moveviewsample.java

The Definitive Guide to Java Swing, Third Edition by John Zukowski (Author) 源码

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

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
      viewport.setViewPosition(origin);
    }
  }

  public static void main(String args[]) {
    Runnable runner = new Runnable() {
      public void run() {
        JFrame frame = new JFrame("JViewport Sample");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        Icon icon = new ImageIcon("dog.jpg");
        JLabel dogLabel = new JLabel(icon);
        JViewport viewport = new JViewport();
        viewport.setView(dogLabel);

        InputMap inputMap = viewport.getInputMap(JComponent.WHEN_IN_FOCUSED_WINDOW);
        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, BLOCK);
        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, BLOCK);
        KeyStroke shiftPgDnKey = KeyStroke.getKeyStroke("shift PAGE_DOWN");
        inputMap.put(shiftPgDnKey, "shiftPgDn");
        actionMap.put("shiftPgDn", shiftPgDnKeyAction);

        frame.add(viewport, BorderLayout.CENTER);
        frame.setSize(300, 200);
        frame.setVisible(true);
      }
    };
    EventQueue.invokeLater(runner);
  }
}