I have been trying to understand JViewports and tried to work with one. I have been using this gentleman's class, which just extends the JViewport class.
If I want to set the viewport in the middle of a 6480*4860 object implementing the JPanel Class, how come this code gives me a blank view, even if, upon debugging,I have confirmation that the class implementing JPanel I am using has been added to the view? Am I completely mixed up in my calls to the different methods or in my comprehension of the coordinates used and their meaning? And one more : Does calling
v.setOpaque(true);
set only the viewport opaque or it will set all its children too? I guess I will quickly know the answer to this one if I figure out how to properly use viewports.
public myProgram(){
...
myCustomJPanel = new MyCustonJPanel();
myCustomJPanel.setBackground(Color.WHITE);
GrabbableViewport v = new GrabbableViewport();
v.setViewSize(new Dimension(720,540));
v.setViewPosition(new Point(720,540));
v.setView(myCustomJPanel);
v.setViewPosition(new Point(720,540));
v.setLocation(43, 5);
appropriateParentPanel.add(v);
}
Here is the class I am trying to use. It takes much more space for this short question, but formatted text should please you more than plain text! If I am not mistaken, though, the problem should not come from here.
// Copyright (c) 2006 - 2008, Markus Strauch.
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
// * Redistributions of source code must retain the above copyright notice,
// this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above copyright notice,
// this list of conditions and the following disclaimer in the documentation
// and/or other materials provided with the distribution.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
// THE POSSIBILITY OF SUCH DAMAGE.
package net.sf.sdedit.ui.components;
import java.awt.Component;
import java.awt.Cursor;
import java.awt.Image;
import java.awt.Point;
import java.awt.Rectangle;
import java.awt.Toolkit;
import java.awt.event.MouseEvent;
import javax.swing.ImageIcon;
import javax.swing.JComponent;
import javax.swing.JViewport;
import javax.swing.event.MouseInputListener;
/**
* A <tt>GrabbableViewport</tt> is a <tt>JViewport</tt> that scrolls its
* view when the mouse is dragged. While the mouse is being dragged, its cursor
* is set to a "grabbing hand", like in applications such as Acrobat
* Reader.
*
* @author Markus Strauch
*
*/
public class GrabbableViewport extends JViewport implements MouseInputListener {
private static Cursor HAND = new Cursor(Cursor.MOVE_CURSOR);
private static Cursor DFLT = new Cursor(Cursor.DEFAULT_CURSOR);
public static void setHandCursorIcon(ImageIcon icon) {
Image grabbingHand = icon.getImage();
HAND = Toolkit.getDefaultToolkit().createCustomCursor(grabbingHand,
new Point(0, 0), "hand cursor");
}
/**
* Constructor.
*/
public GrabbableViewport () {
super ();
}
private Rectangle rect;
private Point point;
private JComponent view;
public void setView(Component view) {
super.setView(view);
if (this.view != view) {
if (this.view != null) {
this.view.removeMouseListener(this);
this.view.removeMouseMotionListener(this);
}
if (view != null) {
view.addMouseListener(this);
view.addMouseMotionListener(this);
}
this.view = (JComponent) view;
}
}
public void mouseClicked(MouseEvent e) {
}
public void mouseEntered(MouseEvent e) {
}
public void mouseExited(MouseEvent e) {
}
public void mousePressed(MouseEvent e) {
view.setCursor(HAND);
//((Component) e.getSource()).setCursor(HAND);
rect = getViewRect();
point = screenLocation(e);
}
private Point screenLocation(MouseEvent e) {
Point root = view.getLocationOnScreen();
Point mouse = e.getPoint();
if (rect != null && !rect.contains(mouse)) {
return null;
}
Point screenPoint = new Point(root.x + mouse.x, root.y + mouse.y);
return screenPoint;
}
public void mouseReleased(MouseEvent e) {
view.setCursor(DFLT);
scrollTo(screenLocation(e));
clear();
}
public void mouseDragged(MouseEvent e) {
scrollTo(screenLocation(e));
}
public void mouseMoved(MouseEvent e) {
}
private void scrollTo(Point newPoint) {
if (point != null && newPoint != null && rect != null) {
int deltaX = point.x - newPoint.x;
int deltaY = point.y - newPoint.y;
rect.x = rect.x + deltaX;
rect.y = rect.y + deltaY;
((JComponent) getView()).scrollRectToVisible(rect);
point = newPoint;
}
}
private void clear() {
rect = null;
point = null;
}
}
I could give you a sscce but I think this should be simple enough, although I can piece together some example quickly if you ask.
