UIView背景颜色始终为黑色 [英] UIView Background Color Always Black

问题描述

当我以编程方式向视图控制器中添加UIView时，无法将背景颜色更改为任何其他颜色，它始终保持黑色.

When I add a UIView to a View Controller programmatically I am not able to change the background color to any other color, it always remains black.

- (void)drawRect:(CGRect)rect
{
    // Drawing code
    self.backgroundColor = [UIColor blueColor];

    UIBezierPath *path = [[UIBezierPath alloc] init];
    [path moveToPoint:CGPointMake(100, 33)];
    [path addLineToPoint:CGPointMake(200, 33)];
    path.lineWidth = 5;
    [[UIColor redColor] setStroke];
    [path stroke];
}

当我注释掉drawrect:并将self.backgroundColor = [UIColor blueColor];添加到初始化程序时，颜色会发生变化:

When I comment drawrect: out and add self.backgroundColor = [UIColor blueColor]; to the initializer the color changes:

- (id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        // Initialization code
        self.backgroundColor = [UIColor blueColor]
    }
    return self;
}

这是为什么，我需要更改什么?实际上，我希望背景是透明的.

Why is this and what do I need to change? Actually I would like the background to be transparent.

推荐答案

backgroundColor将被忽略.将您的代码更改为

backgroundColor of your view is ignored if you draw view yourself using drawRect. Change your code to

- (void)drawRect:(CGRect)rect
{
    // Drawing code
    [[UIColor blueColor] setFill];  // changes are here
    UIRectFill(rect);               // and here 

    UIBezierPath *path = [[UIBezierPath alloc] init];
    [path moveToPoint:CGPointMake(100, 33)];
    [path addLineToPoint:CGPointMake(200, 33)];
    path.lineWidth = 5;
    [[UIColor redColor] setStroke];
    [path stroke];
}

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