Java Swing：如何动态更改GUI

Question

我需要动态添加组件。此外，我需要动态更改布局。

Answer 1

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();

  }

}

记住一件事是您在面板上设置了新的布局，不要忘记调用面板上的方法validate()，如果不调用此方法，则不会看到布局更改的影响。如果要通过调用来查看效果，则必须调整框架的大小。你也可以很容易像设置相同的布局FlowLayout，GridLayout和BoxLayout，但设置时BorderLayout就需要限制添加元素，所以我们首先从面板中删除所有组件remove(Component comp)方法然后通过约束添加的组件面板