L0036 - Creating Views and Editors

Creating Views and Editors

A detailed description of how to create and manage views, editors and
perspectives.

Redistribution and other use of this material requires written permission from The RCP Company.

L0001 - 2010-11-27

Views and Editors in Eclipse Applications

In any Eclipse Application (RCP or IDE) the
primary user interface is via views and editors
organized in one or more perspectives

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Basic Eclipse UI Information Model

Workspace

Window

Top-level Menu Page Perspective

Top-level Toolbar

Status Line
Editors Views
Switcher

Local Toolbar Drop-Down Menu

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Editors and Views

The main functionality of an Eclipse application is handled via editors and
views and the actions provided by these

The use of editors and views is different
 Editors express the state of one or more editor inputs – typically file
resources

Editors have an associated life-cycle
 Views express additional navigational or context-oriented information –
e.g. problems, outline or search – and is usually stateless

Views have no state, only configuration – e.g. colors and column
directions

Editors are explicitly saved whereas views are implicitly saved

Editors and views are grouped together via perspectives

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Visual Differences between Editors and Views

These are some visual differences between editors and views:
 Editors provide additional actions to the top-level menu and the tool
bar; views do not
 Views have an independent menu bar and tool bar; editors do not
 There are at most one active editor in a perspective; there can be any
number of active views
 The are at most one view of each “type”; there can be any number of
editors
 Editors are all placed in the “editor area”; views are placed in a number
of “view stacks”

Using the Presentation API, the visual difference can be ironed out

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Sites, Parts and References

Views and Editors are represented in three
different ways in the workbench page:
 The site object (IViewSite and IEditorSite) Site
represents the workbench state that is
specific for a part

Access to the workbench, the
workbench window, and the workbench
page

Access to the ID and name of the part Reference
(from the view or editor extension)

Registration of context menus
 The part object (IViewPart and IEditorPart)
represents the actual part of a site Part

This comes from the developed plug-in
 The reference object (IViewReference and
IEditorReference) represents a reference
to a specific part object

Used to prevent premature activation of
plug-ins

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Views

The Editor IDE contains views with all sorts of content. Some relevant
examples are:
 A table with items: Problems
 A styled text: Javadoc
 A big (virtual) tree: Package Explorer
 Using the Forms UI: Properties (depends on the current editor)
 A graph: Metrics
 A view with content supplied by the editor: Outline
 Tables and trees with sorting and filtering: Problems and Outline

If in doubt about how to implement a specify feature, always have a look at
the views from the IDE. Although these sometimes can seem overly
complicated, they can provide good inspiration.

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Adding a View

Views are defined via the extension point org.eclipse.ui.views/view
 Has id, name, class, category, icon, fastViewWidthRatio, allowMultiple,
restorable and description (a sub-element)
 Most attributes are optional

<extension point="org.eclipse.ui.views">
<view
category="com.rcpcompany.cexx.viewCategories.Main"
class="com.rcpcompany.cexx.views.ContactTableView"
id="com.rcpcompany.cexx.views.ContactTableView"
name="Contact Table"
restorable="true">
<description>
This view contains a simple table with all defined contacts along with a filter.
</description>
</view>
</extension>

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View Life Cycle

Before the view is shown
 init(IViewSite) or init(IViewSite, IMemento): marks the start of the view.
The second version is called for views that have saved a memento
 createPartControl(Composite): Creates the visual content of the view
 setFocus(): Sets the initial focus of the view

When the view is closed
 saveState(IMemento): Saves the state of the view in a memento
 dispose(): Disposes all resources – especially images and fonts

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Standard Views (RCP only)

The platform contains a number of standard views that can be added to an
RCP application via plugin.xml

For example, to add the Progress view, use:

<extension
point="org.eclipse.ui.views">
<view
class="org.eclipse.ui.ExtensionFactory:progressView"
id="com.rcpcompany.gir.application.views.progress"
name="Progress"/>
</extension>

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Editors

Content
 Text – e.g. a programming language
 Graphical – e.g. a model or an XML file
 Form – e.g. an XML file or a configuration
file
 A combination – e.g. the plugin.xml editor

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Editors

Interface more complicated than for views, with many more mandatory
methods
 Saving editor content (ISaveablePart)
 Introduces IEditorInput

