UIView不透明度梯度

Question

是否有可能具有纹理背景图像和不透明度梯度的UIIView？即，bg图像应该从背景容器视图的左边向右淡入。

感谢

Answer 1

alpha通道（即PNG）保存您的背景图像和做任何图形应用程式使用褪色。

然后，把它作为你的UIView的第一个孩子是一个UIImageView

Answer 2

- (void)viewDidLoad { 
    [super viewDidLoad]; 
    image1=[[UIImageView alloc]initWithImage:[UIImage imageNamed:@"Default.png"]]; 
    image1.frame=CGRectMake(0, 0, 320, 460); 
    image2=[[UIImageView alloc]initWithImage:[UIImage imageNamed:@"directoryPage.png"]]; 
    image2.frame=CGRectMake(0, 0, 320, 480); 
    [self.navigationController setNavigationBarHidden:YES]; 
} 

- (void)fade 
{ 
    image2.alpha = 0; 
    [self.view addSubview:image2]; 
    // The upper layer will transition from alpha 1 to 0s 
    [self.view addSubview:image1]; 
    BSheepAppDelegate *appD=(BSheepAppDelegate *)[[UIApplication sharedApplication]delegate]; 
    if(appD.flag==0){ 
     timer = [NSTimer scheduledTimerWithTimeInterval:.01 target:self selector:@selector(fadeTimerEvent) userInfo:nil repeats:YES]; 
     appD.flag=1; 
    } 
    else if (appD.flag==1) { 
    [self.view addSubview:image2]; 
    image2.alpha=1; 
    } 
} 

// Rate of transition for alpha values 
#define FADE_IN_RATE  1.0/100.0 
#define FADE_OUT_RATE 2.0/200.0 
- (void)fadeTimerEvent 
{ 
    if (image2.alpha >= 1) 
    { 
     // At this point, image2 is now visible 
     [timer invalidate]; 
     timer = nil; 

    } 
    else 
    { 
     // Fade lower layer in (increase alpha) 
     image2.alpha += FADE_IN_RATE; 
     // Fade upper layer out (decrease alpha) 
     image1.alpha -= FADE_OUT_RATE; 
    } 
} 

使用这个代码来设置