Develop Reference

Keeping Shapes on Screen Help, can't figure out how to keep track of X,Y coordinates

I have tried and tried, I looked up many examples for keeping Shapes on the screen but can't seem to adapt to my code. In Summary, a left click prints a square, a right click prints a circle. I would like to fill the window with squares (rects) and circles. Any help and explanation so I can learn the concept would be great. I understand I have to keep track on the coordinates, perhaps in a loop but can seem to get it to work. Thanks again.
import java.awt.*;
import javax.swing.JFrame;
import java.awt.event.MouseListener;
import java.awt.event.MouseEvent;
public class MouseButtonTester extends JFrame implements MouseListener
{
private int mouseX, mouseY;
private int mouseButton;
private boolean isFirstRun;
private static final int WIDTH = 640;
private static final int HEIGHT = 480;
private static final long serialVersionUID = 0; //use this if you do not like warnings
public MouseButtonTester() //constructor
{
super("Mouse Button Tester");
//set up all variables
mouseX = mouseY = 0;
mouseButton = 0;
isFirstRun = true;
//set up the Frame
setSize(WIDTH,HEIGHT);
setBackground(Color.WHITE);
setVisible(true);
//start trapping for mouse clicks
addMouseListener(this);
}
public void mouseClicked(MouseEvent e)
{
mouseX=e.getX(); //Tracks x coordinates
mouseY=e.getY(); //Tracker y coordinates
mouseButton = e.getButton(); //gets button number
repaint();
}
public void paint( Graphics window ) // Draws the Window
{
if(isFirstRun)
{
window.setColor(Color.WHITE);
window.fillRect(0,0,WIDTH, HEIGHT);
//change isFirstRun
}
window.setFont(new Font("TAHOMA",Font.BOLD,12));
window.setColor(Color.BLUE);
window.drawString("MOUSE BUTTON TESTER", 420,55);
draw(window);
}
public void draw(Graphics window)
{
if(mouseButton==MouseEvent.BUTTON1) //left mouse button pressed
{
//window.drawString("BUTTON1", 50,200); //debug code
window.setColor(Color.RED);
window.drawRect(mouseX,mouseY,10,10);
}
//right mouse button pressed
{
if (mouseButton == MouseEvent.BUTTON2)
window.setColor(Color.BLUE);
window.drawOval(mouseX,mouseY,10,10);
}
//any other mouse button pressed
{
}
}
public void mouseEntered(MouseEvent e) { }
public void mouseExited(MouseEvent e) { }
public void mousePressed(MouseEvent e) {
}
public void mouseReleased(MouseEvent e) { }
}
------ Main Method --------------
public class MouseButtonTesterRunner
{
public static void main(String[] args)
{ MouseButtonTester prog = new MouseButtonTester();
}
}

First, start by having a read through:
Performing Custom Painting
Painting in AWT and Swing
So you can get a understanding how painting in Swing works, how you can work with it and your responsibilities when doing so.
Next, have a read through:
How can I set in the midst?
Java JFrame .setSize(x, y) not working?
How to get the EXACT middle of a screen, even when re-sized
Graphics rendering in title bar
for reasons why you should avoid overriding paint of top level containers like JFrame
Finally...
Painting in Swing is destructive, that is, every time your component is painted, you are expected to completely repaint the component state from scratch.
In order to achieve your goal, you will need to maintain a cache of the items you want to paint.
The concept itself it's very difficult, but there might be some "gotchas" along the way
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Font;
import java.awt.FontMetrics;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.util.ArrayList;
import java.util.List;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
public class Test {
public static void main(String[] args) {
new Test();
}
public Test() {
EventQueue.invokeLater(new Runnable() {
#Override
public void run() {
JFrame frame = new JFrame();
frame.add(new TestPane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class TestPane extends JPanel {
private List<Point> circles;
private List<Point> squares;
public TestPane() {
circles = new ArrayList<>();
squares = new ArrayList<>();
addMouseListener(new MouseAdapter() {
#Override
public void mouseReleased(MouseEvent e) {
if (SwingUtilities.isLeftMouseButton(e)) {
circles.add(e.getPoint());
} else if (SwingUtilities.isRightMouseButton(e)) {
squares.add(e.getPoint());
}
repaint();
}
});
}
#Override
public Dimension getPreferredSize() {
return new Dimension(200, 200);
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
// I'm picky
Graphics2D g2d = (Graphics2D) g.create();
g2d.setColor(Color.RED);
for (Point p : circles) {
g2d.drawOval(p.x, p.y, 10, 10);
}
g2d.setColor(Color.BLUE);
for (Point p : squares) {
g2d.drawRect(p.x, p.y, 10, 10);
}
g2d.setFont(new Font("TAHOMA", Font.BOLD, 12));
g2d.setColor(Color.BLUE);
FontMetrics fm = g2d.getFontMetrics();
String text = "MOUSE BUTTON TESTER";
int x = getWidth() - fm.stringWidth(text) - 10;
int y = getHeight() - (fm.getAscent() - fm.getHeight()) - 10;
g2d.drawString(text, x, y);
g2d.dispose();
}
}
}

