c# - Xamarin：Android / iOS 的不同行为（静态类？）
问题描述
我正在接管 Xamarin 上的一个项目。它适用于android，我希望它适用于iOS。
最初，它已经完成了，所以我希望它可能只适用于设置？
无论如何，它适用于Android，但不适用于iOS。
我有这个代码：
public App()
{
Debug.WriteLine(Current.Properties); //return default value
try
{
ViewModelLocator.MainViewModel.RestoreState(Current.Properties);
BindingContext = ViewModelLocator.MainViewModel;
MainTabPage = new SGC400Tab();
MainPage = MainTabPage;
}
catch (Exception ex)
{
Debug.WriteLine(ex);
}
}
public static class ViewModelLocator
{
private static GlobalViewModel _myViewModel = new GlobalViewModel();
public static GlobalViewModel MainViewModel
{
get
{
return _myViewModel;
}
}
}
public class GlobalViewModel : INotifyPropertyChanged
{
public void RestoreState(IDictionary<string, object> dictionary)
{
Thing1.SelectedUnitySystem_Presure = GetDictionaryEntry(dictionary, "SavedUnitySystem_Pression", "Bars");
Thing1.SelectedUnitySystem_Flow = GetDictionaryEntry(dictionary, "SavedUnitySystem_Debit", "m3/h");
Thing1.SelectedUnitySystem_Temperature = GetDictionaryEntry(dictionary, "SavedUnitySystem_Temperature", "°C");
Thing1.SelectedLanguageKey = GetDictionaryEntry(dictionary, "SavedLanguage", "en");
}
}
返回错误：
System.NullReferenceException 上线：
private static GlobalViewModel _myViewModel = new GlobalViewModel();
我对它在android上工作的事实有点困惑......但在iOS上却不行......
我不得不说我对 Xamarin 很陌生，你能给我一些指导吗？
先感谢您 ！
PS：类 GlobalViewModel 在这里：
public class GlobalViewModel : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
//#####################################
//Enneigeur
public Enneigeur _Enneigeur1 = new Enneigeur();
public Enneigeur Enneigeur1
{
get { return _Enneigeur1; }
set
{
_Enneigeur1 = value;
}
}
//Com
public ComSGC400 _comSGC400 = new ComSGC400();
public ComSGC400 ComSGC400
{
get { return _comSGC400; }
set { _comSGC400 = value; }
}
public const int TIMOUT_COM_MS = 500;
public const int DELAI_ENTRE_TRAME_MS = 1000;
//#####################################
//Bluetooth
public ObservableCollection<string> ListOfDevices { get; set; } = new ObservableCollection<string>();
public string inputBuffer;
public string SelectedBthDevice { get;set; } = "";
private bool _isConnected { get; set; } = false;
public bool IsConnected {
get { return _isConnected; }
set
{
_isConnected = value;
if (_isConnected == true)
{
((App)Application.Current).AddPages();
} else
{
((App)Application.Current).RemovePages();
}
}
}
private bool _isSelectedBthDevice { get { if (string.IsNullOrEmpty(SelectedBthDevice)) return false; return true; }}
public bool IsConnectEnabled { get { if (_isSelectedBthDevice == false) return false; return !IsConnected; }}
public bool IsDisconnectEnabled { get { if (_isSelectedBthDevice == false) return false; return IsConnected; } }
public Color ConnectBackgroundcolor { get { if (IsConnectEnabled) return Color.Green; return Color.FromRgb(48, 48, 48); } }
public Color DisconnectBackgroundColor { get { if (IsDisconnectEnabled) return Color.Red; return Color.FromRgb(48, 48, 48); } }
public bool IsConnectionInit { get { if (EtatGrafcet_loop < 2 || IsConnected == false ) return false; return true; } }
public bool IsModeManuOK { get { if (EtatGrafcet_loop >= 2 && IsConnected == true && _Enneigeur1.Manu == true) return true; return false; } }
public bool IsBoutonRotaOK { get { if (EtatGrafcet_loop >= 2 && IsConnected == true && ( _Enneigeur1._VersionSGC400 > 10213 || _Enneigeur1.Manu == true)) return true; return false; } }
