Within a XAML user control, the Frame object is null:
this.Frame.Navigate(typeof(FaxPropertiesPage));
How do I navigate between pages with a Windows 8 XAML User Control? I have placed the control within a Callisto Flyout on a XAML page.
The search button below must navigate the user to another XAML page.
I've successfully used the code from app.xaml.cs
Frame frame = Window.Current.Content as Frame;
and then used the standard Navigate code.
There's the nice way and the not-so-nice way:
Both of them start with a navigation service:
public interface INavigationService
{
bool CanGoBack { get; }
void GoBack();
void GoForward();
bool Navigate<T>(object parameter = null);
bool Navigate(Type source, object parameter = null);
void ClearHistory();
event EventHandler<NavigatingCancelEventArgs> Navigating;
}
public class NavigationService : INavigationService
{
private readonly Frame _frame;
public NavigationService(Frame frame)
{
_frame = frame;
frame.Navigating += FrameNavigating;
}
#region INavigationService Members
public void GoBack()
{
_frame.GoBack();
}
public void GoForward()
{
_frame.GoForward();
}
public bool Navigate<T>(object parameter = null)
{
Type type = typeof (T);
return Navigate(type, parameter);
}
So, where do I get the Frame? In App.xaml.cs
protected async override void OnLaunched(LaunchActivatedEventArgs args)
{
// Do not repeat app initialization when already running, just ensure that
// the window is active
if (args.PreviousExecutionState == ApplicationExecutionState.Running)
{
Window.Current.Activate();
return;
}
// Create a Frame to act as the navigation context and navigate to the first page
var rootFrame = new Frame();
if (DesignMode.DesignModeEnabled)
SimpleIoc.Default.Register<INavigationService, DesignTimeNavigationService>();
else
SimpleIoc.Default.Register<INavigationService>(() => new NavigationService(rootFrame));
I'm using MVVM Light here. This makes life easy because all my viewmodels get created using dependency injection and have their services injected into them.
If you're not using something like MVVM Light and rely on code-behind then you can still make this work: Just make the navigation service static
public class NavigationService : INavigationService
{
public static INavigationService Current{
get;set;}
blah blah blah
}
And change App.xaml.cs to:
protected async override void OnLaunched(LaunchActivatedEventArgs args)
{
// Do not repeat app initialization when already running, just ensure that
// the window is active
if (args.PreviousExecutionState == ApplicationExecutionState.Running)
{
Window.Current.Activate();
return;
}
// Create a Frame to act as the navigation context and navigate to the first page
var rootFrame = new Frame();
NavigationService.Current= new NavigationService(rootFrame));
}
And you can then access your main Frame anywhere in the app by saying:
NavigationService.Current.Navigate<MyView>();
simple code ( may not be 100% efficient) is :
Frame frame = new Frame();
frame.Navigate(typeof(ExerciseAddPage)
Related
I have a requirement as follows, I want to print the screen elements present on the screen to printer. Implementation is done through MVVM. so If I click on print button on the screen it should display a print dialogue and selecting the printer should proceed with printing all the UI elemnts with their data . I have tried with solution present at print WPF visual from viewmodel but its missing the margings and not displaying properly
Also I have another button Print Preview which should display print preview dialogue to see the preiview.
Thanks in advance.
Regards,
Krishna.
In my opinion the printing of the View in an MVVM application is not the responsiblity or concern of the ViewModel. I believe you are better of doing this from the View.
How I've achieved this before is to use a WPF Behavior on a button - I use a Behavior because I'm using DataTemplates for the View and there isn't a 'code behind' file.
The Behavior exposes a DependencyProperty, this is a binding to what is to be printed or contains what is going to be printed.
XAML:
<Button Margin="0,2,5,2"
HorizontalAlignment="Right"
Content="PRINT"
ToolTip="Prints the current report">
<i:Interaction.Behaviors>
<b:ReportPrintClickBehavior Content="{Binding ElementName=SelectedReportContent, Mode=OneWay}" />
</i:Interaction.Behaviors>
</Button>
To reference the Behavior in the XAML you'll need to reference System.Windows.Interactivity, this can be found on NuGet here.
Code-Behind (Behavior):
In this case I'm printing a FlowDocument hosted inside a FlowDocumentReader.
public sealed class ReportPrintClickBehavior : Behavior<Button>
{
public static readonly DependencyProperty ContentProperty = DependencyProperty.Register("Content",
typeof(DependencyObject),
typeof(ReportPrintClickBehavior),
new PropertyMetadata(null));
public DependencyObject Content
{
get { return (DependencyObject)GetValue(ContentProperty); }
set { SetValue(ContentProperty, value); }
}
protected override void OnAttached()
{
base.OnAttached();
AssociatedObject.Loaded += OnLoaded;
AssociatedObject.Unloaded += OnUnloaded;
}
protected override void OnDetaching()
{
base.OnDetaching();
AssociatedObject.Loaded -= OnLoaded;
AssociatedObject.Unloaded -= OnUnloaded;
}
private void OnLoaded(object sender, RoutedEventArgs args)
{
AssociatedObject.Click += OnClick;
}
private void OnUnloaded(object sender, RoutedEventArgs args)
{
AssociatedObject.Click -= OnClick;
}
private void OnClick(object sender, RoutedEventArgs args)
{
var flowDocumentReader = Content.GetVisualDescendent<FlowDocumentReader>();
if (flowDocumentReader != null)
{
flowDocumentReader.Print();
}
}
}
Please help me, as I will go mad with this soon:
When I run the code, on first occasion loadNewPoint() is executed and displays some data from global variable - allPointsAndPlaces
However when I click a button (from a child class), the same method loadNewPoint() gives me null pointer for allPointsAndPlaces.
I have changed the code structure a lot from an original trying to solve this issue, and moved this method (loadNewPoint()) to a parent class to see, if it would solve the issue.
Parent class:
public class CabbieApp implements EntryPoint {
private GetLocationsServiceAsync getAllLocationsService = GWT.create(GetLocationsService.class);
CabbiePoint[] allPointsAndPlaces;
PointsQuiz quiz;
/**
* Entry point method.
*/
public void onModuleLoad() {
//Get all the required data from DB
getAllPointsAndLocations();
}
private void loadAppPages(){
// Associate the Main panel with the HTML host page.
RootPanel rootPanel = RootPanel.get("pointsList");
quiz = new PointsQuiz();
rootPanel.setStyleName("GWTapp");
rootPanel.add(quiz.getMainPanel());
loadNewPoint();
}
private void getAllPointsAndLocations() {
// Initialize the service proxy.
if (getAllLocationsService == null) {
getAllLocationsService = GWT.create(GetLocationsService.class);
}
// Set up the callback object.
AsyncCallback<CabbiePoint[]> callback = new AsyncCallback<CabbiePoint[]>() {
public void onFailure(Throwable caught) {
System.out.println(caught.getMessage());
}
public void onSuccess(CabbiePoint[] result) {
//allPointsAndPlaces = result;
System.out.println(result.length);
allPointsAndPlaces = result;
loadAppPages();
}
};
// Make the call to the service.
getAllLocationsService.getLocations(callback);
}
void loadNewPoint(){
int r = Random.nextInt(allPointsAndPlaces.length);
quiz.CurrentPlace = allPointsAndPlaces[r].getPlaceName();
quiz.CurrentLocation = allPointsAndPlaces[r].getPlaceLocation();
quiz.point.setText(quiz.CurrentPlace);
quiz.location.setText(quiz.CurrentLocation);
quiz.location.setStyleName("invisibleText");
}
}
Child class:
public class PointsQuiz extends CabbieApp{
VerticalPanel mainPanel = new VerticalPanel();
HorizontalPanel navigation = new HorizontalPanel();
TextBox point = new TextBox();
TextBox location = new TextBox();
Button showLocation = new Button("Show Location");
Button nextPoint = new Button("Next Point");
String CurrentPlace, CurrentLocation;
public PointsQuiz() {
// Assemble Add Stock panel.
navigation.add(showLocation);
navigation.add(nextPoint);
navigation.setCellHorizontalAlignment(nextPoint, HasHorizontalAlignment.ALIGN_RIGHT);
navigation.addStyleName("addPanel");
mainPanel.setSpacing(5);
mainPanel.setStyleName("body");
mainPanel.setVerticalAlignment(HasVerticalAlignment.ALIGN_MIDDLE);
mainPanel.setHorizontalAlignment(HasHorizontalAlignment.ALIGN_CENTER);
// Assemble Main panel.
