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Difference between revisions of "E4/DeclarativeUI/XWT"

(1. Hello, world)
(5. Data Binding)
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org.eclipse.core.databinding
 
org.eclipse.core.databinding
 
org.eclipse.core.databinding.beans
 
org.eclipse.core.databinding.beans
 +
org.eclipse.core.databinding.property
 
com.ibm.icu
 
com.ibm.icu
 
</source>
 
</source>

Revision as of 16:33, 23 July 2009

Name of Technology

XWT Here is a presentation of our vision File:XWT.pdf

Purpose

Adopt a direct mapping XML to SWT/JFace with the support of JFace DataBinding

Contact

Yves YANG

Committers

Yves YANG, Thomas Guiu and others

Current License

XWT is an Open Source under EPL Licnese.

Description

XWT is a markup language for declarative application programming. It is a specific solution of using XML grammar for SWT/JFace directly.

XWT simplifies UI programming. You can create visible UI elements in the declarative XML markup with a physical separation of the UI definition from the run-time logic. An XML based declarative language is very intuitive for creating interfaces ranging from prototype to production, especially for people with a background in web design and technologies. Unlike most other markup languages, XWT directly represents the instantiation of managed objects.

The benefices of XWT for e4 are following:

  1. More human-readable and light-weight markup without ambiguity between properties and child type
  2. High Extensible
  3. Well defined and complete specification
  4. Mature and Generic Declarative UI solution

Examples of XWT

1. Hello, world

Here is a simple example.

<Shell xmlns="http://www.eclipse.org/xwt/presentation"
    xmlns:x="http://www.eclipse.org/xwt">
    <Shell.layout>
       <FillLayout/>
    </Shell.layout>
    <Button text="Hello, world!">
    </Button>
</Shell>

The same UI can be developed in Java corresponding:

Shell parent = new Shell();
parent.setLayout(new FillLayout());
Button button = new Button(parent, SWT.NONE);
button.setText("Hello, world!");

XAMl4SWT HelloWorld.png

To load and start a simple application, we use the class XWT:

Shell shell = (Shell) XWT.load(file));
shell.pack();
shell.open();
while (!shell.isDisposed()) {
   if (!shell.getDisplay().readAndDispatch()) {
	shell.getDisplay().sleep();
   }
}

Or simply

XWT.open(file));

It is possible to load a UI resource under a Composite:

XWT.load(parent, uri);

To use XWT, your Java project must import at least the following plugins

org.eclipse.swt
org.eclipse.jface
org.eclipse.e4.xwt
org.eclipse.jface.databinding
org.eclipse.core.databinding
com.ibm.icu

2. Appearance and Event

In the previous example, we just rewrite Java code in XML. This example illustrates the separation between UI and event handling.

The appearance is defined in XWT.

<Shell xmlns="http://www.eclipse.org/xwt/presentation"
    xmlns:x="http://www.eclipse.org/xwt"
    x:Class="ui.EventHandler">
    <Shell.layout>
       <GridLayout/>
    </Shell.layout>
    <Button text="Click Me!" SelectionEvent="clickButton">
    </Button>
</Shell>

The extension attribute x:Class declares the Java class to handle all events. The Button event is handled by clickButton method in the class ui.EventHandler. The association is setup during the loading:

package ui;
import org.eclipse.swt.Event;
import org.eclipse.swt.Button;
 
public class EventHandler {
    protected void clickButton(Event event) {
        Button button = (Button )event.widget;
        button.setText("Hello, world!");
    }
}

When the button gets selected, the method clickButton is invoked to change the Button text to "Hello, world!".

3. Layout

<Composite xmlns="http://www.eclipse.org/xwt/presentation"
    xmlns:x="http://www.eclipse.org/xwt">
   <Composite.layout>
       <GridLayout numColumns="2"/>
   </Composite.layout>
   <Label text="Hello, world"/>
   <Text x:style="BORDER">
      <Text.layoutData>
         <GridData horizontalAlignment="FILL"
            grabExcessHorizontalSpace="true"/>
      </Text.layoutData>
   </Text>   
</Composite>

XAMl4SWT HelloWorld2.png

  1. The simple element name (<Composite>) corresponds to a class name.
  2. The qualified element name (i.g. <Composite.layout>) corresponds to a property defined by an element.
  3. The default namespace corresponds to system packages.
  4. User defined package can be declared as a namespace in the format: ”clr-namespace:<package>=<jar>”

This is functionally equivalent to:

Composite parent = new Composite(shell, SWT.NONE);
parent.setLayout(new GridLayout(2, false);
Label label = new Label(parent, SWT.NULL);
label.setText("Hello, world");
Text text = new Text(parent, SWT.BORDER);
text.setLayoutData(new GridData(GridData.FILL_HORIZONTAL | GridData.GRAB_HORIZONTAL));

4. Extensibility and Re-usability

In case, if you have your own layout named as ui.MyGridLayout, it can be used directly. The code will be:

<Composite xmlns="http://www.eclipse.org/xwt/presentation"
    xmlns:x="http://www.eclipse.org/xwt"
    xmlns:y="cls-namespace:ui">
    <Composite.layout>
        <y:MyGridLayout numColumns="2"/>
    </Composite.layout>
    <Label text="Hello, world"/>
    <Text x:style="BORDER">
        <Text.layoutData>
           <GridData horizontalAlignment="FILL"
               grabExcessHorizontalSpace="true"/>
        </Text.layoutData>
    </Text>
</Composite>

In the same way, a customized UI component can be used directly:

<Composite xmlns="http://www.eclipse.org/xwt/presentation"
    xmlns:x="http://www.eclipse.org/xwt"
    xmlns:y="cls-namespace:ui">
    <Composite.layout>
        <GridLayout numColumns="2"/>
    </Composite.layout>
    <y:PersonView />
        <y:PersonView.layoutData>
           <GridData horizontalAlignment="FILL"
               grabExcessHorizontalSpace="true"/>
        </y:PersonView.layoutData>
    </y:PersonView>
</Composite>

Where the ui.PersonView is a UI component developed by two files:

XWT file PersonView.xwt

<Composite xmlns="http://www.eclipse.org/xwt/presentation"
    xmlns:x="http://www.eclipse.org/xwt"
    x:Class="ui.PersonView"
    xmlns:y="cls-namespace:ui">
    <Composite.layout>
        <GridLayout numColumns="2"/>
    </Composite.layout>
    <Label text="Name"/>
    <Text x:style="BORDER">
        <Text.layoutData>
           <GridData horizontalAlignment="FILL"
               grabExcessHorizontalSpace="true"/>
        </Text.layoutData>
    </Text>
</Composite>

Java class PersonView.java

package ui;
import org.eclipse.swt.widgets.Composite;
 
public class PersonView extends Composite {
   ...
}

5. Data Binding

The DataBinding engine relies on Eclipse DataBinding component. To enable this feature, your Java project must import at least the following plugins

org.eclipse.swt
org.eclipse.jface
org.eclipse.e4.xwt
org.eclipse.jface.databinding
org.eclipse.core.databinding
org.eclipse.core.databinding.beans
org.eclipse.core.databinding.property
com.ibm.icu

If we bind the text attribute of Label to a property “Name” of a Person, here is the data binding expression:

<Label text="{binding path=Name}"/>

It has the same result as following, but the expression is in pure XML:

 
<Label>
   <Label.text>
      <Binding path=”Name”/>
   </Label.text>
<Label>

The data context of Label should be a person.

6. JFace integration

The following example shows the JFace direct integration with ListViewer.

We have a Class Company that has a name and a collection of Employee. The company is bound to the root Composite object. The child Text is bound to Name of company and ListViewer to property employees of type Java Collection.

 
<Composite xmlns="http://www.eclipse.org/xwt/presentation"
    xmlns:x="http://www.eclipse.org/xwt"
    xmlns:j="clr-namespace:jface.listviewer"
    x:DataContext="{StaticResource myCompany}">
   <Composite.layout>
      <GridLayout numColumns="2"/>
   </Composite.layout>
   <x:Composite.Resources>
      <j:Company x:Key="myCompany" Name="Soyatec">
         <j:Company.employees>
            <j:Employee Name="Thomas"/>
            <j:Employee Name="Jin"/>
         </j:Company.employees>
      </j:Company>
   </x:Composite.Resources>
   <Label text="Name"/>
   <Text text="{Binding Path=Name}"/>
   <ListViewer input="{Binding Path=employees}">
      <ListViewer.contentProvider>
         <j:ContentProvider/>
      </ListViewer.contentProvider>
      <ListViewer.labelProvider>
         <j:LabelProvider/>
      </ListViewer.labelProvider>
 
      <ListViewer.control.layoutData>
         <GridData horizontalAlignment="FILL"
            grabExcessHorizontalSpace="true"
            horizontalSpan="2"/>
      </ListViewer.control.layoutData>
   </ListViewer>
</Composite>