Question

我有一个自定义的UIView子类，它覆盖了drawrect。视图从数据源获取其数据，并将其中的一些信息传递给其委托（视图控制器），以将其处理为需要绘制的字符串。第一次调用setneedsdisplay时，视图显示为黑色矩形，但如果第二次调用它就可以正常工作。所有的帧大小和位置都设置正确，所以我确信委托和数据源从一开始就正确设置。这是令人讨厌的正确代码：

- (void)drawRect:(CGRect)rect
{

    CGContextRef context = UIGraphicsGetCurrentContext();

    CGContextSetLineWidth(context, 2.0);
    CGColorSpaceRef colorSpace=CGColorSpaceCreateDeviceRGB();
    CGFloat components[] = {0, 0, 0, 1.0};
    CGColorRef color = CGColorCreate(colorSpace, components);
    ;
    //CGContextStrokeRect(context, CGRectMake(1, 1, self.frame.size.width-1.0, self.frame.size.height-1.0));

    CGContextMoveToPoint(context, 0, [_delegate denominatorPoint:self].y);
        if ([_delegate numeratorBiggerThanDenominator:self]==YES) 
    CGContextAddLineToPoint(context,[[_delegate numeratorString:self]sizeWithFont:[_delegate fontToDrawWith:self]].width , [_delegate denominatorPoint:self].y);
        else
            CGContextAddLineToPoint(context,[[_delegate denominatorString:self]sizeWithFont:[_delegate fontToDrawWith:self]].width , [_delegate denominatorPoint:self].y);
    if ([_delegate hasAFraction:self]==YES) {


    CGContextSetStrokeColorWithColor(context, color);


    CGContextStrokePath(context);

    }

    CGColorSpaceRelease(colorSpace);
    CGColorRelease(color);



    self.backgroundColor=[UIColor clearColor];


    [[_delegate numeratorString:self] drawAtPoint:[_delegate numeratorPoint:self] withFont:[_delegate fontToDrawWith:self]];
    NSLog([_delegate numeratorString:self]);
    if ([_delegate hasAFraction:self]==YES) 
        [[_delegate denominatorString:self] drawAtPoint:[_delegate denominatorPoint:self] withFont:[_delegate fontToDrawWith:self]];
    [[_delegate Variable:self] drawAtPoint:[_delegate variablePoint:self] withFont:[_delegate fontToDrawWith:self]];
    if ([_delegate hasAParenthesTerm:self]==YES) {
        //NSLog(@"parentheses being drawn");
        NSString* openParentheses=@" (";
        [openParentheses drawAtPoint:[_delegate openParenthesesPoint:self] withFont:[_delegate fontToDrawWith:self]];
        NSString* closedParentheses=@")";
        [closedParentheses drawAtPoint:[_delegate closeParenthesesPoint:self] withFont:[_delegate fontToDrawWith:self]];
    }

}

如果有其他代码可以帮助解决问题，请告诉我。

Answer 1

您是否尝试将self.backgroundColor = [UIColor clearColor];移至init方法？

你应该只需要一次运行该行，我可以想象在draw方法中间调用它可能会导致问题（并且在第二次调用drawRect时，backgroundColor已经设置为clearColor，所以UIView可以忽略它，让你的问题随着第二次setNeedsDisplay调用而消失）

uiview子类显示为黑色矩形第一次调用setneedsdisplay，但之后确定

1 个答案: