Best Practices - SWT Table, TableViewer, EditingSupport

Question

I am adding a table to my main GUI. It does show up and has the data it is suppose to show. But I feel like I have a big mess of code and it is not structured correctly. I am looking for someone that uses SWT a lot to help me put the right pieces of code in the right places.

Class A - Main GUI with TableViewer

Class B - (ArrayList) Data for table / Class B1 - DataModel for ArrayList Structure

Class A - has method for creating TableViewer

  //////////////////////////////////////////////////////////////////////////
  //                         createTableViewer()                          //
  //////////////////////////////////////////////////////////////////////////
private TableViewer createTableViewer(Composite parent) {
    viewer = new TableViewer(parent, SWT.MULTI | SWT.H_SCROLL | SWT.V_SCROLL | SWT.FULL_SELECTION | SWT.BORDER);
    createColumns(parent, viewer);
    table = viewer.getTable();
    table.setHeaderVisible(true);
    table.setLinesVisible(true);

    // Layout the viewer
    GridData gridData = new GridData(SWT.FILL, SWT.FILL, true, true);
    viewer.setContentProvider(new ArrayContentProvider());
    *** Getting Array from Class B ***       
    viewer.setInput(AplotDataModel.getInstance().getArrayData());
    viewer.getControl().setLayoutData(gridData);
    return viewer;
}

Class A also has createColumns() method and a createTableViewerColumn() method.

 //////////////////////////////////////////////////////////////////////////
 //                         createColumns()                              //
 //////////////////////////////////////////////////////////////////////////
private void createColumns(final Composite parent, final TableViewer viewer) {
    String[] titles = { "ItemId", "RevId", "PRL", "Dataset Name", "EC Markup" };
    int[] bounds = { 150, 150, 100, 150, 100 };

    TableViewerColumn col = createTableViewerColumn(titles[0], bounds[0], 0);
    col.setLabelProvider(new ColumnLabelProvider() {
        @Override
        public String getText(Object element) {
            AplotDatasetData item = (AplotDatasetData) element;
            return item.getDataset().toString();
        }
    });

    col = createTableViewerColumn(titles[1], bounds[1], 1);
    col.setLabelProvider(new ColumnLabelProvider() {
        @Override
        public String getText(Object element) {
            AplotDatasetData item = (AplotDatasetData) element;
            return item.getRev().toString();
        }
    });

    col = createTableViewerColumn(titles[2], bounds[2], 2);
    col.setLabelProvider(new ColumnLabelProvider() {
        @Override
        public String getText(Object element) {
            AplotDatasetData item = (AplotDatasetData) element;
            return item.getPRLValue();
        }
    });

    col = createTableViewerColumn(titles[3], bounds[3], 3);
    col.setLabelProvider(new ColumnLabelProvider() {
        @Override
        public String getText(Object element) {
            AplotDatasetData item = (AplotDatasetData) element;
            return item.getDatasetName();
        }
    });

    col = createTableViewerColumn(titles[4], bounds[4], 4);
    col.setLabelProvider(new ColumnLabelProvider() {
        @Override
        public String getText(Object element) {
            AplotDatasetData item = (AplotDatasetData) element;
            return item.getECMarkupValue();
        }
    });
}

 //////////////////////////////////////////////////////////////////////////
 //                       createTableViewerColumn()                      //
 //////////////////////////////////////////////////////////////////////////
private TableViewerColumn createTableViewerColumn(String title, int bound, final int colNumber) {
    final TableViewerColumn viewerColumn = new TableViewerColumn(viewer, SWT.NONE);
    final TableColumn column = viewerColumn.getColumn();
    column.setText(title);
    column.setWidth(bound);
    column.setResizable(true);
    column.setMoveable(true);
    return viewerColumn;
}

Question 1: Is this the best practice to adding a table to my GUI class? Seems like a lot of code for the GUI class.

Question 2: Should the createColumns() method and the createTableViewerColumn() method be moved to Class B?

Question 3: My last column in the table is going to be a dropdown/combo box. So I am going to have to extend one class with EditingSupport. Should it be Class A or Class B?

Before I go any farther with this project I want to make sure I have it correctly structured.

Answer 1

Answering this question is like answering which ice-cream flavor do you like :)

Q & A

Question 1: Is this the best practice to adding a table to my GUI class? Seems like a lot of code for the GUI class.

