I'm trying to find a way to set default value to combobox. I have to run a method if a value changes in combobox but not when I set default value.
You can set the event handlers after setting the default value.
ComboBox b = new ComboBox();
b.addItem(1);
b.select(1);
b.addValueChangeListener(event -> someMethod());
you can also remove the event handler and then set the value then set the value change listener again.
ComboBox b = new ComboBox();
b.addItem(1);
ValueChangeListener vcl = new
ValueChangeListener()
{
#Override
public void valueChange(ValueChangeEvent event)
{
System.out.println("value changed");
}
};
b.addValueChangeListener(vcl);
b.removeValueChangeListener(vcl);
b.select(1);
b.addValueChangeListener(vcl);
Related
I am using vaadin 7.7.7
In a grid i have a combobox as an edited item in one of the columns
as
grid.addColumn("columnProperty").setEditorField(combobox);
I need to update a property/cell in same row based on the combobox selection change
My issue is , the selection change event triggers twice, once when the combobox in clicked and second when the selection value is changed. But the updated value in next cell gets reflected on UI only first time.
Below is the code written . Any solutions?
Combobox.addValueChangeListener(new ValueChangeListener()
#Override
public void valueChange(ValueChangeEvent event) {
// below line works only first time when the combobox is clicked,but i want
//it when the item in the combobox is changed
gridContainer.getContainerProperty(editedRow,"editedColumProperty").setValue("ValueTobeUpdated");}
});
Need to update the unit column on combobox change in edited mode(before saving)
Refer below link for image
example image
You will get value change events even when the field gets value that it should show to the user. In order to get event that indicates that the user has accepted the input you should use field group (setEditorFieldGroup).
From Book of Vaadin example for grid editing:
grid.getColumn("name").setEditorField(nameEditor);
FieldGroup fieldGroup = new FieldGroup();
grid.setEditorFieldGroup(fieldGroup);
fieldGroup.addCommitHandler(new CommitHandler() {
private static final long serialVersionUID = -8378742499490422335L;
#Override
public void preCommit(CommitEvent commitEvent)
throws CommitException {
}
#Override
public void postCommit(CommitEvent commitEvent)
throws CommitException {
Notification.show("Saved successfully");
}
});
Edit
I assume that you want to connect Parameter and Unit comboboxes. I would do that with this kind of value change lister
BeanItemContainer container = new BeanItemContainer<>(
Measurement.class,
measurements);
Grid grid = new Grid(container);
grid.setEditorEnabled(true);
ComboBox parameterComboBox = new ComboBox();
ComboBox unitComboBox = new ComboBox();
parameterComboBox.addItems(Parameter.Pressure, Parameter.Temperature, Parameter.Time);
parameterComboBox.addValueChangeListener(v -> setUnits(parameterComboBox, unitComboBox));
grid.getColumn("parameter").setEditorField(parameterComboBox);
grid.getColumn("unit").setEditorField(unitComboBox);
Units could be updated like this. I think you need to preserve current value and set it back if you replace available items in the combobox.
private void setUnits(ComboBox parameterComboBox, ComboBox unitComboBox) {
Object currentValue = unitComboBox.getValue();
List<String> units = unitsForParameter(parameterComboBox.getValue());
unitComboBox.removeAllItems();
unitComboBox.addItems(units);
if (units.contains(currentValue)) {
unitComboBox.setValue(currentValue);
} else {
unitComboBox.setValue(null);
}
}
private List<String> unitsForParameter(Object value) {
if (value == null) {
return Collections.emptyList();
} else if (value == Parameter.Pressure) {
return asList("Pascal", "Bar");
} else if (value == Parameter.Temperature) {
return asList("Celcius", "Kelvin");
} else if (value == Parameter.Time) {
return asList("Second", "Minute");
} else {
throw new IllegalArgumentException("Unhandled value: " + value);
}
}
I have a combobox of type List. I have the ItemsSource and the ItemSelected bound through the datacontext. If the selected item has been changed then I show a pop up message confirming the users action. On clicking of 'Ok' the selection gets changed. But on clicking of cancel, the selection should be cancelled and previous item should be retained. Below is the property that is bound to SelectedItem of the combobox.
Public SomeClass Sel
{
get
{
return _sel;
}
set
{
if (_sel != value)
{
var sview = _sel;
if (Compare())
{
_sel = value;
if (Sel != null)
IsDefault = Sel.IsDefault;
OnPropertyChanged(() => Sel);
}
else
{
MessageBoxResult result = MessageBox.Show("Message.", "Owb Message", MessageBoxButton.OKCancel);
if (result == MessageBoxResult.OK)
{
_sel = value;
if (Sel != null)
IsDefault = Sel.IsDefault;
OnPropertyChanged(() => Sel);
}
else
{
Application.Current.Dispatcher.BeginInvoke(new Action(() =>
{
_sel = sview;
OnPropertyChanged("Sel");
}), DispatcherPriority.Send, null);
return;
}
}
}
}
}
The combo box is in a pop window. So would Dispatcher object work in that case?
I'm guessing the selected value is retained, but the View doesn't update correctly.
Have a look at this article: http://www.codeproject.com/Articles/407550/The-Perils-of-Canceling-WPF-ComboBox-Selection. Basically, the few workarounds that did exist in .Net 3.5 no longer work in .Net 4.0..
As a general rule, if you've got visual controls leaking into your viewmodel, you're going down a path you don't want to go down.
Create a Behavior that intercepts the OnChanged event of the ComboBox and launches a message box. Here's a tutorial on using behaviours
This keeps all the UI logic in the UI and leaves your viewmodel to manage data and validation.
It works like magic now! I missed out setting the value before calling dispatcher.
_sel = sview
I have a QuestionsFile class, which has questions, a name etc...
Now I have created a wpf application and I have a window which has different pages. These pages inherit the BaseViewModel class. I create my pages in the WindowViewModel class (where I pass a new QuestionsFile object to the constructor and dispatch it through the constructors of the other viewmodels):
var chooseQFVM = new ChooseQuestionsFileViewModel(this.QuestionsFile);
var showChosenQFVM = new ShowChosenQuestionsFileViewModel(this.QuestionsFile);
var pages2 = new List<WizardControlViewBaseModel>();
pages2.Add(chooseQFVM);
pages2.Add(showChosenQFVM);
pages = new ReadOnlyCollection<WizardControlViewBaseModel>(pages2);`
All these viewmodels inherit the BaseViewModel class which has the QuestionsFile property.
so when let's say I change the QuestionsFile property of the chooseQFView variable from a combobox and I give it through - the same property in the BaseBiewModel class must be changed. So this is this code of the property in the BaseBiewModel class:
public QuestionsFile QuestionsFile
{
get { return qfile; }
set
{
qfile = value;
OnPropertyChanged("QuestionsFile");
}
}
So I call the PropertyChanged event, but when i want to call this property in the next page and I debug it says that all the properties of my QuestionsFile are null..
this is the code where I change the value of the QuestionsFile property:
public OptionViewModel<QuestionsFile> SelectedFile
{
get
{
return selectedFile;
}
set
{
selectedFile = value;
OnPropertyChanged("SelectedFile");
this.QuestionsFile = value.GetValue();
}
}
From what I understand on your view you have a collection of QuestionFiles (via OptionsViewModel) that you are selecting one of them via the SelectedFile property. At this point in time you are setting the chosen QuestionFile property.
This is all good for the ChooseQuestionViewModel (which I assume contains the SelectedFile property). I am not sure this is your issue but the SelectedFile will not reflect inside the ShowQuestionsFileViewModel because now both view models refer to a different instance.
Is this your issue? That you cannot see change of the selected QuestionFile in the ShowQuestionsFileViewModel?
If so you will need to tell the other view model that it has changed via events or having it reference the ChooseQuestionViewModel so it can listen for the PropertyChanged event so you can grab the selected item from and update itself.
i.e.
//Ctor
public ShowQuestionsFileViewModel(ChooseQuestionViewModel chooseViewModel)
{
_chooseViewModel = chooseViewModel;
chooseViewModel.PropertyChanged += ChoosePropertyChanged
}
private void ChoosePropertyChanged(object sender, PropertyChangedEventArgs e)
{
if(e.Property == "SelectedFile")
{
this.SelectedFile = _chooseViewModel.SelecteFile;
}
}
When the user tabs into a CheckBox to give it focus, a dotted border appears around the CheckBox to indicate that it has focus.
When the CheckBox gets focused by code calling myCheckBox.Focus(), no such indicator appears (even though pressing the space bar toggles the state).
How can I make the CheckBox focus border appear when I have programmatically focused the CheckBox?
The border is intentionally only shown if you are navigating by the keyboard (Tab key). The MSDN page on this topic has further details:
Focus visual styles act only when the
focus action was initiated by the
keyboard. Any mouse action or
programmatic focus change disables the
mode for focus visual styles.
If you want to show a border, you could use a Trigger on the IsFocused- Property to do some visual changes (although you can't set the border with this) or if you actually want a border, you would have to create your own ControlTemplate.
There is also a thread here on SO on a somewhat related topic where the suggestion is to simulate a key press, but I would suggest not to use this solution for your problem.
By editing the KeyboardNavigationEx file from ControlzEx I managed to solve the issue (full credit goes, as always, to punker76).
Just call the KeyboardHelper.Focus method passing the UIElement that shoud be focused (e.g. KeyboardHelper.Focus(myCheckBox))
Here's the KeyboardHelper class:
public sealed class KeyboardHelper
{
private static KeyboardHelper _Instance;
private readonly PropertyInfo _AlwaysShowFocusVisual;
private readonly MethodInfo _ShowFocusVisual;
// Explicit static constructor to tell C# compiler
// not to mark type as beforefieldinit
static KeyboardHelper()
{
}
private KeyboardHelper()
{
var type = typeof(KeyboardNavigation);
_AlwaysShowFocusVisual = type.GetProperty("AlwaysShowFocusVisual", BindingFlags.NonPublic | BindingFlags.Static);
_ShowFocusVisual = type.GetMethod("ShowFocusVisual", BindingFlags.NonPublic | BindingFlags.Static);
}
internal static KeyboardHelper Instance => _Instance ?? (_Instance = new KeyboardHelper());
internal void ShowFocusVisualInternal()
{
_ShowFocusVisual.Invoke(null, null);
}
internal bool AlwaysShowFocusVisualInternal
{
get { return (bool)_AlwaysShowFocusVisual.GetValue(null, null); }
set { _AlwaysShowFocusVisual.SetValue(null, value, null); }
}
public static void Focus(UIElement element)
{
element?.Dispatcher.BeginInvoke(DispatcherPriority.Background, new Action(() =>
{
var keybHack = KeyboardHelper.Instance;
var oldValue = keybHack.AlwaysShowFocusVisualInternal;
keybHack.AlwaysShowFocusVisualInternal = true;
try
{
Keyboard.Focus(element);
keybHack.ShowFocusVisualInternal();
}
finally
{
keybHack.AlwaysShowFocusVisualInternal = oldValue;
}
}));
}
}
'initially set chkCheckBox.Appearance = 1
'on Got Focus set appearance = 0 - Flat
Private Sub chkCheckBox_GotFocus()
chkCheckBox.Appearance = 0
End Sub
'on Lost Focus set appearance = 1 - 3D
Private Sub chkCheckBox_LostFocus()
chkCheckBox.Appearance = 1
End Sub
I'm using a MVVM approach with WPF to let the user select one item in a combobox. The model contains a set of possible options, the combobox is bound to this set, the current selection is again bound to a property of my model. This part works fine.
Now I'd like to allow the user to enter an arbitrary text into the combobox. If the text doesn't correspond to an existing item the program should ask him if he wants to add a new item. He should also be allowed to cancel the action and select another item.
How would I do that within the MVVM pattern?
You would check the "already existing" status of the text from your ViewModel's bound property setter. At that point, you need a mechanism to raise an event and decide what to do based on what happens.
An example:
enum Outcome { Add, Cancel }
class BlahEventArgs : EventArgs
{
Outcome Outcome { get; set; }
}
class ViewModel
{
private string name;
public EventHandler<BlahEventArgs> NotExistingNameSet;
public Name
{
get { return this.name; }
set
{
if (/* value is existing */) {
this.name = value;
return;
}
var handler = this.NotExistingNameSet;
if (handler == null) {
// you can't just return here, because the UI
// will desync from the data model.
throw new ArgumentOutOfRangeException("value");
}
var e = new BlahEventArgs { Outcome = Outcome.Add };
handler(this, e);
switch (e.Outcome) {
case Outcome.Add:
// Add the new data
this.name = value;
break;
case Outcome.Cancel:
throw new Exception("Cancelled property set");
}
}
}
}
Your View would add an event handler to NotExistingNameSet to present appropriate UI and set the value of e.Outcome accordingly.