For a "common" look and feel I have an app that shows the paste/cut/copy buttons in a ribbon but I want to have paste always disabled no matter what field is selected. How do I approach this?
By default all the controls in WPF have a default ContextMenu that allows copy, paste and cut. You can disable this menu by setting this property as “{x:Null}”, but the keys associated with the menu options still work. In order to disable this commands we can use the DataObject class, which have handlers to attach any DepencencyObject in case on Copy or Paste:
DataObject.AddPastingHandler(control, this.OnCancelCommand);
DataObject.AddCopyingHandler(control, this.OnCancelCommand);
Finally in the event handler we need to cancel the current command:
private void OnCancelCommand(object sender, DataObjectEventArgs e)
{
e.CancelCommand();
}
The CancelCommand method will cancel any ApplicationCommand.Copy, ApplicationCommand.Paste and ApplicationCommand.Cut sent over the control.Now if you want to enable copying than delete the dateobject calling AddCopyingHandler code and it will work than.
Related
I have a class with public DownloadAsync Method inside, that downloads Content over Webclient. I create an Object of that class and call the download Method.
My problem is: I would like to block Elements on UI (e.g. Buttons) until the download is done. I could not find any solution so far.
One Idea is: I could call a MessageBox with message like "download is done" in the Downloadcomplete Method and to call somehow an Eventhandler for MessageBox. But how?
Any idea how to solve my problem?
EDIT: I know hot to disable Elements, but because of asynchronuous download in the download method, I don't know when the download is over in order to enable back the elements
add an event to your data class, and when the download has finished then trigger the event handler.
then in your page do something like this in your initialiser
BusyMessage.Visibility = Visibility.Visible;
this.DataContext = MYDownloaderClass.downloadedData;
MyDownloaderClass.hasFinished += new EventHandler(hasFinished);
}
void hasFinished(object sender, EventArgs e){
BusyMessage.Visibility = Visibility.Collapsed
}
You should just disable all the elements - set IsEnabled to false on buttons etc. If you want a quick and dirty solution - you can overlay the screen with a Rectangle, Border, Grid or Popup.
Try a busy indicator with an overlay.
http://www.minddriven.de/index.php/technology/dot-net/windows-phone/wp7-xaml-viewmodel-busy-indicator
I have a WPF form with Next and Prev buttons for navigating to the next and previous months of a custom made calendar. I want to disable these buttons as soon as the user clicks on them and enable them when the mext/prev month data loads. That would prevent the user from clicking on the buttons repeatedly and the events queuing up and getting fired slowly one by one.
So far, I have tried putting the calendar data load stuff in a Dispatcher thread, and maintaining a flag to indicate whether the page is busy or not. Doesn't seem to work, and the events still pile up.
I also tried using a command for the button clicks, have the execute handler load the data, and CanExecute decide whether data can be loaded, based on a IsBusy flag. Doesn't work either.
Any pointers?
I suppose you have an event fired when the month is loaded.
To me the best solution would be to manually disable the buttons on their click event, and enable them back when the month is loaded.
I see no problem on adding some code behind in the view if needed.
What type of Command are you using?
A RelayCommand will re-run the CanExecute method when one of the properties changes, however a DelegateCommand will not.
You need to manually raise the CanExecuteChanged event on a DelegateCommand when your CanExecute parameters change.
void MyViewModel_PropertyChanged(object sender, PropertyChangedEventArgs e)
{
if (e.PropertyName == "IsBusy")
{
// Might need a Cast here if your command is of type ICommand
LoadDataCommand.RaiseCanExecuteChanged();
}
}
I fixed this by using a BackgroundWorker to load the view and checking BackgroundWorker.IsBusy in the next/prev event handlers.
Found an interesting problem that I first found in WinForms, and found again in Silverlight, and more than likely WPF as well when it comes to databinding.
I have a tab control with several tabs. As users click across the tabs, each time should be valid before allowing the user to switch from the tab.
For example, user is in a text box which is updated. Binding of text boxes is not flushed until the control loses focus. Loss of focus occurs when the cursor is moved from the control, and focus is given to another control.
In this scenario, the user tabs into a control (let's use text box for this example), and updates the text box. At this point the databinding has not flushed the control, and hence the VM has not yet seen the change. The user then uses their mouse to click the next tab of the control.
At this point things get interesting. I used the PreviewSelectionChanged (Telerik RadTabControl), as I want to check things out before the jump to the next tab occurs, and it also gives me the ability to cancel the event.
However, when I look at the VM, in this event, it still does not have the updated data. I see the VM is clean, and go ahead and allow the jump to the next tab.
