Advanced use of the filtered items selection dialog

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

Adding selected items history

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

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: