#import "FlipsideViewController.h"@interface MainViewController : UIViewController <FlipsideViewControllerDelegate> {UILabel *usernamelable;UILabel *passwordlable;UILabel *warplable;UILabel *warpfactorlable;
}- (IBAction)showInfo:(id)sender;
@property (nonatomic, strong) IBOutlet UILabel *usernamelable;
@property (nonatomic, strong) IBOutlet UILabel *passwordlable;
@property (nonatomic, strong) IBOutlet UILabel *warpDrivelable;
@property (nonatomic, strong) IBOutlet UILabel *warpfactorlable;
//自定义方法用于刷新数据
- (void)refreshFields;
//自定义方法用于后台返回响应
-(void)backupdata;
@end

MainViewController.m

#import "MainViewController.h"@implementation MainViewController
@synthesize usernamelable;
@synthesize passwordlable;
@synthesize warpDrivelable;
@synthesize warpfactorlable;- (void)didReceiveMemoryWarning
{[super didReceiveMemoryWarning];// Release any cached data, images, etc that aren't in use.
}
#pragma mark obtain source from plist
//刷新方法：
-(void)refreshFields{//与系统设置(Setting.bundle)相连，可相互传递数据NSUserDefaults *defaults=[NSUserDefaults standardUserDefaults];//从沙盒里取值，这里的key是plist文件里定义好的usernamelable.text=[defaults objectForKey:@"name"];passwordlable.text=[defaults objectForKey:@"password"];warpDrivelable.text=[defaults boolForKey:@"wrap"]?@"Enable":@"Disable";warpfactorlable.text=[[defaults objectForKey:@"slider"] stringValue] ;NSLog(@"%@",[[defaults objectForKey:@"slider"] stringValue]);
}#pragma mark - View lifecycle
//视图每次切换呈现时都会调用这个方法，这里需要注意的就是当按下iphone的home键时程序进入后台，程序再走到前台时并不会调用这个方法。
-(void)viewDidAppear:(BOOL)animated{//刷新[self refreshFields];[super viewDidAppear:animated];
}- (void)viewDidLoad
{//得到应用程序的单例对象UIApplication *app=[UIApplication sharedApplication];//将当前类作为观察着，来接收应用程序的通知(从后台走到前台)来响应backupdata方法[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(backupdata) name:UIApplicationWillEnterForegroundNotification object:app];[super viewDidLoad];// Do any additional setup after loading the view, typically from a nib.
}-(void)backupdata{NSUserDefaults *defaults=[NSUserDefaults standardUserDefaults];//同步系统,当从手机自带系统设置更改，程序从后台回到前台时将系统(磁盘)的setting数据同步到应用程序的Setting。[defaults synchronize];[self refreshFields];
}- (void)viewDidUnload
{[self setUsernamelable:nil];[self setPasswordlable:nil];[self setWarpDrivelable:nil];[self setWarpfactorlable:nil];[super viewDidUnload];// Release any retained subviews of the main view.// e.g. self.myOutlet = nil;
}- (void)viewWillAppear:(BOOL)animated
{[super viewWillAppear:animated];
}- (void)viewWillDisappear:(BOOL)animated
{[super viewWillDisappear:animated];
}- (void)viewDidDisappear:(BOOL)animated
{[super viewDidDisappear:animated];
}- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{// Return YES for supported orientationsreturn (interfaceOrientation != UIInterfaceOrientationPortraitUpsideDown);
}#pragma mark - Flipside View- (void)flipsideViewControllerDidFinish:(FlipsideViewController *)controller
{[self dismissModalViewControllerAnimated:YES];
}- (IBAction)showInfo:(id)sender
{    FlipsideViewController *controller = [[FlipsideViewController alloc] initWithNibName:@"FlipsideViewController" bundle:nil];controller.delegate = self;//设置view的过渡模式controller.modalTransitionStyle = UIModalTransitionStyleFlipHorizontal;//呈现模式（效果就是切换视图）。[self presentModalViewController:controller animated:YES];
}@end

#import <UIKit/UIKit.h>@class FlipsideViewController;@protocol FlipsideViewControllerDelegate
- (void)flipsideViewControllerDidFinish:(FlipsideViewController *)controller;
@end@interface FlipsideViewController : UIViewController {UISwitch *_MySwitch;UISlider *_MySilder;
}@property (weak, nonatomic) IBOutlet id <FlipsideViewControllerDelegate> delegate;
@property (nonatomic, strong) IBOutlet UISwitch *MySwitch;
@property (nonatomic, strong) IBOutlet UISlider *MySilder;- (IBAction)done:(id)sender;
//自定义方法视图从后台返回时将被调用。
-(void)applicationWillEnterForeground;//用于改变系统数据
- (IBAction)myswitchchange:(id)sender;
- (IBAction)mysliderchange:(id)sender;//刷新数据
-(void)refreshField;
@end

FlipsideViewController.m

#import "FlipsideViewController.h"@implementation FlipsideViewController@synthesize delegate = _delegate;
@synthesize MySwitch = _MySwitch;
@synthesize MySilder = _MySilder;- (void)didReceiveMemoryWarning
{[super didReceiveMemoryWarning];// Release any cached data, images, etc that aren't in use.
}#pragma mark - View lifecycle- (void)viewDidLoad
{//得到应用程序对象用于做通知的过滤条件UIApplication *app=[UIApplication sharedApplication];//添加观察者为self，接收应用程序的通知，响应方法为applicationWillEnterForeground。（也就是程序从后台进入前台）[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(applicationWillEnterForeground) name:UIApplicationWillEnterForegroundNotification object:app];//刷新数据[self refreshField];[super viewDidLoad];// Do any additional setup after loading the view, typically from a nib.
}- (void)viewDidUnload
{[self setMySwitch:nil];[self setMySilder:nil];[super viewDidUnload];// Release any retained subviews of the main view.// e.g. self.myOutlet = nil;
}- (void)viewWillAppear:(BOOL)animated
{[super viewWillAppear:animated];
}- (void)viewDidAppear:(BOOL)animated
{[super viewDidAppear:animated];
}- (void)viewWillDisappear:(BOOL)animated
{[super viewWillDisappear:animated];
}- (void)viewDidDisappear:(BOOL)animated
{[super viewDidDisappear:animated];
}- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{// Return YES for supported orientationsreturn (interfaceOrientation != UIInterfaceOrientationPortraitUpsideDown);
}
-(void)applicationWillEnterForeground{NSUserDefaults *defau=[[NSUserDefaults alloc]init];//同步系统，刷新系统(磁盘)的Setting[defau synchronize];[self refreshField];
}- (IBAction)myswitchchange:(id)sender {NSUserDefaults *defau=[[NSUserDefaults alloc] init];[defau setBool:self.MySwitch.on forKey:@"wrap"];//同步系统，刷新系统(磁盘)的setting[defau synchronize];
}- (IBAction)mysliderchange:(id)sender {NSUserDefaults *defau=[[NSUserDefaults alloc] init];[defau setFloat:self.MySilder.value forKey:@"slider"];//同步系统，刷新系统(磁盘)的setting[defau synchronize];
}-(void)refreshField{NSUserDefaults *defua=[[NSUserDefaults alloc] init];//同步系统，刷新系统(磁盘)的setting[defua synchronize];self.MySwitch.on=[defua boolForKey:@"wrap"];self.MySilder.value=[defua floatForKey:@"slider"];
}
#pragma mark - Actions- (IBAction)done:(id)sender
{[self.delegate flipsideViewControllerDidFinish:self];
}@end

3）小结：这个小程序里也包含了很多别的知识如：系统自动生成的部分，页面间的反转切换方法的调用，信息传递等。以前写过，有详细讲解（点击参见：(7)---02 iphone 开发 数据传递 ： 页面切换与数据的反向传递以及协议(protocol)作用的体现）。