I suggest creating 2 classes.
1) Circle class
2) Square Class
Those classes will store info that you need, like X, y etc..
Initialize an array list that stores those objects & read from it in your paint method, proceed with painting them just like you do in your code.
(On a click event you simply create new object (circle/square) and add it into your array list)

So here's how i understand how your code works so far: The user left clicks, those coordinates are recorded, and a square is rendered on the screen at those coordinates.
When we click the coordinates are updated and on the next draw, the square is moved to a new position.
You were on the right track about needing a loop.
Here's the logic you need to implement:
Create an ArrayList as a member variable. The type can be a pair<int,int> object. So this arraylist will hold a list of X,Y coordinates. This arraylist will look something like this:
ArrayList<pair<int,int>> myRightClickCoords;
Once you make that list, every time the user clicks, record the click coordinates and insert them into the arraylist. That will look something like this:
myRightClickCoords.insert(new pair<int,int>(e.getX(),e.getY()));
Then, once that is added to your code, in your draw function, you can have a look that runs through the entire myRightClickCoords list and runs drawRect for each set of coordinates.
Once you get that working, you can do the same thing for left click and circles. Good luck!

Behavior of repaint() when painting circles on a JComponent

I had an assignment about making painting circles on a JComponent when I click on it and that if you click on an existing circle, it will print a message. Everything works fine, except that the first circle that I draw will have a black border when the following ones wont.
I think it has to do with the repaint method but I cant seems to find what is going on.
import javax.swing.*;
import java.awt.*;
import java.awt.Shape;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.geom.Ellipse2D;
import java.util.ArrayList;
public class GraphComponent extends JComponent {
private int defaultWidth = 500;
private int defaultHeight = 500;
protected Point spot;
protected int width = 50;
protected int height = 50;
private ArrayList<Ellipse2D> shapeList = new ArrayList();
public GraphComponent() {
super();
this.setPreferredSize(new Dimension(defaultWidth,defaultHeight));
addMouseListener(new MouseAdapter() {
public void mouseClicked(MouseEvent e) {
boolean contains = false;
spot = e.getPoint();
for (Shape shape : shapeList) {
if (shape.contains(spot)) {
System.out.println("WIN");
System.out.println();
contains = true;
break;
}
}
System.out.println();
System.out.println(shapeList.contains(spot));
if(contains == false){
shapeList.add(new Ellipse2D.Double(spot.x - width / 2,
spot.y - width / 2, width, height));
}
repaint();
}
});
addMouseMotionListener(new MouseAdapter() {
public void mouseDragged(MouseEvent e) {
//moveSquare(e.getX(),e.getY());
}
});
}
public void paintComponent(Graphics gfx) {
super.paintComponents(gfx);
for (Ellipse2D shape : shapeList) {
gfx.drawOval((int)shape.getX(), (int)shape.getY(),width,height);
gfx.setColor(Color.YELLOW);
gfx.fillOval((int)shape.getX(), (int)shape.getY(),width,height);
}
}
}
I expect all the circles to look the same, yet the first created has black borders

You are using a unique Graphics object, so the first call (from the first iteration) to drawOval will paint with the default Graphics 's color, which is black .
Next iterations will all paint in yellow .
for (Ellipse2D shape : shapeList) {
gfx.drawOval((int)shape.getX(), (int)shape.getY(),width,height);// BLACK (at first iteration, YELLOW for next ones)
gfx.setColor(Color.YELLOW);// YELLOW (from now on)
gfx.fillOval((int)shape.getX(), (int)shape.getY(),width,height);
}

Why does this attempt to animate my moving sprite work?

I'm trying to animate the sprite in my game when a button is pressed, but when I press the button, it skips the animation. Its supposed to go one pixel, change sprites, and then go one more pixel and change back. Here is the code
//for all
import java.nio.file.*;
import javax.imageio.ImageIO;
import java.io.IOException;
import java.awt.image.*;
import java.net.*;
import java.awt.*;
import javax.swing.*;
import static java.lang.invoke.MethodHandles.*;
import java.awt.event.*;
//my Mario class (cut down a lot)
class Mario {
// all numbers multiplied by 2 from OG game
protected Direction dir;
protected int x, y;
protected BufferedImage sprite;
protected String currentSpriteName;
public Mario() {
this.x = 54;
this.y = 808;
dir = Direction.RIGHT;
setSprite(MVCE.SMALLSTANDFACERIGHT);
currentSpriteName = MVCE.SMALLSTANDFACERIGHT;
}
public void moveRight(){
if(this.dir == Direction.LEFT){
this.dir = Direction.RIGHT;
}
else if(this.dir == Direction.RIGHT){
this.x+=1;
}
}
public void animateMoveRight(){
if (currentSpriteName.equals(MVCE.SMALLSTANDFACERIGHT)){
setSprite(MVCE.SMALLWALKFACERIGHT);
}
else if (currentSpriteName.equals(MVCE.SMALLWALKFACERIGHT)){
setSprite(MVCE.SMALLSTANDFACERIGHT);
}
}
public void jump() {
this.y -= 46;
}
public void setSprite(String spriteName) {
URL spriteAtLoc = MVCE.urlGenerator(spriteName);
this.sprite = MVCE.generateAndFilter(sprite, spriteAtLoc);
}
public void getSprite(){
System.out.println(this.currentSpriteName);
}
public void paint(Graphics g) {
Graphics2D g2 = (Graphics2D) g;
g2.drawImage(sprite, 0, 0, null); // DO NOT SET x and y TO ANYTHING,
// this sets 0,0 to top left!!
}
}
// my MarioRender class:
class MarioRender extends JLabel {
protected Mario marioSprite;
public MarioRender() {
marioSprite = new Mario();
}
public void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g;
marioSprite.paint(g2);
setBounds(marioSprite.x, marioSprite.y, marioSprite.sprite.getWidth(), marioSprite.sprite.getHeight());
}
public void moveMarioRight(){
marioSprite.moveRight();
marioSprite.animateMoveRight();
setLocation(this.marioSprite.getX(), this.marioSprite.getY());
repaint();
//this is my attempt to make it animate
marioSprite.moveRight();
marioSprite.animateMoveRight();
setLocation(this.marioSprite.getX(), this.marioSprite.getY());
repaint();
}
public void jumpMario() {
marioSprite.jump();
setLocation(this.marioSprite.x, this.marioSprite.y);
repaint();
}
}
// direction class, solely for moving
enum Direction {
LEFT, RIGHT
}
// my calling class, which I called MVCE where I make the frame
public class MVCE extends JFrame {
MarioRender m = new MarioRender();
JLabel bg;
public MVCE() {
bg = new JLabel();
