The Code Like This:
JFrameT.java:
import java.awt.Color;
import java.awt.Dimension;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class JFrameT extends JFrame {
private JButton testButton;
private JPanel panelMain;
private JPanelOne panel;
public JFrameT() {
// setting up JFrame
setLayout(null);
setPreferredSize(new Dimension(420, 90));
setResizable(false);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
// creating main JPanel (white)
panelMain = new JPanel();
panelMain.setBackground(Color.WHITE);
panelMain.setBounds(0, 0, 420, 90);
panelMain.setPreferredSize(new Dimension(200, 40));
add(panelMain);
// creating JButton in the main JPanel (white)
testButton = new JButton("Button from main class");
panelMain.add(testButton);
// creating new JPanelOne object from JPanelOne class containing black JPanel
panel = new JPanelOne();
// adding black JPanel to main JPanel (white)
panelMain.add(panel);
pack();
}
public static void main(String[] arguments) {
//Creat JFrame object and setting it visible
JFrameT frame = new JFrameT();
frame.setVisible(true);
}
}
JPanelOne.java:
import java.awt.Color;
import java.awt.Dimension;
import javax.swing.JButton;
import javax.swing.JPanel;
import javax.swing.SwingConstants;
public class JPanelFirst extends JPanel
{
public JPanelFirst()
{
// setting up black JPanel
JPanel panel = new JPanel();
panel.setPreferredSize(new Dimension(220, 40));
panel.setBackground(Color.BLACK);
// creating button on external JPanel
JButton button = new JButton("Button (+JPanel) from external class");
// adding button to the black JPanel
panel.add(button);
// adding blackJPanel
add(panel);
}
}
You can find it helpful more in this problem.