FrameOne上的按钮应关闭FrameTwo。在JAVA中，ActionListener指的是另一个类的对象[英] Button on FrameOne shall close FrameTwo. ActionListener referes object of another class in JAVA

问题描述

I have two frames in separate classes (FrameOne and FrameTwo) FrameOne has two buttons. One to open FrameTwo and One shall close FrameTwo. How to open FrameTwo I know. But not how to close from Frame One. How do I code it to make it working? Thanks. (I know that there are similar questions. I red them all. But it didn't gave me the answer. Also GUI guides didn't helped.)

public class Main {

    public static void main(String[] args) {

        FrameOne frame = new FrameOne();
    }
}

FrameOne class:

    public class FrameOne extends JFrame implements ActionListener{

    private JButton btn1, btn2;

    FrameOne () {

        setVisible(true);
        setSize(400,400);
        setLayout(new FlowLayout());
        setTitle("Main");
        setDefaultCloseOperation(EXIT_ON_CLOSE);

        btn1 = new JButton("opens FrameTwo");
        btn2 = new JButton("close FrameTwo");
        btn1.addActionListener(this);
        btn2.addActionListener(this);
        add(btn1);
        add(btn2);
    }

    @Override
    public void actionPerformed (ActionEvent e) {
        if(e.getSource()== btn1) {  
            FrameTow frameTwo = new FrameTwo(); 
        }

        else if(e.getSource()== btn2) ;
        // {???.dispose(); }
    }
}

` Frame2 class:

    public class FrameTow extends JFrame {

    FrameTwo () {

        setVisible(true);
        setSize(400,400);
        setTitle("FrameTwo");
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        this.setLocation(400, 400);

    }
}

推荐答案

Any of the below solutions will work

frameTwo.dispatchEvent(new WindowEvent(frameTwo, WindowEvent.WINDOW_CLOSING));

OR

frameTwo.setVisible(false);

其他推荐答案

The short answer is modify FrameOne :

private JFrame frameTwo; //introduce a field  


@Override
public void actionPerformed (ActionEvent e) {
    if(e.getSource()== btn1) {
        frameTwo = new FrameTwo();  //use field in action listener 
    }

    else if(e.getSource()== btn2){
        frameTwo.dispose();         //use field in action listener 
    }
}

The longer answer: using a JDialog for the 2nd frame is a better practice:

import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JDialog;
import javax.swing.JFrame;

public class Main {

    public static void main(String[] args) {

       new FrameOne();
    }
}

class FrameOne extends JFrame implements ActionListener{

    private final JButton btn1, btn2;
    private JDialog frameTwo; //introduce a field

    FrameOne () {

        setSize(400,400);
        setLayout(new FlowLayout());
        setTitle("Main");
        setDefaultCloseOperation(EXIT_ON_CLOSE);

        btn1 = new JButton("opens FrameTwo");
        btn2 = new JButton("close FrameTwo");
        btn1.addActionListener(this);
        btn2.addActionListener(this);
        add(btn1);
        add(btn2);
        setVisible(true); //make it visible after construction is completed
    }

    @Override
    public void actionPerformed (ActionEvent e) {
        if(e.getSource()== btn1) {
            frameTwo = new FrameTwo();  //use field in action listener
        }

        else if(e.getSource()== btn2){
            frameTwo.dispose();         //use field in action listener
        }
    }
}

class FrameTwo extends JDialog {

    FrameTwo() {

        setSize(400,400);
        setTitle("FrameTwo");
        setDefaultCloseOperation(DISPOSE_ON_CLOSE);
        this.setLocation(400, 400);
        setVisible(true); //make it visible after construction is completed
    }
}

其他推荐答案

In the example you show, one can open several instances of FrameTwo. Which one should the second button close?

Assuming you want there to be only one, you could introduce a field in in FrameOne, initially set to null. btn1 would then only open a frame if the field is null, and assign it to the field. Then btn2 can call dispose() on the field (and reset it to null).

Example, based on your attempt:

public class FrameOne extends JFrame implements ActionListener {

private JButton btn1, btn2;
private FrameTwo frameTwo = null;

FrameOne () {

setVisible(true);
setSize(400,400);
setLayout(new FlowLayout());
setTitle("Main");
setDefaultCloseOperation(EXIT_ON_CLOSE);

btn1 = new JButton("opens FrameTwo");
btn2 = new JButton("close FrameTwo");
btn1.addActionListener(this);
btn2.addActionListener(this);
add(btn1);
add(btn2);



}

@Override
public void actionPerformed (ActionEvent e)
{if(e.getSource()== btn1) 
{
    if (frameTwo == null) {    
        frameTwo = new FrameTwo();
    }
}

else if(e.getSource()== btn2) {

    frameTwo.dispatchEvent(new WindowEvent(frameTwo, WindowEvent.WINDOW_CLOSING));
    frameTwo = null;

}}}