Как получить снимок экрана текущего представления и повторное использование в коде? (iPhone SDK)
Просто запустите job2 из сферы действия job1. Job2 унаследует область, и поэтому, если job1 отменяется, то и job2 тоже.
3 ответа
I can guarantee you [window drawRect:] won't work. Most views don't implement drawRect: and it's certainly not recursive like on the mac.
drawInContext: is also pretty much hosed simalarly, as it's fundamentally asking the layer to draw itself, not its sublayers recursively. "Default implementation does nothing." says it all.
I implementing this for the Clif Bar Save Our Snow app in the app store by doing the following:
- Walk the layer hierarchy recursively, getting the contents from each layer. If it smells like an image, use the CGContext methods to draw it into your context.
- While walking, make sure to apply the transformations/positions of each layer as you call recursively
Yes, a rather large pain in the ass. But yes, it works pretty well and got through by Apple :).
On Mac this is so easy... you just need -bitmapImageRepForCachingDisplayInRect:, but of course iPhone has no such thing.
I think I would attack this by setting up a graphics context and calling [window drawRect:...] on it to capture the current image of the screen. This is a bit out of spec, because you're not really supposed to go calling -drawRect: yourself. I'd be a bit nervous of side-effects on doing this, but it may be fine. If it's a full-screen view you control, you could of course hoist the drawing code out of -drawRect: so you're not calling that directly.
A similar approach would be to use CALayer -drawInContext: of the current -presentationLayer. That might be slightly more "in spec" since it's legal to pass that your own context. But I don't know if you'd actually be able to get all the sub-views correctly. Might depend on the nature of your UIWindow.
Anyway, great question. Maybe someone has a more clever solution, but this is the way I'd attack it.
EDIT: Thanks to Rob Terrell, and his clever UIApplication+TVOut.m, I was introduced в частный метод UIGetScreenImage (), который возвращает CGImageRef. Если вы хотите использовать частные методы, это хороший вариант для вас. Учитывая его название и функциональность, он кажется мне довольно стабильным и вряд ли нарушит намерения Apple. Я также наткнулся на довольно приятное обсуждение на Air Source . Прочтите комментарии к нескольким ссылкам.
- (UIImage *)captureView:(UIView *)view {
CGRect screenRect = [[UIScreen mainScreen] bounds];
UIGraphicsBeginImageContext(screenRect.size);
CGContextRef ctx = UIGraphicsGetCurrentContext();
[[UIColor blackColor] set];
CGContextFillRect(ctx, screenRect);
[view.layer renderInContext:ctx];
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return newImage;
}
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