JAVA: For this project, you will create a GUI drawing application. *The user can
ID: 654195 • Letter: J
Question
JAVA: For this project, you will create a GUI drawing application.
*The user can select from three different pen colors.
*The user can also select an "eraser" pen.(Hint: You dont really need to "erase" a point. use a shortcut )
*When the user clicks in the drawing space, the pen is activated. The user can then move the mouse to draw. The user clicks again to de-activate the pen.(Note: the user does not click-and-drag to draw. Instead, it's click once to turn on, move to draw, click once to turn off.)
*There is a clear button that clears the entire drawing space.
*You need to keep track of both the location and color of a point on which the user has drawn. Use an ArrayList to keep track of this.(What kind of object should the ArrayList hold? Does Java provide a class that represents a Point with Color?)
*For full credit, design an object-oriented solution to keep track of an object with a location and a color.
* Include an additional drawing functionality. This must be different from simply choosing another pen color.
Explanation / Answer
import java.awt.*;
import java.awt.event.*;
import java.util.ArrayList;
import javax.swing.*;
public class SimplePaint extends JApplet {
/**
* The main routine opens a window that displays a drawing area
* and color palette. This main routine allows this class to
* be run as a stand-alone application as well as as an applet.
* The main routine has nothing to do with the function of this
* class as an applet.
*/
public static void main(String[] args) {
JFrame window = new JFrame("Simple Paint");
SimplePaintPanel content = new SimplePaintPanel();
window.setContentPane(content);
window.setSize(600,480);
window.setLocation(100,100);
window.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
window.setVisible(true);
}
/**
* The init method of the applet simply creates a SimplePaintPanel and
* uses it as the content pane of the applet.
*/
public void init() {
setContentPane( new SimplePaintPanel() );
}
/**
* A simple paint panel contains a large white drawing surface where
* the user can draw curves and a color palette that the user can click
* to select the color to be used for drawing.
*/
public static class SimplePaintPanel extends JPanel
implements MouseListener, MouseMotionListener {
private ArrayList<PointWithColor> pc; //arraylist to store locations of clicked points and color
/**
* Some constants to represent the color selected by the user.
*/
private final static int BLACK = 0,
RED = 1,
GREEN = 2,
BLUE = 3,
CYAN = 4,
MAGENTA = 5,
WHITE = 6;
private int currentColor = BLACK; // The currently selected drawing color,
// coded as one of the above constants.
/* The following variables are used when the user is sketching a
curve while moving a mouse. */
private int prevX, prevY; // The previous location of the mouse.
private boolean clicked; //variable to store whether mouse is clicked
private Graphics graphicsForDrawing; // A graphics context for the panel
// that is used to draw the user's curve.
/**
* Constructor for SimplePaintPanel class sets the background color to be
* white and sets it to listen for mouse events on itself.
*/
SimplePaintPanel() {
pc=new ArrayList<PointWithColor>();
setBackground(Color.WHITE);
addMouseListener(this);
addMouseMotionListener(this);
}
/**
* Draw the contents of the panel.
*/
public void paintComponent(Graphics g) {
super.paintComponent(g); // Fill with background color (white).
int width = getWidth(); // Width of the panel.
int height = getHeight(); // Height of the panel.
int colorSpacing = (height - 56) / 7;
// Distance between the top of one colored rectangle in the palette
// and the top of the rectangle below it. The height of the
// rectangle will be colorSpacing - 3. There are 7 colored rectangles,
// so the available space is divided by 7. The available space allows
// for the gray border and the 50-by-50 CLEAR button.
/* Draw a 3-pixel border around the applet in gray. This has to be
done by drawing three rectangles of different sizes. */
g.setColor(Color.GRAY);
g.drawRect(0, 0, width-1, height-1);
g.drawRect(1, 1, width-3, height-3);
g.drawRect(2, 2, width-5, height-5);
/* Draw a 56-pixel wide gray rectangle along the right edge of the applet.
The color palette and Clear button will be drawn on top of this.
(This covers some of the same area as the border I just drew. */
g.fillRect(width - 56, 0, 56, height);
/* Draw the "Clear button" as a 50-by-50 white rectangle in the lower right
corner of the applet, allowing for a 3-pixel border. */
g.setColor(Color.WHITE);
g.fillRect(width-53, height-53, 50, 50);
g.setColor(Color.BLACK);
g.drawRect(width-53, height-53, 49, 49);
g.drawString("CLEAR", width-48, height-23);
/* Draw the seven color rectangles. */
g.setColor(Color.BLACK);
g.fillRect(width-53, 3 + 0*colorSpacing, 50, colorSpacing-3);
g.setColor(Color.RED);
g.fillRect(width-53, 3 + 1*colorSpacing, 50, colorSpacing-3);
g.setColor(Color.GREEN);
g.fillRect(width-53, 3 + 2*colorSpacing, 50, colorSpacing-3);
g.setColor(Color.BLUE);
g.fillRect(width-53, 3 + 3*colorSpacing, 50, colorSpacing-3);
g.setColor(Color.CYAN);
g.fillRect(width-53, 3 + 4*colorSpacing, 50, colorSpacing-3);
g.setColor(Color.MAGENTA);
g.fillRect(width-53, 3 + 5*colorSpacing, 50, colorSpacing-3);
g.setColor(Color.WHITE);
g.fillRect(width-53, 3 + 6*colorSpacing, 50, colorSpacing-3);
g.setColor(Color.BLACK);
g.drawRect(width-53, 3 + 6*colorSpacing, 50, colorSpacing-3);
g.drawString("ERASER", width-52, height-63);
/* Draw a 2-pixel white border around the color rectangle
of the current drawing color. */
g.setColor(Color.WHITE);
g.drawRect(width-55, 1 + currentColor*colorSpacing, 53, colorSpacing);
g.drawRect(width-54, 2 + currentColor*colorSpacing, 51, colorSpacing-2);
} // end paintComponent()
/**
* Change the drawing color after the user has clicked the
* mouse on the color palette at a point with y-coordinate y.
* (Note that I can't just call repaint and redraw the whole
* panel, since that would erase the user's drawing!)
*/
private void changeColor(int y) {
int width = getWidth(); // Width of applet.
int height = getHeight(); // Height of applet.
int colorSpacing = (height - 56) / 7; // Space for one color rectangle.
int newColor = y / colorSpacing; // Which color number was clicked?
if (newColor < 0 || newColor > 6) // Make sure the color number is valid.
return;
/* Remove the hilite from the current color, by drawing over it in gray.
Then change the current drawing color and draw a hilite around the
new drawing color. */
Graphics g = getGraphics();
g.setColor(Color.GRAY);
g.drawRect(width-55, 1 + currentColor*colorSpacing, 53, colorSpacing);
g.drawRect(width-54, 2 + currentColor*colorSpacing, 51, colorSpacing-2);
currentColor = newColor;
g.setColor(Color.WHITE);
g.drawRect(width-55, 1 + currentColor*colorSpacing, 53, colorSpacing);
g.drawRect(width-54, 2 + currentColor*colorSpacing, 51, colorSpacing-2);
g.dispose();
} // end changeColor()
/**
* This routine is called in mousePressed when the user clicks on the drawing area.
* It sets up the graphics context, graphicsForDrawing, to be used to draw the user's
* sketch in the current color.
*/
private void setUpDrawingGraphics() {
graphicsForDrawing = getGraphics();
switch (currentColor) {
case BLACK:
graphicsForDrawing.setColor(Color.BLACK);
break;
case RED:
graphicsForDrawing.setColor(Color.RED);
break;
case GREEN:
graphicsForDrawing.setColor(Color.GREEN);
break;
case BLUE:
graphicsForDrawing.setColor(Color.BLUE);
break;
case CYAN:
graphicsForDrawing.setColor(Color.CYAN);
break;
case MAGENTA:
graphicsForDrawing.setColor(Color.MAGENTA);
break;
case WHITE:
graphicsForDrawing.setColor(Color.WHITE);
break;
}
} // end setUpDrawingGraphics()
/**
* This is called when the user presses the mouse anywhere in the applet.
* There are three possible responses, depending on where the user clicked:
* Change the current color, clear the drawing, or start drawing a curve.
* (Or do nothing if user clicks on the border.)
*/
public void mousePressed(MouseEvent evt) {
int x = evt.getX(); // x-coordinate where the user clicked.
int y = evt.getY(); // y-coordinate where the user clicked.
int width = getWidth(); // Width of the panel.
int height = getHeight(); // Height of the panel.
if (x > width - 53) {
// User clicked to the right of the drawing area.
// This click is either on the clear button or
// on the color palette.
if (y > height - 53)
repaint(); // Clicked on "CLEAR button".
else
changeColor(y); // Clicked on the color palette.
}
else if (x > 3 && x < width - 56 && y > 3 && y < height - 3) {
// The user has clicked on the white drawing area.
// Start drawing a curve from the point (x,y).
prevX = x;
prevY = y;
if(clicked==false){
setUpDrawingGraphics();
clicked=true;
}else{
graphicsForDrawing.dispose();
graphicsForDrawing = null;
clicked=false;
}
}
} // end mousePressed()
public void mouseReleased(MouseEvent evt) { }
public void mouseDragged(MouseEvent evt) { } // end mouseDragged()
public void mouseEntered(MouseEvent evt) { } // Some empty routines.
public void mouseExited(MouseEvent evt) { } // (Required by the MouseListener
public void mouseClicked(MouseEvent evt) { } // and MouseMotionListener
public void mouseMoved(MouseEvent evt) { //mouse is moved for drawing
int x = evt.getX(); // x-coordinate of mouse.
int y = evt.getY(); // y-coordinate of mouse.
if (x < 3) // Adjust the value of x,
x = 3; // to make sure it's in
if (x > getWidth() - 57) // the drawing area.
x = getWidth() - 57;
if (y < 3) // Adjust the value of y,
y = 3; // to make sure it's in
if (y > getHeight() - 4) // the drawing area.
y = getHeight() - 4;
pc.add(new PointWithColor(x,y,currentColor)); //add points and color in arraylist
graphicsForDrawing.drawLine(prevX, prevY, x, y); // Draw the line.
prevX = x; // Get ready for the next line segment in the curve.
prevY = y;
} // interfaces).
} // End class SimplePaintPanel
} // end class SimplePaint
class PointWithColor{ //class to store the points x and y and color
private int x,y;
private int color;
PointWithColor(int x,int y,int color){
this.x=x;
this.y=y;
this.color=color;
}
}
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