JViewport: Move and View : Scrollpane « Swing JFC « Java

JViewport: Move and View

JViewport: Move and View
Definitive Guide to Swing for Java 2, Second Edition
By John Zukowski     
ISBN: 1-893115-78-X
Publisher: APress

import java.awt.BorderLayout;
import java.awt.Container;
import java.awt.Dimension;
import java.awt.Point;
import java.awt.event.ActionEvent;

import javax.swing.AbstractAction;
import javax.swing.Action;
import javax.swing.ActionMap;
import javax.swing.Icon;
import javax.swing.ImageIcon;
import javax.swing.InputMap;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JViewport;
import javax.swing.KeyStroke;

public class MoveViewSample {

  public static final int INCREASE = 0; // direction

  public static final int DECREASE = 1; // direction

  public static final int X_AXIS = 0; // axis

  public static final int Y_AXIS = 1; // axis

  public static final int UNIT = 0; // type

  public static final int BLOCK = 1; // type

  static class MoveAction extends AbstractAction {
    JViewport viewport;

    int direction;

    int axis;

    int type;

    public MoveAction(JViewport viewport, int direction, int axis, int type) {
      if (viewport == null) {
        throw new IllegalArgumentException(
            "null viewport not permitted");
      this.viewport = viewport;
      this.direction = direction;
      this.axis = axis;
      this.type = type;

    public void actionPerformed(ActionEvent actionEvent) {
      Dimension extentSize = viewport.getExtentSize();
      int horizontalMoveSize = 0;
      int verticalMoveSize = 0;
      if (axis == X_AXIS) {
        if (type == UNIT) {
          horizontalMoveSize = 1;
        } else { // type == BLOCK
          horizontalMoveSize = extentSize.width;
      } else { // axis == Y_AXIS
        if (type == UNIT) {
          verticalMoveSize = 1;
        } else { // type == BLOCK
          verticalMoveSize = extentSize.height;
      if (direction == DECREASE) {
        horizontalMoveSize = -horizontalMoveSize;
        verticalMoveSize = -verticalMoveSize;
      // Translate origin by some amount
      Point origin = viewport.getViewPosition();
      origin.x += horizontalMoveSize;
      origin.y += verticalMoveSize;
      // set new viewing origin

  public static void main(String args[]) {
    JFrame frame = new JFrame("JViewport Sample");

    Icon icon = new ImageIcon("dog.jpg");
    JLabel dogLabel = new JLabel(icon);
    JViewport viewport = new JViewport();

    InputMap inputMap = viewport
    ActionMap actionMap = viewport.getActionMap();

    // Up key moves view up unit
    Action upKeyAction = new MoveAction(viewport, DECREASE, Y_AXIS, UNIT);
    KeyStroke upKey = KeyStroke.getKeyStroke("UP");
    inputMap.put(upKey, "up");
    actionMap.put("up", upKeyAction);

    // Down key moves view down unit
    Action downKeyAction = new MoveAction(viewport, INCREASE, Y_AXIS, UNIT);
    KeyStroke downKey = KeyStroke.getKeyStroke("DOWN");
    inputMap.put(downKey, "down");
    actionMap.put("down", downKeyAction);

    // Left key moves view left unit
    Action leftKeyAction = new MoveAction(viewport, DECREASE, X_AXIS, UNIT);
    KeyStroke leftKey = KeyStroke.getKeyStroke("LEFT");
    inputMap.put(leftKey, "left");
    actionMap.put("left", leftKeyAction);

    // Right key moves view right unit
    Action rightKeyAction = new MoveAction(viewport, INCREASE, X_AXIS, UNIT);
    KeyStroke rightKey = KeyStroke.getKeyStroke("RIGHT");
    inputMap.put(rightKey, "right");
    actionMap.put("right", rightKeyAction);

    // PgUp key moves view up block
    Action pgUpKeyAction = new MoveAction(viewport, DECREASE, Y_AXIS, BLOCK);
    KeyStroke pgUpKey = KeyStroke.getKeyStroke("PAGE_UP");
    inputMap.put(pgUpKey, "pgUp");
    actionMap.put("pgUp", pgUpKeyAction);

    // PgDn key moves view down block
    Action pgDnKeyAction = new MoveAction(viewport, INCREASE, Y_AXIS, BLOCK);
    KeyStroke pgDnKey = KeyStroke.getKeyStroke("PAGE_DOWN");
    inputMap.put(pgDnKey, "pgDn");
    actionMap.put("pgDn", pgDnKeyAction);

    // Shift-PgUp key moves view left block
    Action shiftPgUpKeyAction = new MoveAction(viewport, DECREASE, X_AXIS,
    KeyStroke shiftPgUpKey = KeyStroke.getKeyStroke("shift PAGE_UP");
    inputMap.put(shiftPgUpKey, "shiftPgUp");
    actionMap.put("shiftPgUp", shiftPgUpKeyAction);

    // Shift-PgDn key moves view right block
    Action shiftPgDnKeyAction = new MoveAction(viewport, INCREASE, X_AXIS,
    KeyStroke shiftPgDnKey = KeyStroke.getKeyStroke("shift PAGE_DOWN");
    inputMap.put(shiftPgDnKey, "shiftPgDn");
    actionMap.put("shiftPgDn", shiftPgDnKeyAction);

    Container contentPane = frame.getContentPane();
    contentPane.add(viewport, BorderLayout.CENTER);
    frame.setSize(300, 200);


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