Question

我的android视图中有三个MvxSpinners。这些微调器绑定到三个不同的列表。对于这些微调器，数据绑定模式是TwoWay。当这个观点是显示时，所有这三个微调器都会显示预定义值。

When user change the value in first spinner,then second spinner will be clear and  
get loaded with new values based on the selected value in first spinner.

我怎样才能做到这一点？

Answer 1

有很多方法可以实现这一点，代码放置真的取决于你。总体而言，我们的想法是拥有一个“SelectedItem”对象，您可以将其传递给您的方法并“加载”下一个List。

请记住，此代码是更传统的MVVM，但可以轻松转换为MVVMCross等效。我相信所有这些类型都应该得到MVVMCross的支持。

        private MyFirstObject _selectedFirstObject;

        public MyFirstObject SelectedFirstObject
        {
            get { return _selectedFirstObject; }
            set
            {
                _selectedFirstObject = value;
                RaisePropertyChanged("SelectedFirstObject");
                if(value != null)
                LoadMySecondObjects(value);
            }

        }

        private ObservableCollection<MyFirstObject> _myFirstObjects;

        public ObservableCollection<MyFirstObject> MyFirstObjects
        {
            get { return _myFirstObjects; }
            set
            {
                _myFirstObjects = value;
                RaisePropertyChanged("MyFirstObjects");
            }
        }

        private ObservableCollection<MySecondObject> _mySecondObjects;

        public ObservableCollection<MySecondObject> MySecondObjects
        {
            get { return _mySecondObjects; }
            set
            {
                _mySecondObjects = value;
                RaisePropertyChanged("MySecondObjects");
            }
        }

        public void LoadMySecondObjects(MyFirstObject current)
        {
           //Wherever you're pulling data from
           MySecondObjects = MyDataService.GetAll(current);
        }

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

        public event PropertyChangedEventHandler PropertyChanged;

Answer 2

我遇到了同样的问题但是只有在你的ItemsSource中添加空值（作为默认值）并尝试将SelectedItem重置为null时。 SelectedItem在ViewModel中更改，但不在微调器中更改。在那种情况下有很多解决方案，但我使用消息来通知View设置所选项目

public class SpinnerSelectionChanged : MvxMessage
{
    public SpinnerSelectionChanged(object sender, string spinnerName, int position): base(sender)
    {
        SpinnerName = spinnerName;
        Position = position;
    }

    public string SpinnerName { get; set; }
    public int Position { get; set; }
}

在视图

中

private void OnSpinnerSelectionChanged(SpinnerSelectionChanged obj)
{
    switch (obj.SpinnerName)
    {
        case "City":
            _spinnerCity.SetSelection(obj.Position);
            break;
        case "Office":
            _spinnerOffice.SetSelection(obj.Position);
            break;
    }
}

Mvvminner中的MvxSpinner

2 个答案: