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CSE190L Sample Program handout #10
Driver class ColorsMain.java
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// Driver class that launches the application
public class ColorsMain {
public static void main(String[] args) {
ColorsFrame frame = new ColorsFrame();
frame.start();
}
}
Panel class ColorsPanel.java
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// This class draws a colored panel with some text in it.
import java.awt.*;
import java.awt.geom.*;
import javax.swing.*;
public class ColorsPanel extends JPanel {
private boolean textIsBlack;
private String text;
private int x;
private int y;
public ColorsPanel() {
textIsBlack = true;
setPreferredSize(new Dimension(200, 200));
}
public void setTextParameters(String text, int x, int y) {
this.text = text;
this.x = x;
this.y = y;
repaint();
}
// switches the color uses for the text
public void switchTextColor() {
textIsBlack = !textIsBlack;
repaint();
}
public void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g;
if (textIsBlack)
g2.setPaint(Color.BLACK);
else
g2.setPaint(Color.WHITE);
g2.drawString(text, x, y);
}
}
Frame class ColorsFrame.java
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// This class sets up the user interface controls for a program that controls
// a panel with text in it. The user is given buttons to change the panel's
// background color and when the user clicks on the panel, it switches the
// text color.
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.event.*;
public class ColorsFrame {
private JFrame frame;
private ColorsPanel panel;
private JTextField textEntry;
private JTextField xEntry;
private JTextField yEntry;
private static final String INITIAL_TEXT = "Hello World!";
private static final int INITIAL_XY = 50;
public ColorsFrame() {
frame = new JFrame();
frame.setTitle("Colors fun");
// frame.setSize(300, 300);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
// construct panel and set up a mouse listener to switch its text
// color when the user clicks on the panel
panel = new ColorsPanel();
panel.setTextParameters(INITIAL_TEXT, INITIAL_XY, INITIAL_XY);
panel.addMouseListener(new MouseAdapter() {
public void mouseClicked(MouseEvent e) {
panel.switchTextColor();
}
});
frame.add(panel, BorderLayout.CENTER);
// add the panel of buttons at the top of the frame
frame.add(buttonPanel(), BorderLayout.NORTH);
frame.add(textFieldPanel(), BorderLayout.SOUTH);
frame.pack();
}
// call this method to start the program executing
public void start() {
frame.setVisible(true);
}
// constructs and returns a panel with five buttons that change the
// background color of the panel.
private JPanel buttonPanel() {
JPanel result = new JPanel();
result.setLayout(new GridLayout(0, 3));
result.add(makeButton("Yellow", Color.YELLOW), BorderLayout.NORTH);
result.add(makeButton("Blue", Color.BLUE), BorderLayout.SOUTH);
result.add(makeButton("Red", Color.RED), BorderLayout.EAST);
result.add(makeButton("Magenta", Color.MAGENTA), BorderLayout.WEST);
result.add(makeButton("Green", Color.GREEN), BorderLayout.CENTER);
return result;
}
// constructs and returns a JButton with the given text that when pressed
// will set the background color of the panel to the given color
private JButton makeButton(String text, final Color c) {
JButton button = new JButton(text);
button.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
panel.setBackground(c);
}
});
return button;
}
// Constructs a panel that has three text fields for controlling the
// colored panel: one for the text to draw, and two for x/y coordinates
// of where to draw the string.
private JPanel textFieldPanel() {
JPanel result = new JPanel();
ActionListener textFieldListener = new ActionListener() {
public void actionPerformed(ActionEvent e) {
updatePanel();
}
};
FocusListener textFocusListener = new FocusAdapter() {
public void focusLost(FocusEvent e) {
updatePanel();
}
};
textEntry = makeField(INITIAL_TEXT, 30, textFieldListener,
textFocusListener, "text to display", result);
xEntry = makeField("" + INITIAL_XY, 3, textFieldListener,
textFocusListener, "x", result);
yEntry = makeField("" + INITIAL_XY, 3, textFieldListener,
textFocusListener, "y", result);
return result;
}
// constructs and returns a text field with given text and columns; adds
// the given focus listener and action listener; adds to the given panel
// along with a label using the given label text.
private JTextField makeField(String text, int cols, ActionListener action,
FocusListener focus, String label, JPanel p) {
JTextField field = new JTextField(text, cols);
field.addActionListener(action);
field.addFocusListener(focus);
p.add(new JLabel(label));
p.add(field);
return field;
}
// updates the panel's string and x/y coordinates
private void updatePanel() {
int x, y;
try {
x = Integer.parseInt(xEntry.getText().trim());
} catch (NumberFormatException e) {
x = INITIAL_XY;
xEntry.setText("" + x);
Toolkit.getDefaultToolkit().beep();
}
try {
y = Integer.parseInt(yEntry.getText().trim());
} catch (NumberFormatException e) {
y = INITIAL_XY;
yEntry.setText(y + "");
Toolkit.getDefaultToolkit().beep();
}
panel.setTextParameters(textEntry.getText(), x, y);
}
}
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