Question

我希望在调整框架大小时将一些数据存储在DS中，并且我很困惑应该重新定义哪个方法（覆盖）以完成我的工作。

Answer 1

首先，您对事件处理的理解可能有点偏差。在框架中没有任何东西可以覆盖。调整组件大小时，它会触发事件，就像按下按钮触发事件一样。如果没有侦听器侦听按钮触发的ActionEvent，则不会发生任何事情。

当您调整框架或任何组件的大小时，同样适用。发生这种情况时，会触发一个事件（在本例中为ComponentEvent）。所以你需要为这些事件的监听器注册一个监听器。

使用ComponentListener并覆盖componentResize()。这是一个例子

import java.awt.event.ComponentAdapter;
import java.awt.event.ComponentEvent;

import javax.swing.JFrame;
import javax.swing.SwingUtilities;

public class ComponentResizeDemo {

    public ComponentResizeDemo() {
        final JFrame frame = new JFrame();
        frame.setSize(300, 300);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setLocationByPlatform(true);
        frame.setVisible(true);
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                addComponentListener(frame);
            }
        });
    }

    public static void addComponentListener(JFrame frame) {
        frame.addComponentListener(new ComponentAdapter() {
            @Override
            public void componentResized(ComponentEvent e) {
                System.out.println("Frame resized");
            }
        });
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                new ComponentResizeDemo();
            }
        });
    }
}

Answer 2

请参阅Java教程How to Write a Component Listener。有一个完整的例子......

package events;

/*
 * ComponentEventDemo.java requires no other files.
 */

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

public class ComponentEventDemo extends JPanel
                                implements ComponentListener,
                                           ItemListener {
    static JFrame frame;
    JTextArea display;
    JLabel label;
    String newline = "\n";

    public ComponentEventDemo() {
        super(new BorderLayout());

        display = new JTextArea();
        display.setEditable(false);
        JScrollPane scrollPane = new JScrollPane(display);
        scrollPane.setPreferredSize(new Dimension(350, 200));

        JPanel panel = new JPanel(new BorderLayout());
        label = new JLabel("This is a label", JLabel.CENTER);
        label.addComponentListener(this);
        panel.add(label, BorderLayout.CENTER);

        JCheckBox checkbox = new JCheckBox("Label visible", true);
        checkbox.addItemListener(this);
        checkbox.addComponentListener(this);
        panel.add(checkbox, BorderLayout.PAGE_END);
        panel.addComponentListener(this);

        add(scrollPane, BorderLayout.CENTER);
        add(panel, BorderLayout.PAGE_END);
        frame.addComponentListener(this);
    }

    public void itemStateChanged(ItemEvent e) {
        if (e.getStateChange() == ItemEvent.SELECTED) {
            label.setVisible(true);

            //Need to revalidate and repaint, or else the label
            //will probably be drawn in the wrong place.
            label.revalidate();
            label.repaint();
        } else {
            label.setVisible(false);
        }
    }

    protected void displayMessage(String message) {
        //If the text area is not yet realized, and
        //we tell it to draw text, it could cause
        //a text/AWT tree deadlock. Our solution is
        //to ensure that the text area is realized
        //before attempting to draw text.
       // if (display.isShowing()) {
        display.append(message + newline);
            display.setCaretPosition(display.getDocument().getLength());
        //}
    }

    public void componentHidden(ComponentEvent e) {
        displayMessage(e.getComponent().getClass().getName() + " --- Hidden");
    }

    public void componentMoved(ComponentEvent e) {
        displayMessage(e.getComponent().getClass().getName() + " --- Moved");
    }

    public void componentResized(ComponentEvent e) {
        displayMessage(e.getComponent().getClass().getName() + " --- Resized ");           
    }

    public void componentShown(ComponentEvent e) {
        displayMessage(e.getComponent().getClass().getName() + " --- Shown");

    }

    /**
     * Create the GUI and show it.  For thread safety,
     * this method should be invoked from the
     * event-dispatching thread.
     */
    private static void createAndShowGUI() {
        //Create and set up the window.
        frame = new JFrame("ComponentEventDemo");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        //Create and set up the content pane.
        JComponent newContentPane = new ComponentEventDemo();
        newContentPane.setOpaque(true); //content panes must be opaque
        frame.setContentPane(newContentPane);

        //Display the window.
        frame.pack();
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        //Schedule a job for the event-dispatching thread:
        //creating and showing this application's GUI.
        javax.swing.SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                createAndShowGUI();
            }
        });
    }
}

在JAVA中调整框架大小时运行哪种方法？

2 个答案: