Question

我的JTextArea附加了文本，然后用

更新

jTexaArea.update(jTextArea.getGraphics());

但是在追加时我无法选择或编辑文字也无法滚动。 NetBeans系统输出允许这些功能，如何将它们包含在我的程序中？

Answer 1

如果由JButton点击事件触发，则附加文本时，UI会在事件结束前无响应。这是因为事件调度线程在继续执行下一个事件之前等待事件完成。

如果您的要求是在处理事件时处理文本区域，您可以选择以下方法：

使用SwingWorker
在JTextArea中实现Lazy附加文本

以下是一个示例延迟附加示例：

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JTextArea;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
import javax.swing.SwingWorker;

import java.awt.Font;

import javax.swing.JScrollPane;

import java.awt.GridLayout;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import java.util.Date;
import java.util.List;

import javax.swing.Timer;
import javax.swing.text.DefaultCaret;

public class LazyAppender extends JFrame implements ActionListener  {

    /**
     * Demonstrates two different ways of appending text into TextArea
     */
    private static final long serialVersionUID = 1L;
    JTextArea textArea1;
    JTextArea textArea2;

    public LazyAppender() {
        initUI();
    }

    public final void initUI() {
        GridLayout experimentLayout = new GridLayout(2,2);
        JPanel panel = new JPanel();
        getContentPane().add(panel);

        panel.setLayout(experimentLayout);

        //Button 1
        JButton button1 = new JButton("Button 1");
        button1.setToolTipText("Append JtextArea1 without using Swing Timer");  
        button1.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent evt) {

                textArea1.append(getText());
                textArea1.update(textArea1.getGraphics());
            }
        });



        //Button 2
        JButton button2 = new JButton("Button 2");
        button2.setToolTipText("Lazy Append JtextArea2 using Swing Timer");

        Timer timer2 = new Timer(1000, new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent ae) {
                textArea2.append(getText());                    
            }
        });
        timer2.setRepeats(false); //Execute only once


        button2.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent evt) {
                //Start timer, this will release the button immediately
                timer2.start();
            }
        });


        //TextArea 1
        textArea1 = new JTextArea("This is an editable JtextArea1. " +
                "A text area is a \"plain\" text component, " +
                "which means that although it can display text " +
                "in any font, all of the text is in the same font."
                );
        textArea1.setFont(new Font("Serif", Font.ITALIC, 16));
        textArea1.setLineWrap(true);
        textArea1.setWrapStyleWord(true);

        //ScrollPane 1
        JScrollPane areaScrollPane1 = new JScrollPane(textArea1);
        areaScrollPane1.setViewportView(textArea1);


        //TextArea 2
        textArea2 = new JTextArea("This is an editable JtextArea2. " +
                "A text area is a \"plain\" text component, " +
                "which means that although it can display text " +
                "in any font, all of the text is in the same font."
                );
        textArea2.setFont(new Font("Serif", Font.ITALIC, 16));
        textArea2.setLineWrap(true);
        textArea2.setWrapStyleWord(true);

        //ScrollPane 2
        JScrollPane areaScrollPane2 = new JScrollPane(textArea2);
        areaScrollPane2.setViewportView(textArea2);


        //Add Components into Panel
        panel.add(button1);
        panel.add(button2);
        panel.add(areaScrollPane1);
        panel.add(areaScrollPane2);


        setTitle("Text Area Append Verify");
        setSize(300, 200);
        setLocationRelativeTo(null);
        setDefaultCloseOperation(EXIT_ON_CLOSE);
    }


    public void actionPerformed(ActionEvent e) {

    }

    public String getText(){
        String stringToAppend = "This is your life. Do what you want and do it often." +
                "If you don't like something, change it." +
                "If you don't like your job, quit." +
                "If you don't have enough time, stop watching TV." +
                "If you are looking for the love of your life, stop; "+
                "they will be waiting "+ 
                "for you when you start doing things you love." +
                "Stop over-analysing, life is simple." +
                "All emotions are beautiful." +
                "When you eat, appreciate every last bite." +
                "Life is simple." +
                "Open your heart, mind and arms to new things and people, "+ 
                "we are united in our differences." +
                "Ask the next person you see what their passion is and "+
                "share your inspiring dream with them." +
                "Travel often; getting lost will help you find yourself." +
                "Some opportunities only come once, seize them." +
                "Life is about the people you meet and the things you create "+
                "with them, so go out and start creating." +
                "Life is short, live your dream and wear your passion." +
                "~ Holstee Manifesto, The Wedding Day ";
        //Simulated delay
        long start = new Date().getTime();
        while(new Date().getTime() - start < 1000L){}
        return stringToAppend;
    }


    public static void main(String[] args) {

        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                LazyAppender ex = new LazyAppender();
                ex.setVisible(true);
            }
        });


    }
}

另外，请查看此问题JTextArea thread safe?，深入讨论在多线程环境中对JTextArea的安全性是否安全。

处理时，JTextArea无法滚动或访问文本

1 个答案: