可以在后台线程中使用UIPasteboard吗？

Question

UIPasteboard线程安全吗？

我正在试着做这样的事情

dispatch_async(dispatch_get_global_queue(0, 0), ^{
     UIPasteboard *generalPasteBoard = [UIPasteboard generalPasteboard];
     NSData *settingsData = [generalPasteBoard dataForPasteboardType:@"SomeType"];

    if (settingsData == nil) {

        UIPasteboard *pasteBoard = [UIPasteboard pasteboardWithName:@"SomeName" create:YES];
        settingsData = [pasteBoard dataForPasteboardType:@"SomeType"];
    }   
    // Do something with settingsData
});

这样做安全吗?或者我应该只在主线程上使用UIPasteboard？

Answer 1

我在iOS 9和10的后台线程上使用它，没有任何问题。当粘贴板访问全局的、共享的系统资源时，我假设它是线程安全的，即使它在UIKit框架中。显然，没有文档来支持我，只有我自己的经验。

使用我为MBProgressHUD创建的类别的示例代码：

typedef void (^ImageBlock)(UIImage* image);
#define DISPATCH_ASYNC_GLOBAL(code) dispatch_async(dispatch_get_global_queue(0, 0), ^{ code });
#define DISPATCH_ASYNC_MAIN(code) dispatch_async(dispatch_get_main_queue(), ^{ code });

+ (void) pasteboardImageWithCompletion:(ImageBlock)block
{
    // show hud in main window
    MBProgressHUD* hud = [MBProgressHUD showHUDAnimated:YES];
    DISPATCH_ASYNC_GLOBAL
    ({
        UIImage* img = [UIPasteboard generalPasteboard].image;
        if (img == nil)
        {
            NSURL* url = [UIPasteboard generalPasteboard].URL;
            if (url == nil)
            {
                NSData* data = [[UIPasteboard generalPasteboard] dataForPasteboardType:(NSString*)kUTTypeImage];
                img = [UIImage imageWithData:data];
            }
            else
            {
                img = [UIImage imageWithData:[NSData dataWithContentsOfURL:url]];
            }
        }
        DISPATCH_ASYNC_MAIN
        ({
            block(img);
            [hud hideAnimated:YES];
        });
    });
}