I've a listbox in a userControl and I want to select the first item in the listbox whenever datacontext of my userControl is changed. (listbox's ItemsSource is Bind to userControl dataContext :
<userControl>
<ListBox Name="listBox_Resources" ItemsSource="{Binding Path=Resources}" DataContextChanged="listBox_Resources_DataContextChanged">
</ListBox>
</userControl>
private void listBox_Resources_DataContextChanged(object sender, DependencyPropertyChangedEventArgs e)
{
MessageBox.Show(listBox_Resources.SelectedIndex.ToString() + " " + listBox_Resources.Items.Count.ToString());
listBox_Resources.SelectedIndex = 0;
}
it seems that dataContextChanged is fired before the listbox items is populated because my messagebox in the eventhandler will return me count of the previous listbox items.
please help me finding the solution.
thanks
Try this
private void listBox_Resources_DataContextChanged(object sender, DependencyPropertyChangedEventArgs e)
{
EventHandler eventHandler = null;
eventHandler = new EventHandler(delegate
{
if (listBox_Resources.ItemContainerGenerator.Status == GeneratorStatus.ContainersGenerated)
{
listBox_Resources.SelectedIndex = 0;
listBox_Resources.ItemContainerGenerator.StatusChanged -= eventHandler;
}
});
listBox_Resources.ItemContainerGenerator.StatusChanged += eventHandler;
}
If you put a breakpoint at the last line
listBox_Resources.ItemContainerGenerator.StatusChanged += eventHandler;
and watch the value of listBox_Resources.ItemContainerGenerator.Status in the debugger it will should read "ContainersGenerated". If you then add a breakpoint within the delegate EventHanler at
if (listBox_Resources.ItemContainerGenerator.Status == GeneratorStatus.ContainersGenerated)
you should see that "c_listBox.ItemContainerGenerator.Status = GeneratingContainers" a first time and then when it hits again it should be ContainersGenerated and then we can set SelectedIndex. Anyway, that's working for me.
Related
I am having a master window in which there are plenty of user control. and using navigation i am able to access the user controls. But by question is how to set focus on the first text box when ever the user control is opened.
I tried with dependency property and boolean flags, i was able to succeeded a bit. When i first render the UserControl i was able to focus but when i open for the second time i was not able to set focus on the TextBox.
And one more thing, i have validation for TextBoxes, if the validation fails then the textbox should be emptied and the focus should be on the respective text box.
How can i achieve this using MVVM in WPF (CLR 3.5, VS2008)
thanks in advance.
If you have a UserControl then you also have CodeBehind.
Place this inside your codebehind and you will do fine.
this.Loaded += (o, e) => { Keyboard.Focus(textBox1) }
Place this inside your UserControl XAML if you wish to listen to validation errors.
<UserControl>
<Grid Validation.Error="OnValidationError">
<TextBox Text{Binding ..., NotifyOnValidationError=true } />
</Grid>
<UserControl>
Inside the CodeBehind of your UserControl you will have something like this:
public void OnValidationError(o , args)
{
if(o is TextBox)
{
(TextBox)o).Text = string.Empty;
}
}
You should use AttachedProperty to stick to MVVM pattern it'll keep your view model independent of UI code and fully unit testable. Following attached property binds a boolean property to focus and highlight the TextBox, if you do not want the highlighting then you can remove the highlighting code and just work with focus code.
public class TextBoxBehaviors
{
#region HighlightTextOnFocus Property
public static readonly DependencyProperty HighlightTextOnFocusProperty =
DependencyProperty.RegisterAttached("HighlightTextOnFocus", typeof (bool), typeof (TextBoxBehaviors),
new PropertyMetadata(false, HighlightTextOnFocusPropertyChanged));
public static bool GetHighlightTextOnFocus(DependencyObject obj)
{
return (bool) obj.GetValue(HighlightTextOnFocusProperty);
}
public static void SetHighlightTextOnFocus(DependencyObject obj, bool value)
{
obj.SetValue(HighlightTextOnFocusProperty, value);
}
private static void HighlightTextOnFocusPropertyChanged(DependencyObject sender,
DependencyPropertyChangedEventArgs e)
{
var uie = sender as UIElement;
if (uie == null) return;
if ((bool) e.NewValue)
{
uie.GotKeyboardFocus += OnKeyboardFocusSelectText;
uie.PreviewMouseLeftButtonDown += OnMouseLeftButtonDownSetFocus;
}
else
{
uie.GotKeyboardFocus -= OnKeyboardFocusSelectText;
uie.PreviewMouseLeftButtonDown -= OnMouseLeftButtonDownSetFocus;
}
}
private static void OnKeyboardFocusSelectText(object sender, KeyboardFocusChangedEventArgs e)
{
var textBox = sender as TextBox;
if (textBox == null) return;
textBox.SelectAll();
}
private static void OnMouseLeftButtonDownSetFocus(object sender, MouseButtonEventArgs e)
{
var textBox = sender as TextBox;
if (textBox == null) return;
if (!textBox.IsKeyboardFocusWithin)
{
textBox.Focus();
e.Handled = true;
}
}
#endregion
}
You can use this attached property in on your TextBox which you want to focus/highlight...
<TextBox ... local:TextBoxBehaviors.HighlightTextOnFocus="{Binding IsScrolledToEnd}" ... />
You can also try using FocusManager
<UserControl>
<Grid FocusManager.FocusedElement="{Binding Path=FocusedTextBox, ElementName=UserControlName}">
<TextBox x:Name="FocusedTextBox" />
</Grid>
<UserControl>
In I have created a control that has a text box and a text changed event handler attached to it - this is in xaml.
The problem: when control is loaded the text changed event is fired, I do not want it to happen when the control is loaded only when I make actually make it change on the control by typing something.
What do you pros suggest I do? :)
All you have to do is check the textbox's IsLoaded property inside the event handler before handling it.
Attach Your EventHandler after the InitializeComponent Method in your constructor not in the Xaml.
i.e.
public MainWindow()
{
InitializeComponent();
textBox1.TextChanged+=new TextChangedEventHandler(textBox1_TextChanged);
}
I noticed that you are talking about an usercontrol, the only thing I can think of off the top of my head is to to create a property that can be used to inhibit the TextChanged Event until the Parent Form finishes loading. See if something like this works.
MainForm Xaml:
<my:UserControl1 setInhibit="True" HorizontalAlignment="Left" Margin="111,103,0,0" x:Name="userControl11" VerticalAlignment="Top" Height="55" Width="149" setText="Hello" />
MainForm CS
private void Window_Loaded(object sender, RoutedEventArgs e)
{
userControl11.setInhibit = false;
}
UserControl:
public UserControl1()
{
InitializeComponent();
textBox1.TextChanged += new TextChangedEventHandler(textBox1_TextChanged);
}
public string setText
{
get { return textBox1.Text; }
set { textBox1.Text = value; }
}
public bool setInhibit { get; set; }
void textBox1_TextChanged(object sender, TextChangedEventArgs e)
{
if (setInhibit) return;
// Do your work here
}
UserControl1.xaml:
<Grid>
<TextBox Text="{Binding MyText, UpdateSourceTrigger=PropertyChanged}" TextChanged="TextBox_TextChanged"/>
</Grid>
where TextChanged is the original event for TextBox
UserControl1.xaml.cs:
public partial class UserControl1 : UserControl
{
public UserControl1()
{
_isFirstTime = true;
DataContext = this;
InitializeComponent();
}
public event TextChangedEventHandler TextBoxTextChanged;
bool _isFirstTime;
//MyText Dependency Property
public string MyText
{
get { return (string)GetValue(MyTextProperty); }
set { SetValue(MyTextProperty, value); }
}
public static readonly DependencyProperty MyTextProperty =
DependencyProperty.Register("MyText", typeof(string), typeof(UserControl1), new UIPropertyMetadata(""));
private void TextBox_TextChanged(object sender, TextChangedEventArgs e)
{
if (TextBoxTextChanged != null)
if (!_isFirstTime)
{
TextBoxTextChanged(sender, e);
}
_isFirstTime = false;
}
}
where TextBox_TextChanged is the customized eventHandler for original TextChanged
and TextBoxTextChanged is more like a wrapper for the original TextChanged
Window.xaml:
<Grid>
<c:UserControl1 TextBoxTextChanged="TextBoxValueChanged"/>
</Grid>
as you see you can add an eventHandler to the event wrapper (TextBoxTextChanged)
Window.xaml.cs:
private void TextBoxValueChanged(object sender, TextChangedEventArgs e)
{
MessageBox.Show("asd");
}
finally TextBoxValueChanged won't be fired the first time Text is changed
private void TextBoxValueChanged(object sender, TextChangedEventArgs e)
{
if (Textbox1.IsFocused)
{
App.Current.Properties["TextChanged"] = "1"; // Set Flag
}
}
private void TextBoxLostFocus(object sender, RoutedEventArgs e)
{
if (App.Current.Properties["TextChanged"] == "1")
{
// Do Your Wor Here
App.Current.Properties["TextChanged"] = "0"; // Clear Flag
}
}
On your XAML:
<TextBox xName="TextBox1" LostFocus="TextBoxLostFocus" TextChanged="TextBoxValueChanged"/>
(This is a very rudimentary, dirty, codebehind hack... checking the IsLoaded property as stated by Brent I found to be efficient)
Here since on textbox control creation it's not focused, the TextChanged event will fire but the flag "1" is NOT set...
Later when user leaves field after editing it, since it had focus the Flag is set... the LostFocus is fired, but only runnig code if textbox was changed.
I found a way of preventing this behavior across multiple inputs without having to create a unique bool for each input...
private void TextChanged_UpdateItem(object sender, TextChangedEventArg e)
{
TextBox txtBox = sender as TextBox;
if (!txtBox.IsFocused)
return;
//The rest of your code here
}
So basically, if the text field doesn't have focus (like on initialization) it just returns. This also prevents it from firing if the data is changed elsewhere. :)
Alternatively, as mentioned by Brent, you can just look for "IsLoaded":
private void TextChanged_UpdateItem(object sender, TextChangedEventArg e)
{
TextBox txtBox = sender as TextBox;
if (!txtBox.IsLoaded)
return;
//The rest of your code here
}
In my WPF MVVM Project I have a button that triggers a function that should add a node to a xml and then set the focus to a textbox.
My question is, how can i receive a reference to a control?
View:
<Button Command="{Binding Path=ButtonAddCategory_Click}" />
ViewModel:
RelayCommand buttonAddCategory_Click;
public ICommand ButtonAddCategory_Click
{
get
{
return buttonAddCategory_Click ?? (buttonAddCategory_Click = new RelayCommand(param => this.AddCategory(),
param => true));
}
}
public void AddCategory()
{
...
//get the "node" -> reference?
XmlNode selectedItem = (XmlNode)treeView.SelectedItem;
..
//add the node to the xml
..
//change focus -> reference?
textBoxTitel.Focus();
textBoxTitel.SelectAll();
}
Don't do it in the ViewModel. The ViewModel shouldn't know anything about the view.
You can do it in code-behind:
handle the TreeView.SelectedItemChanged event in code-behind, and update a SelectedItem property on the ViewModel (you could also do it with an attached behavior)
to focus the TextBox, raise an event from the ViewModel and handle it in code-behind:
ViewModel:
public XmlNode SelectedItem { get; set; }
public event EventHandler FocusTitle;
public void AddCategory()
{
...
//get the "node" -> reference?
XmlNode selectedItem = this.SelectedItem;
..
//add the node to the xml
..
// Notify the view to focus the TextBox
if (FocusTitle != null)
FocusTitle(this, EventArgs.Empty);
}
Code-behind:
// ctor
public MyView()
{
InitializeComponent();
DataContextChanged += MyView_DataContextChanged;
}
private void MyView_DataContextChanged(object sender, DependencyPropertyChangedEventArgs e)
{
MyViewModel vm = (MyViewModel)e.NewValue;
vm.FocusTitle += ViewModel_FocusTitle;
}
private void TreeView1_SelectedItemChanged(object sender, RoutedPropertyChangedEventHandler<Object> e)
{
MyViewModel vm = (MyViewModel)DataContext;
vm.SelectedItem = (XmlNode)e.NewValue;
}
private void ViewModel_FocusTitle(object sender, EventArgs e)
{
textBoxTitle.Focus();
}
You could use the FocusManager.FocusedElement attached property to handle ensuring the TextBox receives focus.
