Question

一旦用户点击特定按钮，我需要对图像执行闪烁效果。但我的代码不起作用：

- (void)next
{
    [UIView animateWithDuration:2.0f delay:0 options:UIViewAnimationOptionAutoreverse | UIViewAnimationOptionRepeat animations:^{
        NSLog(@"Done"); // <- USED AS COUNTER
        [image setAlpha:0];
        [image setAlpha:0.5];
    } completion:nil];
}

我的image将其alpha值更改为0.5并停止。此外，我的控制台只显示DONE一次。我错了什么？

Answer 1

我刚刚创建了一个测试项目，这眨了眨眼......

#import "ViewController.h"

@interface ViewController ()

@property (nonatomic, strong)UIView *blinker;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    self.blinker = [[UIView alloc]initWithFrame:CGRectMake(0, 0, 100, 100)];
    self.blinker.backgroundColor = [UIColor greenColor];
    [self.view addSubview:self.blinker];

    [self next];
}

- (void)next
{
    [UIView animateWithDuration:2.0f delay:0 options:UIViewAnimationOptionAutoreverse | UIViewAnimationOptionRepeat animations:^{
        NSLog(@"Done"); // <- USED AS COUNTER
        [self.blinker setAlpha:0];
        [self.blinker setAlpha:0.5];
    } completion:nil];
}

除了您希望日志继续在控制台中打印出来之外。所以我怀疑你正在为你的形象做些什么。你不是在称自己。所以我猜它是一个实例变量（ivar），你正在改变它指向代码中其他地方的东西。

如果您需要一个计数器来熄灭每一次眨眼，您可能需要考虑这样的事情......

#import "ViewController.h"

@interface ViewController ()

@property (nonatomic, strong)UIView *blinker;
@property (nonatomic,)NSInteger counter;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    self.blinker = [[UIView alloc]initWithFrame:CGRectMake(0, 0, 100, 100)];
    self.blinker.backgroundColor = [UIColor greenColor];
    [self.view addSubview:self.blinker];

    [self next];
}

- (void)next
{
    [UIView animateWithDuration:1.0 animations:^{
        self.counter++;
        NSLog(@"Counter: %@", @(self.counter));
        self.blinker.alpha = 0.0;
    } completion:^(BOOL finished) {
        [UIView animateWithDuration:1.0 animations:^{
            self.blinker.alpha = 1.0;
        } completion:^(BOOL finished) {

            //check to see if you want to continue blinking if so call next again
            [self next];
        }];
    }];
}

我没有任何关于你为什么要数数的背景，但希望这有帮助。

为什么我的动画不循环？

1 个答案: