JPanel, a part of the Java Swing package, is a container that can store a group of components. The main task of JPanel is to organize components, various layouts can be set in JPanel which provide better organization of components, however, it does not have a title bar.
Constructors of JPanel
- JPanel(): creates a new panel with a flow layout
- JPanel(LayoutManager l): creates a new JPanel with specified layoutManager
- JPanel(boolean isDoubleBuffered): creates a new JPanel with a specified buffering strategy
- JPanel(LayoutManager l, boolean isDoubleBuffered): creates a new JPanel with specified layoutManager and a specified buffering strategy
Commonly used Functions of JPanel
- add(Component c): Adds a component to a specified container
- setLayout(LayoutManager l): sets the layout of the container to the specified layout manager
- updateUI(): resets the UI property with a value from the current look and feel.
- setUI(PanelUI ui): sets the look and feel of an object that renders this component.
- getUI(): returns the look and feel object that renders this component.
- paramString(): returns a string representation of this JPanel.
- getUIClassID(): returns the name of the Look and feel class that renders this component.
- getAccessibleContext(): gets the AccessibleContext associated with this JPanel.
Let us take a sample program in order to illustrate the use of JPanel class by appending sequential execution snapshots of outputs justifying the below program sets as follows:
Example:
Java
// Java Program to Create a Simple JPanel// and Adding Components to it // Importing required classesimport java.awt.*;import java.awt.event.*;import javax.swing.*; // Class 1// Helper class extending JFrame classclass solution extends JFrame { // JFrame static JFrame f; // JButton static JButton b, b1, b2; // Label to display text static JLabel l; // Main class public static void main(String[] args) { // Creating a new frame to store text field and // button f = new JFrame("panel"); // Creating a label to display text l = new JLabel("panel label"); // Creating a new buttons b = new JButton("button1"); b1 = new JButton("button2"); b2 = new JButton("button3"); // Creating a panel to add buttons JPanel p = new JPanel(); // Adding buttons and textfield to panel // using add() method p.add(b); p.add(b1); p.add(b2); p.add(l); // setbackground of panel p.setBackground(Color.red); // Adding panel to frame f.add(p); // Setting the size of frame f.setSize(300, 300); f.show(); }} |
Output:
Example 2:
Java
// Java Program to Create a JPanel with a Border Layout// and Adding Components to It // Importing required classesimport java.awt.*;import java.awt.event.*;import javax.swing.*; // Main class// Extending JFrame classclass solution extends JFrame { // JFrame static JFrame f; // JButton static JButton b, b1, b2, b3; // Label to display text static JLabel l; // Main driver method public static void main(String[] args) { // Creating a new frame to store text field and // button f = new JFrame("panel"); // Creating a label to display text l = new JLabel("panel label"); // Creating a new buttons b = new JButton("button1"); b1 = new JButton("button2"); b2 = new JButton("button3"); b3 = new JButton("button4"); // Creating a panel to add buttons // and a specific layout JPanel p = new JPanel(new BorderLayout()); // Adding buttons and textfield to panel // using add() method p.add(b, BorderLayout.NORTH); p.add(b1, BorderLayout.SOUTH); p.add(b2, BorderLayout.EAST); p.add(b3, BorderLayout.WEST); p.add(l, BorderLayout.CENTER); // setbackground of panel p.setBackground(Color.red); // Adding panel to frame f.add(p); // Setting the size of frame f.setSize(300, 300); f.show(); }} |
Output:
Example 3:
Java
// Java Program to Create a JPanel with a Box layout// and Adding components to it // Importing required classesimport java.awt.*;import java.awt.event.*;import javax.swing.*; // Main class// Extending JFrame classclass solution extends JFrame { // JFrame static JFrame f; // JButton static JButton b, b1, b2, b3; // Label to display text static JLabel l; // Main drive method public static void main(String[] args) { // Creating a new frame to store text field and // button f = new JFrame("panel"); // Creating a label to display text l = new JLabel("panel label"); // Creating a new buttons b = new JButton("button1"); b1 = new JButton("button2"); b2 = new JButton("button3"); b3 = new JButton("button4"); // Creating a panel to add buttons and // textfield and a layout JPanel p = new JPanel(); // Setting box layout p.setLayout(new BoxLayout(p, BoxLayout.Y_AXIS)); // Adding buttons and textfield to panel p.add(b); p.add(b1); p.add(b2); p.add(b3); p.add(l); // Setting background of panel p.setBackground(Color.red); // Adding panel to frame f.add(p); // Setting the size of frame f.setSize(300, 300); f.show(); }} |
Output:
Henceforth, we are successfully able to generate buttons in our panel.
Note: In the previous Program, border layout and Box Layout are used. Different other layouts can be used to organize the components in a definite pattern, such as card layout, grid layout, etc.
