;
		NSNumber *backgroundColorDefault;
		
		NSDictionary *prefItem;
		for (prefItem in prefSpecifierArray)
		{
			NSString *keyValueStr = [prefItem objectForKey:@"Key"];
			id defaultValue = [prefItem objectForKey:@"DefaultValue"];
			
			if ([keyValueStr isEqualToString:kFirstNameKey])
			{
				firstNameDefault = defaultValue;
			}
			else if ([keyValueStr isEqualToString:kLastNameKey])
			{
				lastNameDefault = defaultValue;
			}
			else if ([keyValueStr isEqualToString:kNameColorKey])
			{
				nameColorDefault = defaultValue;
			}
			else if ([keyValueStr isEqualToString:kBackgroundColorKey])
			{
				backgroundColorDefault = defaultValue;
			}
		}

		// since no default values have been set (i.e. no preferences file created), create it here		
		NSDictionary *appDefaults = [NSDictionary dictionaryWithObjectsAndKeys:
										firstNameDefault, kFirstNameKey,
										lastNameDefault, kLastNameKey,
										nameColorDefault, kNameColorKey,
										backgroundColorDefault, kBackgroundColorKey,
									  nil];
		[[NSUserDefaults standardUserDefaults] registerDefaults:appDefaults];
		[[NSUserDefaults standardUserDefaults] synchronize];
	}
	
	// we're ready to do, so lastly set the key preference values
	firstName = [[NSUserDefaults standardUserDefaults] stringForKey:kFirstNameKey];
	lastName = [[NSUserDefaults standardUserDefaults] stringForKey:kLastNameKey];
	textColor = [[NSUserDefaults standardUserDefaults] integerForKey:kNameColorKey];
	backgroundColor = [[NSUserDefaults standardUserDefaults] integerForKey:kBackgroundColorKey];
}