this.setSize(868, 915);
this.setVisible(true);
this.add(bg, BorderLayout.CENTER);
bg.setLayout(null);
bg.add(m);
m.setBounds(m.marioSprite.x, m.marioSprite.y, m.marioSprite.sprite.getWidth(),
m.marioSprite.sprite.getHeight());
KeyListener kl = new MoveListener();
this.addKeyListener(kl);
this.setFocusable(true);
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
public static final String SMALLSTANDFACERIGHT = "SmallStandFaceRight.bmp"; // 30
// x
// 32
public static final String SMALLJUMPFACERIGHT = "SmallJumpFaceRight.bmp"; // 32
// x
// 32
// generate URL
public static URL urlGenerator(String name) {
URL u = lookup().lookupClass().getResource(name);
return u;
}
// return image with filtered color
public static BufferedImage generateAndFilter(BufferedImage b, URL u) {
try {
b = ImageIO.read(u);
int width = b.getWidth();
int height = b.getHeight();
int[] pixels = new int[width * height];
b.getRGB(0, 0, width, height, pixels, 0, width);
for (int i = 0; i < pixels.length; i++) {
// System.out.println(pixels[i]);
if (pixels[i] == 0xFFff00fe) {
pixels[i] = 0x00ff00fe;
}
}
BufferedImage newSprite = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);
newSprite.setRGB(0, 0, width, height, pixels, 0, width);
b = newSprite;
} catch (IOException e) {
System.out.println("sprite not found");
e.printStackTrace();
}
return b;
}
// key listener
class MoveListener implements KeyListener {
public void keyPressed(KeyEvent k) {
if ((k.getKeyCode() == 39)) {
m.moveMarioRight();
///THIS IS SUPPOSED TO MOVE HIM 1, change sprite, and automatically move him back, it moves 2 pixels but no animation
}
if (k.getKeyCode() == 83) { // S key
m.marioSprite.setSprite(SMALLJUMPFACERIGHT);
m.jumpMario();
}
}
public void keyReleased(KeyEvent k) {
}
public void keyTyped(KeyEvent k) {
}
}
public static void main(String[] args) {
MVCE m = new MVCE();
}
}
I tried putting this between the calls to marioMoveRight():
try {
Thread.sleep(200);
} catch(InterruptedException ex) {
Thread.currentThread().interrupt();
}
but it just delays the whole thing. I had also tried using an ActionListener, but I don't know how to make it react only when the key is pushed. as I had it,
I had this class inside of MVCE:
class TickListener implements ActionListener{
public void actionPerformed(ActionEvent a){
m.marioSprite.setSprite(Constants.SMALLWALKFACERIGHT);
repaint();
}
}
and this at the end of the MVCE constructor:
ActionListener ac = new TickListener();
final int DELAY = 1000;
Timer t = new Timer(DELAY, ac);
t.start();
but then, the Mario just moves automatically. I do not want to use a sprite sheet for this project, I am trying to do it as this guy did for SMB1.

