HEDropdownMenu.h 的代码

#import <UIKit/UIKit.h>

@class HEDropdownMenu;

@protocol HEDropdownMenuDelegate <NSObject>
@optional
- (void)dropdownMenuDidDismiss:(HEDropdownMenu *)menu;
- (void)dropdownMenuDidShow:(HEDropdownMenu *)menu;
@end

@interface HEDropdownMenu : UIView

@property (nonatomic, weak) id<HEDropdownMenuDelegate> delegate;

+ (instancetype)menu;

/**
 *  显示
 */
- (void)showFrom:(UIView *)from;
/**
 *  销毁
 */
- (void)dismiss;

/**
 *  内容
 */
@property (nonatomic, strong) UIView *content;
/**
 *  内容控制器
 */
@property (nonatomic, strong) UIViewController *contentController;

@end

HEDropdownMenu.m 的代码

#import "HEDropdownMenu.h"

@interface HEDropdownMenu()
/**
 *  将来用来显示具体内容的容器
 */
@property (nonatomic, weak) UIImageView *containerView;
@end

@implementation HEDropdownMenu


- (UIImageView *)containerView
{
    if (!_containerView) {
        // 添加一个灰色图片控件
        UIImageView *containerView = [[UIImageView alloc] init];
        containerView.image = [UIImage imageNamed:@"popover_background"];
        containerView.userInteractionEnabled = YES; // 开启交互
        [self addSubview:containerView];
        self.containerView = containerView;
    }
    return _containerView;
}

- (id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        // 清除颜色
        self.backgroundColor = [UIColor clearColor];
    }
    return self;
}


+ (instancetype)menu
{
    return [[self alloc] init];
}

- (void)setContent:(UIView *)content
{
    _content = content;
    
    // 调整内容的位置
    content.frame = CGRectMake(10, 15, content.frame.size.width, content.frame.size.height);

    // 调整内容的宽度
    //    content.width = self.containerView.width - 2 * content.x;
    
  
    
    self.containerView.frame = CGRectMake(0, 0, CGRectGetMaxX(content.frame) + 10, CGRectGetMaxY(content.frame) + 11);
    
    
    // 添加内容到灰色图片中
    [self.containerView addSubview:content];
}

- (void)setContentController:(UIViewController *)contentController
{
    _contentController = contentController;
    
    self.content = contentController.view;
}

/**
 *  显示
 */
- (void)showFrom:(UIView *)from
{
    // 1.获得最上面的窗口
    UIWindow *window = [[UIApplication sharedApplication].windows lastObject];
    
    // 2.添加自己到窗口上
    [window addSubview:self];
    
    // 3.设置尺寸
    self.frame = window.bounds;
    
    // 4.调整灰色图片的位置
    // 默认情况下，frame是以父控件左上角为坐标原点
    // 转换坐标系
    CGRect newFrame = [from convertRect:from.bounds toView:window];
    //    CGRect newFrame = [from.superview convertRect:from.frame toView:window];
//    self.containerView.centerX = CGRectGetMidX(newFrame);
//    self.containerView.y = CGRectGetMaxY(newFrame);
    self.containerView.center = CGPointMake(CGRectGetMidX(newFrame), self.containerView.center.y);
    self.containerView.frame = CGRectMake(self.containerView.frame.origin.x, CGRectGetMaxY(newFrame), self.containerView.frame.size.width, self.containerView.frame.size.height);
    
    
    // 通知外界，自己显示了
    if ([self.delegate respondsToSelector:@selector(dropdownMenuDidShow:)]) {
        [self.delegate dropdownMenuDidShow:self];
    }
}

/**
 *  销毁
 */
- (void)dismiss
{
    [self removeFromSuperview];
    
    // 通知外界，自己被销毁了
    if ([self.delegate respondsToSelector:@selector(dropdownMenuDidDismiss:)]) {
        [self.delegate dropdownMenuDidDismiss:self];
    }
}

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    [self dismiss];
}
@end