Question

我有一个tableview，在第一行中，我试图最初向detailtextlabel添加一个静态值。因此，当最初加载tableview时，detailtextlabel显示默认值。当我点击detailtextlabel时，它会切换。我添加了将默认值切换为另一个值的代码。这工作正常。这是我的代码：

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
    [tableView deselectRowAtIndexPath:indexPath animated:YES];
    cell = [tableView cellForRowAtIndexPath:indexPath];
    switch (indexPath.row) {
        case 0:
            if ([cell.detailTextLabel.text isEqualToString:@"digital"]) {
                cell.detailTextLabel.text = @"analog";
                userdefaults = [NSUserDefaults standardUserDefaults];
                [userdefaults setObject:@"analog" forKey:@"clock"];
            }
            else {
                cell.detailTextLabel.text = @"digital";
                [userdefaults setObject:@"digital" forKey:@"clock"];
            }
            [userdefaults synchronize];
            break;

        default:
            break;
    }
}

但我的问题是当标签从数字变为模拟时，数字视图控制器（作为主窗口中的第一个标签添加）应该更改为模拟视图控制器，当模拟更改为数字时，数字视图控制器应由第一个选项卡中的模拟视图控制器替换。

//在appdidfinish启动时我已完成此代码，但它不会在运行时更改标签栏。

NSString *clockswitch = [[NSUserDefaults standardUserDefaults]objectForKey:@"clock"];
if ([clockswitch isEqualToString:@"digital"]) {
    DigitalClockViewController *dig = [[DigitalClockViewController alloc]init];
    //self.tabBarController.selectedViewController = [self.tabBarController.viewControllers objectAtIndex:0];
}
else
{
    AnalogClockViewController *ana = [[AnalogClockViewController alloc]init];
    //self.tabBarController.selectedViewController = [self.tabBarController.ana objectAtIndex:0];
}

Answer 1

UITabBarController.viewControllers is an immutable array you need to make a mutable copy.

NSString *clockswitch = [[NSUserDefaults standardUserDefaults]objectForKey:@"clock"];
UIViewController *desiredController = nil;
if ([clockswitch isEqualToString:@"digital"]) {
    desiredController = [[DigitalClockViewController alloc]init];
}
else {
    desiredController = [[AnalogClockViewController alloc]init];
}
NSMutableArray *controllersCopy = [self.tabBarController.viewControllers mutableCopy];
[controllersCopy replaceObjectAtIndex:0 withObject:desiredController];
self.tabBarController.viewControllers = controllersCopy;

如何在运行时更改标签栏的选项卡

1 个答案: