Question

我下载了一系列图片来制作动画。当下载开始显示活动指示符以及何时完成隐藏活动指示符时，我该怎么做？

self.img = [[UIImageView alloc] initWithFrame:CGRectMake(0, 65, self.view.frame.size.width, self.view.frame.size.width-70)];



        img.animationImages = [NSArray arrayWithObjects:

                                   [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:@"URL"]]],

                                   [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:@"URL"]]],

                                   [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:@"URL"]]],

                                   [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:@"URL"]]],




        img.animationDuration = 20.0f;

        img.animationRepeatCount = 0;

        [img startAnimating];

        [self.view addSubview: img];

Answer 1

您的图片正在同步下载，这意味着您正在阻止主线程（这很糟糕）。相反，在后台线程上运行下载，这将允许主线程，并且在扩展中，应用程序的UI仍然可以运行。使用您的示例代码，这是在后台运行时的样子：

self.img = [[UIImageView alloc] initWithFrame:CGRectMake(0, 65, self.view.frame.size.width, self.view.frame.size.width-70)];
self.img.animationDuration = 20.0f;
self.img.animationRepeatCount = 0;
[self.img startAnimating];
[self.view addSubview:self.img];

// START ANIMATING YOUR ACTIVITY INDICATOR HERE

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^(void) {

    NSArray *images = @[
        [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:@"URL"]]],
        [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:@"URL"]]],
        [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:@"URL"]]],
        [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:@"URL"]]],
    ];

    dispatch_async(dispatch_get_main_queue(), ^(void) {

        // STOP ANIMATING YOUR ACTIVITY INDICATOR HERE

        [self.img setAnimationImages:images];

    });

});

Answer 2

下载开始时编写此代码： UIActivityIndicatorView * spinner = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle：UIActivityIndicatorViewStyleGray]; spinner.frame = CGRectMake（0,0,320,50）; [spinner startAnimating];

下载结束时编写此代码：[spinner stopAnimating];

下载图像iOS时的活动指示灯

2 个答案: