重构代码--Extract Method

重构太经典了!
重构里面比较简单的又算是Extract Method,这是我的代码里的一个类,经过我Extract Method后,我自己是越看越喜欢:P
本来createControl方法看起来很晕得,重构够变得非常简单了,几乎不需要注释,每个方法名就是注释.
当然有时候Extract Method是很麻烦的,比如碰到很多其它外部变量时.
对于这个简单的例子,我的心得就是取个好的方法名!

/** *//**
 * @author Rey
 */
public class AutoSqlDataSetPage extends WizardPage ...{

    public static final String ID = "AutoSqlDataSetPage";

    private static final int OK = 0;

    private static final int CANCEL = -1;

    private List tableList = null;

    private DataTable initDataTable = null, resultDataTable = null;

    private TableViewer initTableViewer = null, resultTableViewer = null;

    private String[] names = new String[] ...{ "" };

    public AutoSqlDataSetPage() ...{
        super(ID);
    }

    private int index = 1;// input

    private int click = -1;

    private Image image = null;

    private int WIDTH = 40, HEIGHT = 40;

    private Canvas canvas = null;

    private ColumnMoveCommand columnMoveCommand = null;

    public void createControl(final Composite parent) ...{

        setTitle("AutoSqlDataSet Wizard");
        setMessage("XXXXXXXXXXXXXXXX", IMessageProvider.INFORMATION);

        Composite composite = new Composite(parent, SWT.NULL);
        GridLayout glayout = new GridLayout(9, true);
        composite.setLayout(glayout);

        Composite mainBtnsComposite = createMainBtnsComposite(composite);

        Button mainBtnAdd = createMainBtn(mainBtnsComposite, "Add");
        Button mainBtnRemove = createMainBtn(mainBtnsComposite, "Remove");
        Button mainBtnProperties = createMainBtn(mainBtnsComposite, "Properties");
        Button mainBtnPreview = createMainBtn(mainBtnsComposite, "Preview");

        createSeparator(composite);

        createImage(composite);
        createCanvas(composite);

        addListener2Canvas(parent);

        Table initTable = createTable(composite);
        initTableViewer = new TableViewer(initTable);
        initTableViewer.setContentProvider(new ColumnContentProvider());
        initTableViewer.setLabelProvider(new ColumnLabelProvider());

        Composite tableBtnsComposite = createTableBtnsComposite(composite);

        final Button add = createTableBtn(tableBtnsComposite, ">>");
        final Button remove = createTableBtn(tableBtnsComposite, "<<");
        final Button addAll = createTableBtn(tableBtnsComposite, ">>>");
        final Button removeAll = createTableBtn(tableBtnsComposite, "<<<");
        final Button undo = createUndoAndRedoBtn(tableBtnsComposite, "undo");
        final Button redo = createUndoAndRedoBtn(tableBtnsComposite, "redo");

        Table resultTable = createTable(composite);
        resultTableViewer = new TableViewer(resultTable);
        resultTableViewer.setContentProvider(new ColumnContentProvider());
        resultTableViewer.setLabelProvider(new ColumnLabelProvider());

        /** *//***********************************************************************
         * Main Btns' SelectionListener
         **********************************************************************/

        addListener2MainBtnAdd(parent, mainBtnAdd);

        /** *//***********************************************************************
         * Table and Column Btns' SelectionListener
         **********************************************************************/

        addListener2AddBtn(add, undo, redo);

        addListener2RemoveBtn(remove, undo, redo);

        addListener2UndoBtn(undo);

        addListener2RedoBtn(redo);

        addListener2AddAllBtn(addAll, undo, redo);

        addListener2RemoveAllBtn(removeAll, undo, redo);

        setControl(composite);
        setPageComplete(true);
    }

    private Composite createMainBtnsComposite(Composite composite) ...{
        GridLayout glayout;
        Composite mainBtnsComposite = new Composite(composite, SWT.NULL);
        GridData gd = new GridData(GridData.FILL_HORIZONTAL);
        gd.horizontalSpan = 9;
        mainBtnsComposite.setLayoutData(gd);
        glayout = new GridLayout(9, true);
        mainBtnsComposite.setLayout(glayout);
        return mainBtnsComposite;
    }

    private Button createMainBtn(Composite mainBtnsComposite, String text) ...{
        GridData gd;
        Button mainBtnAdd = new Button(mainBtnsComposite, SWT.PUSH);
        mainBtnAdd.setText(text);
        gd = new GridData(GridData.FILL_HORIZONTAL);
        mainBtnAdd.setLayoutData(gd);
        return mainBtnAdd;
    }

    private void createSeparator(Composite composite) ...{
        GridData gd;
        Label label = new Label(composite, SWT.SEPARATOR | SWT.HORIZONTAL);
        gd = new GridData(GridData.HORIZONTAL_ALIGN_FILL);
        gd.horizontalSpan = 9;
        label.setLayoutData(gd);
    }

    private void createCanvas(Composite composite) ...{
        GridData gd;
        canvas = new Canvas(composite, SWT.NO_REDRAW_RESIZE | SWT.V_SCROLL
                | SWT.H_SCROLL);
        gd = new GridData(GridData.FILL_BOTH);
        gd.horizontalSpan = 9;
        canvas.setLayoutData(gd);
    }

    private void addListener2Canvas(final Composite parent) ...{
        final Point origin = new Point(0, 0);

        final ScrollBar hBar = canvas.getHorizontalBar();
        hBar.addListener(SWT.Selection, new Listener() ...{
            public void handleEvent(Event e) ...{
                int hSelection = hBar.getSelection();
                int destX = -hSelection - origin.x;
                Rectangle rect = image.getBounds();
                canvas.scroll(destX, 0, 0, 0, rect.width, rect.height, false);
                origin.x = -hSelection;
            }
        });
        final ScrollBar vBar = canvas.getVerticalBar();
        vBar.addListener(SWT.Selection, new Listener() ...{
            public void handleEvent(Event e) ...{
                int vSelection = vBar.getSelection();
                int destY = -vSelection - origin.y;
                Rectangle rect = image.getBounds();
                canvas.scroll(0, destY, 0, 0, rect.width, rect.height, false);
                origin.y = -vSelection;
            }
        });
        canvas.addListener(SWT.Resize, new Listener() ...{
            public void handleEvent(Event e) ...{
                Rectangle rect = image.getBounds();
                Rectangle client = canvas.getClientArea();
                hBar.setMaximum(rect.width);
                vBar.setMaximum(rect.height);
                hBar.setThumb(Math.min(rect.width, client.width));
                vBar.setThumb(Math.min(rect.height, client.height));
                int hPage = rect.width - client.width;
                int vPage = rect.height - client.height;
                int hSelection = hBar.getSelection();
                int vSelection = vBar.getSelection();
                if (hSelection >= hPage) ...{
                    if (hPage <= 0)
                        hSelection = 0;
                    origin.x = -hSelection;
                }
                if (vSelection >= vPage) ...{
                    if (vPage <= 0)
                        vSelection = 0;
                    origin.y = -vSelection;
                }
                canvas.redraw();
            }
        });
        canvas.addListener(SWT.Paint, new Listener() ...{
            public void handleEvent(Event e) ...{
                GC gc = e.gc;
                gc.drawImage(image, origin.x, origin.y);
                Rectangle rect = image.getBounds();
                Rectangle client = canvas.getClientArea();
                int marginWidth = client.width - rect.width;
                if (marginWidth > 0) ...{
                    gc.fillRectangle(rect.width, 0, marginWidth, client.height);
                }
                int marginHeight = client.height - rect.height;
                if (marginHeight > 0) ...{
                    gc
                            .fillRectangle(0, rect.height, client.width,
                                    marginHeight);
                }
            }
        });

        canvas.addMouseListener(new MouseListener() ...{

            public void mouseDown(MouseEvent e) ...{
                int x = e.x, y = e.y;
                int min = HEIGHT, max = HEIGHT + HEIGHT;
                if (WIDTH < x && x < WIDTH + WIDTH) ...{
                    for (int i = 0; i < index; i++) ...{
                        if (min < y && y < max) ...{

                            click = i;

                            createImage(parent);
                            canvas.redraw();
                            break;
                        }
                        min = max + HEIGHT;
                        max = min + HEIGHT;
                    }
                }
            }

            public void mouseDoubleClick(MouseEvent e) ...{
            }

            public void mouseUp(MouseEvent e) ...{
            }
        });
    }

    private void createImage(final Composite parent) ...{
        int CANVAS_WIDTH = 3 * WIDTH, CANVAS_HEIGHT = (2 * index + 1) * HEIGHT;
        image = new Image(parent.getDisplay(), CANVAS_WIDTH, CANVAS_HEIGHT);
        GC gc = new GC(image);

        drawTable(parent, gc, names);

        drawLine(gc);

        gc.dispose();
    }

    private void drawLine(GC gc) ...{
        for (int i = 0, x = (int) (WIDTH + 0.5 * WIDTH), y = 2 * HEIGHT; i < index - 1; i++) ...{
            gc.drawLine(x, y, x, y + HEIGHT);
            y = y + HEIGHT;
            y += HEIGHT;
        }
    }

    private void drawTable(final Composite parent, GC gc, String[] name) ...{
        for (int i = 0, x = WIDTH, y = HEIGHT; i < index; i++) ...{
            if (i > 0)
                y += 2 * HEIGHT;

            if (i == click) ...{
                gc.drawRectangle(x, y, WIDTH, HEIGHT);
                gc.setBackground(parent.getShell().getDisplay().getSystemColor(
                        SWT.COLOR_CYAN));
                gc.fillRectangle(x + 1, y + 1, WIDTH - 1, HEIGHT - 1);
                gc.drawText(name[i], x + 5, y + 5);
            } else ...{
                gc.setBackground(parent.getShell().getDisplay().getSystemColor(
                        SWT.COLOR_WHITE));
                gc.drawRectangle(x, y, WIDTH, HEIGHT);
                gc.drawText(name[i], x + 5, y + 5);
            }
        }
    }

    private Table createTable(Composite composite) ...{
        Table table = new Table(composite, SWT.MULTI | SWT.FULL_SELECTION
                | SWT.BORDER);
        GridData gd;
        TableColumn tc = new TableColumn(table, SWT.LEFT);
        tc.setWidth(100);
        tc.setText("name");
        tc = new TableColumn(table, SWT.LEFT);
        tc.setWidth(100);
        tc.setText("type");
        table.setHeaderVisible(true);
        table.setLinesVisible(true);

        gd = new GridData();
        gd.horizontalAlignment = GridData.FILL;
        gd.verticalAlignment = GridData.FILL;
        gd.grabExcessHorizontalSpace = true;
        gd.horizontalSpan = 4;
        table.setLayoutData(gd);
        return table;
    }

    private Composite createTableBtnsComposite(Composite composite) ...{
        GridLayout glayout;
        GridData gd;
        Composite tableBtnsComposite = new Composite(composite, SWT.NULL);
        gd = new GridData(GridData.FILL_VERTICAL);
        gd.horizontalAlignment = GridData.FILL;
        gd.horizontalSpan = 1;
        tableBtnsComposite.setLayoutData(gd);
        glayout = new GridLayout(1, true);
        tableBtnsComposite.setLayout(glayout);
        return tableBtnsComposite;
    }

    private Button createTableBtn(Composite tableBtnsComposite, String text) ...{
        GridData gd;
        Button btn = new Button(tableBtnsComposite, SWT.PUSH);
        btn.setText(text);
        gd = new GridData(GridData.FILL_HORIZONTAL);
        btn.setLayoutData(gd);
        return btn;
    }

    private Button createUndoAndRedoBtn(Composite tableBtnsComposite,
            String text) ...{
        GridData gd;
        final Button btn = new Button(tableBtnsComposite, SWT.PUSH);
        btn.setText(text);
        btn.setEnabled(false);
        gd = new GridData(GridData.FILL_HORIZONTAL);
        btn.setLayoutData(gd);
        return btn;
    }

    private void addListener2MainBtnAdd(final Composite parent,
            Button mainBtnAdd) ...{
        mainBtnAdd.addSelectionListener(new SelectionAdapter() ...{
            @Override
            public void widgetSelected(SelectionEvent e) ...{
                // TODO
                SelectJoinTableDialog sjtd = new SelectJoinTableDialog(parent
                        .getShell());
                sjtd.setInput(tableList);
                sjtd.open();
                int returnCode = sjtd.getReturnCode();
                if (returnCode == OK) ...{
                    Object[] result = sjtd.getResult();
                    DataTable dt = (DataTable) result[0];
                    index++;

                    createImage(parent);
                    canvas.redraw();
                }
            }
        });
    }

    private void addListener2AddBtn(Button add, final Button undo,
            final Button redo) ...{
        add.addSelectionListener(new SelectionAdapter() ...{
            @Override
            public void widgetSelected(SelectionEvent e) ...{
                StructuredSelection selection = (StructuredSelection) initTableViewer
                        .getSelection();
                columnMoveCommand = new ColumnMoveCommand(initDataTable,
                        resultDataTable, selection);
                columnMoveCommand.execute();
                undo.setEnabled(true);
                redo.setEnabled(true);

            }
        });
    }

    private void addListener2RemoveBtn(Button remove, final Button undo,
            final Button redo) ...{
        remove.addSelectionListener(new SelectionAdapter() ...{
            @Override
            public void widgetSelected(SelectionEvent e) ...{
                StructuredSelection selection = (StructuredSelection) resultTableViewer
                        .getSelection();
                columnMoveCommand = new ColumnMoveCommand(resultDataTable,
                        initDataTable, selection);
                columnMoveCommand.execute();
                undo.setEnabled(true);
                redo.setEnabled(true);
            }
        });
    }

    private void addListener2UndoBtn(final Button undo) ...{
        undo.addSelectionListener(new SelectionAdapter() ...{
            @Override
            public void widgetSelected(SelectionEvent e) ...{
                columnMoveCommand.undo();
            }
        });
    }

    private void addListener2RedoBtn(final Button redo) ...{
        redo.addSelectionListener(new SelectionAdapter() ...{
            @Override
            public void widgetSelected(SelectionEvent e) ...{
                columnMoveCommand.redo();
            }
        });
    }

    private void addListener2AddAllBtn(Button addAll, final Button undo,
            final Button redo) ...{
        addAll.addSelectionListener(new SelectionAdapter() ...{
            @Override
            public void widgetSelected(SelectionEvent e) ...{
                columnMoveCommand = new ColumnMoveCommand(initDataTable,
                        resultDataTable);
                columnMoveCommand.execute();
                undo.setEnabled(true);
                redo.setEnabled(true);

            }
        });
    }

    private void addListener2RemoveAllBtn(Button removeAll, final Button undo,
            final Button redo) ...{
        removeAll.addSelectionListener(new SelectionAdapter() ...{
            @Override
            public void widgetSelected(SelectionEvent e) ...{
                columnMoveCommand = new ColumnMoveCommand(resultDataTable,
                        initDataTable);
                columnMoveCommand.execute();
                undo.setEnabled(true);
                redo.setEnabled(true);

            }
        });
    }

    public void onEnterPage() ...{
        AutoDataSetWizardController controller = ((AutoDataSetWizard) getWizard())
                .getController();
        tableList = controller.getTableList();
        initDataTable = controller.getSelectedTable();
        initTableViewer.setInput(initDataTable);

        resultDataTable = DoradoFactory.eINSTANCE.createDataTable();
        resultTableViewer.setInput(resultDataTable);

        setNames();

        redrawImage();
    }

    private void setNames() ...{
        names = new String[tableList.size()];
        int i = 0;
        for (Iterator it = tableList.iterator(); it.hasNext(); i++) ...{
            DataTable table = (DataTable) it.next();
            names[i] = table.getName();
        }
    }

    private void redrawImage() ...{
        Composite parent = canvas.getParent();
        createImage(parent);
        canvas.redraw();
    }

    private class ColumnContentProvider implements IStructuredContentProvider ...{
        public Object[] getElements(Object inputElement) ...{
            DataTable table = (DataTable) inputElement;
            return table.getColumns().toArray();
        }

        public void dispose() ...{
        }

        public void inputChanged(Viewer viewer, Object oldInput, Object newInput) ...{
        }
    }

    private class ColumnLabelProvider implements ITableLabelProvider ...{
        public Image getColumnImage(Object element, int columnIndex) ...{
            return null;
        }

        public String getColumnText(Object element, int columnIndex) ...{
            Column column = (Column) element;
            String text = "";

            switch (columnIndex) ...{
            case 0:
                text = column.getName();
                break;
            case 1:
                text = column.getType();
                break;
            }
            return text;
        }

        public void addListener(ILabelProviderListener listener) ...{
        }

        public void dispose() ...{
        }

        public boolean isLabelProperty(Object element, String property) ...{
            return false;
        }

        public void removeListener(ILabelProviderListener listener) ...{
        }
    }

    private class ColumnMoveCommand ...{
        DataTable src, dest;

        List columns;

        StructuredSelection selection;

        public ColumnMoveCommand(DataTable src, DataTable dest) ...{
            this.src = src;
            this.dest = dest;
            columns = new ArrayList();
            for (Iterator it = src.getColumns().iterator(); it.hasNext();) ...{
                Column column = (Column) it.next();
                columns.add(column);
            }

        }

        public ColumnMoveCommand(DataTable src, DataTable dest,
                StructuredSelection selection) ...{
            this.src = src;
            this.dest = dest;
            this.selection = selection;
            columns = new ArrayList();
            for (Iterator it = selection.iterator(); it.hasNext();) ...{
                Column column = (Column) it.next();
                columns.add(column);
            }
        }

        public void execute() ...{
            for (Iterator it = columns.iterator(); it.hasNext();) ...{
                Column c = (Column) it.next();
                src.getColumns().remove(c);
                dest.getColumns().add(c);
            }
            refreshTable();
        }

        public void undo() ...{
            for (Iterator it = columns.iterator(); it.hasNext();) ...{
                Column c = (Column) it.next();
                src.getColumns().add(c);
                dest.getColumns().remove(c);
            }
            refreshTable();
        }

        public void redo() ...{
            execute();
        }

        private void refreshTable() ...{
            initTableViewer.refresh();
            resultTableViewer.refresh();
        }
    }

}