1.封裝彈出框，包括設置彈出界面 設置彈出地點 彈出 消失等方法。大概封裝如下

 

#import 

@interface WBDropdownMenu : UIView

@property (nonatomic,strong) UIView *contentView;

@property (nonatomic,strong) UIViewController *cntController;

+(instancetype)menu;

-(void)showFrom:(UIView *)view;

-(void)dismiss;

@end

 

2.其實現如下：

 

#import "WBDropdownMenu.h"
@interface WBDropdownMenu()

@property (nonatomic ,weak) UIImageView *containerView;

@end

@implementation WBDropdownMenu

-(UIImageView *)containerView
{
    if (!_containerView) {
        UIImageView *iv=[[UIImageView alloc] init];
        iv.image=[UIImage imageNamed:@"popover_background"];
        iv.width=217;
        [self addSubview:iv];
        _containerView=iv;
    }
    return _containerView;
}
#pragme 初始化透明背景界面 和彈出框背景
- (instancetype)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        self.frame=[UIScreen mainScreen].bounds;
        self.backgroundColor=[UIColor clearColor];
        
        [self containerView].userInteractionEnabled=YES;
    }
    return self;
}

+(instancetype)menu
{
    return [[WBDropdownMenu alloc] init];
}
#pragme 設置彈出框內容
-(void)setContentView:(UIView *)contentView
{
    contentView.x=10;
    contentView.y=15;
    
    contentView.width=self.containerView.width-2 * contentView.x;
    self.containerView.height=CGRectGetMaxY(contentView.bounds)+25;
    
    [self.containerView addSubview:contentView];
}

-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    [self dismiss];
}
#pragme 擴展內容view的另一種形式viewController
-(void)setCntController:(UIViewController *)cntController
{
    _cntController=cntController;
    [self setContentView:_cntController.view];
}
#pragme 設置顯示位置 該位置為windiow的絕對位置
-(void)showFrom:(UIView *)view
{
   UIWindow *window= [[UIApplication sharedApplication].windows lastObject];
    [window addSubview:self];
    CGRect absRect=[view convertRect:view.bounds toView:self];
    self.containerView.y=CGRectGetMaxY(absRect);
    self.containerView.midX=CGRectGetMidX(absRect);
    
}

-(void)dismiss
{
    [self removeFromSuperview];
}

@end

3.調用如下：

 

self.menu=[WBDropdownMenu menu];
    
    WBDropdownViewController *tableViewController=[[WBDropdownViewController alloc] init];
    tableViewController.tableView.height=44*3;
    
    [self.menu setCntController:tableViewController];
    
    [self.menu showFrom:target];

 

（大部分彈出框顯示為當前最前的window的內容,ios8中開始默認提供一個鍵盤window）