更改完成UIBarButtonItem的背景图像

Question

我想创建一个自定义UIBarButtonItem来表示完成按钮.我希望能够将应用程序国际化,因此我希望文本可以直接编辑.考虑到"完成"标签的不同长度,我设计了一个可伸缩的图像.是否可以直接更改默认编辑按钮背景或是否需要自定义UIBarButtonItem？如果是这样,根据标签的长度动态调整背景stretchchableImage的方法是什么？

Answer 1

如果您仅定位iOS 5.0,则可以使用新UIAppearance方法更改默认外观-setBackButtonBackgroundImage:forState:barMetrics:.

如果你需要支持旧版本的iOS,你应该子类化UIBarButtonItem,添加一个UIButton实例变量,创建它并调用你–initWithCustomView:的init方法UIBarButtonItem.那是因为UIBarButtonItem它不是子类,UIView你不能在其中绘制自定义图像.您还应该手动设置width属性UIBarButtonItem.

@interface MYCustomBarButtonItem : UIBarButtonItem
{
    UIButton *button;
}
- (id)initWithTitle:(NSString *)title; // name it in concordance with your needs
@end

#define kButtonHeight 30
#define kButtonTitleFontSize 12
#define kButtonTitlePadding 5

@implementation MYCustomBarButtonItem

- (id)initWithTitle:(NSString *)title
{
    button = [UIButton buttonWithType:UIButtonTypeCustom]; // add retain here, and write the dealloc method if you aren't using ARC. Also, release it if self == nil.
    self = [super initWithCustomView:button];
    if (self) {
        UIFont *titleFont = [UIFont boldSystemFontOfSize:kButtonTitleFontSize];
        CGSize titleSize = [title sizeWithFont:titleFont];
        CGFloat buttonWidth = titleSize.width + kButtonTitlePadding * 2;
        button.frame = CGRectMake(0, 0, buttonWidth, kButtonHeight);
        self.width = buttonWidth;

        [button setTitle:title forState:UIControlStateNormal];

        // Set your styles
        button.titleLabel.font = titleFont;

        // Normal state background
        UIImage *backgroundImage = ...; // create your normal stretchable background image
        [button setBackgroundImage:backgroundImage forState:UIControlStateNormal];

        // Pressed state background
        backgroundImage = ...; // create your pressed stretchable background image
        [button setBackgroundImage:backgroundImage forState:UIControlStateHighlighted];

        // and so on...
    }
    return self;
}

@end

PS.不要忘了覆盖target和action你的子类的属性与你的工作button实例.