如何在程序底部找到这两个按钮

Question

Write a program that displays two buttons labeled “Green” and “Orange”.

If the user clicks on the green button, the background of the window changes to green. If the user clicks on the orange button, the background of the window changes to Orange.

Create a JFrame for this GUI. The GUI employs the default layout manager. A JPanel is needed.

Place the two buttons inside the panel and add the panel to the south region of the border layout.

Notice the text in the title bar. The green button should have white text and a green background. The orange button should have black text with an orange background.

Below is what I have so far, it doesn't seem to work.

public class LabAssign91 extends JFrame implements ActionListener{
private JPanel loc1Panel;
private JButton greenButton, orangeButton;

public LabAssign91()
{
    super("Colored Buttons");
    setLayout(new GridLayout(2, 2));
    setSize(300,250);
    setVisible(true);
    this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    add(loc1Panel);
    loc1Panel = new JPanel();
    add(loc1Panel, BorderLayout.SOUTH);


    greenButton = new JButton("Green");
    greenButton.addActionListener(this);
    loc1Panel.add(greenButton, BorderLayout.WEST);
    greenButton.setBackground(Color.green);;
    orangeButton = new JButton("Orange");
    orangeButton.addActionListener(this);
    loc1Panel.add(orangeButton, BorderLayout.EAST);
    orangeButton.setBackground(Color.orange);

}

public static void main(String[] args) {
    LabAssign91 app = new LabAssign91();

}

public void actionPerformed(ActionEvent e) {
    throw new UnsupportedOperationException("Not supported yet.");
}

}

Answer 1

I have used BorderLayout for the JFrame and FlowLayout for the ButtonPanel . ButtonPanel is the bottom panel of the frame.

frame = new JFrame();
frame.setLayout(new BorderLayout());

topPanel = new JPanel();
topPanel.add(new JLabel("Top Panel"));

middlepanel = new JPanel();
middlepanel.add(new JLabel("Middle Panel"));

bottomPanel = new JPanel();

bottomPanel.setLayout(new FlowLayout(FlowLayout.CENTER));
bottomPanel.add(new JButton("Orange"));
bottomPanel.add(new JButton("Green"));

frame.add(topPanel, BorderLayout.NORTH);
frame.add(middlepanel, BorderLayout.CENTER);
frame.add(bottomPanel, BorderLayout.SOUTH);

Answer 2

The default layout for a JFrame is BorderLayout which has a SOUTH constraint. So there is no need for this statement.

//setLayout(new GridLayout(2, 2));

The default layout for a JPanel is a FlowLayout. So the following statements do nothing:

loc1Panel.add(greenButton, BorderLayout.WEST);
loc1Panel.add(orangeButton, BorderLayout.EAST);

Read the section from the Swing tutorial on Using Layout Managers . There is a section on using a BorderLayout and on using a FlowLayout. I don't know if you are supposed to use just panels with a BorderLayout or panels with a combination of BorderLayout and FlowLayout. I'll let you fix the code to meet your requirement.