Question

In the below code I am attempting to move the three buttons to the left when you click the left button. When I click it; nothing happens currently. Can anyone explain to me what I am doing wrong here? Also, for some reason it has stopped compiling correctly and I am unsure why but I BELIEVE it is because of a mistake in my code while attempting to get the buttons to move to the left when you click the button. I do NOT want the window to move. Just the buttons within the window. Does any one see what I am doing wrong and can you explain it?

import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class Buttons extends JFrame {
//Control Definitions

    JButton resetButton;
    JButton leftButton;
    JButton colorButton;
    JPanel buttonPanel;
// Layout Definiton
    eventHandle evt;
    FlowLayout flt;
    Point point; //to Hold Previous Window Position
    Color color; //to Hold Previous Color

    public Buttons() {
        super("Buttons Window");
        flt = new FlowLayout();//inialize the Flow Layout
        buttonPanel = new JPanel(flt);
        //inialize the buttonPanel With Flow Layout
        //initialize buttons
        resetButton = new JButton("Reset");
        leftButton = new JButton("Left");
        colorButton = new JButton("Blue");
        evt = new eventHandle(); //initiate the eventhandle class
        buttonPanel.add(leftButton); //add leftButton
        buttonPanel.add(colorButton);//add colorButton
        buttonPanel.add(resetButton);//add colorButton
        getContentPane().add(buttonPanel);//buttonPanel
        //add actionlistners
        leftButton.addActionListener(evt);
        colorButton.addActionListener(evt);
        resetButton.addActionListener(evt);
        setBounds(20, 120, 250, 70);
        //following Initate the point with Center of Scren
        point = new Point((Toolkit.getDefaultToolkit().
                getScreenSize().width - getWidth()) / 2, 
                (Toolkit.getDefaultToolkit().getScreenSize().height
                - getHeight()) / 2);
        setLocation(point); //locates the window in center
        color = buttonPanel.getBackground();//stores the initial color
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        setVisible(true);
    }

    class eventHandle implements ActionListener { //Event Handler

        public void actionPerformed(ActionEvent e) {
            {
                if (e.getSource() == leftButton) ///if its from leftButton
                {
                    leftButton.setAlignmentX(Component.LEFT_ALIGNMENT);
                    colorButton.setAlignmentX(Component.LEFT_ALIGNMENT);
                    resetButton.setAlignmentX(Component.LEFT_ALIGNMENT);
    //setLocation( (point.x -150), point.y);//shift the window 150 pixels left
                } else if (e.getSource() == colorButton) {
                    buttonPanel.setBackground(color.BLUE); 
                    //sets the backgorund to Blue
                } else {
                    leftButton.setAlignmentX(Component.CENTER_ALIGNMENT); 
                    //sets the location to previous location
                    colorButton.setAlignmentX(Component.CENTER_ALIGNMENT);
                    resetButton.setAlignmentX(Component.CENTER_ALIGNMENT);
                }

            }
        }
    }

    public static void main(String[] args) {
        Buttons buttonwindow = new Buttons();
    }
}

Answer 1

It has stopped compiling, because you deleted one accolade, so put one accolade “}” just above the method:

public static  void main(String[] args)

and the code should compile. pls feedback.

EDIT:

Also rewrite your main method like this:

public static void main(String[] args) {

        SwingUtilities.invokeLater(new Runnable() {

                    @Override
                    public void run() {
                        Buttons buttonwindow = new Buttons();
                    }
                }
            );           
    }

Every usage of Swing components must be done thorugh the Event Dispatch Thread (abbreviated EDT) or you will probably get unwanted visual effects. See here for explanation.

EDIT^2:

To achieve the desired behavior, rewrite the the action listener like this:

if (e.getSource() == leftButton)  {
    ((FlowLayout)buttonPanel.getLayout()).setAlignment(FlowLayout.LEFT); //1
    buttonPanel.revalidate(); //2
}
else if (e.getSource() == colorButton) {
    buttonPanel.setBackground(color.BLUE); 
} 
else {
    ((FlowLayout)buttonPanel.getLayout()).setAlignment(FlowLayout.CENTER);
    buttonPanel.revalidate();
}

Any change to the visual appereance to the Swing component must be done through the assigned layout manager, in this case FlowLayout – in line 1.

To see the change you must notify the Swing components layout manager to rearrange the components – in line 2 the revalidate() method “notifies” the layout manager to recalculate the new positions and eventually “notifies” the EDT to draw it on the screen.