写在JTextArea的底部 [英] Writing at the bottom of JTextArea

问题描述

我有一个 JScrollPane 和一个 JTextArea （可编辑）有10行。我希望第一个用户输入显示在 JTextArea 的底部，最近的输入应该向上推送上一个输入。为了实现这一点，我使用 textArea.setMargin（new Insets（x，0,0,0））; 并且一切正常 - 除了我的第二个输入将切换 JScrollPane 。

I have a JScrollPane and a JTextArea (editable) with 10 rows. I want the first user input to appear at the bottom of the JTextArea and the most recent input should push the previous input upward. To achieve this I use textArea.setMargin(new Insets(x,0,0,0)); and everything works as it should - except that my second input will toggle the JScrollPane.

如何从 JTextArea的底部开始并且仅在整个原始视口填充时启用滚动？

How can I start at the bottom of the JTextArea and only enable scrolling when the entire original viewport is filled?

推荐答案

基本上，您可以添加 JTextText 到 JPanel 上，另一个 JPanel 作为填充符，导致 JTextArea 占用它实际需要的最小空间。

Basically, you could add the JTextText onto a JPanel with another JPanel which acts a filler, causing the JTextArea to occupy the smallest space it actually needs.

我是通过使用 GridBagLayout 强迫填充占据大部分空间......

I did this by using GridBagLayout to force the fill to occupy the most of space it could...

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.EventQueue;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class TestTextArea {

    public static void main(String[] args) {
        new TestTextArea();
    }

    public TestTextArea() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                }

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setLayout(new BorderLayout());
                frame.add(new JScrollPane(new TestPane()));
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        private JTextArea ta;

        public TestPane() {
            setLayout(new GridBagLayout());
            GridBagConstraints gbc = new GridBagConstraints();
            gbc.gridx = 0;
            gbc.gridy = 0;
            gbc.weightx = 1;
            gbc.weighty = 1;
            gbc.fill = GridBagConstraints.BOTH;

            JPanel filler = new JPanel();
            filler.setBackground(Color.WHITE);
            add(filler, gbc);

            gbc.gridy = 1;
            gbc.weighty = 0;
            ta = new JTextArea(1, 20);
            add(ta, gbc);
        }
    }

}

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