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Editor Input

The subject of an editor is specified via an IEditorInput
 Simple interface:

public interface IEditorInput extends IAdaptable {
public boolean exists();
public ImageDescriptor getImageDescriptor();
public String getName();
public IPersistableElement getPersistable();
public String getToolTipText();
}

 Typically a file based on the resource API
 But can be anything – specialized as

IPathEditorInput: Local file system resource

IFileEditorInput: Resource API-based resource

IStorageEditorInput: Storage-based resource – any sequence of bytes

Subclass EditorInput for your own new editor inputs

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Editor Life Cycle

Before the view is shown
 init(IEditorSite, IEditorInput): marks the start of the editor
 createPartControl(Composite): Creates the visual content of the editor
 setFocus(): Sets the initial focus of the editor

When the editor is closed
 isDirty() and isSaveAsAllowed(): Returns whether saving is needed or
indeed allowed

Used by workbench to determine whether exit is allowed
 doSave(IProgressMonitor) or doSaveAs(): Saves the state of the editor
 dispose(): Disposes all resources – especially images and fonts

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Lab Exercise

Create a number of views using the UI designer
 If you use the Visual Designer, then start Eclipse 3.2 with its own
workspace and import the existing plug-ins!

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Saving State (IMemento)

When the workbench closes, all state is saved – including all workbench-related
state
When the workbench is reopened, all state is re-read
State saved in an IMemento
 Hierarchical structure
 Normally XML based
 Data can be

Strings, integers or floats

Text blocks

The view life cycle explicitly handles state
 init(IViewSite, IMemento)
 saveState(IMemento)

Saved as file in the local configuration directory
 Can be saved anywhere
 Workbench reads file workbench.xml

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Saving State (IMemento)

The IMemento interface has three groups of operations:
 Operations to get or create a child context
 Operations to get or set the values of a context
 A few operations to handle the IDs

public interface IMemento {
public IMemento createChild(String type);
public IMemento createChild(String type, String id);
public IMemento getChild(String type);
public IMemento[] getChildren(String type);
public Float getFloat(String key);
public String getID();
public Integer getInteger(String key);
public String getString(String key);
public String getTextData();
public void putFloat(String key, float value);
public void putInteger(String key, int value);
public void putMemento(IMemento memento);
public void putString(String key, String value);
public void putTextData(String data);
}

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Saving State in Views and Editors

The view life cycle explicitly handles state
 init(IViewSite, IMemento)

Will be null the first time!
 saveState(IMemento)
 Because views are shared between perspectives, init and saveState will
only be called once per WorkbenchWindow!

In Eclipse 3.3 an editor can also save state
 Must implement IPersistableEditor

restoreState(IMemento)

saveState(IMemento)

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Lab Exercise

Save and restore the content of the first text field of the first view using
IMemento:
 In WorkbenchAdvisor.preStartup() use
getWorkbenchConfigurer().setSaveAndRestore(true) to enable saved
state (RCP only)

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Perspectives

A perspective is a description of a number of user interface elements that is
used to perform a specific task
 Whether or not an editor is used
 A specific type of resources that will be shown in the navigator (if used)
 A specific set of views that is used in the perspective
 A specific set of shortcuts to be added to certain menus

Wizards to be shown at the top of the “File” → “New…” menu

Views to be shown at the top of the “Window” → “Show View” menu

Perspectives shown at the top of the perspective switcher
 A specific set of action sets to be added to the top-level menu and tool
bar

A perspective also specifies the layout of the editors and the associated
views using a “slice” system

Additions can be made to a perspective using the perspectiveExtensions
extension point

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Standard Perspectives

The Eclipse IDE includes a large number of perspectives that correspond to
the many tasks that must be performed in a development environment. For
example:
 Java
 Debug
 Team
 CVS Repository

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Perspective Implementation

Perspective is a specific layout and views and editors within a Workbench
window
Workspace

Window

Top-level Menu Page Perspective

Top-level Toolbar

Status Line
Editors Views
Switcher

Local Toolbar Drop-Down Menu

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Adding a New Perspective

A new perspective can easily be added using
the extensions page for the plugin.xml file
 Add a new extension with the name
“org.eclipse.ui.perspectives”
 Select the new line and add a
“New”→”perspective” using the context
menu
 Specify ID, name and factory class
 Click on the “class” link to create the new
View class automatically

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Designing Perspectives

Nearly any layout with an editor (optional) and zero, one or more views can
be designed using addView(…)

The method is rather simple:
 You start with the editor area
 You then add one new view at a time
 Each time, you divide an already placed view according to an edge (TOP,
RIGHT, BOTTOM, or LEFT) and a percentage (in the range [0.05; 0.95])

Thus addView("view2", IPageLayout.LEFT, 0.4f, "view1") means
 Find the already placed view view1
 Place view2 to the LEFT of view1
 Assign 40% of the original area of view1 to view2

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1
2

4
Some layouts cannot be created this way – for
example, this “ wheel” layout 3

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An Example

The parts of layout (the editor and the four views) are represented by the
rectangles

The numbers refers to the next start of the line to be executed

Editor
3 Area
4 5 View1

View2 View4 View2
6 View2 View1 7 View1 8 View1

View3 View3

public void createInitialLayout(IPageLayout layout) {
final String area = layout.getEditorArea();
layout.setEditorAreaVisible(false);
layout.addView("com.rcpcompany.cex.view1", IPageLayout.LEFT, 1.0f, area);
layout.addView("com.rcpcompany.cex.view2", IPageLayout.LEFT, 0.666f, "com.rcpcompany.cex.view1");
layout.addView("com.rcpcompany.cex.view3", IPageLayout.BOTTOM, 0.75f, "com.rcpcompany.cex.view2");
layout.addView("com.rcpcompany.cex.view4", IPageLayout.LEFT, 0.5f, "com.rcpcompany.cex.view2");
}

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Views can be added to a designated spot in a number of ways
 As a normal view with tab using addView(…)
 As a view with no tab using addStandaloneView(…)
 As a stack or folder using createFolder(…)
 As a fast view using addFastView(…)

Views can also be added as a placeholder for a future view using
addPlaceholder(…) or createFolderPlaceholder(…)

The editor area has ID org.eclipse.ui.editorss (with ss!)

Views can be set un-closeable or un-moveable via getViewLayout(id)

See IPageLayout for more information

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Extending an Existing Perspective

Used when extending an existing perspective
with information from a new (usually
independent) plug-in
 E.g. adding a new profile view to the Java
perspective

Using extension point
org.eclipse.ui.perspectiveExtensions
 Specify the target perspective ID
 Can add fast views, action set, shortcuts
 Cannot hide or show the editor

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Lab Exercise

Implement the following perspective using four views via a Java class
 You make the perspective switcher visible in the
WorkbenchWindowAdvisor.preWindowOpen() (RCP Only):
configurer.setShowPerspectiveBar(true)

Then re-implement the layout in a new perspective using the
perspectiveExtensions extension point
 Or just add a new view to the old existing perspective

Later possibly move view3 to a fast view

Make view1 not moveable in both perspectives

Add the new perspective as a shortcut in the old perspective – using
perspectiveExtensions

Stack with View2
and View 4 View1

View3

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Lab Exercise

Implement the following perspective using four views

Stack with View2
and View 4 Editor
View1
Area

View3

Add one of the above views to the existing Resource perspective using the
perspectiveExtensions extension point
 The ID of the Resource perspective is org.eclipse.ui.resourcePerspective
 The ID of the Task view is org.eclipse.ui.views.TaskList

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How to open editors, views and perspectives

Perspectives
 IWorkbenchWindow.openPage(String perspectiveId, IAdaptable input)

Editors
 IDE.openEditor(IWorkbenchPage page, IFile file)

One of a large number of methods
 IWorkbenchPage.findEditor(IFile file)

Views
 IWorkbenchPage.showView(String id)

Will open the view in the site according to the perspective definition

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More Information

“Using Perspectives in the Eclipse UI”
 http://www.eclipse.org/resources/resource.php?id=232

Visual Editor Project
 http://www.eclipse.org/vep/WebContent/main.php

Advanced workbench concepts from Eclipse Help
 http://help.eclipse.org/help32/index.jsp?topic=/
org.eclipse.platform.doc.isv/guide/wrkAdv.htm

“Code Access Guide to Eclipse 3.4”
 http://www.eclipse.org/resources/resource.php?id=428

Among other things an introduction to the PDE Spy.

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L0036 - Creating Views and Editors

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