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SWT Text focusLost event sended multiple times

I use a SWT Text field and I want to prevent it from being de-focused while it has no Text entered or just white spaces. Also I want to inform the User if that´s the case.
My current solution is that I check it inside a FocusListener´s focusLostMethod.
But the focusLost Event is sended twice so the User will get informed twice and thats not what I want. So my Questions are:
Is it normal that the focusLostEvent ist sended multiple times? Or is there something wrong in my application?
If it is normal: Is there a possibility to ensure the User gets informed just once?

This code here works just fine. SWT.FocusOut is only fired one:
public static void main(String[] args)
{
Display display = new Display();
Shell shell = new Shell(display);
shell.setText("StackOverflow");
shell.setLayout(new FillLayout());
final Text text = new Text(shell, SWT.BORDER);
text.addListener(SWT.FocusOut, new Listener()
{
#Override
public void handleEvent(Event event)
{
if (text.getText().trim().length() < 1)
{
Display.getDefault().asyncExec(new Runnable()
{
#Override
public void run()
{
System.out.println("Please enter something!");
if (text != null && !text.isDisposed())
{
text.setFocus();
text.forceFocus();
}
}
});
}
else
{
System.out.println("Nothing to see here, move along.");
}
}
});
new Text(shell, SWT.BORDER);
shell.pack();
shell.open();
while (!shell.isDisposed())
{
if (!display.readAndDispatch())
{
display.sleep();
}
}
display.dispose();
}

Java SWT List - make it unselectable

I wish to use org.eclipse.swt.widgets.List just to present some data. User should not be allowed to select any item.
I could just:
List list = new List(this, SWT.V_SCROLL);
list.setEnabled(false);
But then I will loose scrolling feature. How can I just make list items unselectable?

Another alternative is to use a Table instead of List and disable selection painting like this:
table.addListener(SWT.EraseItem, new Listener() {
#Override
public void handleEvent(Event event) {
event.detail &= ~SWT.SELECTED;
event.detail &= ~SWT.HOT;
}
});

You could try to clear selection each time user selects an item. The selection will be visible for a short time interval, though.
list.addListener(SWT.Selection, new Listener() {
#Override
public void handleEvent(Event event) {
list.setSelection(new String[0]);
}
});

If you don't like my other answer with clearing selection, you could try to keep the list disabled, but inside a ScrolledComposite. It will look disabled, but scrolling will work. Here is a snippet:
public static void main(String[] args) {
final Display display = new Display();
final Shell shell = new Shell(display);
shell.setLayout(new FillLayout());
final ScrolledComposite scrolledComposite = new ScrolledComposite(shell, SWT.H_SCROLL | SWT.V_SCROLL);
scrolledComposite.setExpandHorizontal(true);
scrolledComposite.setExpandVertical(true);
scrolledComposite.setBackground(display.getSystemColor(SWT.COLOR_CYAN));
final List list = new List(scrolledComposite, SWT.NONE);
list.setEnabled(false);
scrolledComposite.setContent(list);
scrolledComposite.addListener(SWT.Resize, new Listener() {
#Override
public void handleEvent(Event event) {
final Point size = list.computeSize(SWT.DEFAULT, SWT.DEFAULT, true);
scrolledComposite.setMinSize(size);
}
});
for (int i = 0; i < 1000; i++) {
list.add(Integer.toString(i));
}
shell.open();
while (!shell.isDisposed()) {
if (!display.readAndDispatch()) {
display.sleep();
}
}
display.dispose();
}
Arrow keys and page up/down down do not work, so you will have to register key listeners and implement scrolling with keyboard.

SWT Popup Composite unexpected disposal

So I've stolen this cool PopupComposite, and I am really satisfied with it.
There's just one issue. If it put a org.eclipse.swt.widgets.Text in it, I open the popup, focus the Text, and press ESC, then both the Text and the PopupComposite dispose themselves.
I really can't figure out where the dispose call is coming from. Is it a Shell issue? What Shell should I use with the popup?
SSCCE:
/**
*
* #author ggrec
*
*/
public class PopupCompositeTester
{
public static void main(final String[] args)
{
new PopupCompositeTester();
}
private PopupCompositeTester()
{
final Display display = new Display();
final Shell shell = new Shell(display);
shell.setLayout(new GridLayout(1, false));
createContents(shell);
shell.pack();
shell.open();
while (!shell.isDisposed())
{
if ( !display.readAndDispatch() )
display.sleep();
}
display.dispose();
}
private static void createContents(final Composite parent)
{
final Button button = new Button(parent, SWT.PUSH);
button.setText("Poke Me");
final PopupComposite popup = new PopupComposite(parent.getShell());
new Text(popup, SWT.NONE);
popup.pack();
button.addSelectionListener(new SelectionAdapter()
{
#Override public void widgetSelected(final SelectionEvent e)
{
popup.show( Display.getDefault().map(parent, null, button.getLocation()) );
}
});
}
}

The reason for this is because when you focus the text field and press Escape, the field sends a SWT.TRAVERSE_ESCAPE event to its parent shell. The shell (in your case not being a top-level shell) responds by calling Shell.close(). You can work around that by adding a traverse listener to your text field, which would cancel the event (code below).
new Text(popup, SWT.NONE).addTraverseListener(new TraverseListener() {
#Override
public void keyTraversed(TraverseEvent e) {
if(e.detail == SWT.TRAVERSE_ESCAPE) {
e.doit = false;
}
}
});
Keep in mind, this is a rather crude solution to your specific issue. I would not recommend using this for anything other than testing purposes. You can read more about this here -> http://help.eclipse.org/indigo/index.jsp?topic=%2Forg.eclipse.platform.doc.isv%2Freference%2Fapi%2Forg%2Feclipse%2Fswt%2Fevents%2FTraverseEvent.html
And here: http://help.eclipse.org/helios/index.jsp?topic=%2Forg.eclipse.platform.doc.isv%2Freference%2Fapi%2Forg%2Feclipse%2Fswt%2Fwidgets%2FShell.html

Because my "bug" is actually a normal behaviour of the SWT platform, I've used the following workaround:
/**
* Lazy initialization of the popup composite
*/
private void createPopup()
{
// popupContainer is now a field
if (popupContainer != null && !popupContainer.isDisposed())
return;
// ... create popup AND its contents ...
}
and in the button listener:
createPopup();
popup.show( Display.getDefault().map(parent, null, button.getLocation()) );
Thank you #blgt

How to update/refresh a view in an eclipse plug-in?

I have an eclipse plug-in with a single view (like the eclipse helloworld-view-plugin-project). In the view-file I get an event when I want to update the view.
In this view I have a GridData in a Group with multiple labels. I have several services which register to the programe and whose status should be shown in this GridData.
Edit: In order to better show my problem I updated this post and added the whole code:
CreatePartControl():
public void createPartControl(Composite _parent) {
parent = _parent;
createContents();
addBindings();
makeActions();
contributeToActionBars();
}
CreateContents():
protected void createContents() {
// fixed
checkIcon = //...
errorIcon = //...
smallFont = SWTResourceManager.getFont("Segoe UI", 7, SWT.NORMAL);
// content
gl_shell = new GridLayout(1, false);
//margins, etc. for gl_shell
parent.setLayout(gl_shell);
final Label lblGreeting = new Label(parent, SWT.NONE);
lblGreeting.setLayoutData(new GridData(SWT.FILL, SWT.TOP, false, false, 1, 1));
lblGreeting.setText("Hi " + Preferences.getPreName());
// -- GROUP YOUR STATS (show all services)
createStatusGroupBox();
}
createStatusGroupBox():
private Group grpYourStatus = null; // outside the method for access in listener (below)
private void createStatusGroupBox() {
grpYourStatus = new Group(parent, SWT.NONE);
grpYourStatus.setLayoutData(new GridData(SWT.FILL, SWT.TOP, true, false, 1, 1));
grpYourStatus.setText("Your upload status");
grpYourStatus.setLayout(new GridLayout(3, false));
// add message if no service is registered
if ( r.getServiceList().size() == 0 ) {
Label status = new Label(grpYourStatus, SWT.NONE);
status.setText("No service registered.");
new Label(grpYourStatus, SWT.NONE); //empty
new Label(grpYourStatus, SWT.NONE); //empty
}
// add labels (status, message, name) for each registered service
for ( IRecorderObject service : r.getServiceList() ) {
Label name = new Label(grpYourStatus, SWT.NONE);
Label status = new Label(grpYourStatus, SWT.NONE);
Label message = new Label(grpYourStatus, SWT.NONE);
message.setFont(smallFont);
message.setLayoutData(new GridData(SWT.LEFT, SWT.CENTER, true, false, 1, 1));
service.getServiceViewItem().setLabelsAndIcons(name, status, message, checkIcon, errorIcon); //this also sets the values of the labels (label.setText(...) via data binding)
}
Unfortunately, I don't know what the right way is to update/reset it. I tried the following:
listener (which should update the view / the services-list):
r.addPropertyChangeListener(BindingNames.SERVICE_ADDED, new PropertyChangeListener() {
public void propertyChange(final PropertyChangeEvent evt) {
Display.getDefault().asyncExec(new Runnable() {
public void run() {
// This "redraws" the view, but just places the whole content (generated in createStatusGroupBox()) above the other parts.
//Display.getCurrent().update();
//createStatusGroupBox();
//parent.layout(true);
//parent.redraw();
// disposes grpYourStatus-Group but doesn't show anything then
grpYourStatus.dispose();
createStatusGroupBox();
grpYourStatus.layout();
grpYourStatus.redraw();
}
});
}
});
I also tried the following statements (individually); all without success:
parent.redraw();
parent.update();
parent.layout();
parent.layout(true);
parent.refresh();
In this post I read the following:
createPartControls is that time of the life cycle of a view, where its
contained widgets are created (when the view becomes visible
initially). This code is only executed once during the view life
cycle, therefore you cannot add anything here directly to refresh your
view.
Eclipse parts typically update their content as a reaction to a
changed selection inside of the workbench (e.g. the user might click
on another stack frame in the debug view).
Unfortunately, I don't know what to else I could try and I didn't find anything helpful with searches... thank's for your help and suggestions!

