I have a win form with lot of controls:
I want to know when user enters 'txt2' exactly after he entered 'txt1'. In other words when user is in 'txt2' I want to know was previous control 'txt1' or not.
What is the best way to such thing?
You could just keep a module-level variable of the type Control that stores the last control to receive focus. Since you need to keep track of each control which receives focus, each control needs to subscribe to a common event handler for the Enter event. In that event you will assign the control that has been entered to the module-level variable, but before that you can test for the jump between 'txt1' and 'txt2'.
Related
I have windows form application which has several user controls - each one is displayed when the relevant option is selected from a listbox.
Some of the user controls need to have access to data stored in a different user control so User Control A needs to know a value of a textbox stored in User Control B. I have done my exposing some properties in the user control B. This all works fine when the application first loads and no values are changed.
The problem I am having is if the value of the textbox in user control B is changed it is not picked up by user control A.
Do I have to do something with NotifyPropertyChanged? Any suggestions please?
Two solutions here:
Create a series of public properties and handle passing values where the Form objects are newed up.
Create an event to communicate when things change and register an event handler in the target Form to accept the change. This is similar in theme to the INotifyPropertyChanged interface but that's only required/advised for formal databinding scenarios.
I prefer events for this kind of thing.
I have implemented a custom Undo/Redo stack and Im trying to get it to work with the WPF TextBox.
I have turned off the built in Undo-mechanism and hooked up my custom Undo on Ctrl+Z. Everything works fine accept that the caret in the TextBox is always being moved to index 0 on every undo/redo. The question is how to solve this?
I have tried having a custom behaviour on the TextBox which listens to TextChanged and is localizing the last change in the text-string. But this only works unless you start typing the same letter several times in a row. The my method breaks down.
What I ideally want is some kind of behaviour that only makes actual changes to the TextBox.Text-property. As it is now it is updated completely for every Undo, even if its only the last entered letter that is removed. This is of course no suprise since it listens to the Text-property on my PresentationModel which is triggering PropertyChanged on Undo.
But wouldnt it be great if there was some more fine-detailed way of telling exactly what had changed with the property-value, that only one or a couple of letters where inserted/removed in the string value. Then the TextBox could change only that without having to refresh its entire Text-value. Is there any such way of telling the TextBox this allready or could it be possible to make a custom TextBox that behaved in this way? Then it would be possible to pinpoint the exact location for the new caret without having it go straight back to 0 for every propertychange-update!
In WPF 3.5, is there a property of the combo box will allow the user to undo the selection they've made?
Code
If you look to a way to reset the selection from code (you wrote a property), try the following:
cboYourCombo.SelectedIndex=-1
or
cboYourCombo.SelectedItem=null;
Keyboard Shortcut
If you look for a keyboard shortcut to reset, I've never seen. But if you want, you can do it on your own, it's probably easy:
Attach an EventHandler to the PreviewKeyDown-event of your combobox (or register a general event-handler that works for all comboboxes in your window/app), check the key and if its the key you want to reset, use the code above to reset the selection. Please note, in the PreviewKeyDown-event you can also check for special-keys such as the control-key.
Provide an empty Value
However I think, better would be to add an empty entry and then preselect this empty value. If the user has changed the selection and wants to reset, he can select the empty value. Otherwise you change the standard UI-behaviour and not all people like this.
What do you mean by "undo"? Do you mean something like CTRL+Z (or an undo button), or something like CANCEL? Implementing true undo/ctrl+z on a combo box is something very few applications do, and it will surprise the user. This is a very bad idea, unless you have a very good reason.
If you have a very good reason to go against the design of most windows apps, you can add a handler for SelectionChanged, and implement your own history. Then, if the user either uses a keydown (ctrl+z), or clicks an "undo" button, you can set the selection yourself.
Alternately, if you don't really want an UNDO feature, and actually want a CANCEL feature (a common feature in UI apps), then you shouldn't worry about each control individually. Just keep a set of stored settings (in some custom class), and set all the controls back to the values that were stored. In the case of a combo box, you'd want to set the Selection property.
Suppose I have a Window with TextBoxes I want to use the values. Right now I'm thinking of either:
1) Updating each associated value once the cursor is out of focus, and once the user presses Ok I start the program
2) Once the user presses Ok, I retrieve all the values at once then start the program
I'm not sure which one is better though. First alternative seems more modular, but there's more semantic coupling since I each new box is supposed to be updating its respective value.
I realize this isn't all that important, but I'm trying to understand when to centralize and when not to. Other better approachers are appreciated too.
Use data binding to bind the text boxes' contents to objects in your code behind. WPF will take care of updating your attributes. Usually updating the data-bound value is done when the focus is lost on text boxes. However, you can also specify that it will happen whenever the value changes.
I hope this makes sense.
I have created several WPF User Controls. The lowest level item is 'PostItNote.xaml'. Next, I have a 'NotesGroup.xaml' file that has an ItemsControl bound to a List of PostItNotes. Above that, I have a 'ProgrammerControl.xaml' file. Each ProgrammerControl has a grid with four different NotesGroup user controls on it (and each NotesGroup contains 0-many PostItNotes.
Then, I have my main window. It also has an ItemsControl, bound to a list of Programmers.
So, you end up with a high level visual view of a list of programmers, each programmer has four groups of tickets, each group of tickets has many PostItNotes.
The trouble I'm having, is that I want to respond to a mouse click event in my mainWindow's code behind file.
I can add a MouseClick event into my PostItNote.xaml.vb file and that is getting called when the user clicks a PostItNote, and I can re-raise the event; but I can't seem to get the NotesGroup to listen for that event. I'm not sure if that's even the correct approach.
When the user clicks the PostItNote, I'm going to do a bunch of business-logic type stuff that the PostItNote control doesn't have a reference to/doesn't know about it.
Can anyone point me in the right direction?
You have a couple choices:
Use the PreviewXXX events which are fired during the "tunneling" phase of WPF event routing. The parent controls can always preview the events going down through them to children.
Use the more advanced approach to hooking up events leveraging the AddHandler method to which you can pass a parameter called "handledEventsToo" which basically means you want to know when the event happened "within" you even if some descendent element handled the event itself.
I am going to take a flyer here. You probably don't want to be handling the event that high up; not really anyway. You are catching the event at the lower levels, which is unavoidable. Consider invoking a routed command from the PostItNote click event handler.
The routed commands bubble up and tunnel down through the tree. You can have an architecture where a high-level handler can listen to a logical event (Opening a postit note perhaps?). The handler for this doesn't need to care where the command originates from. It might be from you clicking something, it might be from clicking on a toolbar button. Both are valid scenarios.
It sounds like you are creating some kind of custom UI, am I right? You want the application to respond to the users interactions. That is what the RoutedCommands are for.