保存布局管理器

Question

import java.awt.LayoutManager;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class LayoutTest extends JFrame {

    public LayoutTest() {
        initComponents();
    }

    private void initComponents() {

        jPanel1 = new javax.swing.JPanel();
        jButton = new JButton();

        jPanel1.setBackground(new java.awt.Color(204, 204, 255));
        jPanel1.setBorder(javax.swing.BorderFactory.createEtchedBorder());

        jButton.addActionListener(new ActionListener() {

            public void actionPerformed(ActionEvent e) {
                LayoutManager tempGroupLayout = jPanel1.getLayout();
                jPanel1.setLayout(layoutManager2);
                layoutManager = layoutManager2;
                layoutManager2 = tempGroupLayout;
            }
        });

        javax.swing.GroupLayout jPanel1Layout = new javax.swing.GroupLayout(jPanel1);
        jPanel1.setLayout(jPanel1Layout);
        jPanel1Layout.setHorizontalGroup(
                jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING).
                addGroup(javax.swing.GroupLayout.Alignment.TRAILING, jPanel1Layout.createSequentialGroup().
                addContainerGap(286, Short.MAX_VALUE).
                addComponent(jButton, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)));
        jPanel1Layout.setVerticalGroup(
                jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING).
                addComponent(jButton, javax.swing.GroupLayout.DEFAULT_SIZE, 442, Short.MAX_VALUE));
        layoutManager = jPanel1Layout;

        javax.swing.GroupLayout jPanel1Layout2 = new javax.swing.GroupLayout(jPanel1);
        jPanel1Layout2.setHorizontalGroup(
                jPanel1Layout2.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING).
                addGroup(javax.swing.GroupLayout.Alignment.TRAILING, jPanel1Layout2.createSequentialGroup().
                addComponent(jButton, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)));
        jPanel1Layout2.setVerticalGroup(
                jPanel1Layout2.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING).
                addComponent(jButton, javax.swing.GroupLayout.DEFAULT_SIZE, 442, Short.MAX_VALUE));
        layoutManager2 = jPanel1Layout2;
        getContentPane().add(jPanel1);
        pack();
    }

    public static void main(String args[]) {
        java.awt.EventQueue.invokeLater(new Runnable() {

            public void run() {
                new LayoutTest().setVisible(true);
            }
        });
    }
    private JButton jButton;
    private JPanel jPanel1;
    private LayoutManager layoutManager;
    private LayoutManager layoutManager2;
}

这段代码不起作用，为什么？ 但是如果我每次在actionListener中创建一个布局，它就会起作用。

Answer 1

您只需在切换布局管理器后调用 validate() 即可。

public void actionPerformed(ActionEvent e) {
    LayoutManager tempGroupLayout = jPanel1.getLayout();
    jPanel1.setLayout(layoutManager2);
    getContentPane().validate();  // <= added line
    layoutManager = layoutManager2;
    layoutManager2 = tempGroupLayout;
}

注意：在发布的代码中缺少一些行（例如jButton 的初始化）。