这个类是用来做弹出窗口的，原本是ipad专用到iOS8之后iPhone也可以用了。用他可以轻松实现类似微信右上角加号那个弹窗。
这个类是UIPresentationController的子类。UIPresentationController是iOS8之后开放，专门用来persent一个viewController使用的。在modal转场中用来做containerView。
下面用它实现一个右上角弹出菜单。当然不只是菜单，他可以弹出任何视图，以为他弹出来的是个UIViewController，vc中可以放任何视图，来构建你的弹出窗口.

实现步骤

不需要去创建UIPopoverPresentationController类，因为可以从UIViewController的popoverPresentationController属性获取他。实现弹出窗口时,只需要配置被弹出VC的popoverPresentationController属性，然后将其present出来就可。

核心代码

//配置被弹出vc
//popMenuVC是将要以窗口形式弹出的vc
    self.popMenuVC.modalPresentationStyle = UIModalPresentationPopover;
   //箭头方向
    self.popMenuVC.popoverPresentationController.permittedArrowDirections = UIPopoverArrowDirectionAny;
//箭头颜色
    self.popMenuVC.popoverPresentationController.backgroundColor = [UIColor whiteColor];
//代理必须设置
    self.popMenuVC.popoverPresentationController.delegate = self;
//窗口size
    self.popMenuVC.preferredContentSize = CGSizeMake(120, 160);

//箭头指向的视图
    self.popMenuVC.popoverPresentationController.sourceView = btn;
//这里只需要箭头指向视图的size可以通过他来调整箭头与其指向视图的距离
    self.popMenuVC.popoverPresentationController.sourceRect = btn.bounds;

//可以指向navigation的barButtonitem
   // self.popMenuVC.popoverPresentationController.barButtonItem = self.navigationItem.rightBarButtonItem;

delmo

#import "ViewController.h"
#import "EDPopMenuVC.h"
@interface ViewController ()<UIPopoverPresentationControllerDelegate>
{
    UIButton *btn;
}
@property(nonatomic,strong)EDPopMenuVC *popMenuVC;
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    [self popMenuVC];
    self.view.backgroundColor = [UIColor orangeColor];
    self.navigationItem.rightBarButtonItem = [[UIBarButtonItem alloc]initWithBarButtonSystemItem:UIBarButtonSystemItemAdd target:self action:@selector(rightBarAction:)];
    
    btn = [[UIButton alloc]initWithFrame:CGRectMake(150, 150, 40, 40)];
    btn.backgroundColor = [UIColor greenColor];
    [btn addTarget:self action:@selector(buttonAction:) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:btn];
    
    
}
-(void)popConfig
{
    self.popMenuVC.modalPresentationStyle = UIModalPresentationPopover;
    self.popMenuVC.popoverPresentationController.permittedArrowDirections = UIPopoverArrowDirectionAny;
    self.popMenuVC.popoverPresentationController.backgroundColor = [UIColor whiteColor];
    self.popMenuVC.popoverPresentationController.delegate = self;
    self.popMenuVC.preferredContentSize = CGSizeMake(120, 160);
}
-(EDPopMenuVC *)popMenuVC
{
    if (!_popMenuVC) {
        _popMenuVC = [EDPopMenuVC new];
    }
    return _popMenuVC;
}
-(void)buttonAction:(UIButton *)sender
{
    [self popConfig];
    self.popMenuVC.popoverPresentationController.sourceView = btn;
    self.popMenuVC.popoverPresentationController.sourceRect = btn.bounds;
    [self presentViewController:self.popMenuVC animated:YES completion:nil];

}
-(void)rightBarAction:(UIBarButtonItem *)item
{
    [self popConfig];
    self.popMenuVC.popoverPresentationController.barButtonItem = self.navigationItem.rightBarButtonItem;
    [self presentViewController:self.popMenuVC animated:YES completion:nil];
    
}


- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

//不要用这个方法，用下面那个（这个在plus上横屏的时候样式有问题）
//-(UIModalPresentationStyle)adaptivePresentationStyleForPresentationController:(UIPresentationController //*)controller
//{
//   return UIModalPresentationNone;
//}
- (UIModalPresentationStyle)adaptivePresentationStyleForPresentationController:(UIPresentationController *)controller traitCollection:(UITraitCollection *)traitCollection
{
    return UIModalPresentationNone;
    
}
@end


//被弹出VC
#import "EDPopMenuVC.h"

@interface EDPopMenuVC ()<UITableViewDelegate,UITableViewDataSource>
@property(strong,nonatomic)UITableView *contentTable;
@property(strong,nonatomic)NSArray *dataSource;

@end

@implementation EDPopMenuVC

- (void)viewDidLoad {
    [super viewDidLoad];
    [self createSubView];
    
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}
-(void)createSubView
{
    _dataSource   = @[@"扫一扫",@"加好友",@"创建讨论组",@"收钱",@"付钱"];
    _contentTable = [[UITableView alloc]initWithFrame:self.view.frame style:UITableViewStylePlain];
    _contentTable.separatorStyle  = UITableViewCellSeparatorStyleNone;
    _contentTable.delegate   = self;
    _contentTable.dataSource = self;
    [self.view addSubview:_contentTable];
}

#pragma mark -----
#pragma mark --------UITableViewDelegate && UITableViewDataSource--------

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    return _dataSource.count;
}

- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
{
    return 30;
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    NSString *CellIdentifier = [NSString stringWithFormat:@"%@ident",NSStringFromClass(self.class)];
    UITableViewCell  *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier];
    if (cell == nil)
    {
        cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier];
        cell.selectionStyle = 0;
    }
    cell.textLabel.text = _dataSource[indexPath.row];
     return cell;
}
     
 - (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
{
    [tableView deselectRowAtIndexPath:indexPath animated:NO];
    NSLog(@"%@",_dataSource[indexPath.row]);
}

@end