component-based developmentpro.unibz.it/staff/mscotto/cbd/cbd3ex - views.pdf · 2005-05-04 ·...

Component-Based Development

Component-Based Development

2004-2005Marco Scotto ([email protected])

2Component-Based Development

Outline

Views • Introduction• View Declaration• View Model• Content Provider• Label Provider


Introduction (1/5)

Many plug-ins either add a new Eclipse view or enhance an existing Eclipse view as a way to provide information to the user


Introduction (2/5)

Views must implement the org.eclipse.ui.IViewPart interface. Typically views are subclasses of org.eclipse.ui.part.ViewPart and thus indirectly subclasses of org.eclipse.ui.part.WorkbenchPart, inheriting much of the behavior needed to implement the IViewPart interface


Introduction (3/5)


Introduction (4/5)

Views are contained in a view site, (an instance of org.eclipse.ui.IViewSite), which in turn are contained in a workbench page (an instance of org.eclipse.ui.IWorkbenchPage). In the spirit of lazy initialization, the IWorkbenchPage holds on to instances of org.eclipse.ui.IViewReference rather than the view itself so that views can be enumerated and referenced without actually loading the plug-in defining the view.


Introduction (5/5)

Because there are potentially 100’s of views in the workbench, views are organized into categories. The Show View dialog presents a list of views organized by category so that the user can more easily find the desired view.


View Declaration

There are three parts involved in creating a new view:• Define the view category in the plug-in

manifest file• Define the view in the plug-in manifest file• Create the view part containing the code


Declaring a View Category (1/4)

First, to define the new view category, edit the plug-in manifest and navigate to the Extensions pageClick the Add… button to add the org.eclipse.ui.views extension if it is not already present


Declaring a View Category (2/4)The Main View Settings dialog is used modify the attributes of the viewFor the category containing the Tasks view, the attributes would be as follows:• Java Package Name – “it.unibz.plugins.tasks.views”

the package of the view class • View Class Name – “TasksView”

the name of the class defining the view and implementing the org.eclipse.ui.IViewPart interface. The class is instantiated using its no argument constructor, but may be parameterized using the IExecutableExtension interface.

• name – “Tasks View”the human readable name for the view displayed in the view’s title bar and in the Show View dialog

• View Category Id – “it.unibz.plugins”the unique identifier for the category

• View Category Name – “UniBZ plugins”the human readable name for the category that appears in the Show View dialog



Click on NextUnselect all checkboxesClick on “Finish”


ViewPart

The code defining the view’s behavior is found in a class implementing the org.eclipse.ui.IViewPart interface, typically by subclassing the org.eclipse.ui.part.ViewPart abstract class


View Methods (1/2)

createPartControl(Composite) – required. Create the controls comprising the view. Typically this method simply calls more finely grained methods such as createTable, createSortActions, createFilters, etc. dispose() – Cleanup any platform resources, such as images, clipboard, etc, that were created by this class. This follows the if you create it you destroy it theme that runs throughout Eclipse


View Methods (2/2)getAdapter(Class) – Returns the adapter associated with the specified interface so that the view can participate in various workbench actions. Adapters returned by views include IShowInSource, IShowInTarget, and IContributedContentsView among otherssaveState(IMemento) - Save the local state of this view, such as the current selection, current sorting, current filter, etc.setFocus() – required. Set focus to the appropriate control within the view


View Controls (1/4)

Views can contain any type and number of controls, but typically a view such as the Tasks view contains a single table or tree control


View Controls (2/4)

The Tasks view could use the SWT table widget directly, but the higher level JFacetable viewer wraps the SWT table widget and is easier to use• It handles much of the underlying grunt work,

allowing us to add, select, and remove our model objects directly rather than dealing with the underlying instances of TableItem


View Controls (3/4)With this in mind, we start by enhancing the createPartControl(…) method

Table table = new Table(parent, SWT.SINGLE | SWT.H_SCROLL | SWT.V_SCROLL | SWT.FULL_SELECTION);

table.setHeaderVisible(true);table.setLinesVisible(true);TableColumn column = new TableColumn(table, SWT.NONE, 0);column.setText("Completed");column.setWidth(50);column.setAlignment(SWT.LEFT);column = new TableColumn(table, SWT.NONE, 1);column.setText("Description");column.setWidth(100);column.setAlignment(SWT.LEFT);column = new TableColumn(table, SWT.NONE, 2);column.setText("Owner");column.setWidth(100);column.setAlignment(SWT.LEFT);


View Controls (4/4)column = new TableColumn(table, SWT.NONE, 3);column.setText("Percentage");column.setWidth(50);column.setAlignment(SWT.LEFT);viewer = new TableViewer(table);viewer.setContentProvider(new TaskViewContentProvider());viewer.setLabelProvider(new TaskViewLabelProvider());viewer.setInput(TaskManager.getManager());


View Model

A view may have its own internal model such as the our view, or use existing model objects such as an IResource and its subtypes, or not have any model at allIn our case, we create:• Task – a class that represents our business

objects• TaskManager – holds task objects


Task class (1/2)package it.unibz.plugins.tasks.model;

public class Task {

private boolean completed = false;private String description = "";private String owner = "?";private int percentComplete = 0;

public Task(String string) {

super();setDescription(string);

