iOS7's drawViewHierarchyInRect doesn't work?

Question

From what I've read, iOS7's new drawViewHierarchyInRect is supposed to be faster than CALayer's renderInContext. And according to this and this, it should be a simple matter of calling:

[myView drawViewHierarchyInRect:myView.frame afterScreenUpdates:YES];

instead of

[myView.layer renderInContext:UIGraphicsGetCurrentContext()];

However, when I try this, I just get blank images. Full code that does the capture, where "self" is a subclass of UIView,

        // YES = opaque. Ignores alpha channel, so less memory is used.
        // This method for some reasons renders the
    UIGraphicsBeginImageContextWithOptions(self.bounds.size, YES, self.window.screen.scale);    // Still slow.

    if ( [AIMAppDelegate isOniOS7OrNewer] )
        [self drawViewHierarchyInRect:self.frame afterScreenUpdates:YES]; // Doesn't work!
    else
        [self.layer renderInContext:UIGraphicsGetCurrentContext()];     // Works!

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

    contentImageView.image = image; // this is empty if done using iOS7's way

and contentImageView is a UIImageView that is added as a subView to self during initialization.

Additionally, the drawing that I want captured in the image is contained in other sub-views that are also added to self as a sub-view during initialization (including contentImageView).

Any ideas why this is failing when using drawViewHierarchyInRect?

* Update *

I get an image if I draw a specific sub-view, such as:

[contentImageView drawViewHierarchyInRect:contentImageView.frame afterScreenUpdates:YES];

or

[self.curvesView drawViewHierarchyInRect:self.curvesView.frame afterScreenUpdates:YES];

however I need all the visible sub-views combined into one image.

score 6 · Accepted Answer · answered Nov 06 '13 at 20:54

6

Try it with self.bounds rather than self.frame—it’s possible you’re getting an image of your view rendered outside the boundaries of the image context you’ve created.

answered Nov 06 '13 at 20:54

Noah Witherspoon

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Haha, through experimentation I just found the same result. That was the issue! Thanks. – Vern Jensen Nov 06 '13 at 21:31
Only other weird thing is that drawViewHierarchyInRect is actually a good bit SLOWER than renderInContext. I thought it should be faster? Any idea why it's not? – Vern Jensen Nov 06 '13 at 22:25
Might be the `afterScreenUpdates:YES`—I believe that forces it to wait for the next time the layer tree gets presented. Does the speed change if you turn that off? – Noah Witherspoon Nov 06 '13 at 22:29
In my case, some times `drawViewHierarchyInRect:afterScreenUpdates:` returns NO. I get the same result by using both self.frame and self.bounds. However, my issue is solved by using `renderInContext` as told by @VernJensen above. Thanks. – Lisarien Aug 27 '15 at 12:57

iOS7's drawViewHierarchyInRect doesn't work?

1 Answers1