Eclipse Plug-in Developer Guide
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Advanced use of the filtered items selection dialog

In the previous example, we saw how to create a simple subclass of FilteredItemsSelectionDialog. Now let's explore some of the advanced capabilities provided by this dialog:

• Adding selected items history
• Adding custom filters
• Adding an extra check-box to the dialog

Adding selected items history

The dialog can be configured to save and restore the history of items that have been selected.

1. In the previous part we created a subclass of FilteredItemsSelectionDialog.SelectionHistory but it do nothing. Now, we should fill out methods responsible for saving and loading objects:

      private class ResourceSelectionHistory extends SelectionHistory {
         /*
          * @see org.eclipse.ui.dialogs.FilteredItemsSelectionDialog.SelectionHistory#restoreItemFromMemento(org.eclipse.ui.IMemento)
          */
         protected Object restoreItemFromMemento(IMemento element) {
            return element.getString("resource"); //$NON-NLS-1$
         }
         /*
          * @see org.eclipse.ui.dialogs.FilteredItemsSelectionDialog.SelectionHistory#storeItemToMemento(java.lang.Object,
          *      org.eclipse.ui.IMemento)
          */
         protected void storeItemToMemento(Object item, IMemento element) {
            element.putString("resource", item.toString()); //$NON-NLS-1$
         }
      }

2. Open the dialog.
3. Select listed elements and click OK:
   • AbCdEfGh
   • AbCdEfGi
   • AbCdEfGj
   • AbCdEfHh
   • AbCdEfHi
   • AbCdEfHj
   • abCd
   • abCe
   • abCf
   • abDd
   • abDe
4. Our example dialog now looks like this:

   

Adding custom filters

Next we will expand the filter to hide all strings that start with a lower case character.

1. Create a subclass of FilteredItemsSelectionDialog.ItemsFilter, implement the necessary abstract methods and override equalsFilter(ItemsFilter) and isSubFilter(ItemsFilter). These two methods are used to optimize filtering of the view. If a new filter is added that is equal to the existing filter, no further filtering is required. If the new filter is a sub-filter of the existing filter, then filtering is only done on the items that matched the existing filter.

      private boolean onlyLowerCase = true;
     	
      private class ResourceFilter extends ItemsFilter {
      public final boolean onlyLowerCase = FilteredResourcesSelectionDialogExample.this.onlyLowerCase;
   
         public boolean matchItem(Object item) {
            String resource = item.toString();
            if (onlyLowerCase && Character.isUpperCase(resource.charAt(0)))
               return false;
            return matches(resource);
         }
         public boolean equalsFilter(ItemsFilter filter) {
            ResourceFilter resourceFilter = (ResourceFilter) filter;
            if (onlyLowerCase != resourceFilter.onlyLowerCase)
               return false;
            return super.equalsFilter(filter);
         }
         public boolean isSubFilter(ItemsFilter filter) {
            ResourceFilter resourceFilter = (ResourceFilter) filter;
            if (onlyLowerCase != resourceFilter.onlyLowerCase)
               return false;
            return super.isSubFilter(filter);
         }
         public boolean isConsistentItem(Object item) {
            return true;
         }
      }

2. On your subclass of FilteredItemsSelectionDialog, override the createFilter() method:

      protected ItemsFilter createFilter() {
         return new ResourceFilter();
      }

3. Now the dialog will only display strings that start with a lower case letter.

   

Adding an extra check-box to the dialog

We will use a check-box and a menu action to indicate whether to filter strings that start with a lower case character.

1. Extend the dialog's content area by implementing createExtendedContentArea(Composite) method:

      private Button checkButton;
     	
      protected Control createExtendedContentArea(Composite parent) {
         checkButton = new Button(parent, SWT.CHECK);
         checkButton.setText("Only Lower Case Strings"); //$NON-NLS-1$
         checkButton.addSelectionListener(new SelectionListener() {
            public void widgetDefaultSelected(SelectionEvent e) {
            }
            public void widgetSelected(SelectionEvent e) {
               if (onlyLowerCase != ((Button) e.widget).getSelection()) {
                  onlyLowerCase = ((Button) e.widget).getSelection();
                  applyFilter();
               }
            }
         });
         return checkButton;
      }

2. Next, create a new action and add it to the menu by overriding fillViewMenu(IMenuManager). Eg.:

      private Action showOnlyLowerCaseStringsAction = new ShowOnlyLowerCaseStringsAction();
      
      private class ShowOnlyLowerCaseStringsAction extends Action {
         /**
          * Creates a new instance of the action.
          */
         public ShowOnlyLowerCaseStringsAction() {
            super("Only Lower Case String", //$NON-NLS-1$
               IAction.AS_CHECK_BOX);
         }
         public void run() {
            if (onlyLowerCase != isChecked()) {
               onlyLowerCase = isChecked();
               applyFilter();
            }
         }
      }
      
      protected void fillViewMenu(IMenuManager menuManager) {
         super.fillViewMenu(menuManager);
         menuManager.add(showOnlyLowerCaseStringsAction);
      }
     

3. At the end override applyFilter() as follows:

      protected void applyFilter() {
         super.applyFilter();
         checkButton.setSelection(onlyLowerCase);
         showOnlyLowerCaseStringsAction.setChecked(onlyLowerCase);
      }

4. Now open the dialog: