Section: 5.3.3 Example Menu Bar

5.3.3 Example Menu Bar

We're going to look at how to extend the menu bar.

In the /home/idv/idv/ucar/unidata/apps/example/resources directory copy the file defaultmenu.xml up a level to the example directory.
Bring the defaultmenu.xml file into an editor.
Run the ExampleIdv. Note the new menu entry. For kicks, select Example->Show resources. This shows all of the resources loaded into the ExampleIdv.
Let's add in a Hello World menu item.
- Add in the following under the "Example" menu tag.
```
    <menuitem
       action="jython:idv.helloWorld();"
       label="Hello World"/>
```
- Run ExampleIdv. Select Example->Hello World
- We get an error. We need to add the helloWorld method to ExampleIdv:
```
  public void helloWorld() {
      System.err.println("Hello World");
  }
```
  The method needs to be public.
- Compile and run again.
Note that we now have code embedded in our menubar xml file. This might not be good practice. We'll use the "actions"resource to define an action.
- Copy the file resources/actions.xml to the example directory.
- This defines an action called "example.helloworld":
```
  <action
     id="example.helloworld"
     image="/ucar/unidata/apps/example/resources/HelloWorld.gif"
     description="Call hello world"
     action="jython:idv.helloWorld();"/>
```
- Add the following into the defaultmenu.xml. Note the "action:" prefix.
```
    <menuitem
       action="action:example.helloworld"
       label="Hello World from action"/>
    <separator/>
```
- Run ExampleIdv.
- The example.helloworld action is now also available in the toolbar. Bring up the User Preferences
So, this added our own menu into the menu bar. How do we not use any of the system menus?
- Bring up the idv.rbi and change
```
  <resources name="idv.resource.menubar">
  </resources>
```
  To:
```
  <resources name="idv.resource.menubar" loadmore="false">
    <resource
       location="/ucar/unidata/apps/example/defaultmenu.xml"/>
  </resources>
```
  The loadmore tells the IDV not to use the system resources.
- Run the ExampleIdv.
- Remove the above entries from the example idv.rbi file.
Now, lets look at the default system menubar in /home/idv/idv/ucar/unidata/idv/resources/defaultmenu.xml
- Note the "id=" attributes. The IDV uses these ids to know where to dynamically add in different menus, e.g., available windows, display lists, data, etc.

Unidata IDV Workshop for version 3.0u2 > Java Developer Topics > IDV User Interfaces