Xcode：UIImageView 图像未更新

Question

当按下按钮时，我试图在 UIImageView 容器中显示 34 个连续图像。

- (IBAction)buttonPressed {
    [self updateUI:(0)];
}

-(void)updateUI:(int)yesser{

    //if GO is pressed

        //display 34 images MG_8842.PNG -> MG_8875.PNG stored in Supporting Files
        for(int j = 0;j<34;j++){
            NSString *newPhoto =[NSString stringWithFormat:@"MG_88%i.PNG",42+j];
            NSLog(@"%@",newPhoto);
            sleep(1);
            [self setNextImage:newPhoto];
        }
}

-(void)setNextImage:(NSString*)nextImage{

    [ball performSelectorOnMainThread:@selector(setImage:) withObject: [UIImage imageNamed:nextImage] waitUntilDone:YES];

}

但是，图像没有更新。当所有代码完成并返回时，将显示第一张图片。

我尝试了以下方法：
1) 产品 > 清洁
2) 重新安装应用程序。
3) 检查所有大小写敏感性。
4) 测试了设置 UIImageView 图像的方法数。
5) 检查 34 个静态 NSString 值是否有效，而不是每次更改一个 NSString
6) 删除并重新添加图像到支持文件夹。
7) 重命名所有图像并更新代码以匹配。
8) 关闭自动布局。

任何帮助将不胜感激。

谢谢， 抢

Answer 1

如果您尝试更新 UI，我认为您通常希望避免使用 sleep()。当您调用睡眠时，您是在告诉主线程暂停一段时间。由于 UI 全部在主线程上完成，我可以想象当它试图更新它的视图时，您对 sleep() 的调用会阻止它完全更新。因此，为什么您可能直到最后才看到任何更新。

正如我在评论中提到的，由于您想更新我想象的UIImageView，您应该考虑使用NSTimer。此类便于希望在特定时间间隔内安排定期更新。在这种情况下，我们希望 UIImageView 在调用 buttonPressed 的那一刻开始更新，所以我们可以这样做：

- (IBAction)buttonPressed:(id)sender {
    [self updateUI];
}

- (void)updateUI{
    // If you wanted to keep track of this NSTimer, you could hold onto it 
    // via a property.
    // `fire` basically tells the timer to begin executing what's been set 
    // for the selector.
    NSTimer *timer = [NSTimer scheduledTimerWithTimeInterval:1.0f target:self selector:@selector(setNextImage:) userInfo:nil repeat:YES];
    [timer fire];
}

- (void)setNextImage {
        // Here is where your logic would change. You would need some kind of way 
        // of figuring out which image to display. You could have an NSInteger 
        // property store how many times the method gets called and then 
        // determine which image to show from there, for example.

        // Assume that with your new logic, you have acquired the image you 
        // want to display.
        UIImage *image = imageToDisplay;

        // Also assuming here that (based on your code), `ball` is the 
        // name of your UIImageView.
        ball.image = imageToDisplay;
}

要销毁计时器，只需调用[timer invalidate]。

Answer 2

UIImageView 有一个动画图像的选项，试试这个

imageView.animationImages = [NSArray arrayWithObjects:
                                        [UIImage imageNamed:@"progress-1"],
                                        [UIImage imageNamed:@"progress-2"],
                                        [UIImage imageNamed:@"progress-3"],
                                        [UIImage imageNamed:@"progress-4"], nil];
imageView.animationDuration = 2.0f;
imageView.animationRepeatCount = 1;
[imageView startAnimating];

您必须按顺序重命名图像并在按下按钮时调用它..

Answer 3

试试这个

- (IBAction)buttonPressed {
    [self updateUI:(0)];
}

-(void)updateUI:(int)yesser{

//if GO is pressed

    //display 34 images MG_8842.PNG -> MG_8875.PNG stored in Supporting Files
    for(int j = 0;j<34;j++){
        NSString *newPhoto =[NSString stringWithFormat:@"MG_88%i",42+j];
        NSLog(@"%@",newPhoto);
        sleep(1);
        [self setNextImage:newPhoto];
    }
}

-(void)setNextImage:(NSString*)nextImage{

     [ball performSelectorOnMainThread:@selector(setImage:) withObject: [UIImage imageNamed:nextImage] waitUntilDone:YES];
     UIImageView *imgView = [[UIImageView alloc] initWithFrame:CGRectMake(10, 10, 100, 50)];
     imgView.image = [UIImage imageNamed:[NSString stringWithFormat: @"%@.png", nextImage]];
    [self.view addSubview:imgView];
}