如何从 C# 中的另一个 class 调用变量（移动应用程序）

Question

I'm working on Visual Studio 2019. I have a variable named "batt_lev" which is in BatteryAlert.Android -> BatteryService1.cs I need to call this variable in the shared code in MainPage.xaml.cs in a method named "void Etichetta()" where i have to use the variable. I tried to use BatteryService1.batt_lev, as you can see, but the error is "no BatteryService1 in this context".

Can someone help me?

MainPage.xaml.cs in the shared code

namespace BatteryAlert
{
    public partial class MainPage : ContentPage
    {
        private double batt_lev;
        


        public MainPage()
        {
            
            InitializeComponent();
            DependencyService.Get<IUpLoad>().upLoad();
            //Etichetta();
            //DependencyService.Get<IAndroidService>().StartServicee();
            //Battery.BatteryInfoChanged += Battery_BatteryInfoChanged;
            

        }

        void Etichetta()
        {
            
            //Battery.BatteryInfoChanged += Battery_BatteryInfoChanged;
 
            batt_lev = (float)Battery.ChargeLevel;
            CounterLabel.Text = BatteryService1.batt_lev.ToString("N2");
        }
    }
}

BatteryService1.cs in BatteryAlert.Android

namespace BatteryAlert.Droid
{
    [Service(Name = "com.companyname.BatteryAlert.BatteryService1")]
    public class BatteryService1 : JobIntentService
    {
        private static int MY_JOB_ID = 1000;
        public double batt_lev;
        List<double> valoreControllo = new List<double>()
        {
            0.65, 0.60, 0.55, 0.50, 0.45, 0.40, 0.35, 0.30, 0.25, 0.20, 0.15, 0.10, 0.05
        };


        protected override void OnHandleWork(Intent p0)
        {
            Device.StartTimer(new TimeSpan(0, 0, 10), () =>
            {
                // do something every 10 seconds
                Battery.BatteryInfoChanged += Battery_BatteryInfoChanged;
                //DependencyService.Get<IAudio>().PlayAudioFile("suono_123.wav");
                return true; // runs again, or false to stop
            });
            
        }

        public static void EnqueueWork(Context context, Intent work)
        {
            Java.Lang.Class cls = Java.Lang.Class.FromType(typeof(BatteryService1));

            try
            {
                EnqueueWork(context, cls, MY_JOB_ID, work);
            }
            catch (Exception ex)
            {
                Console.WriteLine("Exception: {0}", ex.Message);
            }

        }

        void Battery_BatteryInfoChanged(Object sender, BatteryInfoChangedEventArgs e)
        {
            batt_lev = (double)e.ChargeLevel;
            batt_lev = Math.Round(batt_lev, 2);

            if (valoreControllo.Contains(batt_lev))
            {
                //CounterLabel.Text = batt_lev.ToString("N2");
                DependencyService.Get<IAudio>().PlayAudioFile("suono_123.wav");
            }

        }
    }
}

Answer 1

If you want to access a variable from another class you should have that class being derived for the class you want to use it.

public partial class MainPage : ContentPage

If you want to still have the MainPage derived for the ContentPage you should derive the class you want (BatteryService1) to the ContentPage or vice-versa. Like this:

public class ContentPage : BatteryService1