iPhone开发【二十一】数据持久化总结之第2篇—属性文件（.plist）

转载请注明出处，原文网址：http://blog.csdn.net/m_changgong/article/details/8269151 作者：张燕广

实现的功能：1）演示使用属性文件持久化数据。

关键词：数据持久化 属性文件 plist

1、新建一个Sigle View Application，命名为Persistence-file，工程结构如下

2、修改ViewController.xib，添加4个Label控件和4个TextField控件，如下：

3、修改ViewController.h，如下：

 #define kFileName @"data.plist"
 #import <UIKit/UIKit.h>

 @interface ViewController : UIViewController
 @property(nonatomic,retain)IBOutlet UITextField *name;
 @property(nonatomic,retain)IBOutlet UITextField *gender;
 @property(nonatomic,retain)IBOutlet UITextField *age;
 @property(nonatomic,retain)IBOutlet UITextField *education;

 -(NSString *)dataFilePath;
 -(void)applicationWillResignActive:(NSNotification *)nofication;

 @end

注意，需要连接各个输出口

4、修改ViewController.m，如下：

 #import "ViewController.h"

 @implementation ViewController
 @synthesize name,gender,age,education;

 #pragma mark - View lifecycle
 - (void)viewDidLoad
 {
     // Do any additional setup after loading the view, typically from a nib.
     [super viewDidLoad];
     UIApplication *app = [UIApplication sharedApplication];
     //订阅通知UIApplicationWillResignActiveNotification，进行数据保存操作
     [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(applicationWillResignActive:) name:UIApplicationWillResignActiveNotification object:app];
     //初始化数据
     [self initData];
 }

 -(void)initData{
     NSString *filePath = [self dataFilePath];
     NSLog(@"filePath=%@",filePath);

     //从文件中读取数据，首先判断文件是否存在
     if([[NSFileManager defaultManager] fileExistsAtPath:filePath]){
         NSArray *array = [[NSArray alloc]initWithContentsOfFile:filePath];
         name.text = [array objectAtIndex:0];
         gender.text = [array objectAtIndex:1];
         age.text = [array objectAtIndex:2];
         education.text = [array objectAtIndex:3];

         [array release];
     }
 }

 -(void)applicationWillResignActive:(NSNotification *)nofication{
     NSMutableArray *array = [[NSMutableArray alloc]init];
     [array addObject:name.text];
     [array addObject:gender.text];
     [array addObject:age.text];
     [array addObject:education.text];
     //将数据写入到文件dataFilePath中
     [array writeToFile:[self dataFilePath] atomically:YES];
     [array release];
 }

 //获得文件路径
 -(NSString *)dataFilePath{
     //检索Documents目录
     NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask,YES);//备注1
     NSString *documentsDirectory = [paths objectAtIndex:0];//备注2
     return [documentsDirectory stringByAppendingPathComponent:kFileName];
 }

 - (void)didReceiveMemoryWarning
 {
     [super didReceiveMemoryWarning];
     // Release any cached data, images, etc that aren't in use.
 }

 - (void)viewDidUnload
 {
     [super viewDidUnload];
     // Release any retained subviews of the main view.
     // e.g. self.myOutlet = nil;
     self.name = nil;
     self.gender = nil;
     self.age = nil;
     self.education = nil;
 }

 -(void)dealloc{
     [name release];
     [gender release];
     [age release];
     [education release];
 }

 - (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 orientations
     return (interfaceOrientation != UIInterfaceOrientationPortraitUpsideDown);
 }

 @end

备注1、备注2：

NSDocumentDirectory:常量，表明正在查找Documents目录的路径
NSUserDomainMask:常量，表面将搜索限制与当前应用程序的沙盒中，这样的话只能找到一个Documents目录，因为每个应用程序沙盒中只有一个Documents目录，所以备注2中从paths中取第一个即为当前应用程序的Documents目录的路径

5、编译、运行，在TextField中输入内容，然后退出Simulator，进行测试：

6、通过上一篇对IOS应用程序沙盒的的介绍，本工程属性文件data.plist，保存的位置是：

/Users/duobianxing/Library/Application Support/iPhone Simulator/5.0/Applications/88528A36-00CB-4900-9762-1FD5D6AC8595/Documents

7、总结：

1）可以简单保存静态数据，但是无法将自定义对象序列化到属性列表中

2）该持久化方法与上一篇中介绍的NSUserDefaults实质上都是将数据写入到.plist属性文件中，区别是文件保存的位置不同。

需要源码的网友请留言哦