I am trying to design a timeline for this media playback application using a JPanel. In order to provide an indication of the current video frame with respect to the timeline, I need to be able to draw a vertical line at a specific x-coordinate in this TimeLinePanel class that extends JPanel. So far, I haven’t had much luck with using the paint() function or overriding the paintComponent(). When I tried to use the paint() function in my NewJApplet (this class extends JApplet) class, the vertical line is drawn, but the JPanel that I’m using as the timeline disappears (the border is no longer visible). In addition, I’ve heard that using the paint() method was not preferrable. As a result, I’ve tried to override paintComponent() method in JPanel and I’ve tried calling the paintComponent method from NewJApplet, but it does not update timeLinePanel1 with the vertical line.
Any help would be appreciated.
The following is the code I have so far:
/*
* To change this template, choose Tools | Templates
* and open the template in the editor.
*/
package helloworld;
import java.awt.GridLayout;
import javax.swing.border.EmptyBorder;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
/**
*
* @author Justin
*/
public class NewJApplet extends javax.swing.JApplet {
/**
* Initializes the applet NewJApplet
*/
@Override
public void init() {
/* Set the Nimbus look and feel */
//<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
/* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
* For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html
*/
try {
/*
for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
if ("Nimbus".equals(info.getName())) {
javax.swing.UIManager.setLookAndFeel(info.getClassName());
break;
}
}
* */
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException ex) {
java.util.logging.Logger.getLogger(NewJApplet.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (InstantiationException ex) {
java.util.logging.Logger.getLogger(NewJApplet.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (IllegalAccessException ex) {
java.util.logging.Logger.getLogger(NewJApplet.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
} catch (javax.swing.UnsupportedLookAndFeelException ex) {
java.util.logging.Logger.getLogger(NewJApplet.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
}
//</editor-fold>
/* Create and display the applet */
try {
java.awt.EventQueue.invokeAndWait(new Runnable() {
public void run() {
initComponents();
timeLinePanel1.paintComponent(timeLinePanel1.getGraphics());
timeLinePanel1.repaint();
}
});
} catch (Exception ex) {
ex.printStackTrace();
}
}
/**
* This method is called from within the init() method to initialize the
* form. WARNING: Do NOT modify this code. The content of this method is
* always regenerated by the Form Editor.
*/
@SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">
private void initComponents() {
myPanel = new javax.swing.JPanel();
timeLinePanel1 = new helloworld.TimeLinePanel();
myPanel.setBackground(new java.awt.Color(51, 51, 51));
javax.swing.GroupLayout myPanelLayout = new javax.swing.GroupLayout(myPanel);
myPanel.setLayout(myPanelLayout);
myPanelLayout.setHorizontalGroup(
myPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(myPanelLayout.createSequentialGroup()
.addContainerGap()
.addComponent(timeLinePanel1, javax.swing.GroupLayout.DEFAULT_SIZE, 600, Short.MAX_VALUE)
.addContainerGap())
);
myPanelLayout.setVerticalGroup(
myPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(javax.swing.GroupLayout.Alignment.TRAILING, myPanelLayout.createSequentialGroup()
.addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
.addComponent(timeLinePanel1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
.addContainerGap())
);
javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
getContentPane().setLayout(layout);
layout.setHorizontalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(layout.createSequentialGroup()
.addComponent(myPanel, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
.addGap(0, 0, 0))
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addComponent(myPanel, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
);
}// </editor-fold>
// Variables declaration - do not modify
private javax.swing.JPanel myPanel;
private helloworld.TimeLinePanel timeLinePanel1;
// End of variables declaration
}
/*
* To change this template, choose Tools | Templates
* and open the template in the editor.
*/
package helloworld;
import java.awt.GridLayout;
import javax.swing.border.EmptyBorder;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
/**
*
* @author Justin
*/
public class TimeLinePanel extends javax.swing.JPanel {
/**
* Creates new form TimeLinePanel
*/
public TimeLinePanel() {
initComponents();
}
@Override
protected void paintComponent(Graphics g) {
Rectangle r = new Rectangle(3, 0, 1, 25);
g.fillRect(25, 0, 1, 25);
}
/**
* This method is called from within the constructor to initialize the form.
* WARNING: Do NOT modify this code. The content of this method is always
* regenerated by the Form Editor.
*/
@SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">
private void initComponents() {
jPanel1 = new javax.swing.JPanel();
jPanel1.setBackground(new java.awt.Color(255, 255, 255));
jPanel1.setBorder(javax.swing.BorderFactory.createLineBorder(new java.awt.Color(0, 0, 0)));
javax.swing.GroupLayout jPanel1Layout = new javax.swing.GroupLayout(jPanel1);
jPanel1.setLayout(jPanel1Layout);
jPanel1Layout.setHorizontalGroup(
jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGap(0, 200, Short.MAX_VALUE)
);
jPanel1Layout.setVerticalGroup(
jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGap(0, 25, Short.MAX_VALUE)
);
javax.swing.GroupLayout layout = new javax.swing.GroupLayout(this);
this.setLayout(layout);
layout.setHorizontalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addComponent(jPanel1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
);
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addComponent(jPanel1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
);
}// </editor-fold>
// Variables declaration - do not modify
private javax.swing.JPanel jPanel1;
// End of variables declaration
}
This is what I get when I try to run the applet. Ideally, I’d like to have a vertical line drawn at some (x,y) coordinate in the white box (timeLinePanel1), such as (25,0) (as indicated in the code) to get an understanding of how I can proceed with drawing vertical lines within a JPanel.
You need to call super.paintComponent in order to paint everything in your panel: