设置一个随机应用程序背景图像iOS 6

Question

我想为我的应用程序设置一个随机背景图像，这样每次有人启动应用程序时都会显示一个新的背景图像。

Here's什么香港专业教育学院试图在- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions 方法至今：

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions 
{ 
    NSMutableArray *myImageNames = [NSMutableArray arrayWithObjects:@"image1.png", @"image2.png", @"image3.png", nil]; 
    int index = arc4random() % [myImageNames count]; 
    UIColor *background = [[UIColor alloc] initWithPatternImage:[myImageNames objectAtIndex:index]]; 
    self.window.backgroundColor = background; 
} 

我没有得到任何错误，但我doesn't工作... 任何想法？ :)

Answer 1

试试这个：

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions 
{ 
    NSMutableArray *myImageNames = [NSMutableArray arrayWithObjects:@"image1.png", @"image2.png", @"image3.png", nil]; 
    int index = arc4random() % [myImageNames count]; 
    UIColor *background = [[UIColor alloc] initWithPatternImage:[UIImage imageNamed:[myImageNames objectAtIndex:index]]]; 
    self.window.backgroundColor = background; 
    [background release]; 
} 

Answer 2

，而不是委托类把这个代码在主viewcontrller的initWithNibName方法：

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil 
{ 
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil]; 
    if (self) { 

     NSMutableArray *myImageNames = [NSMutableArray arrayWithObjects:@"image1.png", @"image2.png", @"image3.png",@"image4.png", @"image5.png",@"image6.png", nil]; 
     int index = arc4random() % [myImageNames count]; 

     self.view.backgroundColor = [UIColor colorWithPatternImage:[UIImage imageNamed:[myImageNames objectAtIndex:index]]]; 
    } 
    return self; 
} 

Answer 3

我认为你缺少的东西在你的代码，而你是从图像设置背景颜色

请参阅[myImageNames objectAtIndex:index]，此代码将返回正好的字符串对象。

因为您只是将string传递给需要image的方法。

所以，你应该有一段代码更改为此

[UIImage imageNamed:[myImageNames objectAtIndex:index]。

现在你的代码看起来像这样

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions 
{ 
    NSMutableArray *myImageNames = [NSMutableArray arrayWithObjects:@"image1.png", @"image2.png", @"image3.png", nil]; 
    int index = arc4random() % [myImageNames count]; 
    UIColor *background = [[UIColor alloc] initWithPatternImage:[UIImage imageNamed: [myImageNames objectAtIndex:index]]]; 
    self.window.backgroundColor = background; 
    [background release]; 
} 

Answer 4

有你需要考虑两件事情。首先，您需要通过UIImage，而不是NSString，至initWithPatternImage。该代码应该是：

NSMutableArray *myImageNames = [NSMutableArray arrayWithObjects:@"image1.png", @"image2.png", @"image3.png", nil]; 
    int index = arc4random() % [myImageNames count]; 
    UIColor *background = [[UIColor alloc] initWithPatternImage:[UIImage imageNamed: [myImageNames objectAtIndex:index]]]; 
    self.window.backgroundColor = background; 
    [background release]; 

的另一件事是，当iOS的实例主要故事板，它做了几件事情你。其中一件事是分配并初始化self.window属性，但它也会实例化包含在故事板中的主视图控制器，并将其分配给UIWindow的rootViewController属性。这意味着如果你的主视图控制器创建了一个UIView（几乎每个视图控制器都会这样做），它的背景将视觉覆盖背景，除非它被设置为透明。由于设置透明UIView可能不是你想要的，并且它的方式很尴尬，我建议在@Dilip答案后面设置背景到你的根视图控制器的视图。

Answer 5

我得到了我的工作，谢谢大家回复，谢谢大家！

的代码应该是：

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions 
{ 
    NSMutableArray *myImageNames = [NSMutableArray arrayWithObjects:@"image1.jpg", @"image2.jpg", @"image3.png", nil]; 
    int index = arc4random() % [myImageNames count]; 
    UIColor *background = [[UIColor alloc] initWithPatternImage:[UIImage imageNamed:[myImageNames objectAtIndex:index]]]; 
    self.window.backgroundColor = background; 
    // Override point for customization after application launch. 
    return YES; 
}