mainPanel.add(point);
point.setWidth("200px");
mainPanel.add(location);
location.setWidth("200px");
mainPanel.add(navigation);
navigation.setWidth("200px");
// Move cursor focus to the input box.
showLocation.setFocus(true);
// Listen for mouse events on the show location button.
showLocation.addClickHandler(new ClickHandler() {
public void onClick(ClickEvent event) {
showCurrentLocation();}
});
// Listen for mouse events on the next point button.
nextPoint.addClickHandler(new ClickHandler() {
public void onClick(ClickEvent event) {
loadNewPoint();
}
});
}
private void showCurrentLocation(){
location.setStyleName("visibleText");
}
public VerticalPanel getMainPanel() {
return mainPanel;
}
}
I managed to find a solution to this problem with Bhumika's help.
To make this work I had to change CabbiePoint[] allPointsAndPlaces to static.
This would solve the reference problem one way - from child to parent.
Also I managed to find out trough debugging, that this reference
quiz = new PointsQuiz();
is also null on a second run of loadNewPoint(). So this child reference (PointsQuiz quiz;) and any other references to children were set also to static.
You are getting null pointer error because of allPointsAndPlaces is null. As per your coding The value of allPointsAndPlaces is assigned after completion of RPC call in getAllPointsAndLocations() method. so the allPointsAndPlaces has some assigned values.
Here you try to directly access loadNewPoint() method in child class. At a time, allPointsAndPlaces is not assigned.
I am new to MvvmCross and I have a question.
I noticed that the following binding code works in one way only:
{ this, "{'CurrentIndex':{'Path':'CurrentIndex','Mode':'TwoWay'}}" }
CurrentIndex is an Int Property in the View
CurrentIndex is also an Int Property in the ViewModel
This way works!
ViewModel => View
But not this way!
View => ViewModel
I have a collection of ViewControllers and my goal was to call a DeleteCommand for the CurrentIndex in the viewModel.
However,
"Android and Touch 2 way bindings are incomplete"
Reference: MvvmCross experiences, hindsight, limitations?
My guess is the TwoWay mode only works for Controls (UILabel, UITextfield, ...) but not for Properties.
So, is there a good way to make it works in both ways? Or Are there any alternatives to my problem?
Patrick
In order for a binding to transfer any value between a View to a ViewModel, then it needs to hook into some event when the value changes.
In the ViewModel, this event is always the event in the INotifyProperty interface.
In the View/Activity, there is one single pattern employed - so each binding has to hook into a separate event. For example, the Text on EditText is hooked up using the TextChanged event (see MvxEditTextTextTargetBinding.cs) while the value in a SeekBar is hooked up using a Listener object rather than an event (see MvxSeekBarProgressTargetBinging.cs).
So if you wanted to implement this two-way binding for your activity, then you could do this by:
declaring an event - CurrentIndexChanged - in your activity (MyActivity) which is fired whenever CurrentIndex changes
declare a custom binding for your MyActivity which programmatically links CurrentIndex and CurrentIndexChanged
adding the custom binding to the binding registry during Setup
For example, your activity might include:
public event EventHandler CurrentIndexChanged;
private int _currentIndex;
public int CurrentIndex
{
get { return _currentIndex; }
set { _currentIndex = value; if (CurrentIndexChanged != null) CurrentIndexChanged(this, EventArgs.Empty); }
}
And you might then declare a binding class like:
public class MyBinding : MvxPropertyInfoTargetBinding<MyActivity>
{
public MyBinding (object target, PropertyInfo targetPropertyInfo)
: base(target, targetPropertyInfo)
{
View.CurrentIndexChanged += OnCurrentIndexChanged;
}
public override MvxBindingMode DefaultMode
{
get
{
return MvxBindingMode.TwoWay;
}
}
private void OnCurrentIndexChanged(object sender, EventArgs ignored)
{
FireValueChanged(View.CurrentIndex);
}
protected override void Dispose(bool isDisposing)
{
base.Dispose(isDisposing);
if (isDisposing)
{
View.CurrentIndexChanged -= OnCurrentIndexChanged;
}
}
}
And you'd need to tell the binding system about this binding in setup like:
registry.RegisterFactory(new MvxSimplePropertyInfoTargetBindingFactory(typeof(MyBinding), typeof(MyActivity), "CurrentIndex"));
However... at a practical level, if you are operating in C# rather than in XML, then you might be better off in this case using C# to simply update the ViewModel rather than using declarative binding in this case.
