Question

使用WPF MVVM，我有一个主窗口和几个usercontrol。基于按钮单击我显示视图和视图模型。当我点击主窗口中的按钮时，我可以导航到不同的视图。因为导航命令仅在主窗口视图模型中。但当我在不同的视图（用户控制）。我如何从viewmodel导航。

MainwindowViewmodel

private void setFragment(int grpPos, int childPos, String fragmentName, boolean isDrawerToBeClosed) {
        try {
            imgHome.setVisibility(View.GONE);
            switch (grpPos) {
                case 0:
                    callHomeFragment();
                    break;
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

private void callHomeFragment() {
        try {
            FragmentManager fragmentManager = getSupportFragmentManager();
            Fragment fragmentExisting = fragmentManager.findFragmentByTag(
                    getResources().getString(R.string.menu_home));
            if (fragmentExisting != null) {
                Fragment Home = fragmentManager.findFragmentByTag(getResources().getString(R.string.menu_home));
                if (fragmentExisting.equals(Home)) {
                    Fragment fragment2 = new HomeFragment();
                    fragmentManager.beginTransaction().replace(R.id.fragment_content_frame, fragment2,
                            getResources().getString(R.string.menu_home)).commit();
                }
                showFragment(fragmentExisting, fragmentManager);
                drawer.closeDrawer(GravityCompat.START);
            } else {
                Fragment fragment = new HomeFragment();
                fragmentManager.beginTransaction().replace(R.id.fragment_content_frame, fragment,
                        getResources().getString(R.string.menu_home)).commit();
                drawer.closeDrawer(GravityCompat.START);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

private void showFragment(Fragment fragmentExisting, FragmentManager fragmentManager) {
        FragmentManager fragmentManagerInternal = getSupportFragmentManager();
        for (int i = 0; i < fragmentManagerInternal.getBackStackEntryCount(); ++i) {
            fragmentManagerInternal.popBackStack();
        }
        fragmentManagerInternal.popBackStack(null, FragmentManager.POP_BACK_STACK_INCLUSIVE);

        try {
            List<Fragment> fragments = fragmentManager.getFragments();
            if (fragments != null && fragments.size() > 0) {
                for (int i = 0; i < fragments.size(); i++) {
                    if (fragments.get(i) != null) {
                        fragmentManager.beginTransaction().hide(fragments.get(i)).commit();
                    }
                }
            }
            fragmentManager.beginTransaction().show(fragmentExisting).commit();
        } catch (Exception exception) {
//            ((MyApplication) getApplicationContext()).printStackTrace(exception);
        }
    }

RegisterViewModel

 public class MainWindowViewModel : BindableBase, INotifyPropertyChanged
{

    private StudyViewModel _studyViewModel = new StudyViewModel();
    private ImageCaptureViewModel _imageCaptureViewModel = new ImageCaptureViewModel();
    private RegisterViewModel _registerViewModel = new RegisterViewModel();

    private BindableBase _CurrentViewModel;

    public BindableBase CurrentViewModel
    {
        get { return _CurrentViewModel; }
        set { SetProperty(ref _CurrentViewModel, value); OnPropertyChanged("_CurrentViewModel"); }
    }

    public MainWindowViewModel()
    {
        NavCommand = new RelayCommand<string>(onNav);
        onNav("study");
    }

   //This is the command am using in xaml to redirect view.
    public RelayCommand<string> NavCommand { get; private set; }

    private void onNav(string destination)
    {
        switch (destination)
        {
            case "study":
                CurrentViewModel = _studyViewModel;
                break;
            case "capture":
                CurrentViewModel = _imageCaptureViewModel;
                break;
            case "register":
                CurrentViewModel = _registerViewModel;
                break;
            default:
                CurrentViewModel = _studyViewModel;
                break;
        }
    }
}

当在鼠标事件中添加命令时，它正在重定向。但我不知道如何从viewmodel重定向

RegisterView.xaml

  public void RegisterPatient(string action)
    {
        if (action == "addnew")
        {

        }
        else
        {
            if (StartImaging)
            {
                //Have to redirect to other screen.

            }
        }
        var a = PatientToAdd;
        MessageBox.Show("triggered");
    }

Answer 1

你的问题不够明确，所以这是基于我认为你需要的。

主窗口：

<Window x:Class="MyApp.MainWindow" ...>
...
    <ContentControl Content={Binding MyCurrentViewModel}>
        <ContentControl.Resources>
            <DataTemplate DataType={x:Type vm:UserListViewModel}>
                <view:UserListView />
            </DataTemplate>
            <DataTemplate DataType={x:Type vm:AnotherViewModel}>
                <view:AnotherView />
            </DataTemplate>
            ...
        </ContentControl.Resources>
    </ContentControl>
</Window>

MainViewModel：

private ViewModelBase _myCurrentViewModel;
public ViewModelBase MyCurrentViewModel
{
    get { return _myCurrentViewModel; }
    set
    {
        if (value != _myCurrentViewModel)
        {
            _myCurrentViewModel = value;
            RaisePropertyChanged("MyCurrentViewModel");
        }
    }
}

UserListViewModel：

public class UserListViewModel : ViewModelBase
{
    private MainViewModel MainVM;
    public UserListViewModel(MainViewModel mainVM)
    {
        this.MainVM = mainVM;
    }

    private ICommand _myCommand;
    public ICommand MyCommand
    {
        get
        {
            if (_myCommand = null)
                _myCommand = new RelayCommand(MyExecuteDelegate, true);
            return _myCommand;
        }
    }
    private void MyExecuteDelegate(object parameter)
    {
        // My other logic
        if (this.MainVM != null)
            this.MainVM.MyCurrentViewModel = new AnotherViewModel();
    }
}

从Viewmodel的WPF MVVM视图重定向

1 个答案: