在NSCollectionViews子视图上绘制

我在NSCollectionView子类中有以下代码:

-(void)drawRect:(NSRect)rect {  
    if(!NSEqualRects(highlightBox,NSZeroRect)) {        
        [[NSColor colorWithCalibratedRed:1.0f green:0.2f blue:0.2f alpha:1.0f] set];    
        NSRectFillUsingOperation(NSInsetRect(tempHighlightBox, -1.0, -1.0),NSCompositeSourceOver);
        [[NSColor colorWithCalibratedRed:0.2f green:0.2f blue:1.0f alpha:0.5f] set];
        NSRectFillUsingOperation(tempHighlightBox,NSCompositeSourceOver);
    }
}