Question

我有UITableView，其中包含UISwitch按钮。我希望当我运行我的应用程序时，UISwitch按钮的默认值应为ON。如果我将开关按钮从打开切换为关闭，则plist中的值应更改为OFF。如果我退出应用程序然后再次运行我的应用程序，该值应再次默认为plist中的ON。

我尝试过使用NSUserDefaults，但是当我将值从ON更改为OFF时，NSUserDefaults中的值也会发生变化。但是，当再次运行应用程序时，默认值不会设置为ON。

- (void)viewDidLoad {
    [super viewDidLoad];
    settings = [[NSMutableArray alloc]initWithObjects:@"Clock",@"Time Format",@"Weather",@"Degrees",nil];
    switchControl = [[UISwitch alloc]initWithFrame:CGRectMake(205, 110, 20, 15) ];
    [self.switchControl addTarget:self action:@selector(switchChanged:) forControlEvents:UIControlEventValueChanged];
    [self.view addSubview:switchControl];
    NSString *viewdid = @"ON";
    userdefaults = [NSUserDefaults standardUserDefaults];
    [userdefaults setObject:viewdid forKey:@"stateOfSwitch"];

}


- (void)viewWillAppear:(BOOL)animated {
    NSString    *_value= [[NSUserDefaults standardUserDefaults] stringForKey:@"stateOfSwitch"];

    if([_value compare:@"ON"] == NSOrderedSame){
        [switchControl setOn:YES animated:YES];
    }
    else {
        [switchControl setOn:NO animated:YES];
    }
    [super viewWillAppear:animated];
}



#pragma mark -
#pragma mark Table view data source

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {
    // Return the number of sections.
    return 1;
}


- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {
    // Return the number of rows in the section.
    return 4;
}
-(void)switchChanged:(id)sender
{

    app= (StopSnoozeAppDelegate*)[[UIApplication sharedApplication]delegate];

        NSString *value = @"ON";
    userdefaults = [NSUserDefaults standardUserDefaults];
        if(!switchControl.on){
            value = @"OFF";
            [userdefaults setObject:value forKey:@"stateOfSwitch"];
        }
        [userdefaults setObject:value forKey:@"stateOfSwitch"];
    [userdefaults synchronize];

}


//this is my second class where i am accessing my userdefaults key and depending on that hiding the views
- (void) viewWillAppear:(BOOL)animated
{

    NSString *_value= [[NSUserDefaults standardUserDefaults] stringForKey:@"stateOfSwitch"];

    if([_value compare:@"ON"] == NSOrderedSame){
        newview.hidden = NO;
        newnewview.hidden =NO;
        firstview.hidden = NO;
        secondview.hidden = NO;
        thirdview.hidden = NO;



    }
    else if([_value compare:@"OFF"] == NSOrderedSame) {

        newview.hidden = YES;
        newnewview.hidden= YES;
        firstview.hidden = YES;
        secondview.hidden = YES;
        thirdview.hidden = YES;
    }

}

Answer 1

在appDelegate中完成加载写下面的语句

[[NSUserDefaults standardUserDefaults] setObject:@"OFF" forKey:@"stateOfSwitch"];
[[NSUserDefaults standardUserDefaults] synchronize];

Answer 2

您可能没有将新值转储到plist？

将新值设置为[[NSUserDefaults standardUserDefaults] synchronize];后，尝试致电NSUserDefaults。

Answer 3

要么

// set when launching the app
- (void)applicationDidFinishLaunching:(UIApplication *)application {
    [[NSUserDefaults standardUserDefaults] setObject:@"OFF" forKey:@"stateOfSwitch"];
    [[NSUserDefaults standardUserDefaults] synchronize];
}

或

// set when terminating
- (void)applicationWillTerminate:(UIApplication *)application
    [[NSUserDefaults standardUserDefaults] setObject:@"OFF" forKey:@"stateOfSwitch"];
    [[NSUserDefaults standardUserDefaults] synchronize];
}

此外，您应该使用isEqualToString:测试您的NSString，因为compare:可能导致误报（例如，如果其中一个字符串为零）。

Answer 4

当NSUserDefaults完全能够直接存储BOOL时，你不应该存储一个有可能解析bug的字符串。

只需将其存储起来：

#define StateOfSwitch @"StateOfSwitch"
-(void)switchChanged:(id)sender
{
    [[NSUserDefaults standardUserDefaults] setBool:switchControl.on forKey:StateOfSwitch];
    [[NSUserDefaults standardUserDefaults] synchronize];
}

然后再加载这样的值：

switchControl.on = [[NSUserDefaults standardUserDefaults] boolForKey:StateOfSwitch];

（注意，永远不要直接使用字符串键是个好主意，最好#define它们以防止拼写错误。另外，你可以通过命令+点击跳转到定义，自动完成等等。）

如何在plist中保存价值并访问plist？

4 个答案: