英文:
Update time in JLabel?
问题
以下是翻译好的内容：
public JLabel timeNow;public static Date dt = new Date(); // 当前时间public static int month = dt.getMonth(); // 获取当前月份public static int hours = dt.getHours(); // 获取小时public static int minute = dt.getMinutes();public static int second = dt.getSeconds();public static void main(String[] args) {GUI g = new GUI(); // GUI是类的名称g.Update();}public void Update() {while (1 == 1) {hours = dt.getHours();minute = dt.getMinutes();second = dt.getSeconds();String timeText = "当前时间：" + hours + ":" + minute + ":" + second;timeNow.setText(timeText);}}
注意：这段代码存在一个问题，即while (1 == 1)会导致无限循环，可能会导致程序无响应。建议使用合适的循环条件来避免这个问题。
英文:
So I would like to update the Time in my program. For that I used a JLabel. So when I put the text.setText("Example"); The JLabel doesnt update? Any Ideas why? (I just included every important part of the code, I dont get any Syntax error)
public JLabel timeNow;public static Date dt = new Date(); // current timepublic static int month = dt.getMonth(); // gets the current monthpublic static int hours = dt.getHours(); // gets hour of daypublic static int minute = dt.getMinutes();public static int second = dt.getSeconds();public static void main(String[] args) {GUI g = new GUI(); //GUI is the name of the classg.Update();}public void Update() {while(1 == 1) {hours = dt.getHours();minute = dt.getMinutes();second = dt.getSeconds();String timeText = "Aktuelle Zeit: " + hours + ":" + minute + ":" + second;timeNow.setText(timeText);}}
答案1
得分: 1
UI的更新应该在EventDispatch线程上进行，要实现这一点，请使用以下代码替换timeNow.setText(timeText)：
SwingUtilities.invokeLater(new Runnable(){public void run(){timeNow.setText(timeText);}});
正如@BeUndead在评论中所说，您没有更新dt对象，因此这样做仍然只会写入原始日期时间，您还需要获取新的日期时间。
一个更好的方法是使用Timer对象，在其中创建一个事件，您可以在其中更新UI。
英文:
Updates to the UI should happen on the EventDispatch thread, to achieve this replace timeNow.setText(timeText) with
SwingUtilities.invokeLater(new Runnable(){public void run(){timeNow.setText(timeText);}});
As @BeUndead said in the comments, you're not updating the dt object, so doing this will still only write the original date time, you need to get a new date time as well.
A better way would be to use a Timer object which creates an event within which you update the UI.
答案2
得分: 1
更新Swing中的GUI应该在“EventDispatch”线程中进行：
import javax.swing.JFrame;import javax.swing.JLabel;import javax.swing.SwingUtilities;import javax.swing.Timer;import javax.swing.WindowConstants;import java.awt.BorderLayout;import java.awt.event.ActionEvent;import java.awt.event.ActionListener;import java.text.DateFormat;import java.text.SimpleDateFormat;import java.util.Date;public class GUI extends JFrame implements ActionListener {private final JLabel timeLabel = new JLabel();private final DateFormat df = new SimpleDateFormat("dd.MM.yyyy HH:mm:ss");public GUI() {setLayout(new BorderLayout());add(timeLabel, BorderLayout.CENTER);setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);setSize(300, 100);new Timer(500, this).start();}public static void main(String[] args) {SwingUtilities.invokeLater(() -> new GUI().setVisible(true));}@Overridepublic void actionPerformed(ActionEvent event) {timeLabel.setText(df.format(new Date()));}}
英文:
To update GUI in Swing you should do it within EventDispatch thread:
import javax.swing.JFrame;import javax.swing.JLabel;import javax.swing.SwingUtilities;import javax.swing.Timer;import javax.swing.WindowConstants;import java.awt.BorderLayout;import java.awt.event.ActionEvent;import java.awt.event.ActionListener;import java.text.DateFormat;import java.text.SimpleDateFormat;import java.util.Date;public class GUI extends JFrame implements ActionListener {private final JLabel timeLabel = new JLabel();private final DateFormat df = new SimpleDateFormat("dd.MM.yyyy HH:mm:ss");public GUI() {setLayout(new BorderLayout());add(timeLabel, BorderLayout.CENTER);setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);setSize(300, 100);new Timer(500, this).start();}public static void main(String[] args) {SwingUtilities.invokeLater(() -> new GUI().setVisible(true));}@Overridepublic void actionPerformed(ActionEvent event) {timeLabel.setText(df.format(new Date()));}}
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