即使应用程序重新启动，也保存 UISwitch 状态

Question

I am trying to save the switch statement in objective-c but it will go back to the default state (which is off) whenever I reopen the app or go to another page and come back to the page that has switch

@property (strong, nonatomic) IBOutlet UISwitch *switch1;
@property (strong, nonatomic) IBOutlet UISwitch *switch2;
@property (strong, nonatomic) IBOutlet UISwitch *switch3;

I have 3 switches and I have 3 IBOutlets for them. I have tried some codes to save the state but it did not work. How can I get them to work?

Answer 1

You need to do two things:

1: Save the state of the switch when it changes:

-(IBAction) switchChanged:(UISwitch *)sender {
    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
    [defaults setBool:sender.isOn forKey:@"MySwitch"];
}

2: Fetch the state of the switch when your view controller loads:

-(void) viewDidLoad {
    [super viewDidLoad];
    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
    switch1.isOn = [defaults boolForKey:@"MySwitch"];
}

Answer 2

You can solve it by storing their states locally and checking the stored value every time you present the UISwitch .

Swift 4:

UserDefaults.standard.set(<#Switch#>.isOn, forKey: "switch_name_here")

let value = UserDefaults.standard.value(forKey: "switch_name_here")

// Then you compare if value == true and set <#Switch#>.isOn = /* stored state */

Objective C:

NSString *valueToSave = @"YES"; // or "NO" if switch is off.
[[NSUserDefaults standardUserDefaults] setObject:valueToSave forKey:@"switch_name_here"];
[[NSUserDefaults standardUserDefaults] synchronize];

NSString *savedValue = [[NSUserDefaults standardUserDefaults] stringForKey:@"switch_name_here"];

// Then you compare to "YES" or "NO" and set [<#Switch#> setOn: /* stored state */]

Note:

After you get the stored value, you update the UISwitch state. You should store their values remotely if you have a login/register system or if you want this data to be updated in multiple devices.