How to handle event in MVVM ?

Hi everyone ,
I'm currently learning to use MVVM model , about command handling, it's ok for me now. But , about Event handling, it causes me some difficulties.
Can anyone help me to solve this problem : I have a window and I want to handle the its Closing event . For example, when the window is closing , if the bool chxAllowToClose.IsChecked = true , the window can be closed, vice versa, the window will display a
warning message : "Please check the checkbox" and then prevent the close operation
Thank you

Windows can be closed in a number of ways and the simplest way to trap them would be to handle Window Closing in code behind.
This is also the easiest way to show dialogs if that's how you wanted the warning message to appear.
This:
chxAllowToClose.IsChecked
Looks like a checkbox to me, seeing as you have IsChecked.
That presumably means you already have that bound to a viewmodel and visible to the user.
You can therefore just test that value from the view.
If you prefer to hide that instead then there are several options.
You could have a dependency property and a binding in code behind which binds to the viewmodel. Test that in your event.
Or
You could save the value when it changes to application.current.resources. Since dependency properties and bindings are a bit wordy this is easier.
Or
You could have just a variable in the view code behind and use messenger to tell that when the value changes from the viewmodel:
http://social.technet.microsoft.com/wiki/contents/articles/26070.communicating-between-classes.aspx
Please don't forget to upvote posts which you like and mark those which answer your question.
My latest Technet article - Dynamic XAML

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Hi Chandan,
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Hi Mahesh,
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Message was edited by:
Shweta R Shanbhag

How to handle Event in JACOB API

Hi,
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Windows can be closed in a number of ways and the simplest way to trap them would be to handle Window Closing in code behind.
This is also the easiest way to show dialogs if that's how you wanted the warning message to appear.
This:
chxAllowToClose.IsChecked
Looks like a checkbox to me, seeing as you have IsChecked.
That presumably means you already have that bound to a viewmodel and visible to the user.
You can therefore just test that value from the view.
If you prefer to hide that instead then there are several options.
You could have a dependency property and a binding in code behind which binds to the viewmodel. Test that in your event.
Or
You could save the value when it changes to application.current.resources. Since dependency properties and bindings are a bit wordy this is easier.
Or
You could have just a variable in the view code behind and use messenger to tell that when the value changes from the viewmodel:
http://social.technet.microsoft.com/wiki/contents/articles/26070.communicating-between-classes.aspx
Please don't forget to upvote posts which you like and mark those which answer your question.
My latest Technet article - Dynamic XAML

How to handle event when the user closing the browser (Urgent Please)

Hi,
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i want to display some alter message when user trying to close the browser...
Please can any one help me how i have to do this...........
Thanks.

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frame.getContentPane().add(label,BorderLayout.CENTER);
frame.setSize(250, 100);
frame.setLocation(300, 400);
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frame.setVisible(true);
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Hi!
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Method 1
Write annonymus inner classes in the same class
Method 2
=======
Write a seperate class which extends the adapter class of the event handling and create an object of that in the main class and assign it to the components with addActionHandler() method.
I am trying to use the second one and I have the following design issue.
I have a class frmMain.java in which I have a frame and to that frame I am adding a panel which consists of 'N' No. of components.
I want to make this panel added to the frame when I click on a menu item (login) and want to remove the panel from frame when I click on a menu item(logout).
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1. Your JFrame is now subject to receive action events from anywhere. You will have to be more careful that you respond only to the right events.
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3. With individual ActionListener classes, it's easier to add the same listener to multiple components and no need to worry about source.
4. Kind of the same thing: With individual classes, the event and its consequences are so tightly coupled.
End preaching....basically, my style boils down to what I call the tool set vs Swiss army knife rule. Java seems designed around the concept of a large number of specific purpose classes vs a smaller number of multi purpose classes and I think its a design methodology that makes sense, because I believe strongly in functional isolation in my code.

How to handle events between two custom components?

Hi ,
i want to handle events between two custom components, example if an event is generated in one custom component ,and i want to handle it any where in the application.....can any one suggest me any tutorial or meterial in this concept...
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How to handle events when artboard list change in Illustrator?

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How to handle events in J Table (Enter event)

I created a J Table having multiple rows and columns. I want to have the event to happen on second column, on entering the code on first column, and then pressing ENTER.
Eg:
first column i enter code : say A010
In the code master, the description matching the above code is "HIGH TENSION CABLE".
When I enter "A010" in the first column and press "ENTER", i want the description to appear in the second column i.e. HIGH TENSION CABLE (by referring the code master, which I already created).
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Thanking you in advance.
PS: I shall appreciate if the reply is also sent to my email id: "[email protected]".
N Murali

This code would do your work
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
import javax.swing.table.*;
public class TestTable
    private JTable table;
    private AbstractTableModel model;
    private DefaultTableModel defaultModel;
    private JScrollPane jsp;
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        table = new JTable();
        defaultModel = new DefaultTableModel(10,5);
        setModel(defaultModel);
        jsp = new JScrollPane(table);
        hookSetTextOnEnter();
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                int column = table.getSelectedColumn();
                System.out.println(" SELECTING NEXT ROW "+row+""+column);
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    public void setModel(TableModel model)
        table.setModel(model);
    public JScrollPane getScrollPane()
        return jsp;
    public JTable getTable()
        return table;
    public static void main(String[] args)
        TestTable tt = new TestTable();
        JFrame frame = new JFrame("Test Table");
        frame.getContentPane().add(tt.getScrollPane());
        frame.pack();
        frame.setVisible(true);
}------- Unformatted Version------------
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
import javax.swing.table.*;
public class TestTable
private JTable table;
private AbstractTableModel model;
private DefaultTableModel defaultModel;
private JScrollPane jsp;
public TestTable()
table = new JTable();
defaultModel = new DefaultTableModel(10,5);
setModel(defaultModel);
jsp = new JScrollPane(table);
hookSetTextOnEnter();
protected void hookSetTextOnEnter()
String actionName = "selectNextRowCell";
final Action enterAction = table.getActionMap().get(actionName);
Action myAction = new AbstractAction()
public void actionPerformed(ActionEvent e)
int row = table.getSelectedRow();
int column = table.getSelectedColumn();
System.out.println(" SELECTING NEXT ROW "+row+""+column);
if(row != -1 && column == 2 )
Object value = table.getValueAt(row,column);
if(value != null && value.toString().equals("A010"))
table.setValueAt("HIGH TENSION CABEL",row,column+1);
enterAction.actionPerformed(e);
table.getActionMap().put(actionName,myAction);
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table.setModel(model);
public JScrollPane getScrollPane()
return jsp;
public JTable getTable()
return table;
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TestTable tt = new TestTable();
JFrame frame = new JFrame("Test Table");
frame.getContentPane().add(tt.getScrollPane());
frame.pack();
frame.setVisible(true);
Thanks,
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If you are young work to Learn, not to earn.

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Proud to use LW/CVI from 3.1 on.
My contributions to the Developer Zone Community
If I have helped you, why not giving me a kudos?

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Hello,
I'm doing some measurement. During the measurement I want the user to see some activity dialog - that's easy to do. Before the measurement starts I dynamically run VI (EX_Progress.vi) that shows some activity and then I do the measurement (in my example simulated by random number generation) . After the measurement is done (or error occurs) I can dynamically abort the activity indicator. But on the other hand I want to give to the user chance to abort the measurement manually via the activity dialog by STOP button. There are some ways how to do it via global variable and check every iteration in the main VI it's state but isn't there some better way? Would be nice to run event in the main VI when the user pushes the STOP button in the Progress VI. Is it possible to achieve this using register events? I tried but don't really now how I'm not familiar with this technique.
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Message Edited by ceties on 11-26-2007 01:34 PM
LV 2011, Win7
Attachments:
Ex.zip ‏374 KB

OK, here's an example using User Events. It doesn't directly have the main VI listen for the Button press event in the subVI. Instead, it has the main VI listen for a custom User Event that the subVI fires every time there's a button press. You could theoretically directly listen to the button press directly from the Main VI, but you would have to somehow get that control's reference to the main VI. That would require storing a copy of it in a global or some such method. This method I will show here is very common and is definitely worth learning.
For more info on User Events, refer to the LabVIEW help. You can learn more by clicking any of the User Event VIs and selecting Help from the shortcut menu.
(I didn't set the subVIs front panel to open automatically, so you'll have to do that yourself to see anything from this demo...)
Message Edited by Jarrod S. on 11-26-2007 02:51 PM
Jarrod S.
National Instruments
Attachments:
Example.zip ‏25 KB

How to handle events on standard toolbar

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You have to enable the menus on toolbar as
form.EnableMenu(1288, True)
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If zou have the datas as UDO, use
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dont forget to take
ObjectType="your udo name"
to the form for specify from which UDO will be the datas.
If you dont have udo, you need enable themenus in toolbar and in menuevent catch the events and create own logic for this.

How to handle event in MVVM ?

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