I'd like to react to changes made by the user and ignore the ones caused by my code.
For example, I've got a TextField that shows the name of an entry. When the user changes it, I want to save the change back so I've registered a change listener:
nameTextField.textProperty().addListener(
(ObservableValue<? extends String> observable, String oldValue, String newValue) -> {
entry.setName(newValue);
saveEntry();
}
);
The problem is that this change listener is also triggered when I update the UI for new entry:
nameTextField.setText(entry.getName());
I can work around this by using a variable that indicates whether I'd like these changes to be applied, but this feels wrong, it "smells".
Also, this not only about TextFields. I have the same issue with ListViews and ComboBoxes.
Since I'm new to JavaFX and I think that this is a common issue I have a feeling that I'm missing something. So, how is this usually solved in JavaFX?
Related
I am trying to dynamically modify the items in a List (ObservableCollection) of a ViewModel and have those changes get updated in the View via MvvmCross bindings. My eventual goal is that when a user clicks on a list item, I will pop up a dialog asking them to edit that item. When the dialog is dimissed, the viewmodel will get updated (through an ICommand I assume) and that modified value will be now be in the list.
I haven't looked into dialogs yet, so for now I am just trying to toggle a boolean value each time a list item is clicked and have that value changed in the MvxListView. I have the MxvListView in my View bound to an ObservableCollection in my ViewModel and have an MvxCommand that is getting called when an item is selected. All this is working and I can see the value getting changed in the debugger, however, the new values are not being displayed in the MvxListView. So my question is: How do I get modified data in individual items in an ObservableCollection to bind to an MvxListView?
All of the examples I have seen online use ObservableCollection for dynamic binding but they only ever Add or Delete items. I haven't found any examples of modifying the items. If I change the code in my MvxCommand from modifying the data to adding or deleting an item, the list will get updated. So that tells me I'm close I think.
Rather than copy paste the code in here, I created a sample project on github here to look at:
https://github.com/smulrich/breaktimer
I appreciate the help.
You can simply replace
Breaks[index] = b;
with
Breaks[index] = new DailyBreak() { Reason = b.Reason, TimeOfDay = b.TimeOfDay, Enabled = b.Enabled };
or more reasonable, you should realize INotifyPropertyChanged for class DailyBreak
Diffrent among List, ObservationCollection and INotifyPropertyChanged, please refer to enter link description here
I am using GWT. I have a textbox and a drop down list box that have change handlers on them. I also sometimes change the text or selected value from the source code but I don't want the change handler to run when I do this, I only want it to run when the user changes it.
How can I implement this?
For the TextBox, use setValue(T value, boolean fireEvents) using false as second argument, to avoid firing any ValueChangeEvent.
For the ListBox, when you call setSelectedIndex(int index) or setItemSelected(int index, boolean selected) the ChangeEvent is never fired, so you are free to use them programmatically and rely on the ChangeHandler on user action.
I have an issue trying to persist entities to the DB using code-first technique. For example of what I am doing you may look at the following MSDN Sample. The app generally works as intended except for one case.
If I have an existing entity and I bind it to a page that has a TextBox to hold the Title field and a AppBar icon to Save (similar to the 'New Task' screenshot in the above link, but with values pre-filled with existing entity with Two-Way binding), the following issue occurs. If I have the TextBox selected and I change the title and hit the save button, it updates the entity in-memory so that the full list now displays the new title. But the new title is not persisted to the DB (it does not auto-detect changes). This is weird, not just because the object in-memory has changed, but also because if I deselect the TextBox and then hit save, it will persist the changes to the DB.
I have seen other questions on SO with some change detection issues, they suggest adding this.Focus() or focusing some other element at the beginning of the save method. This does not help in my case. Unless I tap on screen to deselect the TextBox and hide the keyboard (or press Return key on the keyboard, which I bound to do this.Focus()), it won't detect the object as changed.
How can I address this? What exactly is stopping EF from detecting the object change when the keyboard is still visible?
Not sure if I follow exactly what you described but I think the problem is that the property you have bound your textbox to does not get updated until the TextChanged is fired on the textbox, and this is done first when you leave the Textbox, basically it will lose Focus if you tap somewhere else.
There is a simple workaround for this and it behaviors. By making a small behavior you can force the textbox to update the binding on each keystroke - so everything is updated while you type and keyboard is still there.
Behavior:
/// <summary>
/// Update property on every keystroke in a textbox
/// </summary>
public class UpdateTextSourceTriggerBehavior : Behavior<TextBox>
{
protected override void OnAttached()
{
this.AssociatedObject.TextChanged += OnTextBoxTextChanged;
}
void OnTextBoxTextChanged(object sender, TextChangedEventArgs e)
{
var bindingExpression = AssociatedObject.ReadLocalValue(TextBox.TextProperty) as BindingExpression;
if (bindingExpression != null)
{
bindingExpression.UpdateSource();
}
}
protected override void OnDetaching()
{
this.AssociatedObject.TextChanged -= OnTextBoxTextChanged;
}
}
Now just attach this behavior to your textbox like this:
<TextBox Text="{Binding YourPropertyName, Mode=TwoWay}">
<i:Interaction.Behaviors>
<UpdateTextSourceTriggerBehavior/>
</i:Interaction.Behaviors>
</TextBox>
This will keep the property on your viewmodel updated all the time, so that when you tap on save directly after typing in the textbox it will save the correct value. Hope it helps!
Cheers,
Anders
I have a Suggest box which has 2 hadlers: SelectionHandler for selecting items in SuggestionList and keyDownHandler on TextBox of SuggestBox. I want to prevent default action on event(for example on Enter pressed) when the suggestion list is currently showing. The problem is that SelectionEvent is always fires before KeyDownEvent and suggestion list is closed after SuggestionEvent fired, so in KeyDownEventHandler suggestion list is already closed. And I can't use prevent default action on Enter with checking the suggestion list is showing like this:
if ((nativeCode == KeyCodes.KEY_TAB || nativeCode == KeyCodes.KEY_ENTER) && display.isSuggestionListShowing()) {
event.preventDefault();
}
where display.isSuggestionListShowing() is the method which calls isShowing on SuggestBox .
So how can i change the order of event handling(Selection before KeyDown to the keyDown before Selection) in this case?
I'm assuming you mean SuggestBox instead of SuggestionList, as there is no class by that name in the gwt-user jar.
The SuggestBox uses the keydown event to provide the SelectEvent - if it can't see the keys change (from the browser, which actually picks up the user's action), it can't provide the logical selection event.
This means that reordering events doesn't really make sense - you can't have the effect before the cause. In many cases, the browser emits events in a certain order, and there is no way to change this, so you have to think differently about the problem.
(Also worth pointing out that preventDefault() only prevents the browser from doing its default behavior - other handlers will still fire as normal.)
One option would be to preview all events before they get to the SuggestBox, and cancel the event in certain cases - look into com.google.gwt.user.client.Event.addNativePreviewHandler(NativePreviewHandler) for how this can be done.
I'm not seeing any other option right away - all of the actual logic for handling the keydown is wrapped up in the inner class in the private method of com.google.gwt.user.client.ui.SuggestBox.addEventsToTextBox(), leaving no options for overriding it.
I have a question regarding MVVM for WP7. In my application I have a kind of a datepicker or a calendar if you will. So after picking a day, one can choose to edit the information regarding this day by ckicking on it and getting to another page.
The problem is that when I change some info and click the back button the information that was altered hasn't been updating in the correspongind bindings. That's why on the navigatedto event I call a public method from my VM for that page. The sole purpose of this method (RefreshSelectedDay) is to call RaisePropertyChanged so that the binded text fields on the page get the new info. However, nothing happens. The info is actaully properties of the SelectedDay property whish is an instance of MyDay class.
protected override void OnNavigatedTo(NavigationEventArgs e)
{
ViewModel.ViewModelLocator.CalendarStatic.RefreshSelectedDay();
}
/// <summary>
/// I admit that this is by far the most stupid solution so far.
/// RaisePropertyChanged won't work if you haven't really changed the property.
/// That's why we set it to null and then turn it back.
/// Used for updating the day when returning from
/// the edit screen.
/// </summary>
public void RefreshSelectedDay()
{
MyDay w = selectedDay;
SelectedDay = null;
SelectedDay = w;
}
My solution as you can see is far from being elegant. What happens IMO is that if I just call the RaisePropertyChanged it won't propagate because it is the same variable and just one of it's properties has changed. It would be lovely if someone can explain what is happening.
"The problem is that when I change some info and click the back button the information that was altered hasn't been updating in the correspongind bindings."
That implies to me that the information that supposedly was altered, wasn't actually altered. That would also explain why youre RefreshSelectedDay doesn't seem to work either.
Are you modifying properties on SelectedDay, or creating a new instance, and that isn't getting set?
if you're modifying properties on SelectedDay, does that class properly fire property change notifications?
More code would help us debug, too.