objc Record Screenshot on iPad - Works on simulator but not on devie

Question

I try to record a screenshot programatically. On the simulator the code snipped works like a charm, but on the iPad it only returns a blank page:

UIWindow *keyWindow = [[UIApplication sharedApplication] keyWindow];
UIGraphicsBeginImageContextWithOptions(keyWindow.frame.size, NO, 0);

UIView* screenshotView = [[UIScreen mainScreen] snapshotViewAfterScreenUpdates:YES];

[screenshotView drawViewHierarchyInRect:keyWindow.bounds afterScreenUpdates:YES];
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

The following line should return a view (including the statusbar). It works on the simulator but on a real device this view is empty.

UIView* screenshotView = [[UIScreen mainScreen] snapshotViewAfterScreenUpdates:YES];

What' the reason ? Thanks in advance.

Answer 1

如果要获取UIImage对象，则不调用snapshotViewAfterScreenUpdates API，只需在keyWindow上调用drawViewHierarchyInRect API，但是如果希望已使用图像绘制视图，则调用snapshotViewAfterScreenUpdates，则无需调用drawViewHierarchyInRect API

Answer 2

For anybody who is looking for the correct answer:

NSMutableArray* windows = [[[UIApplication sharedApplication] windows] mutableCopy];

NSString *statusBarString = [NSString stringWithFormat:@"_statusBarWindow"];
UIWindow* statusBarWindow =  [[UIApplication sharedApplication] valueForKey:statusBarString];

/*CGRect statusBarFrame = statusBarWindow.frame;
statusBarFrame.origin.x -= 20;
statusBarFrame.origin.y -= 20;
[statusBarWindow setFrame:statusBarFrame];*/
//statusBarWindow.backgroundColor = [UIColor blackColor];
[windows addObject:statusBarWindow];
[statusBarWindow release];



UIGraphicsBeginImageContextWithOptions(imageSize, YES, 0);
CGContextRef context = UIGraphicsGetCurrentContext();
for (UIWindow *window in windows) {
    CGContextSaveGState(context);
    CGContextTranslateCTM(context, window.center.x, window.center.y);
    CGContextConcatCTM(context, window.transform);
    CGContextTranslateCTM(context, -window.bounds.size.width * window.layer.anchorPoint.x, -window.bounds.size.height * window.layer.anchorPoint.y);
    if (orientation == UIInterfaceOrientationLandscapeLeft) {
        CGContextRotateCTM(context, M_PI_2);
        if(![window isKindOfClass:[UIStatusBarWindow class]])
        {
            CGContextTranslateCTM(context, 20, -imageSize.width+20);
        }
        else
        {
            CGContextTranslateCTM(context, 0, -imageSize.width);
        }
    } else if (orientation == UIInterfaceOrientationLandscapeRight) {
        CGContextRotateCTM(context, -M_PI_2);
        if(![window isKindOfClass:[UIStatusBarWindow class]])
        {
            CGContextTranslateCTM(context, -imageSize.height+20, 20);
        }
        else
        {
            CGContextTranslateCTM(context, -imageSize.height, 0);
        }
    } else if (orientation == UIInterfaceOrientationPortraitUpsideDown) {
        CGContextRotateCTM(context, M_PI);
        if(![window isKindOfClass:[UIStatusBarWindow class]])
        {
            CGContextTranslateCTM(context, -imageSize.width+20, -imageSize.height+20);
        }
        else
        {
            CGContextTranslateCTM(context, -imageSize.width, -imageSize.height);
        }
    }
    if ([window respondsToSelector:@selector(drawViewHierarchyInRect:afterScreenUpdates:)]) {
        [window drawViewHierarchyInRect:window.bounds afterScreenUpdates:YES];
    } else {
        [window.layer renderInContext:context];
    }
    CGContextRestoreGState(context);
}

UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

The answer is taken from here - with the solution above you are allowed to capture the statusbar as well.

PS: check the code for the right orientation and size of the screenshot ...