I need to fire some event when WPF button is pressed (by mouse, keyboard, touchscreen, etc) and to fire event when WPF buttons is unpressed.
How to do this? It should be easy but I can't find how to do this.
You can derive from Button and override the OnIsPressedChanged method and fire a custom event there.
Or you can bind to the ButtonBase.IsPressed property.
Another option is to use DependencyPropertyDescriptor:
var descriptor = DependencyPropertyDescriptor.FromProperty(Button.IsPressedProperty, typeof(Button));
descriptor.AddValueChanged(this.button, new EventHandler(IsPressedChanged));
If you are using MVVM, you can use event triggers to solve your problem. This way, you can still separate your UI requirements from your application logic.
Example 1
Example 2
Related
I have a Grid with a Button inside. The button has Flyout menu attached.
I implemented an action which opens the flyout menu when the button is tapped/clicked. This is the default behavior which does not require event writing. I also implemented an action when the grid is tapped/clicked.
The problem is that I do not want the grid to react when I tap/click the button. Based on this fine read, it all makes sense, but in my case, I do not have any code behind to add the e.Handled = true; line to.
Is there any way I could stop event bubbling up the tree using XAML only? Thanks!
While I hate to poach Gusdor's points. There is a built an enumeration property to deal with this types of situations called ClickMode which you can override the default mode for Button of Release and set it at the instance as ClickMode="Press" to get the desired effect and allow it to receive HitTestVisibility individually before any parent does.
Hope this helps, cheers.
I believe you will need to write some code but not the code behind you are trying to avoid.
Create an attached behavior that subscribes to, and handles the
bubbling event.
Attach the behaviour to the element where you want
the event bubbling to stop.
There is a Microsoft article about plugging Behaviours into UWP apps https://blogs.windows.com/buildingapps/2015/11/30/xaml-behaviors-open-source-and-on-uwp/
I have a search screen in my WPF application. The screen is implemented as a UserControl in a TabItem of a TabControl. When the user switches to the Search tab, I want the focus to go into one particular field.
So I added a Loaded event handler to the UserControl tag in the Xaml and I called the Focus method of the control I want to have the initial focus in the Loaded event handler. This worked great until I upgraded the Telerik control library I'm using today. Now, when I switch to the Search tab, the focus is NOT in the field I want to have it, but I can't tell what control does have the focus.
The field I want to have focus already has GotFocus & LostFocus event handlers for other reasons. I remembered that in Win Forms, the LostFocus event handler arguments tell you which control is going to get the focus. So I put a breakpoint in my LostFocus handler & discovered that the arguments to the LostFocus event handler in WPF don't include that information.
How can I figure out where the focus is going without putting GotFocus handlers on every control in my UserControl?
Tony
You can try putting your breakpoint on the LostKeyboardFocus Attached Event instead of the LostFocus Event. It uses the KeyboardFocusChangedEventArgs Class which does have properties that show which element had focus and where the focus is going.
private void textBox1_LostKeyboardFocus(object sender, KeyboardFocusChangedEventArgs e)
{
textBox1.Text = ((FrameworkElement)e.NewFocus).Name ;
}
Try to press Tab Key and see if it helps you find the control in focus.
You can also use Snoop as suggested in this Q/A: Any tips on debugging focus issues in WPF?
For starters, Snoop shows the current focused element and the current
FocusScope in the status bar.
You can get it to show you all the GotFocus and LostFocus events:
1. Run your app.
2. Run Snoop.
3. Choose your app in the dropdown.
4. Click the binoculars ("Snoop") button.
5. On the right pane, click the Events tab.
6. Click to bring down the dropdown.
7. Scroll down to the Keyboard section and check GotKeyboardFocus, LostKeyboardFocus, and optionally the PreviewXXX events.
8. Now do what you need to do to manipulate focus and watch the Snoop window.
Similarly you can track the FocusManager events the same way.
I just have a form, and using this.Controls.Add in the form I have added a container control which basically fills the whole background area of the form (and contains many other controls like datagridviews, comboboxes etc), so I can't click off of it.
Now, in the form class, I want to add some keyboard shortcuts.. Like, F5 saves my work for instance. Anyway, I have hooked up to the control's keydown even in the form class, but, it doesn't seem to fire!
Can anyone tell me why?
Thanks,
Isaac
It would probably have helped if you would have described which control you were adding. You are most likely adding a control that is trying to read the keyboard events. For the form to still get those events, change this property:
this.KeyPreview = True;
I think I'm going crazy...
I have Canvas with event handlers for MouseMove & MouseLeftButtonUp.
However MouseLeftButtonUp is not being fired when it happens with cursor over TextBlock that is inside canvas.
(it fires just fine when I release mouse button in empty space of the canvas)
I tried attaching handler via AddHandler and using regular += syntax, nothing seems to work.
I tried using Canvas.CaptureMouse() but it doesnt seem to work either (CaptureMouse returns true btw).
MouseLeftButtonUp just doesnt want to propagate to it's parent when it happens over TextBlock (or any other element with IsHitTestVisible = true) inside Canvas.
Please help.
First I'd like to say that you are not going crazy. I've seen this before in Silverlight applications. Silverlight has some interesting event strategies. Silverlight events follow a bubble up approach for routed events but not with all events (msdn has some information on this) The events you are listening to are in that list but they are being handled by the TextBlock. Most UIElements have IsHitTestVisible=true so that mouse events and others are captured by the control and not bubbled up to its parent. Setting IsHitTestVisible=false should solve the problem. Other than that I can tell you what I have tried to overcome this issue when needing IsHitTestVisible=true.
Set the event hanlder from the parent on the TextBlock. Downside is you need to do this for every control in your canvas.
Try to fire the event through an extension class. I could not get this one to work cause i couldn't fire events using reflection.
You mentioned you tried AddHandler - did you try the AddHandler overload that accepts two parameters, the second one being "true" to indicate you want to get handled events as well?
When using a WPF label as a keyboard shortcut mechanism, is there an event fired for this?
and 2 minutes later I actually find this:
AccessKeyManager.AccessKeyPressed