使用用户输入更新 Java Swing 计时器

Question

So I am currently having a problem with my Java Swing timer but first lemme describe what I am trying to do.

So I have a Swing GUI that updates a map with JSON data every 'X' number of seconds. The user can input the number of seconds into a text field and then click a button to start updating the map. The map will then update by querying the JSON based on the input.

So I am using a Swing timer to repeat a certain action event based on the input of the the user. Seen below:

clickOkButton.addActionListener(e1 -> {

  ActionListener actionListener = new ActionListener() {
    @Override
    public void actionPerformed(ActionEvent e) {
      String url = "";
      url = new_text.getText();

      layer[0] = (RenderableLayer) geo.createLayerFromSource(url);
      appFrame.getWwd().getModel().getLayers().set(20, layer[0]);
      ltree.getModel().refresh(appFrame.getWwd().getModel().getLayers());


    }
  };



  int time = Integer.parseInt(queryTime.getText());
  Timer timer = new Timer(time * 1000, actionListener);
  timer.setRepeats(true);
  //timer.setDelay(1);
  timer.start();

  d.setVisible(false);
  //System.out.println(text);

});

When the program is launched whatever time the user enters first works great. But then if they change the time the timer doesn't change.

  int time = Integer.parseInt(queryTime.getText());
  Timer timer = new Timer(time * 1000, actionListener);

It has something to do with these lines but I just can't figure it out. I'm pulling the numerical value from the text field and setting it as the delay in the timer. But it only works the first time the program is launched and not when it is changed.

Any help would be much appreciated.

Answer 1

import java.awt.Dimension;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextArea;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;
import javax.swing.Timer;

public class SwingTimerDemo extends JPanel {


    final static int height = 500;
    final static int width = 500;
    final static String title = "default title";

    JFrame frame = new JFrame(title);
    JTextField field = new JTextField(10);
    JTextArea area = new JTextArea(50,20);


    public static void main(String[] args) {
        SwingUtilities.invokeLater(
                () -> new SwingTimerDemo().start());
    }
    public SwingTimerDemo() {
        frame.setDefaultCloseOperation(
                JFrame.EXIT_ON_CLOSE);
        // add this panel to the frame
        frame.add(this);
        // add the JTextArea and JTextField to the panel
        add(area);
        add(field);
        setPreferredSize(
                new Dimension(500, 500));
        frame.pack();
        // center the frame on the screen
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }
    public void start() {
        // append the string to the JTextArea
        Timer t = new Timer(0, (ae)->area.append("Processing...\n"));

        // set the inter-event delay to 2 seconds
        t.setDelay(2000);
        // start the timer
        t.start();
        field.addActionListener(ae->{
            String text = field.getText();
            field.setText(""); // "erase" the text
            // convert to a number
            int delay = Integer.parseInt(text);
            // reset the timer delay
            t.setDelay(delay*300);
        });     
    }
}

Assuming you are familiar with Frames and Panels I will skip to the JTextField and JTextArea.

• the field is where the user types in the delay. It is notified using an actionListener . That input is then retrieved, parsed as an int and sets the timer delay.
• the area is simply a place where the timer writes the output.

Note that instead of an event when the user types in information, a button could be used instead. The user types in the information and then clicks the button. In that case, there would be no need for JTextField listener. Instead the listener would be for the button to check the text field.

This is a very rudimentary example to demonstrate the interaction between two actionListeners. If the user types in anything but a number an exception will be thrown. You may want to check out the Java Tutorials where they talk about event handling and other things that you would find interesting.