public bool IsPickerEnabled { get { return !IsConnected; }}
public bool IsBalayageDispo { get { if (EtatGrafcet_loop < 2 || IsConnected == false || _Enneigeur1.OptionBalayageDispo == false) return false; return true; } }
public LocalizedResources Resources { get; private set;}
public Color Mode_Manu_Button_Text_Color
{
get
{
if (EtatGrafcet_loop < 2)
return Color.Gray;
else
return Color.White;
}
}
public Color Mode_Manu_Button_Color {
get {
if (EtatGrafcet_loop < 2)
return Color.FromRgb(48, 48, 48);
else
{
if (_Enneigeur1.ModeMarche == 1) return Color.Green; return Color.Black;
}
}
}
public Color Mode_Stop_Button_Text_Color
{
get
{
if (EtatGrafcet_loop < 2)
return Color.Gray;
else
return Color.White;
}
}
public Color Mode_Stop_Button_Color {
get
{
if (EtatGrafcet_loop < 2)
return Color.FromRgb(48, 48, 48);
else
{
if (_Enneigeur1.ModeMarche == 2) return Color.Green; return Color.Black;
}
}
}
public Color Mode_Forcage_Button_Text_Color
{
get
{
if (EtatGrafcet_loop < 2)
return Color.Gray;
else
return Color.White;
}
}
public Color Mode_Forcage_Button_Color
{
get
{
if (EtatGrafcet_loop < 2)
return Color.FromRgb(48, 48, 48);
else
{
if (_Enneigeur1.ModeMarche == 0) return Color.Green; return Color.Black;
}
}
}
private CancellationTokenSource _ct { get; set; }
private int EtatGrafcet_loop { get; set; }
private DateTime timer_send = DateTime.Now;
private bool envoiContinu = false;
private string envoiWrite = "";
private async Task Loop()
{
string bufferEnvoi = "";
bool res;
int erreur_cryptage = 0;
EtatGrafcet_loop = 0;
int reponseLen = 0;
_Enneigeur1.ResetValues();
_ct = new CancellationTokenSource();
ComSGC400.AddrSGC400 = Convert.ToUInt16(SelectedBthDevice.Substring(5));
while (_ct.IsCancellationRequested == false)
{
switch (EtatGrafcet_loop)
{
case 0://Envoi trame clé crypté
if (DateTime.Now > timer_send.AddMilliseconds(DELAI_ENTRE_TRAME_MS)) //Temps entre trames
{
//Test d'echange de clé de cryptage
inputBuffer = "";
reponseLen = ComSGC400.Create_Trame_getKey(ref bufferEnvoi);
if (bufferEnvoi.Length > 0)
{
Xamarin.Forms.MessagingCenter.Send<App, string>((App)Xamarin.Forms.Application.Current, "WriteDatas", bufferEnvoi);
timer_send = DateTime.Now;
EtatGrafcet_loop = 1;
}
}
break;
case 1: //attente reception clé crypté
if (DateTime.Now > timer_send.AddMilliseconds(TIMOUT_COM_MS)){ EtatGrafcet_loop = 0; break; } //timeout
if (inputBuffer != null)
{
ComSGC400.Trame_RechercheDebutTrame(ref inputBuffer);
if (inputBuffer.Length >= reponseLen)
{
inputBuffer = inputBuffer.Substring(0, reponseLen);
res = ComSGC400.Update_ProtectionKey( inputBuffer);
if (res == true)
{
//cle cryptage OK
bufferEnvoi = "";
EtatGrafcet_loop = 2;
erreur_cryptage = 0;
}
else
{
//cle cryptage non ok
bufferEnvoi = "";
EtatGrafcet_loop = 0;
}
inputBuffer = "";
}
}
break;
case 2: //envoi trame readMain
if (envoiWrite != "")
EtatGrafcet_loop = 10; //envoi write
else
{
if (DateTime.Now > timer_send.AddMilliseconds(DELAI_ENTRE_TRAME_MS)) //Temps entre trames
{
reponseLen = ComSGC400.Create_Trame_ReadMain(ref bufferEnvoi);
if (bufferEnvoi.Length > 0)
{
inputBuffer = "";
Xamarin.Forms.MessagingCenter.Send<App, string>((App)Xamarin.Forms.Application.Current, "WriteDatas", bufferEnvoi);
timer_send = DateTime.Now;
EtatGrafcet_loop = 3;
}
}
}
break;
case 3: //attente reponse trame readMain
if (DateTime.Now > timer_send.AddMilliseconds(TIMOUT_COM_MS)) {
