如何在更改变量值时更新JTextField？

我有两个Java(.java) files 。 一个有JButton和JTextField ，另一个有一个Thread 。 在第一个Java file ，我向JButton添加了一个ActionListener ，这样，当按下按钮时，一个线程（创建的第二个.java文件的对象和启动的线程）运行，它会连续修改整数变量。 如何在JTextField （第一个.java文件）中显示该整数变量（第二个.java文件）的值？

Detection.java

 package sample; public class Detection implements Runnable { public String viewers; public int count; public void run() { try { while (true) { // i have written code for displaying video. // and it say how many no. of people in the video // the no of people is stored in a variable "count" viewers=""+count; //storing count as string so as to display in the JTextField } } catch (Exception e) { System.out.println("Exception: "+e); } } } 

UsrInterfac.java

//使用WindowBuilder构建eclipse juno

 package sample; import java.awt.EventQueue; import javax.swing.JFrame; import javax.swing.JButton; import javax.swing.JTextField; import java.awt.event.ActionListener; import java.awt.event.ActionEvent; public class UsrInterfac { private JFrame frame; private JTextField textField; Detection dd = new Detection(); Thread th = new Thread(dd); /** * Launch the application. */ public static void main(String[] args) { EventQueue.invokeLater(new Runnable() { public void run() { try { UsrInterfac window = new UsrInterfac(); window.frame.setVisible(true); } catch (Exception e) { e.printStackTrace(); } } }); } /** * Create the application. */ public UsrInterfac() { initialize(); } /** * Initialize the contents of the frame. */ private void initialize() { frame = new JFrame(); frame.setBounds(100, 100, 450, 300); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.getContentPane().setLayout(null); JButton btnStartThread = new JButton("Start Thread"); btnStartThread.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent arg0) { th.start(); } }); btnStartThread.setBounds(59, 133, 117, 23); frame.getContentPane().add(btnStartThread); textField = new JTextField(); textField.setBounds(270, 134, 104, 20); frame.getContentPane().add(textField); textField.setColumns(10); } } 

Answer 1

从基础知识开始，使用Swing时，最好使用LayoutManagers ，与使用Absolute Positioning相比，它可以使您的工作更轻松。 每当需要从另一个线程中更改View的某些内容时，始终建议使用EventQueue.invokeLater(...)/EventQueue.invokeAndWait(...)来执行此操作。

这个小样本程序，或许可以帮助你了解一个想法，如何实现你所希望的:-)

 import java.awt.*; import java.awt.event.*; import javax.swing.*; public class ThreadCounter { private CustomThread cThread; private JTextField tField; private JButton button; private int counter; public ThreadCounter() { counter = 0; } private void displayGUI() { JFrame frame = new JFrame("Thread Counter Example"); frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE); JPanel contentPane = new JPanel(); tField = new JTextField(10); tField.setText("0"); button = new JButton("Start"); button.addActionListener(new ActionListener() { @Override public void actionPerformed(ActionEvent ae) { if (counter == 0) { cThread = new CustomThread(tField); cThread.setFlagValue(true); cThread.start(); counter = 1; button.setText("Stop"); } else { try { cThread.setFlagValue(false); cThread.join(); } catch(InterruptedException ie) { ie.printStackTrace(); } counter = 0; button.setText("Start"); } } }); contentPane.add(tField); contentPane.add(button); frame.setContentPane(contentPane); frame.pack(); frame.setLocationByPlatform(true); frame.setVisible(true); } public static void main(String[] args) { EventQueue.invokeLater(new Runnable() { @Override public void run() { new ThreadCounter().displayGUI(); } }); } } class CustomThread extends Thread { private int changingVariable; private JTextField tField; private boolean flag = true; public CustomThread(JTextField tf) { changingVariable = 0; tField = tf; } public void setFlagValue(boolean flag) { this.flag = flag; } @Override public void run() { while (flag) { EventQueue.invokeLater(new Runnable() { @Override public void run() { tField.setText( Integer.toString( ++changingVariable)); } }); try { Thread.sleep(1000); } catch(InterruptedException ie) { ie.printStackTrace(); } } System.out.println("I am OUT of WHILE"); } } 

Answer 2

理想情况下，您应该发布您的代码。 无论如何，当您调用线程代码时，要么传递第一个类（对象）的实例，要么传递JTextField的实例，以便线程可以在文本字段中设置新值。