Java Swing – 带有示例的 JPanel

JPanel 是Java Swing 包的一部分，是一个可以存储一组组件的容器。 JPanel 的主要任务是组织组件，在 JPanel 中可以设置各种布局，提供更好的组件组织，但是它没有标题栏。

JPanel 的构造函数

1. JPanel() ：创建一个带有流布局的新面板
2. JPanel(LayoutManager l) : 用指定的 layoutManager 创建一个新的 JPanel
3. JPanel(boolean isDoubleBuffered) : 创建一个具有指定缓冲策略的新 JPanel
4. JPanel(LayoutManager l, boolean isDoubleBuffered) : 用指定的 layoutManager 和指定的缓冲策略创建一个新的 JPanel

JPanel的常用功能

1. add(Component c) : 将组件添加到指定容器
2. setLayout(LayoutManager l) ：将容器的布局设置为指定的布局管理器
3. updateUI() ：使用当前外观的值重置 UI 属性。
4. setUI(PanelUI ui) ：设置呈现此组件的对象的外观。
5. getUI() ：返回呈现此组件的外观对象。
6. paramString() ：返回此 JPanel 的字符串表示形式。
7. getUIClassID() ：返回呈现此组件的外观类的名称。
8. getAccessibleContext() ：获取与此 JPanel 关联的 AccessibleContext。

让我们举一个示例程序，通过附加输出的顺序执行快照来说明 JPanel 类的使用，以证明以下程序集的合理性，如下所示：

例子：

Java

// Java Program to Create a Simple JPanel
// and Adding Components to it
  
// Importing required classes
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
  
// Class 1
// Helper class extending JFrame class
class 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();
    }
}

输出：

示例 2：

Java

// Java Program to Create a JPanel with a Border Layout
// and Adding Components to It
  
// Importing required classes
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
  
// Main class
// Extending JFrame class
class 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();
    }
}

输出：

示例 3：

Java

// Java Program to Create a JPanel with a Box layout
// and Adding components to it
  
// Importing required classes
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
  
// Main class
// Extending JFrame class
class 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();
    }
}

输出：

此后，我们成功地在面板中生成按钮。

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.