I finally found the answer (together with AndreiC's help!):
my listener now looks like this:
r.addPropertyChangeListener(BindingNames.SERVICE_ADDED, new PropertyChangeListener() {
public void propertyChange(final PropertyChangeEvent evt) {
Display.getDefault().asyncExec(new Runnable() {
public void run() {
// remove grpYourStatus from parent
grpYourStatus.dispose();
// add grpYourStatus (with updated values) to parent
createStatusGroupBox();
// refresh view
parent.pack();
parent.layout(true);
}
});
}
});
The rest is the same like the code above.

I do not know the API by heart, but have you tried parent.update()?

SWT/JFace: remove widgets

Group group = new Group(parent, SWT.NONE);
StyledText comment = new StyledText(group, SWT.BORDER_DASH);
This creates a group with a text area inside.
How can I later delete the text (remove it from the screen so that I can replace it with something else)?

Use Widget.dispose.
public class DisposeDemo {
private static void addControls(final Shell shell) {
shell.setLayout(new GridLayout());
Button button = new Button(shell, SWT.PUSH);
button.setText("Click to remove all controls from shell");
button.addSelectionListener(new SelectionListener() {
#Override public void widgetDefaultSelected(SelectionEvent event) {}
#Override public void widgetSelected(SelectionEvent event) {
for (Control kid : shell.getChildren()) {
kid.dispose();
}
}
});
for (int i = 0; i < 5; i++) {
Label label = new Label(shell, SWT.NONE);
label.setText("Hello, World!");
}
shell.pack();
}
public static void main(String[] args) {
Display display = new Display();
Shell shell = new Shell(display);
addControls(shell);
shell.open();
while (!shell.isDisposed()) {
if (!display.readAndDispatch()) {
display.sleep();
}
}
display.dispose();
}
}

Another option is to use a StackLayout to switch between underlying controls. This prevents you from running into a "widget is disposed" error.

You have to either call comment.changeParent(newParent) or comment.setVisible(false) to remove/hide it from the Group. I am unsure if comment.changeParent(null) would work but I would give that a try.
We do it this way because SWT uses the Composite Pattern.

group.getChildren()[0].dispose() will remove the first child. You need to find a way to identify the precise child you want to delete. It could be comparing the id. You can do that by using the setData / getData on that control:
For example:
StyledText comment = new StyledText(group, SWT.BORDER_DASH);
comment.setData("ID","commentEditBox");
and then:
for (Control ctrl : group.getChildren()) {
if (control.getData("ID").equals("commentEditBox")) {
ctrl.dispose();
break;
}
}