So I've been working on a homework on abstraction for my programming class and fell into a problem. The goal for me right now is to be able to use abstraction, then later be able to draw with rectangles and ovals a simple city, like a rectangular building or a oval light on a light post.
The error I am receiving when I compile is: MyTestApp.Rectangle is not abstract and does not override abstract method drawEllipse(java.awt.Graphics) in MyTestApp.Shape. This Error shows up on the line "class Rectangle extends Shape{" right below the class Shape.
My question is what am I doing wrong with my abstraction? I've been messing with the constructors and draw() methods in classes Rectangle and Ellipse for a while now and still to no luck happen to find a solution.
Code is below:
import java.awt.*;
import javax.swing.*;
public class MyTestApp extends JPanel {
Rectangle rect;
Ellipse oval;
public static void main(String [] args) {
MyTestApp myTestApp = new MyTestApp ();
myTestApp.test();
}
public MyTestApp () { //creates the jframe
JFrame frame = new JFrame("MyClass Driver");
setBackground(new Color(200, 250, 200));
setPreferredSize(new Dimension(500, 400));
frame.add(this);
frame.pack();
frame.setVisible(true);
}
public void delay(int msecs) {
try {
Thread.sleep(msecs);
} catch (InterruptedException e) {
}
}
public void paint(Graphics g) {//paints the rectangle and ellipse
super.paint(g);
if (rect != null)
rect.drawRectangle(g);
if (oval != null)
oval.drawEllipse(g);
}
public void test() {//gives the x/y position, width/height, and fill/outline color for the rectangle and oval
delay(1000);
rect = new Rectangle(20, 30, 23, 75, Color.GREEN, Color.BLUE);
oval = new Ellipse(10, 10, 10 , 34, Color.RED, Color.MAGENTA);
repaint();
}
public abstract class Shape{//abstract class Shape that sets the x/y, width/height, and colors for the shapes
private int x, y, width, height;
private Color fillColor;
private Color outlineColor;
public Shape(int x, int y, int width, int height, Color fillColor, Color outlineColor) {
setXY(x, y);
setSize(width, height);
setFillColor(fillColor);
setOutlineColor(outlineColor);
}
public boolean setXY(int x, int y) {
this.x = x;
this.y = y;
return true;
}
public void setSize(int width, int height) {
if (width > 0)
this.width = width;
if (height > 0)
this.height = height;
}
public boolean setFillColor(Color fillColor){
if (fillColor == null) return false;
this.fillColor = fillColor;
return true;
}
public boolean setOutlineColor(Color outlineColor){
if (outlineColor == null) return false;
this.outlineColor = outlineColor;
return true;
}
public Color getFillColor() {
return fillColor;
}
public Color getOutlineColor() {
return outlineColor;
}
public abstract void drawRectangle(Graphics g);//do i need two?
public abstract void drawEllipse(Graphics g);//do i need both?
}
class Rectangle extends Shape{//!!!!!!!!!! where the error shows
public Rectangle(int x, int y, int width, int height, Color fillColor, Color outlineColor) {
super(x, y, width, height, fillColor, outlineColor);
}
public void drawRectangle(Graphics g){//draws the retangle
g.setColor(fillColor);
g.fillRect(x, y, width, height);
g.setColor(outlineColor);
g.drawRect(x, y, width, height);
}
}
class Ellipse extends Shape{
public Ellipse(int x, int y, int width, int height, Color fillColor, Color outlineColor) {
super(x, y, width, height, fillColor, outlineColor);
}
public void drawEllipse(Graphics g){//draws the ellipse
g.setColor(fillColor);
g.fillOval(x, y, width, height);
g.setColor(outlineColor);
g.drawOval(x, y, width, height);
}
}
}
Thanks for reading and helping!
Both classes Rectangle and Ellipse need to override both of the abstract methods.
To work around this, you have 3 options:
Add the two methods
Make each class that extends Shape abstract
Have a single method that does the function of the classes that will extend Shape, and override that method in Rectangle and Ellipse, for example:
abstract class Shape {
// ...
void draw(Graphics g);
}
And
class Rectangle extends Shape {
void draw(Graphics g) {
// ...
}
}
Finally
class Ellipse extends Shape {
void draw(Graphics g) {
// ...
}
}
And you can switch in between them, like so:
Shape shape = new Ellipse();
shape.draw(/* ... */);
shape = new Rectangle();
shape.draw(/* ... */);
Again, just an example.
If you're trying to take advantage of polymorphic behavior, you need to ensure that the methods visible to outside classes (that need polymorphism) have the same signature. That means they need to have the same name, number and order of parameters, as well as the parameter types.
In your case, you might do better to have a generic draw() method, and rely on the subclasses (Rectangle, Ellipse) to implement the draw() method as what you had been thinking of as "drawEllipse" and "drawRectangle".
Related
I faced the problem that I can't write an animation for color change at the Rectangle of JComponent. I use Java 8 and Swing. This animation is supposed to be slow, for any amount of seconds I would like to set. Nit: It feels like the base which I need to wrote his thing is definetly timer.
Here is the code snippet which describes my component's state:
class PBtn extends JComponent {
private LinkedList<MyBtn> myBtns = new LinkedList<>();
LinkedList<MyBtn> getMyBtns(){
return myBtns;
}
static class MyBtn extends Rectangle {
String name;
Color color;
MyBtn(int x, int y, int width, int height, String name, Color color) {
this.setBounds(x, y, width, height);
this.color = color;
}
}
void addBtn(int x, int y, int width, int height, String name, Color color) {
MyBtn myBtn = new MyBtn(x, y, width, height, name, color);
this.addMouseMotionListener(new MouseMotionListener() {
#Override
public void mouseDragged(MouseEvent e) {}
#Override
public void mouseMoved(MouseEvent e) {
if (myBtn.contains(e.getPoint())) {
setToolTipText(name);
}
ToolTipManager.sharedInstance().mouseMoved(e);
}
});
myBtns.add(myBtn);
repaint();
}
void clearBtns() {
myBtns.clear();
repaint();
}
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D graphics2D = (Graphics2D) g;
myBtns.forEach(n -> {
graphics2D.setColor(n.color);
graphics2D.draw(n);
graphics2D.fill(n);
});
}
I tried to use the interpolation-based animation library bu it didn't help. Can you please give me suggestions how to write this code from scratch? Thanks!
I'm making a simple app that allows you to show different circle objects browse through them with buttons.
The problem is i have no idea how to print out my circleobjects into the jPanel.
When you first run the program the first circleobject should appear in the jPanel. Here's my circleclass:
public class Circle {
private int height;
private int width;
private Color color;
public Circle (int height, int width, Color color){
this.height = height;
this.width = height;
this.color = color;
}
public int getHeight() {
return height;
}
public void setHeight(int height) {
this.height = height;
}
public Color getColor() {
return color;
}
public void setColor(Color color) {
this.color = color;
}
public int getWidth() {
return width;
}
public void setWidth(int width) {
this.width = width;
}
}
And here is the first part of the GUI code. I've made 5 circleobjects in an arraylist.
public class CircleGUI extends javax.swing.JFrame{
public ArrayList<Circle> circles = new ArrayList<Circle>();
public CircleGUI(){
initComponents();
circles.add(new Circle(15, 15, Color.blue));
circles.add(new Circle(20, 15, Color.black));
circles.add(new Circle(30, 10, Color.green));
circles.add(new Circle(20, 10, Color.orange));
circles.add(new Circle(35, 35, Color.red));
}
Now, how do i make my first object appear in the jPanel which is marked on the screenshot?
You will have to override the paintComponent(Graphics) method of your JPanel.
Then you do the drawing on the Graphics object, based on the data your current Circle object contains.
Check out Custom Painting Approaches. It does exactly what you want (except it paint Rectangles).
It actually shows two approaches:
Painting objects from an ArrayList (which is what you want)
Painting objects onto a BufferedImage
The basic painting code in your case is:
#Override
protected void paintComponent(Graphics g)
{
super.paintComponent(g);
// Custom code to paint all the Rectangles from the List
for (DrawingArea.ColoredRectangle cr : coloredRectangles)
{
g.setColor( cr.getForeground() );
Rectangle r = cr.getRectangle();
g.drawRect(r.x, r.y, r.width, r.height);
}
}
Of course you would paint ovals and use your Circle class
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I have a combobox in which I can choose to draw either a rectangle, a circle or by freehand.
If I choose to draw a circle it draws it perfectly. If I then switch to draw a rectangle it draws a circle inside the rectangle. The same happens if I first choose to draw a rectangle and then a circle. (See Picture below)
My questions are:
How can I switch between drawing a circle and a rectangle without the circle appearing inside the rectangle?
How can I get the rectangle/circle to show while I'm dragging the mouse. What I mean is how can the lines show until I release the mouse click?
Why doesn't it work drawing by free hand?
This is my testclass:
import java.awt.*;
import java.awt.event.*;
import java.util.*;
import javax.swing.*;
public class Lab6 extends JFrame implements ActionListener {
int startX, startY, endX, endY, w, h;
ArrayList<Shape> shapeList = new ArrayList<Shape>();
Container cp = getContentPane();
private JPanel topPanel;
private JComboBox comboBox;
private final String[] boxOptions = new String[] {"Rektangel", "Cirkel", "Frihand"};
public Lab6(String title) {
super(title);
this.setLayout(new BorderLayout());
this.setDefaultCloseOperation(EXIT_ON_CLOSE);
this.setLocationRelativeTo(null);
this.setSize(840, 500);
this.initComponents();
this.setVisible(true);
}
private void initComponents() {
topPanel = new JPanel(new GridLayout(1,2));
topPanel.setPreferredSize(new Dimension(0,40));
comboBox = new JComboBox(boxOptions);
comboBox.setSelectedIndex(0);
comboBox.addActionListener(this);
topPanel.add(comboBox);
this.add(topPanel, BorderLayout.PAGE_START);
}
#Override
public void paint(Graphics g) {
for (Shape s : shapeList) {
s.draw(g);
}
}
#Override
public void actionPerformed(ActionEvent e) {
if (e.getSource().equals(comboBox)) {
JComboBox cb = (JComboBox)e.getSource();
if (cb.getSelectedItem().equals("Rektangel")) {
cp.addMouseListener(new MouseAdapter() {
#Override
public void mousePressed(MouseEvent e) {
startX = e.getX();
startY = e.getY();
}
#Override
public void mouseReleased(MouseEvent e) {
endX = e.getX();
endY = e.getY();
int width = startX - endX;
int height = startY - endY;
w = Math.abs(width);
h = Math.abs(height);
Rectangle r = new Rectangle(startX, startY, w, h);
shapeList.add(r);
repaint();
}
});
}
else if (cb.getSelectedItem().equals("Cirkel")) {
cp.addMouseListener(new MouseAdapter() {
#Override
public void mousePressed(MouseEvent e) {
startX = e.getX();
startY = e.getY();
}
#Override
public void mouseReleased(MouseEvent e) {
endX = e.getX();
endY = e.getY();
int width = startX - endX;
int height = startY - endY;
w = Math.abs(width);
h = Math.abs(height);
Circle c = new Circle(startX, startY, w, h);
shapeList.add(c);
repaint();
}
});
}
else if (cb.getSelectedItem().equals("Frihand")) { //I need help with this part
cp.addMouseListener(new MouseAdapter() {
#Override
public void mousePressed(MouseEvent e) {
startX = e.getX();
startY = e.getY();
}
#Override
public void mouseDragged(MouseEvent e) {
FreeHand fh = new FreeHand(startX, startY, e.getX(), e.getY());
shapeList.add(fh);
repaint();
}
});
}
}
}
public static void main(String args[]) {
new Lab6("Drawing Program");
}
}
In class Rectangle (class Circle looks the same):
import java.awt.*;
public class Rectangle extends Shape {
public Rectangle(int x, int y, int width, int height) {
super(x, y, width, height);
}
public Rectangle() {
super();
}
#Override
public void draw(Graphics g) {
Graphics2D g2 = (Graphics2D) g;
g2.setColor(Color.RED);
g2.setStroke(new BasicStroke(4));
g.drawRect(getX(), getY(), getWidth(), getHeight());
}
}
In class FreeHand (I need help with this part):
import java.awt.*;
public class FreeHand extends Shape {
public FreeHand(int x, int y, int width, int height) {
super(x, y, width, height);
}
public FreeHand() {
super();
}
#Override
public void draw(Graphics g) {
Graphics2D g2 = (Graphics2D) g;
g2.setColor(Color.BLUE);
g2.setStroke(new BasicStroke(4));
g2.drawLine(getX(), getY(), getWidth(), getHeight());
}
}
In class shape:
import java.awt.Graphics;
import javax.swing.JPanel;
public abstract class Shape extends JPanel {
private int startX, startY, width, height;
public Shape() {
this(0, 0, 1, 1);
}
public Shape(int startX, int startY, int width, int height) {
this.startX = startX;
this.startY = startY;
this.width = width;
this.height = height;
}
public abstract void draw(Graphics g);
#Override
public int getX() {
return startX;
}
#Override
public int getY() {
return startY;
}
#Override
public int getWidth() {
return width;
}
#Override
public int getHeight() {
return height;
}
}
There are a multitude of things going on...
Overriding paint of JFrame
Not calling super.paint before performing custom painting.
Adding a new MosueListener EVERY time you change the shape
Instead, create a custom component, extending from something like JPanel and override it's paintComponent method. Use this component has your basic drawing surface (your controls should contained in another component).
Make sure you call super.paintComponent before performing any custom painting so you don't break the paint chain
See Performing Custom Painting and Painting in AWT and Swing for more details
Create a SINGLE MouseListener and register it to the panel. When the use selects a different shape, change a state variable within the panel (via a setter) which tells the MouseListener what it should do when the user starts drawing.
Updated...
Create a custom class that extends from JPanel...
public static class ShapePane extends JPanel {
}
Override the classes paintComponent method...
public static class ShapePane extends JPanel {
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
// Custom Painting here...
}
}
Provide some sizing hints for the layout manager...
public static class ShapePane extends JPanel {
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
// Custom Painting here...
}
public Dimension getPreferredSize() {
return new Dimension(200, 200);
}
}
Provide a means by which the type of shape can be changed...so you know what to paint...
public static class ShapePane extends JPanel {
public enum ShapeType {
CIRCLE,
RECTANGLE
}
private ShapeType currentShapeType;
public void setCurrentShapeType(ShapeType currentShapeType) {
this.currentShapeType = currentShapeType;
}
public ShapeType getCurrentShapeType() {
return currentShapeType;
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
// Custom Painting here...
}
}
Add a SINGLE MouseListener to the custom class to create the required type of shapes...
public static class ShapePane extends JPanel {
public enum ShapeType {
CIRCLE,
RECTANGLE
}
private ShapeType currentShapeType;
public ShapePane() {
addMouseListener(new MouseAdapter() {
private Point clickPoint;
#Override
public void mousePressed(MouseEvent e) {
clickPoint = e.getPoint();
}
#Override
public void mouseReleased(MouseEvent e) {
Point releasePoint = e.getPoint();
int x = Math.min(releasePoint.x, clickPoint.x);
int y = Math.min(releasePoint.y, clickPoint.y);
int width = Math.abs(clickPoint.x - releasePoint.x);
int height = Math.abs(clickPoint.y - releasePoint.y);
switch (getCurrentShapeType()) {
case CIRCLE:
// Make a circle
break;
case RECTANGLE:
// Make a rectangle...
break;
}
repaint();
}
});
}
public void setCurrentShapeType(ShapeType currentShapeType) {
this.currentShapeType = currentShapeType;
}
public ShapeType getCurrentShapeType() {
return currentShapeType;
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
// Custom Painting here...
}
}
Fill in the blanks...
Create another JPanel (you can simply create an instance this time), add your controls to it
Create an instance of a JFrame, add the custom class to it and the controls panel (make sure they are laid out correctly so they don't override each other - see Laying Out Components Within a Container for more details)
Use appropriate listeners to the controls to determine the type of shape the user wants to draw and set the currentShapeType property accordingly...
Don't know if it was a very specific title, but I have already asked this question but has gone dead.
I am trying to execute paintComponent() so I can draw rectangles, triangles and more with the class being a JComponent.
Here is my code so far:
public class Design extends JComponent {
private static final long serialVersionUID = 1L;
private List<ShapeWrapper> shapesDraw = new ArrayList<ShapeWrapper>();
private List<ShapeWrapper> shapesFill = new ArrayList<ShapeWrapper>();
GraphicsDevice gd = GraphicsEnvironment.getLocalGraphicsEnvironment().getDefaultScreenDevice();
int screenWidth = gd.getDisplayMode().getWidth();
int screenHeight = gd.getDisplayMode().getHeight();
public void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g;
for(ShapeWrapper s : shapesDraw){
g2d.setColor(s.color);
g2d.draw(s.shape);
}
for(ShapeWrapper s : shapesFill){
g2d.setColor(s.color);
g2d.fill(s.shape);
}
}
public void drawRect(int xPos, int yPos, int width, int height) {
shapesDraw.add(new Rectangle(xPos, yPos, width, height));
repaint();
}
public void fillRect(int xPos, int yPos, int width, int height) {
shapesFill.add(new Rectangle(xPos, yPos, width, height));
repaint();
}
public void drawTriangle(int leftX, int topX, int rightX, int leftY, int topY, int rightY) {
shapesDraw.add(new Polygon(
new int[]{leftX, topX, rightX},
new int[]{leftY, topY, rightY},
3));
repaint();
}
public void fillTriangle(int leftX, int topX, int rightX, int leftY, int topY, int rightY) {
shapesFill.add(new Polygon(
new int[]{leftX, topX, rightX},
new int[]{leftY, topY, rightY},
3));
repaint();
}
public Dimension getPreferredSize() {
return new Dimension(getWidth(), getHeight());
}
public int getWidth() {
return screenWidth;
}
public int getHeight() {
return screenHeight;
}
}
class ShapeWrapper {
Color color;
Shape shape;
public ShapeWrapper(Color color , Shape shape){
this.color = color;
this.shape = shape;
}
}
As shown above, everything works perfectly fine, except for being able to choose a colour.
I want to be able to define the rectangles and triangles with their respective positions and lengths but also want to add a colour with it.
But I get an error.
The error says:
The method add(ShapeWrapper) in the type List< ShapeWrapper > is not applicable for the arguments (Rectangle)
And:
The method add(ShapeWrapper) in the type List< ShapeWrapper > is not applicable for the arguments (Polygon)
Please help! I am so stressed trying to figure this out as it is blocking me from doing many things.
The answer is pretty basic...Shape is not a type of ShapeWrapper, therefore it can't be added to a List decalred as List<ShapeWrapper>
What you should be doing instead of
shapesDraw.add(new Rectangle(xPos, yPos, width, height));
is something more like...
shapesDraw.add(new ShapeWrapper(Color.BLACK, new Rectangle(xPos, yPos, width, height)));
The same goes for your ...Triangle methods. You need to wrap the resulting Polygon in a ShapeWrapper before trying to add it to the List
I need to create a rectangle object and then paint it to the applet using paint(). I tried
Rectangle r = new Rectangle(arg,arg1,arg2,arg3);
Then tried to paint it to the applet using
g.draw(r);
It didn't work. Is there a way to do this in java? I have scoured google to within an inch of its life for an answer, but I haven't been able to find an answer. Please help!
Try this:
public void paint (Graphics g) {
Rectangle r = new Rectangle(xPos,yPos,width,height);
g.fillRect(r.getX(), r.getY(), r.getWidth(), r.getHeight());
}
[edit]
// With explicit casting
public void paint (Graphics g) {
Rectangle r = new Rectangle(xPos, yPos, width, height);
g.fillRect(
(int)r.getX(),
(int)r.getY(),
(int)r.getWidth(),
(int)r.getHeight()
);
}
You may try like this:
import java.applet.Applet;
import java.awt.*;
public class Rect1 extends Applet {
public void paint (Graphics g) {
g.drawRect (x, y, width, height); //can use either of the two//
g.fillRect (x, y, width, height);
g.setColor(color);
}
}
where x is x co-ordinate
y is y cordinate
color=the color you want to use eg Color.blue
if you want to use rectangle object you could do it like this:
import java.applet.Applet;
import java.awt.*;
public class Rect1 extends Applet {
public void paint (Graphics g) {
Rectangle r = new Rectangle(arg,arg1,arg2,arg3);
g.fillRect(r.getX(), r.getY(), r.getWidth(), r.getHeight());
g.setColor(color);
}
}
Note：drawRect and fillRect are different.
Draws the outline of the specified rectangle:
public void drawRect(int x,
int y,
int width,
int height)
Fills the specified rectangle. The rectangle is filled using the graphics context's current color:
public abstract void fillRect(int x,
int y,
int width,
int height)