Question

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

/**
 * Created by joshuaogunnote on 31/10/2015.
 */

public class Applet2 extends JApplet {

    JTextField value1, value2;

    public void init() {

        JLabel prompt = new JLabel("Please enter a word");
        JLabel prompt1 = new JLabel("Please enter a letter");

        value1 = new JTextField(3);
        value2 = new JTextField(3);

        setLayout(new FlowLayout());
        add(prompt);
        add(value1);


        setLayout(new FlowLayout());
        add(prompt1);
        add(value2);


        JButton but = new JButton("Add word");
        JButton but1 = new JButton("Clear");
        JButton but2 = new JButton("Remove first occurrence");
        JButton but3 = new JButton("Remove all occurrences");
        JButton but4 = new JButton("Display all words begging with certain letter");
        JButton but5 = new JButton("Search");

        JPanel butPanel = new JPanel();
        JPanel butPanel1 = new JPanel();
        JPanel butPanel2 = new JPanel();

        butPanel.add(but);
        butPanel.add(but1);
        butPanel1.add(but2);
        butPanel1.add(but3);
        butPanel2.add(but4);
        butPanel2.add(but5);

这是我试图确定Applet上按钮位置的地方。我正在使用BorderLayout.SOUTH尝试让按钮显示在applet的底部，但它不起作用。如何让按钮出现在Applet的底部？

        add(butPanel, BorderLayout.SOUTH);
        add(butPanel1, BorderLayout.SOUTH);
        add(butPanel2, BorderLayout.SOUTH);

    }


}

Answer 1

您只能将一个组件添加到BorderLayout位置。因此，创建一个新的JPanel来按住按钮，向其添加按钮，并将其添加到南方位置。但请注意，BorderLayout常量仅在容器（此处为this）使用BorderLayout时才有效！：

JButton but = new JButton("Add word");
JButton but1 = new JButton("Clear");
JButton but2 = new JButton("Remove first occurrence");
JButton but3 = new JButton("Remove all occurrences");
JButton but4 = new JButton("Display all words begging with certain letter");
JButton but5 = new JButton("Search");

JButton[] buttons = {but, but1, but2, but3, but4, but5};
JPanel bottomPanel = new JPanel();
for(JButton btn : buttons) {
    bottomPanel.add(btn);
}

// note this will only work if the layout for *this* is in fact BorderLayout!
add(bottomPanel, BorderLayout.PAGE_END);

更完整的例子：

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

public class Foo extends JPanel {
    private JTextField value1;
    private JTextField value2;

    public Foo() {
        JLabel prompt = new JLabel("Please enter a word");
        JLabel prompt1 = new JLabel("Please enter a letter");

        value1 = new JTextField(3);
        value2 = new JTextField(3);

        setLayout(new BorderLayout());

        JPanel topPanel = new JPanel();
        topPanel.add(prompt);
        topPanel.add(value1);

        topPanel.add(prompt1);
        topPanel.add(value2);

        JButton but = new JButton("Add word");
        JButton but1 = new JButton("Clear");
        JButton but2 = new JButton("Remove first occurrence");
        JButton but3 = new JButton("Remove all occurrences");
        JButton but4 = new JButton(
                "Display all words begging with certain letter");
        JButton but5 = new JButton("Search");

        JButton[] buttons = { but, but1, but2, but3, but4, but5 };
        JPanel bottomPanel = new JPanel();
        for (JButton btn : buttons) {
            bottomPanel.add(btn);
        }

        add(topPanel, BorderLayout.PAGE_START);
        add(new JScrollPane(new JTextArea(30, 40)), BorderLayout.CENTER);
        add(bottomPanel, BorderLayout.PAGE_END);

    }

    private static void createAndShowGui() {
        Foo mainPanel = new Foo();

        JFrame frame = new JFrame("Foo");
        frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
        frame.getContentPane().add(mainPanel);
        frame.pack();
        frame.setLocationByPlatform(true);
        frame.setVisible(true);
    }

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

显示为：

Answer 2

您将布局设置为FlowLayout，因此您无法使用BorderLayout的约束。不要这样做。 JApplet的默认布局是BorderLayout，因此无需更改布局。

此外，您只能将单个组件添加到BorderLayout的任何约束中。

因此，创建一个使用FlowLayout的面板。将按钮添加到面板然后将该面板添加到BorderLayout.SOUTH。

阅读How to Use BorderLayout上的Swing教程中有关工作示例的部分

如何将JButton放在applet的底部？

2 个答案: