如何应用 JFrame 的背景渐变

Question

我想在 JFrame 中应用渐变。 我尽我所能，但我遇到了一些问题。 请帮帮我。

在下面的代码中。 我想将 pnlMain 设置为 BorderLayout 但我使用了渐变绘制，因此 BorderLayout 设置不正确。 而且 graphics2d.fillRect(0, 0, width, height) 也没有填满整个 pnlMain JPanel。 所以请给它一些建议。

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.GradientPaint; 
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.GridLayout;
import java.awt.Point;
import javax.swing.Box;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.SwingConstants;

public class Frame extends javax.swing.JFrame {

// Getter & Setter
public Frame() {
    setExtendedState(Frame.MAXIMIZED_BOTH);
    setTitle("Gradient");
    initComponents();
}
private void initComponents() {

    menu_bar = new javax.swing.JMenuBar();
    jMenu1 = new javax.swing.JMenu();
    pnlMain = new JPanel();

    pnlSuper = new JPanel(new BorderLayout(15,15))
    {

        public void paintComponent(Graphics g)
        {
            super.paintComponent(g);

            Point point1 = new Point(10, 10);
            Point point2 = new Point(
                getWidth() - 10, 
                getHeight() - 10);
            final GradientPaint gp = new GradientPaint(
                point1, Color.YELLOW,
                point2, new Color(255, 225, 100),
                true);
            final Graphics2D g2 = (Graphics2D) g;
            g2.setPaint(gp);
            g.fillRect(0, 0, getWidth(), getHeight());
        }
    };
    pnlSuper.setBorder(new EmptyBorder(30,30,30,30));
    pnlMain.setLayout(new BorderLayout());
    pnlMain.setOpaque(false);
    pnlImage = new JPanel(new BorderLayout());
    pnlFooter = new JPanel(new GridLayout(1,2));

    footerBox = Box.createVerticalBox();
    lblBackground = new JLabel("Image");
    lblBackground.setFont(new java.awt.Font("URW Bookman L", 0, 20));
    lblAddress = new JLabel();
    lblContactNumber = new JLabel();

    lblBackground.setHorizontalAlignment(SwingConstants.CENTER);
    lblAddress.setText("Address");
    lblAddress.setAlignmentX(JLabel.CENTER_ALIGNMENT);
    lblAddress.setFont(new java.awt.Font("URW Bookman L", 0, 20)); // NOI18N
    footerBox.add(lblAddress);

    lblContactNumber.setText("Contact Number ");
    lblContactNumber.setFont(new java.awt.Font("URW Bookman L", 0, 20)); // NOI18N
    lblContactNumber.setAlignmentX(JLabel.CENTER_ALIGNMENT);
    footerBox.add(lblContactNumber);

    pnlFooter.add(footerBox);
    pnlImage.add(lblBackground);

    pnlMain.add(pnlImage, BorderLayout.CENTER);
    pnlMain.add(pnlFooter, BorderLayout.SOUTH);
    pnlSuper.add(pnlMain);

    setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

    jMenu1.setText("File");
    jMenu1.setFont(new java.awt.Font("URW Bookman L", 0, 18));
    jMenu1.setPreferredSize(new java.awt.Dimension(45, 25));
    menu_bar.add(jMenu1);

    setJMenuBar(menu_bar);

    javax.swing.GroupLayout layout = new javax.swing.GroupLayout(
            getContentPane());
    getContentPane().setLayout(layout);
    layout.setHorizontalGroup(layout
            .createParallelGroup(javax.swing.GroupLayout.Alignment.CENTER)
            .addGap(0, 1352, Short.MAX_VALUE).addComponent(pnlSuper));
    layout.setVerticalGroup(layout
            .createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING)
            .addGap(0, 757, Short.MAX_VALUE).addComponent(pnlSuper));
    pack();
}

    public static void main(String args[]) {
        try {
            for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager
                    .getInstalledLookAndFeels()) {
                if ("Nimbus".equals(info.getName())) {
                    javax.swing.UIManager.setLookAndFeel(info.getClassName());
                    break;
                }
            }
        } catch (ClassNotFoundException ex) {
            java.util.logging.Logger.getLogger(Index.class.getName()).log(
                    java.util.logging.Level.SEVERE, null, ex);
        } catch (InstantiationException ex) {
            java.util.logging.Logger.getLogger(Index.class.getName()).log(
                    java.util.logging.Level.SEVERE, null, ex);
        } catch (IllegalAccessException ex) {
            java.util.logging.Logger.getLogger(Index.class.getName()).log(
                    java.util.logging.Level.SEVERE, null, ex);
        } catch (javax.swing.UnsupportedLookAndFeelException ex) {
            java.util.logging.Logger.getLogger(Index.class.getName()).log(
                    java.util.logging.Level.SEVERE, null, ex);
        }
    java.awt.EventQueue.invokeLater(new Runnable() {
        public void run() {
            new Frame().setVisible(true);
        }
    });
}
private javax.swing.JMenu jMenu1;
private javax.swing.JToggleButton jToggleButton1;
private javax.swing.JMenuBar menu_bar;
private JLabel lblBackground;
private JPanel pnlMain;
private JPanel pnlFooter;
private JPanel pnlImage;
private JLabel lblAddress;
private JLabel lblContactNumber;
private Box footerBox;
private JPanel pnlSuper;
}

感谢阅读

Answer 1

为了看到 BG，所有它上面的组件必须是透明的。所以这个：

pnlImage = new JPanel(new BorderLayout());
pnlFooter = new JPanel(new GridLayout(1,2));

应该是：

pnlImage = new JPanel(new BorderLayout());
pnlImage.setOpaque(false);
pnlFooter = new JPanel(new GridLayout(1,2));
pnlFooter.setOpaque(false);