Question

我需要动态添加组件。而且，我需要动态地改变布局。

Answer 1

作为参考，这里有一个显示基本方法sscce的validate()。这个更精细的example显示了两个要求：它更改布局并动态添加组件。

import java.awt.*;
import java.awt.event.ActionEvent;
import javax.swing.*;

/** @see http://stackoverflow.com/questions/5750068 */
public class DynamicLayout extends JPanel {

    private static final LayoutManager H = new GridLayout(1, 0);
    private static final LayoutManager V = new GridLayout(0, 1);

    public DynamicLayout() {
        this.setLayout(H);
        this.setPreferredSize(new Dimension(320, 240));
        for (int i = 0; i < 3; i++) {
            this.add(new JLabel("Label " + String.valueOf(i), JLabel.CENTER));
        }
    }

    private void display() {
        JFrame f = new JFrame("DynamicLayout");
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.add(this);
        JPanel p = new JPanel();
        p.add(new JButton(new AbstractAction("Horizontal") {

            @Override
            public void actionPerformed(ActionEvent e) {
                DynamicLayout.this.setLayout(H);
                DynamicLayout.this.validate();
            }
        }));
        p.add(new JButton(new AbstractAction("Vertical") {

            @Override
            public void actionPerformed(ActionEvent e) {
                DynamicLayout.this.setLayout(V);
                DynamicLayout.this.validate();
            }
        }));
        f.add(p, BorderLayout.SOUTH);
        f.pack();
        f.setLocationRelativeTo(null);
        f.setVisible(true);
    }

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

            @Override
            public void run() {
                new DynamicLayout().display();
            }
        });
    }
}

Answer 2

动态更改布局的示例：

package swinglayout;

import java.awt.BorderLayout;
import java.awt.Container;
import java.awt.FlowLayout;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class LayoutChanger implements ActionListener{
  JButton b1;
  JButton b2;
  JButton b3;
  JButton b4;
  JButton b5;
  JButton b6;
  /** This button set the flowlayout on panel2 with left orientation */
  JButton flowLayout;

  /** This button set the Gridlayout of 2,3 grid on panel2 */
  JButton gridLayout;

  /** This button set the Borderlayout on panel2*/
  JButton borderLayout;

  /** 
   * This panel is control panel where we use button to change
   * layout of another panel
   */
  JPanel panel;

  /** This panel contain multiple button from b1 to b6 */
  JPanel panel2;

  JFrame frame;
  public LayoutChanger() {
    //set Default Look and Feel on frame
    JFrame.setDefaultLookAndFeelDecorated(true);

    frame = new JFrame();
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    Container con = frame.getContentPane();
    con.setLayout(new BorderLayout());

    panel = new JPanel();
    panel2 = new JPanel();
    //This button are used to only showing the layout effect
    b1 = new JButton("HelloButton1");
    b2 = new JButton("HelloButton2");
    b3 = new JButton("HelloButton3");
    b4 = new JButton("HelloButton4");
    b5 = new JButton("HelloButton5");
    b6 = new JButton("HelloButton6");
    // By default panel have layout
    panel2.add(b1);
    panel2.add(b2);
    panel2.add(b3);
    panel2.add(b4);
    panel2.add(b5);
    panel2.add(b6);
    // Layout changer button
    flowLayout = new JButton("FlowLayout");
    gridLayout = new JButton("GridLayout");
    borderLayout = new JButton("BorderLayout");

    //call Action listener on  every layout changer button
    flowLayout.addActionListener(this);
    gridLayout.addActionListener(this);
    borderLayout.addActionListener(this);

    panel.add(flowLayout);
    panel.add(gridLayout);
    panel.add(borderLayout);

    // add layout changer button panel at a top 
    //button panel at the center of container
    con.add(panel, BorderLayout.PAGE_START);
    con.add(panel2, BorderLayout.CENTER);

    frame.setVisible(true);
    frame.pack();

  }

  public void actionPerformed(ActionEvent e) {

    //set the flowlayout on panel2
    if(e.getSource() == flowLayout) {
      FlowLayout flow = new FlowLayout(FlowLayout.LEFT);
      panel2.setLayout(flow);
      panel2.validate();
    }

    //set the gridlayout on panel2
    if(e.getSource() == gridLayout) {
      GridLayout grid = new GridLayout(2,3);
      panel2.setLayout(grid);
      panel2.validate();
    }
    //set the gridlayout but the problem if we don't set the constraint
    //all button are set on center. So you remove the all button from panel
    //Then set grid layout on panel and add them with constraints.
    if(e.getSource() == borderLayout) {
      panel2.remove(b1);
      panel2.remove(b2);
      panel2.remove(b3);
      panel2.remove(b4);
      panel2.remove(b5);
      panel2.remove(b6);

      BorderLayout border = new BorderLayout();
      panel2.setLayout(border);

      panel2.add(b1,BorderLayout.NORTH);
      panel2.add(b2,BorderLayout.SOUTH);
      panel2.add(b3,BorderLayout.EAST);
      panel2.add(b4,BorderLayout.WEST);
      panel2.add(b5,BorderLayout.CENTER);
      panel2.add(b6,BorderLayout.BEFORE_FIRST_LINE);

      panel2.validate();
    }
  }
  public static void main(String args[]) {
    new LayoutChanger();
  }
}

有一点需要记住，你在面板上设置了新的布局，不要忘记在面板上调用方法validate()。如果你不调用这个方法，你就不会看到布局变化的影响。如果要在不调用方法的情况下查看效果，则必须调整框架的大小。您也可以非常轻松地设置相同的布局，例如FlowLayout，GridLayout和BoxLayout，但是当设置BorderLayout时，它需要添加元素的约束，因此我们首先从面板中删除所有组件通过remove(Component comp)方法，然后按约束

在面板中添加组件

Java Swing：如何动态更改GUI

2 个答案: