5

通过在顶部添加以下视图，我设法获得了灰度 UIView：

@interface GreyscaleAllView : UIView

@property (nonatomic, retain) UIView *underlyingView;

@end

@implementation GreyscaleAllView

@synthesize underlyingView;

- (void)drawRect:(CGRect)rect {

    CGContextRef context = UIGraphicsGetCurrentContext();

    // draw the image
    [self.underlyingView.layer renderInContext:context];

    // set the blend mode and draw rectangle on top of image
    CGContextSetBlendMode(context, kCGBlendModeColor);
    CGContextSetRGBFillColor(context, 0.0, 0.0, 0.0, 1.0);
    CGContextFillRect(context, rect);
    [super drawRect:rect];
}

@end

它可以工作，但除非我手动调用 setNeedsDisplay，否则内容不会更新。（我可以按下 UIButton 并触发动作，但外观没有任何变化）因此，为了让它表现得像预期的那样，我每秒调用 setNeedsDisplay 60 次。我究竟做错了什么？

更新：

viewcontroller 用这个初始化overlayview：

- (void)viewDidLoad
{
    [super viewDidLoad];

    GreyscaleAllView *grey = [[[GreyscaleAllView alloc] initWithFrame:self.view.frame] autorelease];
    grey.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;
    grey.userInteractionEnabled = NO;    
    [self.view addSubview:grey];
}

我已经为底层视图添加了这个来重绘：

@implementation GreyscaleAllView

- (void)setup {

    self.userInteractionEnabled = FALSE;
    self.contentMode = UIViewContentModeRedraw;

    [self redrawAfter:1.0 / 60.0 repeat:YES];

}

- (void)redrawAfter:(NSTimeInterval)time repeat:(BOOL)repeat {

    if(repeat) {
        // NOTE: retains self - should use a proxy when finished
        [NSTimer scheduledTimerWithTimeInterval:time target:self selector:@selector(setNeedsDisplay) userInfo:nil repeats:YES];
    }

    [self setNeedsDisplay];
}
4

1 回答 1

1

您真正想要的是仅在父视图重绘时才告诉子视图重绘，在这种情况下，您可以在父视图中覆盖并-setNeedsDisplay使其调用-setNeedsDisplay. 这需要为您的属性GreyscaleAllView子类化 UIView 。UIViewControllerview

即loadView在控制器中实现，并设置

self.view = [[CustomView alloc] initWithFrame:frame];

其中 CustomView 覆盖setNeedsDisplay如上所述：

@implementation CustomView

- (void)setNeedsDisplay
{
    [grayView setNeedsDisplay]; // grayView is a pointer to your GreyscaleAllView
    [super setNeedsDisplay];
}

@end

为了完整起见，您也应该为-setNeedsDisplayInRect:

于 2012-10-31T23:28:59.577 回答