To be clear... in this case, I would most probably just write the Activity property as:
public int CurrentIndex
{
get { return _currentIndex; }
set { _currentIndex = value; ViewModel.CurrentIndex = value; }
}
Or... I'd consider not having this property in the Activity at all.
If it helps, there's some more information on custom bindings in:
MonoTouch MVVMCross binding to instance variables
In MvvmCross how do I do custom bind properties
Hope this helps! IMHO the bindings are there to help you when you're working in XML - you don't have to use them...
Stuart
UPDATE If you are going to do lots of these and follow the same name pattern - using property named X with changed EventHandler event named XChanged then something like this might work - it uses reflection to find the event automagically:
public class MyBinding<T> : MvxPropertyInfoTargetBinding<T>
where T : class
{
private readonly PropertyInfo _propertyInfo;
private readonly EventInfo _eventInfo;
public MyBinding(object target, PropertyInfo targetPropertyInfo)
: base(target, targetPropertyInfo)
{
_propertyInfo = targetPropertyInfo;
var eventName = _propertyInfo.Name + "Changed";
_eventInfo = View.GetType().GetEvent(eventName);
if (_eventInfo == null)
{
throw new MvxException("Event missing " + eventName);
}
if (_eventInfo.EventHandlerType != typeof(EventHandler))
{
throw new MvxException("Event type mismatch for " + eventName);
}
var addMethod = _eventInfo.GetAddMethod();
addMethod.Invoke(View, new object[] { new EventHandler(OnChanged) });
}
public override MvxBindingMode DefaultMode
{
get
{
return MvxBindingMode.TwoWay;
}
}
private void OnChanged(object sender, EventArgs ignored)
{
var value = _propertyInfo.GetValue(View, null);
FireValueChanged(value);
}
protected override void Dispose(bool isDisposing)
{
base.Dispose(isDisposing);
if (isDisposing)
{
var removeMethod = _eventInfo.GetRemoveMethod();
removeMethod.Invoke(View, new object[] { new EventHandler(OnChanged) });
}
}
}
I am developing an Eclipse plug-in that has currently 2 views. In my first view I have a list of connections displayed in a TableViewer (name and connection status).In my second view I want to load the tables in a database (the connection). This loading will be done by clicking a menu item on a connection ("view details"). These tables will be displayed in a TreeViewer because they can also have children. I have tried to do it this way:
My View class:
public class DBTreeView extends ViewPart {
private TreeViewer treeViewer;
private Connection root = null;
public DBTreeView() {
Activator.getDefault().setDbTreeView(this);
}
public void createPartControl(Composite parent) {
treeViewer = new TreeViewer(parent);
treeViewer.setContentProvider(new DBTreeContentProvider());
treeViewer.setLabelProvider(new DBTreeLabelProvider());
}
public void setInput(Connection conn){
root = conn;
treeViewer.setInput(root);
treeViewer.refresh();
}
}
I made a setInput method that is called from the action registered with the menu item in the connections view with the currently selected connection as argument:
MViewContentsAction class:
public void run(){
selectedConnection = Activator.getDefault().getConnectionsView().getSelectedConnection();
Activator.getDefault().getDbTreeView().setInput(selectedConnection);
}
In my ContentProvider class:
public Object[] getChildren(Object arg0) {
if (arg0 instanceof Connection){
return ((Connection) arg0).getTables().toArray();
}
return EMPTY_ARRAY;
}
where EMPTY_ARRAY is an...empty array
The problem I'm facing is that when in debug mode, this piece of code is not executed somehow:
Activator.getDefault().getDbTreeView().setInput(selectedConnection);
And also nothing happens in the tree view when clicking the menu item. Any ideas?
Thank you
Huh. Ok, what you're doing here is.. not really the right way. What you should be doing is registering your TableViewer as a selection provider.
getSite().setSelectionProvider(tableViewer);
Then, define a selection listener and add it to the view with the tree viewer like this:
ISelectionListener listener = new ISelectionListener() {
public void selectionChanged(IWorkbenchPart part, ISelection sel) {
if (!(sel instanceof IStructuredSelection))
return;
IStructuredSelection ss = (IStructuredSelection) sel;
// rest of your code dealing with checking whether selection is what is
//expected and if it is, setting it as an input to
//your tree viewer
}
};
public void createPartControl(Composite parent) {
getSite().getPage().addSelectionListener(listener);
}
Now your tree viewer's input will be changed according to what is selected in the table viewer (btw, don't forget to call treeviewer.refresh() after you set new input).
See an example here.
The Navigation framework in Windows Phone 7 is a cut down version of what is in Silverlight. You can only navigate to a Uri and not pass in a view. Since the NavigationService is tied to the View, how do people get this to fit into MVVM. For example:
public class ViewModel : IViewModel
{
private IUnityContainer container;
private IView view;
public ViewModel(IUnityContainer container, IView view)
{
this.container = container;
this.view = view;
}
public ICommand GoToNextPageCommand { get { ... } }
public IView { get { return this.view; } }
public void GoToNextPage()
{
// What do I put here.
}
}
public class View : PhoneApplicationPage, IView
{
...
public void SetModel(IViewModel model) { ... }
}
I am using the Unity IOC container. I have to resolve my view model first and then use the View property to get hold of the view and then show it. However using the NavigationService, I have to pass in a view Uri. There is no way for me to create the view model first. Is there a way to get around this.
Instead of passing the view through the constructor. You could construct the view first via the NavigationService and pass it into the view-model. Like so:
public class ViewModel : IViewModel
{
private IUnityContainer container;
private IView view;
public ViewModel(IUnityContainer container)
{
this.container = container;
}
public ICommand GoToNextPageCommand { get { ... } }
public IView
{
get { return this.view; }
set { this.view = value; this.view.SetModel(this); }
}
public void GoToNextPage()
{
// What do I put here.
}
}
PhoneApplicationFrame frame = Application.Current.RootVisual;
bool success = frame.Navigate(new Uri("View Uri"));
if (success)
{
// I'm not sure if the frame's Content property will give you the current view.
IView view = (IView)frame.Content;
IViewModel viewModel = this.unityContainer.Resolve<IViewModel>();
viewModel.View = view;
}
If you are using Mvvm Light you could try:
Windows Phone 7 — Navigation between pages using MVVM Light Messaging
(See similar post: Silverlight Navigation using Mvvm-light(oobe)+MEF?)
My opinion is that the view-model should be created and registered at application startup. By placing it inside the root DataContext all pages will automatically get a reference to it without any code-behind or IoC tricks.
// Code to execute when the application is launching (eg, from Start)
// This code will not execute when the application is reactivated
private void Application_Launching(object sender, LaunchingEventArgs e)
{
m_ViewModel = new PrimaryViewModel(RootFrame) ;
RootFrame.DataContext = m_ViewModel;
}
// Code to execute when the application is activated (brought to foreground)
// This code will not execute when the application is first launched
private void Application_Activated(object sender, ActivatedEventArgs e)
{
m_ViewModel = new PrimaryViewModel(RootFrame) ;
m_ViewModel.Activated(PhoneApplicationService.Current.State);
RootFrame.DataContext = m_ViewModel;
}
If you are using MVVM architecture,then you can pass navigationPage after registering using Messenger. Create a model class (say NavigateToPageMessage) with a string(say PageName) variable. You want to pass string from homepage.xaml to newpage.xaml,then in Homepage viewmodel just send the message like this under the command you binded (say HomeNavigationCommand)
private void HomeNavigationCommandHandler()
{
Messenger.Default.Send(new NavigateToPageMessage {PageName = "newpage"});
}
In the newpage Viewmodel,you should register the messenger like this,
Messenger.Default.Register<NavigateToPageMessage>(this, (action) => ReceiveMessage(action));
private object ReceiveMessage(NavigateToPageMessage action)
{
var page = string.Format("/Views/{0}.xaml", action.PageName);
NavigationService.Navigate(new System.Uri(page,System.UriKind.Relative));
return null;
}
//Assuming your views are in View Folder