As soon as this event is over however, the databindings flush, and the VM gets updated. what now? The events are out of sync! When the mouse was used to click the next tab, the textbox should have lost focus, flushed it's bindings, before the Preview of the Tab click! It's to late to jump back and say oops we didn't catch that in time!
I think I found an interesting work around to this issue - but I'm not 100% sure it will work 100% of the time. I cancel the current event, but then I use the Dispatcher and create a delegate pointing to another method with the same signature as the current event. The Dispatcher will add this message to the message pump, which by this time will now (hopefully?) be behind the messages of the VM updating...
My two questions are:
1) I'm assuming that the textbox control either didn't flush when the mouse left the control, or the process that was fired was too slow and hence the preview message was on the pump before the databinding - either way I see this to be a major issue.
2) Is the workaround a good solution?
Ok, first to answer question 1:
Just because the mouse left the textbox area, doesn't mean that the textbox lost focus. It only loses focus once something else gets focus. For example, if you moved the mouse out of the textbox and click on some other control on your page (it can be anything from a scroll viewer to another textbox, etc.) then your textbox will lose focus.
Now, based on that, the events do not happen in the wrong order. What happens is; your click event on the other tab triggers both the textbox to lose focus (and the data binding to take place) and the move to the next frame, and based on that, you basically get a race condition where the moving to the next tab happens before the databinding takes place.
About question 2:
What you can do is, set the UpdateSourceTrigger to Explicit, you will however be forced to then have some kind of text_changed event and manually update the binding.
You can read more about that here. It might not be the most complete explanation but is a good place to start.
On the other hand, you can associate some events to the textbox and force the textbox to lose focus on those events (e.g. mouse out).
Just an idea: Why not do everything in the VM's PropertyChanged event?
protected override void OnThisViewModelPropertyChanged(object sender, PropertyChangedEventArgs e) {
if(e.PropertyName == "WhateverProperty") {
//Do your magic here for whatever you want to set
}
}
Have your TabItems bound to a collection that will control is being disabled or not.
<sdk:TabControl>
<sdk:TabItem IsEnabled="{Binding SomeProperty, Converter={AmIDisabledOrWhatConverter}}" />
</sdk:TabControl>
That way, everything is triggered whenever a property is chaned in the vm. No more timing issues since everything is on the vm.
Just my two cents.
There's a design defect here, and you're trying to work around the defect instead of fixing it. You shouldn't have to figure out how to cancel the Click event on the tab. The tab shouldn't be processing Click events in the first place.
Generally speaking, if it's not legal for the user to click on a control, the control shouldn't be enabled. The tab should be disabled until the state of the view model is valid.
Your view model should be exposing a command for navigating to the next tab, and the tab should be bound to the command. The command's CanExecute method should only return true when the state of the view model on the current tab is valid.
This doesn't fix your other problem, which is that Silverlight doesn't support UpdateSourceTrigger="PropertyChanged" out of the box. But that's a solved problem (here is one example).
Note that if you implement commands to handle this wizard-like navigation in your application, you can, down the road, change the view to use something other than a tab control (e.g. to use navigation buttons like an actual wizard, or something like Telerik's PanelBar) without having to screw around with event handlers.
Change your bindings to include UpdateSourceTrigger="PropertyChanged".
This will ensure that your data sources are updated on every key stroke, not just LostFocus.
MyOwnTextBox()
{
this.TextChanged += (s, e) => UpdateText();
}
private void UpdateText()
{
BindingExpression be = GetBindingExpression(TextProperty);
if (be != null && be.ParentBinding.Mode == BindingModes.TwoWay)
{
be.UpdateSource();
}
}
I am using this class it updates my binding on the fly, however there is issue with empty string and null values, if your destination property is nullable string then this will update empty string in your destination property. You can get workaround by using some sort of string converter which will use null instead of empty string in case of nullable strings.
How can I hide one panel in Visual Studio 2008 Form Designer like a layer in PS? Otherwise, can someone recommend another better method to design multiple "screens" that must be clicked through by the user?
What you describe is a wizard, and you might want to investigate the approach from Eric J.
However, when I have cases where I want to have multiple panels in the same space within my UI and I want to switch between them in the designer, I like to use a TabControl and hide the tabs on the TabControl. This makes the UI easier to manage at design time and the code is pretty simple to switch between the tabs at run time.
I made a custom control that derives from TabControl called HiddenTabsControl that is very simple. The class only overrides the WndProc and lets the TabControl base class handle everything else. All you need to do is:
Add a New Item to your project
Choose Custom Control,
Name it something like HiddenTabsControl.
Change the base Class to TabControl, remove the Constructor and the OnPaint override that Visual Studio added.
