Xamarin Forms DataBinding 不会更新

Question

我正在为 DataBindings 苦苦挣扎。我有一个包含项目的 ListView（显示正确），我需要能够编辑列表中的项目。

我选择了一个项目，该项目使用所选项目的信息打开一个模式（工作正常）（工作正常）。当我点击保存时，该项目未更新 - 显示未更新，但如果我再次选择该项目，则数据正确保存。

我有以下对象：

 public class Investigation : IDisposable
 {
     public List<InjuredPerson> InjuredPersonnel { get; set; }
     ...
 }

我的 ViewModel 是这样的：

public class InvestigateUtilityDamagesViewModel : INotifyPropertyChanged
{
    Investigation investigation;
    private InvestigateDamages damage;

    public event PropertyChangedEventHandler PropertyChanged;

    public InvestigateUtilityDamagesViewModel(InvestigateDamages damage)
    {
        this.damage = damage;
        Investigation = new Investigation();
        Investigation.DamageID = damage.DamageID;
        Investigation.InjuredPersonnel = damage.DamageDetails.InjuredPersonnel;
    }

    public Investigation Investigation
    {
        get { return investigation; }
        set
        {
            if (investigation == value)
            {
                return;
            }
            investigation = value;
            OnPropertyChanged("Investigation");
        }
    }

    void OnPropertyChanged(string propertyName)
    {
        PropertyChangedEventHandler handler = PropertyChanged;
        if (handler != null)
            handler(this, new PropertyChangedEventArgs(propertyName));
        SaveInvestigation();
    }
}

XAML：

 <ListView ItemsSource="{Binding Investigation.InjuredPersonnel, Mode=TwoWay}">
...

更新信息的页面发送消息如下：（工作正常）

MessagingCenter.Send<EditInjuredPerson, InjuredPerson>(this, "InjuredPersonEdited", _injuredPerson);

接收方（工作正常）

private void SaveInjuredPerson(EditInjuredPerson sender, InjuredPerson InjuredPerson)
    {
        var Injured = this.FindByName<ListView>("listInjuries").SelectedItem as InjuredPerson;
        if (Injured != null)

        {
            Injured.Name = InjuredPerson.Name;
            Injured.Position = InjuredPerson.Position;
            Injured.ContactNumber = InjuredPerson.ContactNumber;
            Injured.Injury = InjuredPerson.Injury;
            Injured.NextOfKinName = InjuredPerson.NextOfKinName;
            Injured.NextOfKinNumber = InjuredPerson.NextOfKinNumber;
        }
    }

Answer 1

InjuredPersonnel 列表需要在其上引发的 OnProprertyChanged 事件，而不是调查（或除此之外）。

或者，将 List 转换为 ObservableCollection。

public List<InjuredPerson> InjuredPersonnel { get; set; }

变成

public ObservableCollection<InjuredPerson> InjuredPersonnel { get; set; }

Here is a related thread.

public class Investigation : IDisposable, INotifyPropertyChanged
     {
         private List<InjuredPerson> _injuredPersonnel;
         public List<InjuredPerson> InjuredPersonnel  { 
            get {
                return _injuredPersonnel;
            } 
            set
            {
                _injuredPersonnel = value;
                OnPropertyChanged("InjuredPersonnel");
            }
         }
         ...
     }