<DataTemplate DataType="{x:Type YourViewModel}">
<Grid FocusManager.FocusedElement="{Binding ElementName=userInput}">
<TextBox x:Name="userInput" />
</Grid>
</DataTemplate>
As for your second part (textBox.SelectAll()) you may have to work on a behavior or attached property of your own that handles the focusing and selecting in one fell swoop.
I couldn't find the right event to achieve the functionality.
TargetUpdated event didn't work.
setting SelectedIndex to 0 on xaml would only affect the first load of data.
You can:
Set NotifyOnTargetUpdated on the binding
Add an event handler for Binding.TargetUpdated
In that event handler register for ItemsSource.CollectionChanged
In that event handler set the selected index to zero
The issue is most likely that you didn't set NotifyonTargetUpdated in the binding so the first event wasn't fired or that the collection was being updated but it was the same collection so the second event is necessary.
Here's a working example using a ListBox as the ItemsControl and a MessageBox as a proxy for doing whatever you want to do when the event fires.
Here is the markup:
<Grid>
<DockPanel>
<Button DockPanel.Dock="Top" Content="Update Target" Click="ButtonUpdateTarget_Click"/>
<Button DockPanel.Dock="Top" Content="Update Item" Click="ButtonUpdateItem_Click"/>
<ListBox Name="listBox" Binding.TargetUpdated="ListBox_TargetUpdated" ItemsSource="{Binding Items, NotifyOnTargetUpdated=True}"/>
</DockPanel>
</Grid>
and here is the code-behind:
public class ViewModel : INotifyPropertyChanged
{
ObservableCollection<string> items;
public ObservableCollection<string> Items
{
get { return items; }
set { items = value; OnPropertyChanged("Items"); }
}
public event PropertyChangedEventHandler PropertyChanged;
void OnPropertyChanged(string propertyName)
{
if (PropertyChanged != null) PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
void SetDataContext()
{
DataContext = viewModel;
viewModel.Items = new ObservableCollection<string> { "abc", "def", "ghi" };
}
ViewModel viewModel = new ViewModel();
private void ButtonUpdateTarget_Click(object sender, RoutedEventArgs e)
{
viewModel.Items = new ObservableCollection<string> { "xyz", "pdq" };
}
private void ButtonUpdateItem_Click(object sender, RoutedEventArgs e)
{
viewModel.Items[0] = "xxx";
}
private void ListBox_TargetUpdated(object sender, DataTransferEventArgs e)
{
MessageBox.Show("Target Updated!");
(listBox.ItemsSource as INotifyCollectionChanged).CollectionChanged += new NotifyCollectionChangedEventHandler(listBox_CollectionChanged);
}
void listBox_CollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
{
MessageBox.Show("Item Updated!");
}
Have you tried the SourceUpdated event?
I faced same problem. To overcome this problem, I used the following steps:
create a TextBox
Set visibility of TextBox to Collapsed
Bind Text to ListBox.Items.Count
<TextBox x:Name="txtCount" TextChanged="TextBox_TextChanged" Text="{Binding ElementName=ListBox1, Path=Items.Count, Mode=OneWay}" Visibility="Collapsed" />
In the TextBox_TextChanged event, set SelectedIndex to 0
private void TextBox_TextChanged(object sender, TextChangedEventArgs e)
{
int count = 0;
if(int.TryParse(txtCount.Text,out count) && count>0)
ListBox1.SelectedIndex = 0;
}
How can focus the controls when select a tabitem in a tabcontrol?
You should capture the Selection changed event of the TabControl and inside that you focus the control you need. Just as
private void TabControl1_SelectionChanged(object sender, EventArgs e)
{
control1.Focus();
}
Not sure I understand what you're asking completely, but you probably want to capture the SelectionChanged event for the TabControl:
public Window1()
{
InitializeComponent();
TabControl1.SelectionChanged += TabControl1_SelectionChanged;
}
private void TabControl1_SelectionChanged(object sender, EventArgs e)
{
TabItem item = (TabItem)TabControl1.SelectedItem;
// Find the first control in the TabItem content and focus it?
}