iOS7上的RenderInContext非常慢

时间:2013-10-28 08:29:33

标签: ios objective-c ios7

我正在我的应用程序中实现“临时”功能。用户划伤屏幕并看到“下方”图像。

关于touchesMoved:我更新了蒙版图像并将其应用于图层。通常代码是这样的:

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
    [super touchesMoved:touches withEvent:event];

    UITouch *touch = [touches anyObject];
    CGPoint cPoint = [touch locationInView:self];

    UIImageView *imageView = [[UIImageView alloc] initWithFrame:self.bounds];
    imageView.image = _maskImage;

    // ... add some subviews to imageView corresponding to touch manner

    _maskImage = [UIImage imageFromLayer:imageView.layer];

    [self setNeedsDisplay];
}

- (void)drawRect:(CGRect)rect
{
    _maskImageView.image = _maskImage;
    _viewWithOurImage.layer.mask = _maskImageView.layer;
}

我使用代码(UIImage上的类别)从CALayer获取UIImage:

+ (UIImage*)imageFromLayer:(CALayer*)layer
{
    UIGraphicsBeginImageContextWithOptions([layer frame].size, NO, 0);
    [layer renderInContext:UIGraphicsGetCurrentContext()];
    UIImage *outputImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return outputImage;
}

此代码在iOS6上完美运行(在iPhone 4s和iPad2上测试),完全没有滞后。

但是当我在iOS7(xcode4或xcode5)上运行它时,它非常缓慢而且有点滞后。我使用了时间分析器,它明确指向renderInContext:row。

然后我尝试了以下代码:

...
    if (SYSTEM_VERSION_LESS_THAN(@"7.0"))
        _maskImage = [UIImage imageFromLayer:imageView.layer];
    else
        _maskImage = [UIImage imageFromViewIniOS7:imageView];
...

+ (UIImage*)imageFromViewIniOS7:(UIView*)view
{
    UIGraphicsBeginImageContextWithOptions(view.frame.size, NO, 0);
    CGContextSetInterpolationQuality(UIGraphicsGetCurrentContext(), kCGInterpolationNone);

    // actually there is NSInvocation, but I've shortened for example
    [view drawViewHierarchyInRect:view.bounds afterScreenUpdates:YES];

    UIImage *outputImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return outputImage;
}

它仍然很慢。在iPhone 4s上测试(与iOS6相同),新iPod5和iPad3。

我做错了什么?显然这是iOS7的问题......

我将不胜感激。

1 个答案:

答案 0 :(得分:3)

我建议你尝试其他一些方式,很遗憾地说, touchesMoved 功能在IOS7中运行缓慢,你的代码没有任何问题