UIActivityIndi​​cator和GCD /线程

Question

我从服务器获取照片列表并显示它们。我正在使用GCD来线程化服务器调用。我得到它的工作，但我想为每个UIImageView添加一个UIActivityIndi​​cator，以显示它做了什么，并将出现。

我不确定最好的方法是什么。

代码：

UIScrollView *myScrollView = [[UIScrollView alloc] initWithFrame:CGRectMake(0, 0, [[UIScreen mainScreen] bounds].size.width, photoView.frame.size.height)];
myScrollView.backgroundColor = [UIColor whiteColor];
myScrollView.pagingEnabled = TRUE;
myScrollView.scrollEnabled = TRUE;

myScrollView.frame = CGRectMake(myScrollView.frame.origin.x, myScrollView.frame.origin.y, (6 * THUMBNAIL_SIZE) + (PHOTO_VIEWER_OFFSET_COLUM_1 * 2), myScrollView.frame.size.height);

//get list of photos

for (int i = 0; i < 6; i++)
{
    dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);

    dispatch_async(queue, ^{
        NSLog(@"async thread %@", [NSThread currentThread]);

        //retrieveThumbnailedGeotaggedPhotoWithPhotoID will make a server call
        MyUIImageView *myImageView =  [[MyUIImageView alloc] initWithImage:[self retrieveThumbnailedGeoTaggedPhotoWithPhotoID:@"test"]];
        dispatch_sync(dispatch_get_main_queue(), ^{
            NSLog(@"main thread %@", [NSThread currentThread]);

            myImageView.frame = CGRectMake(myImageView.frame.origin.x, myImageView.frame.origin.y, THUMBNAIL_SIZE, THUMBNAIL_SIZE);
            myImageView.backgroundColor = [UIColor clearColor];
            myImageView.position = i;
            myImageView.isEnlarged = FALSE;
            myImageView.delegate = self;

            int group = (i / 6);

            myImageView.frame = CGRectMake((i * myImageView.frame.size.width) + (PHOTO_VIEWER_OFFSET_COLUM_1 * ((group * 2) + 1)), 
                                           PHOTO_VIEWER_OFFSET_COLUM_1, 
                                           myImageView.frame.size.width, 
                                           myImageView.frame.size.height);

            myScrollView.contentSize = CGSizeMake((myScrollView.frame.size.width * (group + 1)), myScrollView.contentSize.height);

            [myScrollView addSubview:myImageView];
        });
    });
}

我非常确定动画和停止activityIndi​​cator需要在主线程上，但不知道如何包含它。它需要在“retrieveThumbnailedGeoTaggedPhotoWithPhotoID”方法中进行动画处理，该方法位于线程中（但不是主线程）。

Answer 1

k，我重新订购了它：

for (int i = 0; i < 8; i++)
{
    //create the subviews first
    MyUIImageView *myImageView =  [[MyUIImageView alloc] initWithFrame:CGRectMake((i * THUMBNAIL_SIZE) + (PHOTO_VIEWER_OFFSET_COLUM_1 * (((i / 6) * 2) + 1)), 
                                                          PHOTO_VIEWER_OFFSET_COLUM_1, 
                                                          THUMBNAIL_SIZE, 
                                                          THUMBNAIL_SIZE)];

    myImageView.backgroundColor = [UIColor whiteColor];
    [myScrollView addSubview:myImageView];

    UIActivityIndicatorView *spinner = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray];

    spinner.center = CGPointMake(THUMBNAIL_SIZE / 2, THUMBNAIL_SIZE / 2);

    [myImageView addSubview:spinner];
    [spinner startAnimating];

    dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);

    dispatch_async(queue, ^{

        UIImage *myImage = [[UIImage alloc] init];
        //only make the server call in the async queue
        myImage = [self retrieveThumbnailedGeoTaggedPhotoWithPhotoID:@"test"];

        dispatch_sync(dispatch_get_main_queue(), ^{
            NSLog(@"main thread %@", [NSThread currentThread]);

            //MyUIImageView *myImageView =  [[MyUIImageView alloc] initWithImage:myImage];
            [myImageView setImage:myImage];
            myImageView.frame = CGRectMake(myImageView.frame.origin.x, myImageView.frame.origin.y, THUMBNAIL_SIZE, THUMBNAIL_SIZE);
            myImageView.backgroundColor = [UIColor clearColor];
            myImageView.position = i;
            myImageView.isEnlarged = FALSE;
            myImageView.delegate = self;

            int group = (i / 6);

            myImageView.frame = CGRectMake((i * myImageView.frame.size.width) + (PHOTO_VIEWER_OFFSET_COLUM_1 * ((group * 2) + 1)), 
                                           PHOTO_VIEWER_OFFSET_COLUM_1, 
                                           myImageView.frame.size.width, 
                                           myImageView.frame.size.height);

            myScrollView.contentSize = CGSizeMake((myScrollView.frame.size.width * (group + 1)), myScrollView.contentSize.height);

            [spinner stopAnimating];
        });
    });
}