[FIXED] Dynamic population of dropdown list added to Eclipse toolbar within Eclipse plugin

Issue

The subject topic seems easy enough in other areas of Eclipse plugin development such as ones own toolbars on dialogs. In this instance, I've added a drop-down to the main toolbar within my perspective, via the plugin.xml as follows

<menuContribution
        locationURI="toolbar:org.eclipse.ui.main.toolbar">
    <toolbar
            id="com.company.ui.toolbar2">
            // other items removed for clarity

        // following is a drop-down
        <command
                commandId="com.company.ui.mydropdown"
                label="%config.label.default"
                icon="icons/myIcon.png"
                style="pulldown">
            <visibleWhen checkEnabled="false">
                <reference definitionId="com.company.ui.visibilityTester"/>
            </visibleWhen>
        </command>
    </toolbar>
</menuContribution>

I've got the command defined elsewhere and a handler in the plugin.xml file which currently works as it would for a button.

However, the dropdown is unpopulated. I need a way to dynamically populate for the following reasons:

1. Dropdown list content comes from an API
2. One of the list items (or clicking the list like a button) launches a dialog that can edit the list
3. Closing the dialog means the list needs to be refreshed (rebuilt) and the selected/active item re-evaluated

I also need to be able to hook a user selecting a different list item and calling my API.

I've noticed other examples online try and create the dropdown differently, but I have knowledge gaps about how these wire up. For example, where a Contribution is used, it is not always clear how this links back to the particular definition in the plugin.xml file. I have not seen an example that shows this clearly.

I need to support Eclipse 4.4.2 and later, so contemporary Eclipse 4 examples may not be apt.

Any help appreciated.

Solution

The answer is to add a control to the toolbar section of the menu contributions like:

<menuContribution locationURI="toolbar:org.eclipse.ui.main.toolbar">
    <toolbar id="com.company.ui.customToolbar">
        <control
            class="com.company.ui.MyDropDownContribution"
            icon="icons/yourIconHere.png"
            label="%config.label.default">
            id="theDropdown">
            <visibleWhen checkEnabled="false">
                <reference definitionId="com.company.ui.isMyTestCaseSatisfied"/>
            </visibleWhen>
        </control>
    </toolbar>
</menuContribution>

And then to implement a contribution class extending WorkbenchWindowControlContribution. My simplified code, which includes the means to launch an EXE from one of the list items (and could be re-used to do something else), essentially is:

public class MyDropDownContribution extends
        WorkbenchWindowControlContribution {

    private Combo dropdownlist;

    private boolean listenerAdded = false;
    private String currentlySelected = "Item 1";
    private String[] listOfItems = new String[]{ "Item 1", "Item 2", "Item 3", "Launch my EXE" };

    private final SelectionAdapter selectionListener = new SelectionAdapter() {
        @Override
        public void widgetSelected(SelectionEvent e) {
            if(e.widget instanceof Combo) {
                // if the selection is currentlySelected, do nothing
                if(dropdownlist.getText().equals(currentlySelected)) {
                    return;
                }

                //if the selection is to launch 'something', do that
                if(dropdownlist.getText().equals("Launch my EXE")) {
                    launchExecutable();
                } else {
                    // otherwise, a new item has been selected, do what you need to
                }
            }
        }
    };


    private void launchExecutable() {
        // place your code to launch your EXE here - you could do some other special case, not just launch EXE
    }


    @Override
    protected Control createControl(Composite parent) {
        Composite container = new Composite(parent, SWT.NONE);
        GridLayout glContainer = new GridLayout(1, false);
        glContainer.marginTop = 0;
        glContainer.marginHeight = 0;
        glContainer.marginWidth = 0;
        container.setLayout(glContainer);
        GridData glReader = new GridData(SWT.FILL, SWT.FILL, false, false, 1, 1);
        glReader.widthHint = 150;
        dropdownlist = new Combo(container, SWT.BORDER | SWT.READ_ONLY
                | SWT.DROP_DOWN);
        dropdownlist.setLayoutData(glReader);
        populateDropdown();
        toggleComboListener();
        return container;
    }

    private void toggleComboListener() {
        if(listenerAdded) {
            dropdownlist.removeSelectionListener(selectionListener);
        } else {
            dropdownlist.addSelectionListener(selectionListener);
        }
        listenerAdded = !listenerAdded;
    }

    public void populateDropdown() {
        PlatformUI.getWorkbench().getDisplay().syncExec(new Runnable() {
            @Override
            public void run() {
                dropdownlist.setItems(new String[]{});
                for(String itemName : listOfItems) {
                    dropdownlist.add(itemName);
                }
                dropdownlist.setText(currentlySelected);
            }
        });
    }
}

Answered By - majixin