我如何一次不显示同一窗口

Question

In my project, I create some buttons. When a button is clicked then a frame is appeard. But when I click the same button then the same window is come again. It will decrease my project quality. I want that when next time the same button is clicked then the frame is not come because the frame is already visible. How can I do that?

Answer 1

It depends on how you've implemented it. Instead of creating a new frame every time, keep a reference to it, and if it's already been created just show the existing one.

Here's a simple example. It's a frame that has two buttons. One of them creates a new frame every time, and the other one creates a frame the first time you click it, and any time after that will just show that one frame.

import java.awt.*;
import java.awt.event.*;
import java.util.*;
import javax.swing.*;

class test {

  public static void main(String[] args) {

    JFrame main = new JFrame("Test");

    JButton btnAlways = new JButton("Always");
    JButton btnOnce = new JButton("Once");

    btnAlways.addActionListener(
      new ActionListener() {
        public void actionPerformed(ActionEvent e) {
          JFrame frame = new JFrame(new Date().toString());
          frame.setSize(400, 300);
          frame.setVisible(true);
        }
      }
    );

    btnOnce.addActionListener(
      new ActionListener() {
        JFrame frame = null;

        public void actionPerformed(ActionEvent e) {
          if (frame == null) {
            frame = new JFrame(new Date().toString());
            frame.setSize(400, 300);
          }
          frame.setVisible(true);
        }
      }
    );

    main.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    main.getContentPane().add(btnAlways, BorderLayout.NORTH);
    main.getContentPane().add(btnOnce, BorderLayout.SOUTH);
    main.setSize(300, 100);
    main.setVisible(true);

  }
}

The listener for btnOnce has a frame field initially set to null . The first time you click the button, it will go through the if (...) {...} , create a frame, and assign it to the frame field, so that subsequent invocations don't have to, rather they will use the stored value.

Answer 2

一种可能的方式是使用SingleTone设计图案用于使用所述帧class..access getInstance()方法。