将 UIToolBar 子类化为具有自定义背景时，工具栏的下半部分是黑色的? [英] When subclassing UIToolBar to have a custom background the bottom half of toolbar is black?

问题描述

我正在继承 UIToolBar，这里是我如何覆盖 UIToolBar 的 drawRect 方法:

I'm subclassing UIToolBar, here is how I override the drawRect method of UIToolBar:

- (void)drawRect:(CGRect)rect
{
    UIImage *backgroundImage = [UIImage imageNamed:@"UIToolBar_Background.png"];
    [backgroundImage drawInRect:CGRectMake(0, 0, self.frame.size.width, self.frame.size.height)];
}

该应用程序使用 UINavigationController 范式，该范式使用 initWithNavigationBarClass 方法初始化.

The app uses a UINavigationController paradigm initialized with initWithNavigationBarClass method.

问题是工具栏的下半部分是黑色的?UIToolBar_Background.png 的高度为 44 像素(或视网膜为 88).它不应该有它的下半部分黑色.

The issue is that the bottom half of toolbar is black? The UIToolBar_Background.png is 44 pixels height (or 88 for retina). It should not have it's bottom half black.

推荐答案

通过继承 UIToolBar 并覆盖 drawRect，您可以消除一些 UIToolBar 自己的绘图.为什么不使用外观api来设置背景图片:

By subclassing UIToolBar and overriding drawRect, you eliminate some of UIToolBar's own drawing. Why not use the appearance api to set a background image:

[[UIToolbar appearance] setBackgroundImage:[UIImage imageNamed:@"UIToolBar_Background.png"]
                        forToolbarPosition:UIToolbarPositionBottom
                                barMetrics:UIBarMetricsDefault];

或者，您可以使用子类化路线，只需确保在进行自己的绘图之前调用 [super drawrect:rect]:

alternatively, you could use the subclassing route, just make sure you call [super drawrect:rect] before doing your own drawing:

- (void)drawRect:(CGRect)rect
{
    [super drawRect:rect];
    UIImage *backgroundImage = [UIImage imageNamed:@"UIToolBar_Background.png"];
    [backgroundImage drawInRect:CGRectMake(0, 0, self.frame.size.width, self.frame.size.height)];
}

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