如何制作用户可调整大小的 JTextArea？

Question

似乎唯一的选择是设置行数，但我需要我的文本区域可以为用户调整大小。JScrollPane 有帮助，但是当有很多文本时，我想让用户调整区域本身的大小。我该怎么做呢？如果我可以为此目的使用另一个类，我会完全同意的。简化的代码是import javax.swing.*;import java.awt.*;public class Problematic {    public static void main(String[] args) {        JFrame f = new JFrame("frame");        f.setLayout(new BorderLayout());        JPanel p1 = new JPanel();        JPanel p = new JPanel();        JButton button = new JButton("Whatever here");        JTextArea t2 = new JTextArea(5, 30);        JScrollPane scrollPane = new JScrollPane(t2);        scrollPane.setSize(600, 400);        scrollPane.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);        t2.setText("this is some random text\nthat may go for many rows\nso it may look messy");        p1.add(button);        p.add(scrollPane);        f.add(p, BorderLayout.NORTH);        f.add(p1, BorderLayout.CENTER);        f.setSize(600, 500);        f.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);        f.setVisible(true);    }}

Answer 1

您可以使用JSplitPane使窗口的各个区域可调整大小。试试下面的例子。请参阅我在代码中的评论。

import javax.swing.*;

import java.awt.*;

public class Problematic {

  public static void main(String[] args) {

    JFrame f = new JFrame("frame");

    f.setLayout(new BorderLayout());

    JPanel p1 = new JPanel();

    JPanel p = new JPanel();

    // Set BorderLayout so that scroll pane fills the panel

    p.setLayout(new BorderLayout());

    JButton button = new JButton("Whatever here");

    JTextArea t2 = new JTextArea(5, 30);

    JScrollPane scrollPane = new JScrollPane(t2);

    // Setting scroll pane size is not necessary

    //scrollPane.setSize(600, 400);

    scrollPane.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);

    t2.setText("this is some random text\nthat may go for many rows\nso it may look messy");

    p1.add(button);

    p.add(scrollPane);

    // Use JSplitPane to make the panels resizable

    f.add(new JSplitPane(JSplitPane.VERTICAL_SPLIT, p, p1), BorderLayout.CENTER);

    f.setSize(600, 500);

    f.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);

    f.setVisible(true);

  }

}

Answer 2

作为第一个改进，您可以进行一些小的布局更改，这将JTextArea占用整个空间并随着框架调整大小：

import java.awt.BorderLayout;

import java.awt.GridLayout;

import javax.swing.JButton;

import javax.swing.JFrame;

import javax.swing.JPanel;

import javax.swing.JScrollPane;

import javax.swing.JTextArea;

import javax.swing.WindowConstants;

public class Problematic {

    public static void main(String[] args) {

        JFrame f = new JFrame("frame");

        f.setLayout(new BorderLayout()); 

        JPanel p = new JPanel(new GridLayout(1, 1)); //assign gridlayout so text area fills panel 

        JTextArea t2 = new JTextArea(5, 30);

        t2.setText("this is some random text\nthat may go for many rows\nso it may look messy");

        JScrollPane scrollPane = new JScrollPane(t2);

        scrollPane.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);

        p.add(scrollPane);

        f.add(p, BorderLayout.CENTER); //place text area panel in center position 

        JPanel p1 = new JPanel();

        JButton button = new JButton("Whatever here");

        p1.add(button);

        f.add(p1, BorderLayout.PAGE_END);

        f.setSize(600, 500);

        f.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);

        f.setVisible(true);

    }

}

为了获得更大的灵活性，您可以添加JSplitPane：

public class Problematic {

    public static void main(String[] args) {

        JFrame f = new JFrame("frame");

        f.getContentPane().setLayout(new BorderLayout());

        JPanel p1 = new JPanel();

        JButton button = new JButton("Whatever here");

        p1.add(button);

        JPanel p = new JPanel(new GridLayout(1, 1)); //assign gridlayout so text area fills panel

        JTextArea t2 = new JTextArea(5, 30);

        t2.setText("this is some random text\nthat may go for many rows\nso it may look messy");

        JScrollPane scrollPane = new JScrollPane(t2);       scrollPane.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);

        p.add(scrollPane);

        JSplitPane splitPane = new JSplitPane(JSplitPane.VERTICAL_SPLIT, p,p1);

        f.getContentPane().add(splitPane, BorderLayout.CENTER);

        f.setSize(600, 500);

        f.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);

        f.setVisible(true);

    }

}

Answer 3

这是 c0der 的实现，但设置了更简化的生命周期。每一行都解释了正在发生的事情和时间。

import java.awt.*;

import java.awt.event.*;

import javax.swing.*;

import javax.swing.text.JTextComponent;

public class TextApp implements Runnable {

    private static final String APP_NAME = "Text App";

    private JFrame frame;

    private JTextArea txtAra;

    private JButton button;

    // This is a generic action that handles clearing the text of a JTextComponent

    // It can also be a stand-alone class

    private static class ClearAction <T extends JTextComponent> implements ActionListener {

        private T txtAra;

        public ClearAction(T txtAra) {

            this.txtAra = txtAra;

        }

        @Override

        public void actionPerformed(ActionEvent e) {

            this.txtAra.setText("");

        }

    }

    public TextApp() {

        // Initialize instance fields

        frame = new JFrame(APP_NAME);

        txtAra = new JTextArea(5, 30);

        button = new JButton("Clear Text");

        // Internal panels used for layout

        JPanel mainPanel = new JPanel(new GridLayout(1, 1));

        JScrollPane scrollPane = new JScrollPane(txtAra);

        JPanel buttonPanel = new JPanel();

        // Add components to containers

        frame.setLayout(new BorderLayout());

        frame.add(mainPanel, BorderLayout.CENTER);

        frame.add(buttonPanel, BorderLayout.PAGE_END);

        mainPanel.add(scrollPane);

        buttonPanel.add(button);

        // Additional setup

        scrollPane.setSize(600, 400);

        scrollPane.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);

        // Add listeners

        button.addActionListener(new ClearAction(txtAra));

    }

    @Override

    public void run() {

        // Set text

        txtAra.setText("this is some random text\nthat may go for many rows\nso it may look messy");

        // Prepare frame

        frame.pack();

        frame.setLocationRelativeTo(null);

        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        frame.setVisible(true);

    }

    public static void main(String[] args) {

        SwingUtilities.invokeLater(new TextApp());

    }

}