iPhone编程中UIImageView渲染图像的问题

Question

我有一个 UIViewController 和一个 UIImageView，在 UIImageView 上我想在 2 个图像之间翻转，但我无法实现。

这是我写的代码，如果我错了请纠正我。

UIViewController* VC = [[UIViewController alloc]init];
VC.view.backgroundColor = [UIColor redColor];
UIImageView* imgView = [[UIImageView alloc]initWithFrame:CGRectMake(0,0,320,400)];
[imgView setImage:[UIImage imageNamed:@"Image_A.jpg"]];
[VC.view addSubview:imgView];

sleep(2);

[imgView setImage:[UIImage imageNamed:@"Image_B.jpg"]];
[VC.view addSubview:imgView];

[window addSubview:VC.view];

所以当我执行这个项目时，只有 Image_B 显示在屏幕上，而我希望 Image_A 显示然后在 sleep(2) 时，必须显示 Image_B。

我将如何使它成为可能？

谢谢。

Answer 1

使用NSTimer (docs here) 代替sleep。计时器不会阻塞线程，而是返回到运行循环。这样 UIKit 可以提交视图层次结构中的更改并将它们显示在屏幕上。在计时器的回调中，您只需更改图像即可。

Answer 2

.h

    @interface TwoImagesAppDelegate : NSObject <UIApplicationDelegate> {
        UIWindow *window;
        UIViewController* VC;
        UIImageView* imgView1;
        UIImageView* imgView2;
    }

.m

    - (void) toggle
    {
        static int toggle = 0;
        if (toggle) {
            imgView1.hidden = YES;
            imgView2.hidden = NO;
        } else {
            imgView1.hidden = NO;
            imgView2.hidden = YES;
        }
        toggle = toggle ? 0 : 1;
    }

    - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {    

        // Override point for customization after application launch

        [window makeKeyAndVisible];

        VC = [[UIViewController alloc]init];
        VC.view.backgroundColor = [UIColor redColor];
        imgView1 = [[UIImageView alloc]initWithFrame:CGRectMake(0,0,128,128)];
        [imgView1 setImage:[UIImage imageNamed:@"1.png"]];
        [VC.view addSubview:imgView1];
        [window addSubview:VC.view];

        VC.view.backgroundColor = [UIColor blackColor];
        imgView2 = [[UIImageView alloc]initWithFrame:CGRectMake(0,0,128,128)];
        [imgView2 setImage:[UIImage imageNamed:@"2.png"]];
        [VC.view addSubview:imgView2];  
        [window addSubview:VC.view];

        [NSTimer scheduledTimerWithTimeInterval:2.0 target:self selector:@selector(toggle) userInfo:nil repeats:YES];

        return YES;
    }

请注意，这个例子展示了如何使用timer，存在存在内存泄漏。

Answer 3

我假设你在一个窗口中。所以在.h

    @interface TwoImagesAppDelegate : NSObject <UIApplicationDelegate> {
        UIWindow *window;
        UIViewController* VC;
        UIImageView* imgView;
    }

.m

    - (void) addOneMore
    {
        VC.view.backgroundColor = [UIColor blackColor];
        [imgView setImage:[UIImage imageNamed:@"2.png"]];
        [VC.view addSubview:imgView];   
        [window addSubview:VC.view];
    }

    - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {    

        // Override point for customization after application launch

        [window makeKeyAndVisible];

        VC = [[UIViewController alloc]init];
        VC.view.backgroundColor = [UIColor redColor];
        imgView = [[UIImageView alloc]initWithFrame:CGRectMake(0,0,128,128)];
        [imgView setImage:[UIImage imageNamed:@"1.png"]];
        [VC.view addSubview:imgView];
        [window addSubview:VC.view];

        [NSTimer scheduledTimerWithTimeInterval:2.5 target:self selector:@selector(addOneMore) userInfo:nil repeats:NO];

        return YES;
    }