Swing - Thread.sleep() 停止 JTextField.setText() 工作 [英] Swing - Thread.sleep() stop JTextField.setText() working

问题描述

可能的重复:
对单个线程使用 sleep()

我在使用 Thread.sleep() 时遇到了 JTextField.setText() 问题.这是我正在制作的基本计算器.当输入字段中的输入格式不正确时，我希望输入错误"在输出字段中出现 5 秒钟，然后将其清除.setText() 方法 did 当我只将文本设置为INPUT ERROR"并打印出介于两者之间的文本时，我发现它可以同时使用该方法和 setText("") 一个在另一个之后.当我将 Thread.sleep() 放在它们之间时，问题就出现了.这是代码的 SSCCE 版本:

I'm having issues with JTextField.setText() when using Thread.sleep(). This is for a basic calculator I'm making. When the input in the input field is not of the correct format I want "INPUT ERROR" to appear in the output field for 5 seconds and then for it to be cleared. The setText() method did work when I just set the text once to "INPUT ERROR" and by printing out the text in between I found it does work with both that and the setText("") one after the other. The problem arises when I put the Thread.sleep() between them. Here's a SSCCE version of the code:

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.regex.Pattern;
import javax.swing.*;

public class Calc {
    static Calc calc = new Calc();

    public static void main(String args[]) {
        GUI gui = calc.new GUI();
    }

    public class GUI implements ActionListener {

        private JButton equals;

        private JTextField inputField, outputField;

        public GUI() {
            createFrame();
        }

        public void createFrame() {
            JFrame baseFrame = new JFrame("Calculator");
            baseFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            JPanel contentPane = new JPanel();
            BoxLayout layout = new BoxLayout(contentPane, BoxLayout.Y_AXIS);
            contentPane.setLayout(layout);
            baseFrame.setContentPane(contentPane);
            baseFrame.setSize(320, 100);

            equals = new JButton("=");
            equals.addActionListener(this);

            inputField = new JTextField(16);
            inputField.setHorizontalAlignment(JTextField.TRAILING);
            outputField = new JTextField(16);
            outputField.setHorizontalAlignment(JTextField.TRAILING);
            outputField.setEditable(false);

            contentPane.add(inputField);
            contentPane.add(outputField);
            contentPane.add(equals);

            contentPane.getRootPane().setDefaultButton(equals);
            baseFrame.setResizable(false);
            baseFrame.setLocation(100, 100);

            baseFrame.setVisible(true);
        }

        /**
         * When an action event takes place, the source is identified and the
         * appropriate action is taken.
         */

        @Override
        public void actionPerformed(ActionEvent e) {
            if (e.getSource() == equals) {
                inputField.setText(inputField.getText().replaceAll("\s", ""));
                String text = inputField.getText();
                System.out.println(text);
                Pattern equationPattern = Pattern.compile("[\d(][\d-+*/()]+[)\d]");
                boolean match = equationPattern.matcher(text).matches();
                System.out.println(match);
                if (match) {
                    // Another class calculates
                } else {
                    try {
                        outputField.setText("INPUT ERROR"); // This doesn't appear
                        Thread.sleep(5000);
                        outputField.setText("");
                    } catch (InterruptedException e1) {
                    }
                }
            }
        }
    }
}

我实际上并没有使用嵌套类，但我希望它能够为您包含在一个类中.对 GUI 的外观感到抱歉，但这又是为了减少代码.重要部分(if (e.getSource() == equals))与我的代码保持不变.给出错误输入的最简单方法是使用字母.

I'm not actually using a nested class but I wanted it to be able to be contained in one class for you. Sorry about how the GUI looks but again this was to cut down the code. The the important section (if (e.getSource() == equals)) remains unchanged from my code. The simplest way to give an incorrect input is to use letters.

推荐答案

当您使用 Thread.sleep() 时，您是在主线程上执行此操作.这会冻结 gui 5 秒钟，然后更新 outputField.发生这种情况时，它会使用最后一组空白的文本.

When you use Thread.sleep() you're doing it on the main thread. This freezes the gui for five seconds then it updates the outputField. When that happens, it uses the last set text which is blank.

最好使用 Swing Timers 和这里的一个可以完成您要完成的任务的示例:

It's much better to use Swing Timers and here's an example that does what you're trying to accomplish:

if (match) {
    // Another class calculates
} else {
    outputField.setText("INPUT ERROR");
    ActionListener listener = new ActionListener(){
        public void actionPerformed(ActionEvent event){
            outputField.setText("");
        }
    };
    Timer timer = new Timer(5000, listener);
    timer.setRepeats(false);
    timer.start();
}

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