I have a JTextArea and it's riding on top of a JScrollPane. Anyways, I know I can use the getViewPort() method to set the opaque property of the viewport, but I cannot seem to find any sign of how to do that anywhere.
Here is what I have so far:
if (e.getKeyCode() == KeyEvent.VK_F)
{
if (sp.isVisible())
{
sp.setVisible(false);
}
else
{
sp.setVisible(true);
}
}
Your colloquy with @Serplat suggests that you may be confounding opacity and transparency.
Opacity is a boolean property of Swing components used to optimize drawing:
true: The component agrees to paint all of the bits contained within its rectangular bounds.false: The component makes no guarantees about painting all the bits within its rectangular bounds.Transparency is a means of compositing digital images, as seen in this example.
Considering the distinction may help to clarify your question or focus your search for more information.
Addendum: Based on @camickr's example, the example below shows a blue square that "sticks" to the viewport, while the gray checkerboard may be scrolled over it.
import java.awt.*;
import javax.swing.*;
/** @see https://stackoverflow.com/questions/2846497 */
public class ScrollPanePaint extends JFrame {
private static final int TILE = 64;
public ScrollPanePaint() {
JViewport viewport = new MyViewport();
viewport.setView(new MyPanel());
JScrollPane scrollPane = new JScrollPane();
scrollPane.setViewport(viewport);
this.add(scrollPane);
this.setDefaultCloseOperation(DISPOSE_ON_CLOSE);
this.pack();
this.setLocationRelativeTo(null);
this.setVisible(true);
}
private static class MyViewport extends JViewport {
public MyViewport() {
this.setOpaque(false);
this.setPreferredSize(new Dimension(6 * TILE, 6 * TILE));
}
@Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
g.setColor(Color.blue);
g.fillRect(TILE, TILE, 3 * TILE, 3 * TILE);
}
}
private static class MyPanel extends JPanel {
public MyPanel() {
this.setOpaque(false);
this.setPreferredSize(new Dimension(9 * TILE, 9 * TILE));
}
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
g.setColor(Color.lightGray);
int w = this.getWidth() / TILE + 1;
int h = this.getHeight() / TILE + 1;
for (int row = 0; row < h; row++) {
for (int col = 0; col < w; col++) {
if ((row + col) % 2 == 0) {
g.fillRect(col * TILE, row * TILE, TILE, TILE);
}
}
}
}
}
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
new ScrollPanePaint();
}
});
}
}
You need to use setOpaque(false) to make it transparent. Call that both on the JScrollPane, and on it's ViewPort.
sp.setOpaque(false); sp.getViewport().setOpaque(false);
You'll also have to call setOpaque(false) on the JTextArea, if you want that transparent as well.
Your colloquy with @Serplat suggests that you may be confounding opacity and transparency.
Opacity is a boolean property of Swing components used to optimize drawing:
true: The component agrees to paint all of the bits contained within its rectangular bounds.false: The component makes no guarantees about painting all the bits within its rectangular bounds.Transparency is a means of compositing digital images, as seen in this example.
Considering the distinction may help to clarify your question or focus your search for more information.
Addendum: Based on @camickr's example, the example below shows a blue square that "sticks" to the viewport, while the gray checkerboard may be scrolled over it.
import java.awt.*;
import javax.swing.*;
/** @see https://stackoverflow.com/questions/2846497 */
public class ScrollPanePaint extends JFrame {
private static final int TILE = 64;
public ScrollPanePaint() {
JViewport viewport = new MyViewport();
viewport.setView(new MyPanel());
JScrollPane scrollPane = new JScrollPane();
scrollPane.setViewport(viewport);
this.add(scrollPane);
this.setDefaultCloseOperation(DISPOSE_ON_CLOSE);
this.pack();
this.setLocationRelativeTo(null);
this.setVisible(true);
}
private static class MyViewport extends JViewport {
public MyViewport() {
this.setOpaque(false);
this.setPreferredSize(new Dimension(6 * TILE, 6 * TILE));
}
@Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
g.setColor(Color.blue);
g.fillRect(TILE, TILE, 3 * TILE, 3 * TILE);
}
}
private static class MyPanel extends JPanel {
public MyPanel() {
this.setOpaque(false);
this.setPreferredSize(new Dimension(9 * TILE, 9 * TILE));
}
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
g.setColor(Color.lightGray);
int w = this.getWidth() / TILE + 1;
int h = this.getHeight() / TILE + 1;
for (int row = 0; row < h; row++) {
for (int col = 0; col < w; col++) {
if ((row + col) % 2 == 0) {
g.fillRect(col * TILE, row * TILE, TILE, TILE);
}
}
}
}
}
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
new ScrollPanePaint();
}
});
}
}
Code for JScrollpane Transparent Background.
JScrollPane scrollPane = new JScrollPane();
JViewport viewport = new JViewport();
//Component that need to be added in Scroll pane//
viewport.setView(new JPanel());
viewport.setOpaque(false);
scrollPane.setViewport(viewport);
scrollPane.getViewport().setOpaque(false);
scrollPane.setOpaque(false);
// Add Scrollpane to Jframe or JPanel//
add( scrollPane,BorderLayout.CENTER);
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