- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {    self.window = [[UIWindow alloc] initWithFrame:[UIScreen mainScreen].bounds];    UINavigationController *nav =[[UINavigationController alloc]initWithRootViewController:[[ViewController alloc]init]];    self.window.rootViewController =nav;    [self.window makeKeyAndVisible];    return YES;}

#import "ViewController.h"#import "View2Controller.h"@interface ViewController ()<UipopoverControllerDelegate>@PRoperty (nonatomic,strong) UIPopoverController *popoverButtonItem;@property (nonatomic,strong) UIPopoverController *popoverButton;@end@implementation ViewController //popoverButtonItem懶加載-(UIPopoverController *) popoverButtonItem{    if (!_popoverButtonItem) {        UINavigationController *nav= [[UINavigationController alloc]initWithRootViewController: [[View2Controller alloc]init]];     _popoverButtonItem= [[UIPopoverController alloc] initWithContentViewController:nav];     _popoverButtonItem.delegate = self;    }    return _popoverButtonItem;} //popoverButton懶加載-(UIPopoverController *) popoverButton{    if (!_popoverButton) {        _popoverButton= [[UIPopoverController alloc] initWithContentViewController:[[View2Controller alloc]init]];        _popoverButton.delegate = self;    }    return _popoverButton;} //1. 從BarButtonItem點擊彈出-(void) touchButtonItem:(UIBarButtonItem *)btn {    /**     *  從BarButtonItem上點擊　  *  @param item:圍繞著哪個UIBarButtonItem顯示     *  @param permittedArrowDirections:箭頭指的方向     *  @param animated:動畫     */    [self.popoverButtonItem presentPopoverFromBarButtonItem:btn permittedArrowDirections:UIPopoverArrowDirectionAny animated:YES];}//2從界面上的某個按鈕或者某片區域彈出popOver，排除navigationBar或者TabBar上的點擊-(void) touchButton:(UIButton *)btn {    /**     * 從界面上的某個按鈕或者某片區域彈出popOver     *  @param presentPopoverFromRect: 指定箭頭所指區域的矩形框范圍（位置和尺寸）     *  @param inView: rect參數是以view的左上角為坐標原點（0，0）     *  @param permittedArrowDirections:箭頭指的方向     *  @param animated:動畫     */    [self.popoverButton presentPopoverFromRect:btn.bounds                                  inView:btn                permittedArrowDirections:UIPopoverArrowDirectionLeft                                animated:YES];}- (void)viewDidLoad {    [super viewDidLoad];    self.view.backgroundColor = [UIColor grayColor];    self.navigationItem.title = @"導航欄";    self.navigationItem.leftBarButtonItem =[[UIBarButtonItem alloc]initWithTitle:@"點我" style:UIBarButtonItemStyleDone target:self action:@selector(touchButtonItem:)];    //********************************************************************************    UIButton *btn =[[UIButton alloc]initWithFrame:CGRectMake(100, 100, 100, 50)];    [btn setTitle:@"點我啊" forState:UIControlStateNormal];    [btn setTintColor:[UIColor blueColor]];    [btn setBackgroundColor:[UIColor redColor]];    [btn addTarget:self action:@selector(touchButton:) forControlEvents:UIControlEventTouchUpInside];    [self.view addSubview:btn];}// UIPopoverControllerDelegate --在ARC環境下正確的做法是保持popover的生命周期。讓popover是strong類型的成員變量或屬性。 當收到UIPopoverController dismiss的消息的時候將popover＝nil;這樣就可以正常便用了。- (void)popoverControllerDidDismissPopover:(UIPopoverController *)popoverController{    self.popoverButton = nil;    self.popoverButtonItem = nil;}

- (void)viewDidLoad{    [super viewDidLoad];    // 設置控制器在popover中顯示的尺寸 跟 view 一樣    self.preferredContentSize = self.view.frame.size;}