}

public boolean isCompleted() {return completed;

}

public String getDescription() {return description;

}


Task class (2/2)public String getOwner() {

return owner;}

public int getPercentComplete() {return percentComplete;

}

public void setCompleted(boolean b) {completed = b;

}

public void setDescription(String string) {description = string;

}

public void setOwner(String string) {owner = string;

}

public void setPercentComplete(int i) {percentComplete = i;

}}


TaskManager class (1/3)package it.unibz.plugins.tasks.model;

import java.util.*;

public class TaskManager {private static TaskManager manager = null;private Collection tasks;private List listeners = new ArrayList();

private TaskManager() {}

public static TaskManager getManager() {if (manager == null)

manager = new TaskManager();return manager;

}

public Task[] getTasks() {if (tasks == null)

loadTasks();return (Task[]) tasks.toArray(new Task[tasks.size()]);

}


TaskManager class (2/3)public void addTask(Task[] items) {

Task[] removedTasks = new Task[] {}; if (tasks == null)

loadTasks();if (tasks.addAll(Arrays.asList(items)))

fireTaskChanged(items, removedTasks);}

public void removeTask(Task[] items) {Task[] addedTasks = new Task[] {}; if (tasks == null)

loadTasks();if (tasks.removeAll(Arrays.asList(items)))

fireTaskChanged(addedTasks, items);}private void loadTasks() {

tasks = new HashSet(5);Task t1 = new Task("Maintainance");tasks.add(t1);Task t2 = new Task("Development");t2.setOwner("teamA");t2.setPercentComplete(20);tasks.add(t2);

}


TaskManager class (3/3)

/////// TaskManagerListener methods ////////////public void addTasksManagerListener(

TaskManagerListener listener) {if (!listeners.contains(listener))

listeners.add(listener);}

public void removeTaskManagerListener(TaskManagerListener listener) {

listeners.remove(listener);}

private void fireTaskChanged(Task[] itemsAdded, Task[] itemsRemoved) {

TaskManagerEvent event = new TaskManagerEvent(this, itemsAdded, itemsRemoved);for (Iterator iter = listeners.iterator(); iter.hasNext();)

((TaskManagerListener) iter.next()).taskChanged(event);}

}


TaskManagerEvent classpackage it.unibz.plugins.tasks.model;

public class TaskManagerEvent {

private Task[] added;private Task[] removed;private TaskManager manager;

public TaskManagerEvent(TaskManager manager, Task[] added, Task[] removed) {

this.manager = manager;this.added = added;this.removed = removed;

}

public Task[] getItemsRemoved() {

return removed;}

public Task[] getItemsAdded() {

return added;}

}


TaskManagerListener interfacepackage it.unibz.plugins.tasks.model;

public interface TaskManagerListener {

/*** @param event*/

public void taskChanged(TaskManagerEvent event);}


Content Provider

Once the model objects have been created, they need to be linked into the viewA content provider is responsible for extracting objects from an input object, in this case the TaskManager, and handing them to the table viewer for displaying, one object in each row of the tableAlthough the IStructuredContentProvider does not specify this, we will also make the content provider responsible for updating the viewer when the TasksManager’s content changes


Content Provider Class (1/2)package it.unibz.plugins.tasks.views;

import org.eclipse.jface.viewers.*;import it.unibz.plugins.tasks.model.*;

class TaskViewContentProvider implements IStructuredContentProvider, TaskManagerListener

{private TableViewer viewer;private TaskManager manager;

public void inputChanged(Viewer viewer, Object oldInput, Object newInput) {this.viewer = (TableViewer) viewer;if (manager != null)

manager.removeTaskManagerListener(this);manager = (TaskManager) newInput;if (manager != null)

manager.addTasksManagerListener(this);}


Content Provider Class (2/2)public void dispose() { }

public Object[] getElements(Object parent) {

return manager.getTasks();}

public void taskChanged(TaskManagerEvent event){

viewer.getTable().setRedraw(false);try {

viewer.remove(event.getItemsRemoved());viewer.add(event.getItemsAdded());

}finally {

viewer.getTable().setRedraw(true);}

}}


Label Provider

The label provider takes a table row object returned by the content provider and extracts the value to be display in a column. After refactoring the FavoritesView.ViewLabelProvider inner class into a top-level class, and reworking it to extract values from the newly created model object, it looks something like the code shown below:


Label Provider Class (1/2)package it.unibz.plugins.tasks.views;

import it.unibz.plugins.tasks.model.Task;

import org.eclipse.jface.viewers.*;import org.eclipse.swt.graphics.*;

class TaskViewLabelProvider extends LabelProviderimplements ITableLabelProvider

{

public String getColumnText(Object obj, int index) {Task t = (Task) obj;

switch (index) {case 0 : // Completed column

if (t.isCompleted())return "yes";

elsereturn "no";


Label Provider Class (2/2)case 1 : // Description columnreturn t.getDescription();

case 2 : // Location columnreturn t.getOwner();

case 3 :return new Integer(t.getPercentComplete()).toString();

default :return "";

}}public Image getColumnImage(Object obj, int index) {return null;

}}

component-based developmentpro.unibz.it/staff/mscotto/cbd/cbd3ex - views.pdf · 2005-05-04 ·...

Documents