EtatGrafcet_loop = 20; break;
} //timeout
if (inputBuffer != null)
{
ComSGC400.Trame_RechercheDebutTrame(ref inputBuffer);
if (inputBuffer.Length >= reponseLen)
{
inputBuffer = inputBuffer.Substring(0, reponseLen);
res = ComSGC400.Update_Enneigeur( inputBuffer, ref _Enneigeur1);
if (res == true)
{
//Message OK
bufferEnvoi = "";
EtatGrafcet_loop = 4;//Passage readCom
erreur_cryptage = 0;
_Enneigeur1.LastRead = DateTime.Now;
}
else
{
//Message NON OK
EtatGrafcet_loop = 20;
}
inputBuffer = "";
}
}
break;
case 4: //envoi trame readCom
if (envoiWrite != "")
EtatGrafcet_loop = 10; //envoi write
else
{
if (DateTime.Now > timer_send.AddMilliseconds(50)) //Temps entre trames
{
reponseLen = ComSGC400.Create_Trame_ReadCom(ref bufferEnvoi);
if (bufferEnvoi.Length > 0)
{
inputBuffer = "";
Xamarin.Forms.MessagingCenter.Send<App, string>((App)Xamarin.Forms.Application.Current, "WriteDatas", bufferEnvoi);
timer_send = DateTime.Now;
EtatGrafcet_loop = 5;
}
}
}
break;
case 5: //attente reponse trame readCom
if (DateTime.Now > timer_send.AddMilliseconds(TIMOUT_COM_MS)) {
EtatGrafcet_loop = 21; break;
} //timeout
if (inputBuffer != null)
{
ComSGC400.Trame_RechercheDebutTrame(ref inputBuffer);
if (inputBuffer.Length >= reponseLen)
{
inputBuffer = inputBuffer.Substring(0, reponseLen);
res = ComSGC400.Update_Enneigeur( inputBuffer, ref _Enneigeur1);
if (res == true)
{
//Message OK
bufferEnvoi = "";
EtatGrafcet_loop = 2; //Retour read main
erreur_cryptage = 0;
_Enneigeur1.LastRead = DateTime.Now;
if (_Enneigeur1.Reset)
Send_value_bluetooth("reset", false);
}
else
{
//Message NON OK
EtatGrafcet_loop = 21;
}
inputBuffer = "";
}
}
break;
case 10: //envoi trame Write
inputBuffer = "";
Xamarin.Forms.MessagingCenter.Send<App, string>((App)Xamarin.Forms.Application.Current, "WriteDatas", envoiWrite);
timer_send = DateTime.Now;
EtatGrafcet_loop =11;
break;
case 11: //attente reponse trame Write
if (DateTime.Now > timer_send.AddMilliseconds(TIMOUT_COM_MS)) { EtatGrafcet_loop = 20; break; } //timeout
if (inputBuffer != null)
{
ComSGC400.Trame_RechercheDebutTrame(ref inputBuffer);
if (inputBuffer.Length >= 16)
{
bufferEnvoi = "";
if (envoiContinu)
{
EtatGrafcet_loop = 10; //envoi continu
}
else
{
envoiWrite = "";
EtatGrafcet_loop = 2; //Retour read main
}
erreur_cryptage = 0;
_Enneigeur1.LastWrite = DateTime.Now;
inputBuffer = "";
}
}
break;
case 20://Erreur de reception trame readMain
bufferEnvoi = "";
erreur_cryptage = erreur_cryptage + 1;
envoiWrite = "";
if (erreur_cryptage > 3)
{
_Enneigeur1.ResetValues();
erreur_cryptage = 0;
EtatGrafcet_loop = 0;
}
else
{
EtatGrafcet_loop = 2;
}
break;
case 21://Erreur de reception trame readCom
bufferEnvoi = "";
erreur_cryptage = erreur_cryptage + 1;
envoiWrite = "";
if (erreur_cryptage > 3)
{
_Enneigeur1.ResetValues();
erreur_cryptage = 0;
EtatGrafcet_loop = 0;
}
else
{
EtatGrafcet_loop = 4;
}
break;
default:
EtatGrafcet_loop = 0;
break;
}
await Task.Delay(10);
}
EtatGrafcet_loop = 0;
}
public void Send_value_bluetooth(string nom_param, bool value)
{
if (value == true) Send_value_bluetooth( nom_param, 1); else Send_value_bluetooth(nom_param, 0);
}
public void Send_value_bluetooth(string nom_param, double value)
{
//la modif de Enneigeur1 entraine l'envoi d'une trame WRITE en bluetooth (si la liaison est OK)
string bufferEnvoi = "";
if (EtatGrafcet_loop >= 2)
{
switch(nom_param.ToLower())
{
Cases...
