JButton Action Performed?

问题

I have created a Jframe/button with 10x10 grid. Each jbutton is apart of the grid. I am trying to how to affect each button pressed through JFrame/button, as I want to eventually make it into a battleships games.

frame.setLayout(new GridLayout(width,length));
            grid=new JButton[width][length]; 
            for(int y=0; y<length; y++){
                    for(int x=0; x<width; x++){
                            grid[x][y]=new JButton("("+x+","+y+")");     
                            frame.add(grid[x][y]);
                    }
            }

For example I am trying a basic piece of code to see if i can change the color of the Jframe to red by clicking it but it doesn't seem to be working.

 public void actionPerformed(ActionEvent e){
           if( e.getSource() instanceof JButton) {
               ((JButton)e.getSource()).setBackground(Color.red);
           }
        }

Anyone got any ideas?

回答1:

I made this work by creating the JButtons separately rather than as part of a grid, but the general idea is the same. You cannot call actionPerformed like you have it, you must have a class that implements ActionListener and then has an override for the method actionPerformed.

You need to add a actionlistener to each of the JButtons. In this case since you want to apply the same listener to multiple buttons you want a separate class underneath your main.

    class buttonListener implements ActionListener {
    @Override
    public void actionPerformed (ActionEvent e) {
        ((JButton)e.getSource()).setBackground(Color.red);
    }
}

The reason why the button was not changing colours is because you need to add the following in order to change the colour of a JButton

    JButton j = new JButton("test");
    j.setSize(100, 100);
    j.setContentAreaFilled(true);
    j.setOpaque(true);
    j.addActionListener(new buttonListener());

I know this isn't the most direct answer to your question but I hope I at least helped get the colours sorted out.

回答2:

Let's say we have a button: JButton button. To invoke an action when the button is pressed, an action listener must be added to it. There are two ways of doing this (that I know of):

ActionListener

I think this is more often used than the second method. It's also easier and faster to write IMO:

JButton button = new JButton("Click me");
button.addActionListener(new ActionListener() {
    @Override
    public void actionPerformed(ActionEvent e) {
        System.out.println("button was clicked!");
    }
}

Action

Another kind of action listener. The functionality and use is somewhat different. However to achieve a button that behaves simarly to an ActionListener, do this:

Action buttonAction = new AbstractAction("Click me") {
    @Override
    public void actionPerformed(ActionEvent e) {
        System.out.println("button was clicked!");
    }
}

JButton button = new JButton(action);

Note that in both examples I'm using anonymous ~~inner~~ classes. In most cases, using a named inner class or even an external class is more preferable.

Choosing between an ActionListener and an Action depends a little on the situation (as always... sigh), and I'm afraid I cannot shed too much light on this matter. Google is your friend here. A fast search provided this post from SO: link

回答3:

you can create your own action listener:

class MyActionListener implements ActionListener {
    private int x;
    private int y;


    public MyActionListener(int x, int y) {
        this.x = x;
        this.y = y;
    }

    public void actionPerformed(ActionEvent e) {
        DoSomething(x, y);
    }
}

...
grid = new JButton[wid][len]; 
for(int y = 0; y < len; y++){
    for(int x = 0; x < wid; x++){
        grid[x][y]=new JButton("("+x+","+y+")");     
        grid[x][y].addActionListener(new MyActionListener(x, y));
        frame.add(grid[x][y]);
    }
}

来源：https://stackoverflow.com/questions/27255807/jbutton-action-performed

标签

java

arrays

jbutton