在打开页面之间传递参数的最佳实践

Question

我正在开发一个有两个页面的Windows应用程序(UWP),我希望在页面之间传递参数的最佳实践.

这是我的情景:

我们有两个页面,每个页面都打开并保留在屏幕中间,每个页面上都有一个按钮,当我们点击它时,它会将消息发送到另一个页面.

我也想连续不断地传递信息.

在Page1.cs中:

     Page2 page2;
         public Page1()
                {
                    this.InitializeComponent();         
                    CreatPage2();
                }

         // creat page 2
           private async void CreatPage2()
                {
                    var NewWindow = CoreApplication.CreateNewView();
                    int NewWindowid = 0;

                    await NewWindow.Dispatcher.RunAsync(CoreDispatcherPriority.High, () =>
                    {
                        Frame newframe = new Frame();
                        newframe.Navigate(typeof(Page2), this);
                        Window.Current.Content = newframe;
                        Window.Current.Activate();
                        ApplicationView.GetForCurrentView().Title = "page2";
                        NewWindowid = ApplicationView.GetForCurrentView().Id;
                    });

                    await Windows.UI.ViewManagement.ApplicationViewSwitcher.TryShowAsStandaloneAsync(NewWindowid);
                }

                //Button


     private void ChangeP2_Click(object sender, RoutedEventArgs e)
                {
                  // send a message to the texblock in the page2
        page2.TexBlock2.Text=$"From page1 :{e.ToString()}";
// change  text color of the texblock in the page2
page2.Foreground= new SolidColorBrush(Windows.UI.Colors.Red);
                }

在Page2.cs中:

  Page1 page1;
    protected override void OnNavigatedTo(NavigationEventArgs e)
    {
        page1 = e.Parameter as Page1;
        base.OnNavigatedTo(e);
    }

    public Page2()
    {
        this.InitializeComponent();         
    }



    //Button
     private void ChangeP1_Click(object sender, RoutedEventArgs e)
    {
// send a message to the texblock in the page1
      page1.TexBlock1.Text=$"From page2 :{e.ToString()}";
// change  text color of the texblock in the page1
page1.Foreground= new SolidColorBrush(Windows.UI.Colors.Red);
    }

上面的代码只适用于page2到page1.(它可以改变pagea的文本块).请帮助我,我找不到两页工作的解决方案

Answer 1

Naah ......最好的方法是使用由应用程序ViewModel类组成的标准模式,该类包含您要在逻辑层中使用的所有常见应用程序数据.

我总是这样做:

1)我使用自动创建的MainPage作为应用程序的"shell",其属性为AppViewModel.AppViewModel通过将自己设置为自己类中的静态字段,可以从应用程序中的任何位置访问MainPage(以及因此).

这是代码,比你想象的更简单:

public sealed partial class MainPage : Page
{
    public AppViewModel ViewModel { get; set; } = new AppViewModel();
    public static MainPage Current { get; set; }

    public MainPage()
    {
        this.InitializeComponent();
        Current = this;
    }
}

2)将AppViewModel本身是必须实现一类INotifyPropertyChanged接口,以便使可绑定属性和功能.在开发人员中,通常创建一个实现它的基类,然后从中派生出需要可绑定属性的所有类.

这里是:

public class BaseBind : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;

    public void OnPropertyChanged([CallerMemberName] string propertyName = null) =>
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));

    protected bool SetProperty<T>(ref T storage, T value,
        [CallerMemberName] String propertyName = null)
    {
        if (object.Equals(storage, value)) return false;
        storage = value;
        OnPropertyChanged(propertyName);
        return true;
    }
}

然后从中派生AppViewModel类(以及所有其他模型和视图模型类)...使用您需要跨页面共享的所有常见属性填充它.我甚至添加了一个派生属性,以显示如何一次共享多个数据类型,以及一个函数:

public class AppViewModel : BaseBind
{
    public AppViewModel()
    {
        // ...
    }

    // All common app data
    private string sampleCommonString;
    public String SampleCommonString
    {
        get { return sampleCommonString; }
        set { SetProperty(ref sampleCommonString, value); OnPropertyChanged(nameof(SampleDerivedProperty1)); OnPropertyChanged(nameof(SampleDerivedProperty2)); }
    }

    public String SampleDerivedProperty1 =>  "return something based on SampleCommonString";

    public String SampleDerivedProperty2
    {
        get
        {
            <<evaluate SampleCommonString>>
            return "Same thing as SampleDerivedProperty1, but more explicit";
        }
    }

    // This is a property that you can use for functions and internal logic… but it CAN'T be binded
    public String SampleNOTBindableProperty { get; set; }

    public void SampleFunction()
    {
        // Insert code here.

        // The function has to be with NO parameters, in order to work with simple {x:Bind} markup.
        // If your function has to access some specific data, you can create a new bindable (or non) property, just as the ones above, and memorize the data there.
    }
}

3)然后,为了从另一个访问所有这些Page,只需AppViewModel在该页面中创建一个字段,如下所示:

public sealed partial class SecondPage : Page
{
    public AppViewModel ViewModel => MainPage.Current.ViewModel;

    public SecondPage()
    {
        this.InitializeComponent();
    }
}

...并且您可以轻松地将XAML控件属性绑定到AppViewModel自身:

<TextBlock Text="{x:Bind ViewModel.SampleCommonString, Mode=OneWay}"/>
<Button Content="Sample content" Click="{x:Bind ViewModel.SampleFunction}"/>

(Mode=OneWay用于实时绑定,以便即使在UI中也立即更新属性,同时Mode=TwoWay用于可以由控件本身由用户编辑的那些属性,以便与app逻辑交互).

希望这有帮助.

最好的问候和新年快乐.