iOS开发：弹出框、进度条与键盘通知处理

### iOS开发：弹出框、进度条与键盘通知处理 #### 1. 弹出框（Popovers）的使用 弹出框主要用于在iPad屏幕上显示额外信息，例如在iPad的Safari应用中，点击书签按钮时，会弹出一个显示书签内容的弹出框。 ##### 1.1 弹出框的基本特性 - **默认行为**：当用户点击弹出框区域外的地方时，弹出框会自动消失。不过，也可以设置在用户点击屏幕特定部分时不关闭弹出框。 - **内容展示**：弹出框通过视图控制器来展示内容，并且可以在弹出框内展示导航控制器，因为导航控制器是`UIViewController`的子类。 - **设备限制**：弹出框只能在iPad设备上使用。如果视图控制器的代码同时在iPad和iPhone上运行，需要确保不在非iPad设备上实例化弹出框。 - **展示方式**： 1. 从导航按钮（`UIBarButtonItem`的实例）内部弹出。 2. 从视图中的矩形区域弹出。 - **设备方向变化**：当设备方向改变（旋转设备）时，弹出框可能会被关闭或暂时隐藏。需要确保在方向改变稳定后，尽可能重新显示弹出框，以提供良好的用户体验。 ##### 1.2 创建演示弹出框应用 以下是创建演示弹出框应用的详细步骤： 1. **创建项目**：在Xcode中创建一个单视图通用项目，并命名为`Displaying_Popovers_with_UIPopoverControllerViewController`。 2. **定义导航控制器**：在应用委托的头文件中定义一个导航控制器： ```objc #import <UIKit/UIKit.h> @class Displaying_Popovers_with_UIPopoverControllerViewController; @interface Displaying_Popovers_with_UIPopoverControllerAppDelegate : UIResponder <UIApplicationDelegate> @property (nonatomic, strong) UIWindow *window; @property (nonatomic, strong) Displaying_Popovers_with_UIPopoverControllerViewController *viewController; @property (nonatomic, strong) UINavigationController *navigationController; @end ``` 3. **实例化导航控制器**：在应用委托的实现文件中实例化导航控制器，并将其显示给用户： ```objc #import "Displaying_Popovers_with_UIPopoverControllerAppDelegate.h" #import "Displaying_Popovers_with_UIPopoverControllerViewController.h" @implementation Displaying_Popovers_with_UIPopoverControllerAppDelegate - (BOOL) application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions{ self.window = [[UIWindow alloc] initWithFrame: [[UIScreen mainScreen] bounds]]; UIUserInterfaceIdiom uiIdiom = [[UIDevice currentDevice] userInterfaceIdiom]; NSString *viewControllerClass = @"Displaying_Popovers_with_UIPopoverControllerViewController_iPad"; if (uiIdiom == UIUserInterfaceIdiomPhone) { viewControllerClass = @"Displaying_Popovers_with_UIPopoverControllerViewController_iPhone"; } self.viewController = [[Displaying_Popovers_with_UIPopoverControllerViewController alloc] initWithNibName:viewControllerClass bundle:nil]; self.navigationController = [[UINavigationController alloc] initWithRootViewController:self.viewController]; self.window.rootViewController = self.navigationController; [self.window makeKeyAndVisible]; return YES; } ``` 4. **定义弹出框控制器属性**：在视图控制器的定义文件中定义一个`UIPopoverController`类型的属性： ```objc #import <UIKit/UIKit.h> @interface Displaying_Popovers_with_UIPopoverControllerViewController : UIViewController <UIAlertViewDelegate> @property (nonatomic, strong) UIPopoverController *popoverController; @property (nonatomic, strong) UIBarButtonItem *barButtonAdd; @end ``` 5. **创建弹出框内容视图控制器**：创建一个`UIViewController`的子类`PopoverContentViewController`，用于在弹出框中显示内容： ```objc #import <UIKit/UIKit.h> @interface PopoverContentViewController : UIViewController @property (nonatomic, strong) UIButton *buttonPhoto; @property (nonatomic, strong) UIButton *buttonAudio; @property (nonatomic, weak) UIPopoverController *popoverController; @end ``` 6. **合成弹出框控制器**：在`PopoverContentViewController`的实现文件中合成弹出框控制器： ```objc #import "PopoverContentViewController.h" @implementation PopoverContentViewController @synthesize popoverController; ... ``` 7. **创建按钮并处理点击事件**：在`PopoverContentViewController`中创建两个按钮，并处理点击事件以关闭弹出框： ```objc #import "PopoverContentViewController.h" @implementation PopoverContentViewController @synthesize popoverController; - (BOOL) isInPopover{ Class popoverClass = NSClassFromString(@"UIPopoverController"); if (popoverClass != nil && UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad && self.popoverController != nil){ return YES; } else { return NO; } } - (void) gotoAppleWebsite:(id)paramSender{ if ([self isInPopover]){ [self.popoverController dismissPopoverAnimated:YES]; } else { /* Handle case for iPhone */ } } - (void) gotoAppleStoreWebsite:(id)paramSender{ if ([self isInPopover]){ [self.popoverController dismissPopoverAnimated:YES]; } else { /* Handle case for iPhone */ } } - (void)viewDidLoad{ [super viewDidLoad]; self.view.backgroundColor = [UIColor whiteColor]; self.contentSizeForViewInPopover = CGSizeMake(200.0f, 125.0f); CGRect buttonRect = CGRectMake(20.0f, 20.0f, 160.0f, 37.0f); self.buttonPhoto = [UIButton buttonWithType:UIButtonTypeRoundedRect]; [self.buttonPhoto setTitle:@"Photo" forState:UIControlStateNormal]; [self.buttonPhoto addTarget:self action:@selector(gotoAppleWebsite:) forControlEvents:UIControlEventTouchUpInside]; self.buttonPhoto.frame = buttonRect; [self.view addSubview:self.buttonPhoto]; buttonRect.origin.y += 50.0f; self.buttonAudio = [UIButton buttonWithType:UIButtonTypeRoundedRect]; [self.buttonAudio setTitle:@"Audio" forState:UIControlStateNormal]; [self.buttonAudio addTarget:self action:@selector(gotoAppleStoreWebsite:) forControlEvents:UIControlEventTouchUpInside]; self.buttonAudio.frame = buttonRect; [self.view addSubview:self.buttonAudio]; } - (BOOL)shouldAutorotateToInterfaceOrientation :(UIInterfaceOrientation)interfaceOrientation{ return YES; } @end ``` 8. **创建导航按钮并处理点击事件**：在根视图控制器的`viewDidLoad`方法中创建导航按钮，并根据设备类型显示弹出框或警告视图： ```objc - (void)viewDidLoad{ [super viewDidLoad]; Class popoverClass = NSClassFromString(@"UIPopoverController"); if (popoverClass != nil && UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad){ PopoverContentViewController *content = [[PopoverContentViewController alloc] initWithNibName:nil bundle:nil]; self.popoverController = [[UIPopoverController alloc] initWithContentViewController:content]; content.popoverController = self.popoverController; self.barButtonAdd = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemAdd target:self action:@selector(performAddWithPopover:)]; } else { self.barButtonAdd = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemAdd target:self action:@sel ```