问使用eclipse插件开发API在Eclipse工具栏上添加组合框

EN

  <extension
     point="org.eclipse.ui.menus">
    <menuContribution
        allPopups="false"
        locationURI="toolbar:org.eclipse.ui.main.toolbar">
     <toolbar
           id="com.company.module.toolbar"
           label="Sample">
        <control
              class="com.company.module.ui.ComboToolbarContribution"
              id="ratata">
        </control>
    </toolbar>
   </menuContribution>
 </extension>

package com.company.module.ui;

import org.eclipse.swt.SWT;
import org.eclipse.swt.layout.GridData;
import org.eclipse.swt.layout.GridLayout;
import org.eclipse.swt.widgets.Combo;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Control;
import org.eclipse.ui.menus.WorkbenchWindowControlContribution;

public class ComboToolbarContribution extends
    WorkbenchWindowControlContribution {
private Combo mReader;

public ComboToolbarContribution() {

}

@Override
protected Control createControl(Composite parent) {
    Composite container = new Composite(parent, SWT.NONE);
    GridLayout glContainer = new GridLayout(1, false);
    glContainer.marginTop = -1;
    glContainer.marginHeight = 0;
    glContainer.marginWidth = 0;
    container.setLayout(glContainer);
    GridData glReader = new GridData(SWT.FILL, SWT.FILL, false, false, 1, 1);
    glReader.widthHint = 280;
    mReader = new Combo(container, SWT.BORDER | SWT.READ_ONLY
            | SWT.DROP_DOWN);
    mReader.setLayoutData(glReader);

    return container;
}

@Override
protected int computeWidth(Control control) {
    return 300;
} }

<menuContribution
        allPopups="false"
        locationURI="toolbar:org.eclipse.ui.main.toolbar">
  <toolbar id="new">
    <control
          class="org.xy.composite.NewComposite"
          id="org.xy.composite.newcomposite.id">
    </control>
    <command
          commandId="newcomposite"
          icon="resources/nothing.png"
          label="nix"/>
  </toolbar>
</menuContribution>