目标c renderInContext在后台线程崩溃 [英] objective c renderInContext crash on background thread

问题描述

我有一个应用程序，其中屏幕连续捕获在后台线程。这是代码

   - （UIImage *）captureScreen {
 
 UIWindow * keyWindow = [[UIApplication sharedApplication] keyWindow]; 
 CGRect rect = [keyWindow bounds]; 
 UIGraphicsBeginImageContext（rect.size）; 
 CGContextRef context = UIGraphicsGetCurrentContext（）; 
 [[keyWindow layer] renderInContext：context]; 
 UIImage * img = UIGraphicsGetImageFromCurrentImageContext（）; 
 
 UIGraphicsEndImageContext（）; 
 
 UIDeviceOrientation orientation = [UIApplication sharedApplication] .statusBarOrientation; 
 if（（ori​​entation == UIInterfaceOrientationLandscapeLeft）||（orientation == UIInterfaceOrientationLandscapeRight）||（orientation == UIInterfaceOrientationPortraitUpsideDown））{
 img = [self rotatedImage：img]; 
} 
 return img; 
} 
  

它适用于捕获一次或两次。但是一段时间后，应用程序崩溃总是在同一行 [[keyWindow layer] renderInContext：context]; ，它给出 EXC_BAD_ACCESS（code = 1， address = 0x8）消息。我搜索无处不在，没有什么有用的。发现只有renderInContext有内存泄漏问题时，它在后台线程中工作。但是，因为你明白，不解决我的问题:)。
所以有3个问题： -

1. 这个崩溃的原因是什么？

一个苹果建议，因为有renderInContext也使用）。没有呈现的内容...？

解决方案

-renderInContext：不是线程安全的，你不能从后台线程调用它。你必须在主线程上绘图。

I have an app in which the screen continuously is capturing in background thread. Here is the code

- (UIImage *) captureScreen {

    UIWindow *keyWindow = [[UIApplication sharedApplication] keyWindow];
    CGRect rect = [keyWindow bounds];
    UIGraphicsBeginImageContext(rect.size);
    CGContextRef context = UIGraphicsGetCurrentContext();
    [[keyWindow layer] renderInContext:context];
    UIImage *img = UIGraphicsGetImageFromCurrentImageContext();

    UIGraphicsEndImageContext();

    UIDeviceOrientation orientation = [UIApplication sharedApplication].statusBarOrientation;
    if ((orientation == UIInterfaceOrientationLandscapeLeft) || (orientation == UIInterfaceOrientationLandscapeRight) || (orientation==UIInterfaceOrientationPortraitUpsideDown)) {
        img=[self rotatedImage:img];
    }
    return img;
}

It works good for capturing once or twice. But after a while the app crashes always on the same line [[keyWindow layer] renderInContext:context]; and it gives EXC_BAD_ACCESS (code=1, address=0x8) message. I searched everywhere and nothing useful. Found only that renderInContext has memory leak issue when it works in background thread. But as you understand that doesn't solve my issue :) . So have 3 questions :-

1. What is the reason of this crash (problem)?

2. What can I do with this?

3. Is there any other way to capture screen (beside the one that Apple suggests, because there renderInContext is also used). Something without rendering...?

解决方案

-renderInContext: is not thread-safe and you can't call it from a background thread. You'll have to do the drawing on the main thread.

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