}
}
}
public void ExitApp()
{
// Disconnect from bth device
DependencyService.Get<IBtInterface>().Disconnect();
MessagingCenter.Unsubscribe<App, string>(this, "ReadDatas");
IsConnected = false;
if (_ct != null)
{
System.Diagnostics.Debug.WriteLine("Send a cancel to task!");
_ct.Cancel();
}
}
public GlobalViewModel()
{
Resources = new LocalizedResources(typeof(AppResources), Enneigeur1._SelectedLanguageKey
);
MessagingCenter.Subscribe<App>(this, "Sleep", (obj) =>
{
// When the app "sleep", I close the connection with bluetooth
if (IsConnected)
DependencyService.Get<IBtInterface>().Disconnect();
});
MessagingCenter.Subscribe<App>(this, "Resume", (obj) =>
{
// When the app "resume" I try to restart the connection with bluetooth
if (IsConnected)
DependencyService.Get<IBtInterface>().Connect(SelectedBthDevice);
});
this.InitCommand = new Command(() =>
{
// Try to connect to a bth device
DependencyService.Get<IBtInterface>().Init();
});
this.ConnectCommand = new Command(() =>
{
EtatGrafcet_loop = 0;
// Try to connect to a bth device
IsConnected = DependencyService.Get<IBtInterface>().Connect(SelectedBthDevice);
//second essai
if (IsConnected == false) IsConnected = DependencyService.Get<IBtInterface>().Connect(SelectedBthDevice);
if (IsConnected == true)
{
// initialisation des echange de données
MessagingCenter.Subscribe<App, string>(this, "ReadDatas", (sender, arg) =>
{
//inputBuffer = inputBuffer + arg;
inputBuffer = inputBuffer + arg;
});
Task.Run(async () => Loop());
}else
{
//erreur aux 2 tentatives de connection
//Task.Run(async () => ((App)Application.Current).OpenTextBoxDialog());
((App)Application.Current).OpenTextBoxDialog();
}
});
this.DisconnectCommand = new Command(() =>
{
EtatGrafcet_loop = 0;
ExitApp();
});
this.RefreshListDeviceCommand = new Command(() =>
{
try
{
ListOfDevices = DependencyService.Get<IBtInterface>().PairedDevices();
}
catch (Exception ex)
{
Application.Current.MainPage.DisplayAlert("Attention", ex.Message, "Ok");
}
});
// At startup, I load all paired devices
try
{
ListOfDevices = DependencyService.Get<IBtInterface>().PairedDevices();
}
catch (Exception ex)
{
Application.Current.MainPage.DisplayAlert("Attention", ex.Message, "Ok");
}
}
private object Await(App current)
{
throw new NotImplementedException();
}
public ICommand InitCommand { get; protected set; }
public ICommand ConnectCommand { get; protected set; }
public ICommand DisconnectCommand { get; protected set; }
public ICommand RefreshListDeviceCommand { get; protected set; }
public void SaveState(IDictionary<string, object> dictionary)
{
dictionary["SavedLanguage"] = Enneigeur1._SelectedLanguageKey;
dictionary["SavedUnitySystem_Pression"] = Enneigeur1.SelectedUnitySystem_Presure;
dictionary["SavedUnitySystem_Debit"] = Enneigeur1.SelectedUnitySystem_Flow;
dictionary["SavedUnitySystem_Temperature"] = Enneigeur1.SelectedUnitySystem_Temperature;
}
public void RestoreState(IDictionary<string, object> dictionary)
{
Enneigeur1.SelectedUnitySystem_Presure = GetDictionaryEntry(dictionary, "SavedUnitySystem_Pression", "Bars");
Enneigeur1.SelectedUnitySystem_Flow = GetDictionaryEntry(dictionary, "SavedUnitySystem_Debit", "m3/h");
Enneigeur1.SelectedUnitySystem_Temperature = GetDictionaryEntry(dictionary, "SavedUnitySystem_Temperature", "°C");
Enneigeur1.SelectedLanguageKey = GetDictionaryEntry(dictionary, "SavedLanguage", "en");
}
public T GetDictionaryEntry<T>(IDictionary<string, object> dictionary,
string key, T defaultValue)
{
if (dictionary.ContainsKey(key))
return (T)dictionary[key];
return defaultValue;
}
}
解决方案
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