If the code is less than its not a bad idea. But if -

1. The code is large (for me if its more than 100 lines).
2. Overall System is going to be more than some thousand of lines of code.
3. Someone else is going to maintain it
4. If I need plug-and-play nature, for example today Table is sufficient but in future I may use Grid.
5. If I am doing some custom drawing (doing some custom painting on windows paint event) or using custom controls, THEN

I normally prefer to sub-class the viewer/control. In this way I could maintain the separation between the bare-bone message pumping code, GUI controls and my data model.

Question 2: Should the createColumns() method and the createTableViewerColumn() method be moved to Class B?

No, You should not. As in your case the class B is your data model/supplier. The JFace programming model supports MVC architecture and if possible one should follow it. Suggested solution is to have a new class extending the TableViewer.

Question 3: My last column in the table is going to be a dropdown/combo box. So I am going to have to extend one class with EditingSupport. Should it be Class A or Class B?

I would suggest you to go for a new class and use that in the extended TableViewer. One benefit is that in case you are writing data back to some db then your viewer class remain db/persistence layer agnostic.

Code Sample

Below is a simple sample application. As you can see I can change my combo editor to text editor just by changing the OptionEditingSupport class. And also, the code looks clean and concise.

Main Class

package sample;

import org.eclipse.swt.SWT;
import org.eclipse.swt.layout.FillLayout;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Shell;

public class SampleApp 
{
    public SampleApp(Shell shell)
    {
        AppPersonViewer personViewer = new AppPersonViewer(shell, SWT.BORDER|SWT.V_SCROLL|SWT.FULL_SELECTION);
        DataModel model = new DataModel(20);
        personViewer.setInput(model);
    }

    public static void main(String[] args) {
        Display display = new Display ();
        Shell shell = new Shell(display);
        shell.setLayout(new FillLayout());
        new SampleApp(shell);
        shell.open ();

        while (!shell.isDisposed ()) {
            if (!display.readAndDispatch ()) display.sleep ();
        }

        display.dispose ();
    }
}

---

Extended Table Viewer

package sample;

import org.eclipse.jface.viewers.ColumnLabelProvider;
import org.eclipse.jface.viewers.TableViewer;
import org.eclipse.jface.viewers.TableViewerColumn;
import org.eclipse.swt.SWT;
import org.eclipse.swt.layout.GridData;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Table;

public class AppPersonViewer extends TableViewer
{
    public AppPersonViewer(Composite parent, int style) 
    {
        super(parent, style);
        Table table = getTable();
        GridData gridData = new GridData(SWT.FILL, SWT.FILL, true, true);
        table.setLayoutData(gridData);
        createColumns();
        table.setHeaderVisible(true);
        table.setLinesVisible(true);
        setContentProvider(new AppContentProvider());
    }

    private void createColumns()
    {
        String[] titles = { "First Name", "Second Name", "Age", "Country", "Likes SO" };
        int[] bounds = { 150, 150, 100, 150, 100 };

        TableViewerColumn column = createTableViewerColumn(titles[0], bounds[0], 0);
        column.setLabelProvider(new ColumnLabelProvider(){
            public String getText(Object element) {
                if(element instanceof Person)
                    return ((Person)element).getFirst();
                return super.getText(element);
            }
        });

        column = createTableViewerColumn(titles[1], bounds[1], 1);
        column.setLabelProvider(new ColumnLabelProvider(){
            public String getText(Object element) {
                if(element instanceof Person)
                    return ((Person)element).getSecond();
                return super.getText(element);
            }
        });

        column = createTableViewerColumn(titles[2], bounds[2], 2);
        column.setLabelProvider(new ColumnLabelProvider(){
            public String getText(Object element) {
                if(element instanceof Person)
                    return ""+((Person)element).getAge();
                return super.getText(element);
            }
        });

        column = createTableViewerColumn(titles[3], bounds[3], 3);
        column.setLabelProvider(new ColumnLabelProvider(){
            public String getText(Object element) {
                if(element instanceof Person)
                    return ((Person)element).getCountry();
                return super.getText(element);
            }
        });

        column = createTableViewerColumn(titles[4], bounds[4], 4);
        column.setLabelProvider(new ColumnLabelProvider(){
            public String getText(Object element) {
                if(element instanceof Person)
                    return ((Person)element).getLikes();
                return super.getText(element);
            }
        });

        column.setEditingSupport(new OptionEditingSupport(this));
    }

    private TableViewerColumn createTableViewerColumn(String header, int width, int idx) 
    {
        TableViewerColumn column = new TableViewerColumn(this, SWT.LEFT, idx);
        column.getColumn().setText(header);
        column.getColumn().setWidth(width);
        column.getColumn().setResizable(true);
        column.getColumn().setMoveable(true);

        return column;
    }
}

---

Content Provider

package sample;

import org.eclipse.jface.viewers.IStructuredContentProvider;
import org.eclipse.jface.viewers.Viewer;

public class AppContentProvider implements IStructuredContentProvider
{
    /* (non-Javadoc)
     * @see org.eclipse.jface.viewers.IStructuredContentProvider#getElements(java.lang.Object)
     */
    public Object[] getElements(Object inputElement) {
        if(inputElement instanceof DataModel)
            return ((DataModel)inputElement).getData().toArray();
        return null;
    }

    /* (non-Javadoc)
     * @see org.eclipse.jface.viewers.IContentProvider#dispose()
     */
    public void dispose() {
    }

    /* (non-Javadoc)
     * @see org.eclipse.jface.viewers.IContentProvider#inputChanged(org.eclipse.jface.viewers.Viewer, java.lang.Object, java.lang.Object)
     */
    public void inputChanged(Viewer viewer, Object oldInput, Object newInput) {
    }
}

---

Cell Editor Support

package sample;

import org.eclipse.jface.viewers.CellEditor;
import org.eclipse.jface.viewers.ColumnViewer;
import org.eclipse.jface.viewers.ComboBoxCellEditor;
import org.eclipse.jface.viewers.EditingSupport;
import org.eclipse.jface.viewers.TableViewer;

public class OptionEditingSupport extends EditingSupport 
{
    private ComboBoxCellEditor cellEditor;

    public OptionEditingSupport(ColumnViewer viewer) {
        super(viewer);
        cellEditor = new ComboBoxCellEditor(((TableViewer)viewer).getTable(), new String[]{"Y", "N"});
    }
    protected CellEditor getCellEditor(Object element) {
        return cellEditor;
    }
    protected boolean canEdit(Object element) {
        return true;
    }
    protected Object getValue(Object element) {
        return 0;
    }
    protected void setValue(Object element, Object value) 
    {
        if((element instanceof Person) && (value instanceof Integer)) {
            Integer choice = (Integer)value;
            String option = (choice == 0? "Y":"N");
            ((Person)element).setLikes( option );
            getViewer().update(element, null);
        }
    }
}

---

Data Model

package sample;

import java.util.ArrayList;
import java.util.List;

public class DataModel 
{
    private int samples;
    public DataModel(int samples) {
        this.samples = samples;
    }

    List<Person> getData()
    {
        List<Person> persons = new ArrayList<Person>();
        for(int i=0; i<samples; i++)
            persons.add(Person.createRandomPerson());
        return persons;
    }
}

---

The Person Entity

package sample;

import java.util.Random;

public class Person 
{
    private static final String[]   FIRST = {"Favonius", "Tim", "Brad", "Scott", "Linda"};
    private static final String[]   SECOND = {"Cruise", "Temp", "Abbey", "Adam", "Albert", "Thomas"};
    private static final String[]   COUNTRY = {"India", "USA", "Russia", "UK", "France", "Germany"};
    private static final int[]      AGE = {22, 23, 24, 25, 26, 27, 28, 29, 30};

    private static Random random = new Random(System.currentTimeMillis());

    private String first;
    private String second;
    private String country;
    private String likes;

    private int age;

    public Person(String first, String second, String country, String likes, int age) 
    {
        super();
        this.first = first;
        this.second = second;
        this.country = country;
        this.likes = likes;
        this.age = age;
    }
    public String getFirst() {
        return first;
    }
    public String getSecond() {
        return second;
    }
    public String getCountry() {
        return country;
    }
    public String getLikes() {
        return likes;
    }
    public int getAge() {
        return age;
    }
    public void setLikes(String likes) {
        this.likes = likes;
    }
    public static Person createRandomPerson(){
        return new  Person(FIRST[random.nextInt(FIRST.length)], 
                SECOND[random.nextInt(SECOND.length)], COUNTRY[random.nextInt(COUNTRY.length)], 
                "Y", AGE[random.nextInt(AGE.length)]);
    }
}