e4: First e4 RCP Application

The next big thing in Eclipse is Eclipse 4.0 dubbed as e4. It will be released in 2010. That doesn't mean that the 3.x stream will be deprecated or discontinued. The 3.x releases will go on for "few" years till everyone boards the 4.0. But clearly the future of Eclipse is e4 and its already here. I'll be writing a series of blog posts on e4 and this will be the first. You can follow this blog in RSS, or email or even in twitter. I'm still learning about e4, so feel free to correct me if you find any mistakes :-)

First set up your e4 Environment:

1) Download e4 1.0 M1
2) Click e4->Generate e4 Example Project

Step 1:

Use the New Plug-in wizard and create a new plugin. (No RCP - just plain old plugin)

Step 2:

You don't need an Activator. In the Overview tab, remove the Activator class and also delete the Activator.java file from the sources.

Step 3:

The default dependencies of this would have o.e.core.runtime and o.e.ui. In e4, we still need the core.runtime in e4, but not the o.e.ui. Remove it. Now add the following dependencies:

• org.eclipse.swt,
• org.eclipse.jface,
• org.eclipse.e4.ui.workbench
• org.eclipse.e4.ui.workbench.swt

Step 4:

Lets create a view. Instead of o.e.ui.views, now we have to use org.eclipse.e4.workbench.parts extension (which should now serve both the editors and views). The extension point would look like

<extensio point="org.eclipse.e4.workbench.parts">
      <part class="com.eclipse_tips.e4.firstapp.MyFirstView" />
</extension>

public class MyFirstView {

 public MyFirstView(Composite parent){
    
  // this shouldn't be there ideally, investigating
  if(parent.getLayout() == null)
    parent.setLayout(new FillLayout());

  Composite composite = new Composite(parent, SWT.NONE);
  composite.setLayout(new FillLayout());
  
  Button button = new Button(composite, SWT.PUSH);
  button.setText("Hello World");
  button.addSelectionListener(new SelectionAdapter() {
   @Override
   public void widgetSelected(SelectionEvent e) {
    MessageDialog.openInformation(new Shell(), "e4", "Hello e4 World!");
   }
  });
 }

}

Yes, what you are seeing it correct. It doesn't implement the IWorkbenchView or extend ViewPart. Further more, it appears that I've done one of the top 10 mistakes by not having a default constructor. Don't worry, e4 is smart. When it instantiates an object like this thru reflection, it identifies the parameters for the constructor and will pass them from the context. If more than one constructor is present, it can even identify the right one to use (more on this later)

Step 5:

Now, we have the view, lets create an RCP product that will use this view. Fire up the New Wizard and create a Product Configuration file with the basic settings. In the Product Configuration editor, give it some name and click the New for the Product. Specify some id and select 'org.eclipse.e4.ui.workbench.swt.application' for Application.

Step 6:

Go back to your plugin.xml. You should see the newly created application there. Now lets create the missing link between the product and the view - the UI model. In a typical 3.x RCP, you would have specified an application that has a run method, an initial perspective id, the layout for that perspective, the views, menus, actions thru the ActionFactory constants etc. This whole setup would require a little bit of both java coding and plugin.xml configuration. In e4, you can specify the entire UI in a model. Thats the applicationXMI. It can get as complex as your UI can be, but the simplest one looks like this:

<?xml version="1.0" encoding="ASCII"?>
<application:MApplication xmi:version="2.0" 
 xmlns:xmi="http://www.omg.org/XMI" 
 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
 xmlns:application="http://www.eclipse.org/ui/2008/Application">

  <windows name="Main Window" width="200" height="100">
 <children xsi:type="application:MContributedPart" 
  id="MyView" 
  iconURI="platform:/plugin/com.eclipse-tips.e4.firstApp/icons/sample.gif" 
  URI="platform:/plugin/com.eclipse-tips.e4.firstApp/com.eclipse_tips.e4.firstapp.MyFirstView"/>
  </windows>
</application:MApplication>

There is nothing much to explain. It has got nothing more than a window and a view in it. (no menus,no tool bars, no status lines and even no stacks to hold the view) Specify this file in the parameter of the product extension:

<extension
       id="rcpProduct"
       point="org.eclipse.core.runtime.products">
    <product
          application="org.eclipse.e4.ui.workbench.swt.application"
          name="My First e4 RCP">
       <property
             name="applicationXMI"
             value="com.eclipse-tips.e4.firstApp/App.xmi">
       </property>
    </product>
 </extension>

Step 7:

You are all set to go. Switch to the Dependencies tab of the Product Editor and add your plugin. Click 'Add Required plugins' and launch. The launch will fail, because we have not included few more plugins that are required, but not specified in the dependencies (from databinding beans to renderers will be missing) The simplest way to get thru the error, is to edit the launch configuration and launch with 'all workspace and enabled target plugins'.