Copy this override for WndProc into the class:
protected override void WndProc(ref Message m)
{
// Hide tabs by trapping the TCM_ADJUSTRECT message
if (m.Msg == 0x1328 && !DesignMode)
{
m.Result = (IntPtr)1;
}
else
{
base.WndProc(ref m);
}
}
Now you can change tabs in the designer and design the UI easily and in the code you can handle events to change tabs as needed. Changing the Selected tab is easily done with:
this.hiddenTabsControl.SelectedTab = this.tabPageYouWantVisible;
One side effect of removing the tabs is the space that the tabs occupy when the control is constructed. Removing them will make the space the HiddenTabsControl occupies change by shrinking it. I usually set the Anchor of the HiddenTabsControl to bottom to keep it from shrinking.
I used this Wizard code in a recent project and it worked well.
It provides the basic experience you are after.
Another less elegant, but quick hack, approach is to simply not add the panel to the parent form until runtime. In doing that, the designer has no idea where the panel belongs prior to compilation, and it won't be displayed.
For example, find the block of code where you add controls to the parent form:
//this->Controls->Add(this->panel_X);
this->Controls->Add(this->tabControl);
this->Controls->Add(this->menuStrip_topMenu);
Comment or remove the statement, then find the handle to the event that occurs when the form is loaded:
this->Load += gcnew System::EventHandler(this, &MainForm::MainForm_Load);
Then in the definition of the event handler, add the control to the form:
System::Void MainForm_Load(System::Object^ sender, System::EventArgs^ e) {
...
...
this->Controls->Add(this->panel_X);
}
I haven't experienced any unwanted side effects by doing this, but if anyone has a good reason to not I'd be interested in hearing it.
I've done a lot of searching on SO and google around this problem, but can't seem to find anything else to try.
I have a MainView (window) that contains a tab control. The tab control binds to an ObservableCollection of ChildViews (user controls). The MainView's ViewModel has a method that allows adding to the collection of ChildViews, which then creates a new tab. When a new tab is created, it becomes the active tab, and this works fine. This method on the MainView is called from another ViewModel (OtherViewModel).
What I am trying to do is set the keyboard focus to the first control on the tab (an AutoCompleteBox from WPFToolkit*) when a new tab is created. I also need to set the focus the same way, but WITHOUT creating a new tab (so set the focus on the currently active tab).
(*Note that there seem to be some focus problems with the AutoCompleteBox--even if it does have focus you need to send a MoveNext() to it to get the cursor in its window. I have worked around this already).
So here's the problem. The focusing works when I don't create a new tab, but it doesn't work when I do create a new tab. Both functions use the same method to set focus, but the create logic first calls the method that creates a new tab and sets it to active. Code that sets the focus (in the ChildView's Codebehind):
IInputElement element1 = Keyboard.Focus(autoCompleteBox);
//plus code to deal with AutoCompleteBox as noted.
In either case, the Keyboard.FocusedElement starts out as the MainView. After a create, calling Keyboard.Focus seems to do nothing (focused element is still the MainView). Calling this without creating a tab correctly sets the keyboard focus to autoCompleteBox.
Any ideas?
Update:
Bender's suggestion half-worked.
So now in both cases, the focused element is correctly the AutoCompleteBox. What I then do is MoveNext(), which sets the focus to a TextBox. I have been assuming that this Textbox is internal to the AutoCompleteBox, as the focus was correctly set on screen when this happened. Now I'm not so sure. This is still the behavior I see when this code gets hit when NOT doing a create. After a create, MoveNext() sets the focus to an element back in my MainView.
The problem must still be along the lines of Bender's answer, where the state of the controls is not the same depending on whether a new tab was created or not. Any other thoughts?
Final Update
As noted, majocha's suggestion worked.
I wanted to update this in case anyone happened upon this same problem with the AutoCompleteBox. It appears that setting focus does not activate it in the UI--you need to do a MoveNext on it to move focus forward once to the control's internal Textbox. This is based on my debugging experience, which may not be 100% scientific. If I have time, I will attempt to create a small repro project and submit it to the WPFToolkit team.
You can try defering the focus change with
Dispatcher.BeginInvoke(MyChangeFocusAction, DispatcherPriority.ContextIdle);
It will get queued after layout and properties updates are done.
I don't think it's best practice, but it works for me.
The control must be visible to be focused, you may try to defer focusing by subscribing to the IsVisibleChanged event, something similar to the following should work:
public static void setFocusLate(this Control control)
{
DependencyPropertyChangedEventHandler handler = null;
handler = delegate
{
control.Focus();
control.IsVisibleChanged -= handler;
};
control.IsVisibleChanged += handler;
}