ios中NSUserDefaults的使用

创建一个user defaults方法有多个，最简单得快速创建方法:

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NSUserDefaults *accountDefaults = [NSUserDefaults standardUserDefaults];

添加数据到 user defaults:

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[accountDefaults setObject:nameField.text forKey:UserDefaultNameKey];

也可以添加基本数据类型int, float, bool等，有相应得方法

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[accountDefaults setBool:YES forKey:UserDefaultBoolKey];

从user defaults中获取数据:

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[accountDefaults objectForKey:NCUserDefaultNameKey]

[accountDefaults boolForKey: UserDefaultBoolKey];

要点：

NSUserDefaults非常好用，并不需要用户在程序中设置NSUserDefaults的全局变量，需要在哪里使用NSUserDefaults的数据，那么就在哪里创建一个NSUserDefaults对象，然后进行读或者写操作。

针对同一个关键字对应的对象或者数据，可以对它进行重写，重写之后关键字就对应新的对象或者数据，旧的对象或者数据会被自动清理。

以下是一个我自己写的例子,通过checkBtn按钮进行保存用户名和密码：



图片一：保存数据之前；或者上一次没有保存数据，第二次启动的界面



图片二：保存了数据，第二次打开所看到的启动初始界面

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- (void)defaultCheck:(id)sender

{

NSLog(@" check按钮被按下 ");

NSUserDefaults *accountDefaults = [NSUserDefaults standardUserDefaults];

if ([accountDefaults boolForKey:NCUserDefaultBoolForRegister] == NO)

{

((UIButton*)sender).selected = YES;

[accountDefaults setBool:YES forKey:NCUserDefaultBoolForRegister];

[accountDefaults setObject:nameField.text forKey:NCUserDefaultNameKey];

[accountDefaults setObject:pwdField.text forKey:NCUserDefaultPasswordKey];

}

else {//YES

((UIButton*)sender).selected = NO;

[accountDefaults setBool:NO forKey:NCUserDefaultBoolForRegister];

[accountDefaults setObject:nil forKey:NCUserDefaultNameKey];

[accountDefaults setObject:nil forKey:NCUserDefaultPasswordKey];

}

}

- (void)loadView {

[super loadView];

nameField = [[UITextField alloc]initWithFrame:CGRectMake(0, 0, 100, 30)];

pwdField = [[UITextField alloc]initWithFrame:CGRectMake(0, 0, 100, 30)];

[nameField setCenter:CGPointMake(160, 100)];

[pwdField setCenter:CGPointMake(160, 150)];

NSUserDefaults *accountDefaults = [NSUserDefaults standardUserDefaults];

//存的是bool值一定要用boolForKey:获取

//如果之前已经保存了User Defaults,那么在读取的时候就要将数据读取出来，显示在用户名和密码框中（这里没有加密）。

if ([accountDefaults boolForKey:NCUserDefaultBoolForRegister] == YES) {

nameField.text = [accountDefaults objectForKey:NCUserDefaultNameKey];

pwdField.text = [accountDefaults objectForKey:NCUserDefaultPasswordKey];

}

else

{

[nameField setPlaceholder:@"用户名"];

[pwdField setPlaceholder:@"密码"];

}

nameField.borderStyle = UITextBorderStyleBezel;

[pwdField setBorderStyle:UITextBorderStyleRoundedRect];

[self.view addSubview:nameField];

[self.view addSubview:pwdField];

UIButton * loginBtn = [UIButton buttonWithType:UIButtonTypeRoundedRect];

[loginBtn setFrame:CGRectMake(0, 0, 50, 30)];

[loginBtn setCenter:CGPointMake(200, 200)];

[loginBtn addTarget:self action:@selector(loginToWeiBo:) forControlEvents:UIControlEventTouchUpInside];

[self.view addSubview:loginBtn];

UIButton * checkBtn = [UIButton buttonWithType:UIButtonTypeRoundedRect];

[checkBtn setFrame:CGRectMake(0, 0, 20, 20)];

[checkBtn setCenter:CGPointMake(160, 180)];

//选中之后得图标

[checkBtn setBackgroundImage:[UIImage imageNamed:@"lock.png"] forState:(UIControlState)UIControlStateHighlighted];

[checkBtn setBackgroundImage:[UIImage imageNamed:@"lock.png"] forState:(UIControlState)UIControlStateSelected];

//未选中

[checkBtn setBackgroundImage:[UIImage imageNamed:@"unlock.png"] forState:(UIControlState)UIControlStateNormal];

[checkBtn addTarget:self action:@selector(defaultCheck:) forControlEvents:UIControlEventTouchUpInside];

//用户名和密码已经保存

if([accountDefaults boolForKey:NCUserDefaultBoolForRegister] == YES)

{

[checkBtn setSelected:YES];

}

[self.view addSubview:Btn];

}