UIBarButtonItem + Extentsion

• 图片，不要渲染
• 文字，设置属性

/**
 *  快速创建一个显示图片的UIBarButtonItem
 */
+ (instancetype)itemWithTarget:(id)target action:(SEL)action icon:(NSString *)icon highIcon:(NSString *)highIcon
{
    UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
    [button setBackgroundImage:[UIImage imageNamed:icon] forState:UIControlStateNormal];
    [button setBackgroundImage:[[UIImage imageNamed:highIcon] imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal] forState:UIControlStateHighlighted];
    // 设置按钮尺寸
    button.bounds = (CGRect){CGPointZero, button.currentBackgroundImage.size};
    [button addTarget:target action:action forControlEvents:UIControlEventTouchUpInside];
    
    return [[self alloc] initWithCustomView:button];
}

• 注意：一定要把target传过去，否者self是UIBarButtonItem，找不着执行方法，会崩的
• [[UIBarButtonItem alloc] initWithTitle:@"写私信" style:UIBarButtonItemStyleDone target:nil action:nil];