Many problems, don't know which one or if any will fix the problem:
Don't use a KeyListener. If a component doesn't have focus the component won't receive the event. Instead use Key Bindings.
Don't use "==" to compare Objects. Instead you should be using the equals(...) method.
Don't override paintComponent. A painting method is for painting only. You should not be changing the bounds of the component in the painting method.
Do basic debugging (problem solving) before asking a question. A simple System.out.println(...) added to various methods will determine if the code is executing as you expect. Then when you ask a question you can ask a specific question telling us which block of code does not execute as you expect.

You never actually call the method animateMoveRight(), and if I understand correcly, that's what's changing the sprite. Also, I doubt that you see the sprite change when calling the same method twice in a row without any delay.
Try putting the animateMoveRight() method into the moveRight() or the moveMarioRight() method and, if neccessary because the animation is too fast, add your delay code back where you had it. Be careful not to let the main thread sleep, as this causes everything to freeze, so start another one or use a timer etc.
EDIT: Good timers
I'm not too familiar with the Timer class, so I end up using the Thread variant. There are many tutorials for that out there, just search for "java threads" or "java multithreading". This is IMO a solid tutorial you can check out.

Java MouseListener Not Working

I am trying to get the console to print when the mouse is pressed within an object of class RenderCanvas which extends JPanel. However, I am getting no feedback when I press the mouse down in the window. Any suggestions as to what I might be able to change to make the MouseListener work?
Here is my code:
RenderCanvas Class:
import java.awt.event.MouseEvent;
import java.util.ArrayList;
import java.util.List;
import java.awt.Color;
import java.awt.Graphics;
import javax.swing.JPanel;
import java.awt.event.MouseAdapter;
public class RenderCanvas extends JPanel {
private List<Rect> rectangles = new ArrayList<Rect>();
private List<Line> lines = new ArrayList<Line>();
public void renderCanvas() {
addMouseListener(new MouseAdapter() {
public void mousePressed(MouseEvent e) {
addRect(0, 0, 200, 200, Color.ORANGE);
System.out.println(e);
}
});
}
public void paintComponent(Graphics g) {
for (Rect rectangle : rectangles) {
rectangle.draw(g);
}
for (Line line : lines) {
line.draw(g);
}
}
public void addRect(int x, int y, int width, int height, Color color) {
Rect rectangle = new Rect(x, y, width, height, color);
this.rectangles.add(rectangle);
}
public void addLine(int y, int width, Color color) {
Line line = new Line(y, width, color);
this.lines.add(line);
}
}
Main Class:
import javax.swing.*;
import java.awt.*;
import java.util.Random;
public class Main {
public static void main(String[] args) {
JFrame window = new JFrame("Window");
RenderCanvas canvas = new RenderCanvas();
window.setContentPane(canvas);
window.setSize(640, 360);
window.setLocation(640, 360);
window.setVisible(true);
}
}
Thanks in advance for any help!

public void renderCanvas() is NOT a constructor. Change
public void renderCanvas()
to
public RenderCanvas()
Notice the upper-case "R" and the absence of the "void" return type

void RenderCanvas() is not being called. I believe you mean just public RenderCanvas() instead of public void RenderCanvas, since you're only using the ctor in the main method.

I think you're intending this method:
public void renderCanvas() {
to be a constructor for the RenderCanvas class; it's not, though, for two reasons: it's not capitalized the same way (small r vs capital R) and also it has a return type. Constructors have no return type; the line should look like
public RenderCanvas() {
Because this isn't a constructor, it's a method, and nobody's calling it, so your event handler is never being added.

How to make a curve to join two objects editable?

I'm involved in a project in which we're doing a visual editor (written in Java). Now, I'm trying to make curves that join two different objects that I'm painting in a class that extends JPanel (this class is what I'm using to paint, inside a JFrame, overriding the method paintComponent). I'm in troubles because I'm using the class QuadCurve2D to make this, but I cannot make it clickable (I'm using the method contains, but it doesn't work everytime), make it editable (for example, setting a square in its middle point to modify its curvature. The point that is used on the middle of the QuadCurve2D when the constructor is called is outside the curve) or something (method, variable, iterator, etc) that could tell me which Points are in the QuadCurve2D.
After looking for all of that some time, I have no answer, so I'm trying posting it here to find a solution. Is there anyway to make it with the QuadCurve2D class, or do I have to try with some external library?

First of all sorry for the long reply. I am now posting a complete answer to your question. I am sub classing the QuadCurve2D.Double class and with a little math now you define the curve with a start,end and a middle point instead of a control point. Also i have created a new method that checks whether a point is on the curve. The intersects method checks if the convex hull of the shape intersects with the provided shape so in the case of the concave curve this is functional but not accurate. Note that my implementation of the method to check whether a point is on the curve is rather computationally expensive and not 100% accurate since i am checking along the curve length with a specified resolution (0 is the beginning of the curve, 1 is the end. So in the example provided i am checking with a resolution of 0.01 meaning 100 checks are made along the curve). For that matter make sure that the provided step in the resolution is a divider of 0.5 (the middle point) so that you may be able to select it. If that makes no sense don't pay attention it doesn't really matter, you can use my example out of the box. Note that i also provide a check box to switch between the intersects method and my own for checking whether the mouse is on the curve. And when using my new method, i also provide a slider to specify the resolution so that you may see the effects of various values. Here are the classes.
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionListener;
import java.awt.geom.Point2D;
import javax.swing.JCheckBox;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JSlider;
#SuppressWarnings("serial")
public class CurvePanel extends JPanel implements MouseListener,MouseMotionListener{
Point2D startPoint = new Point2D.Double(50, 50);
Point2D middlePoint = new Point2D.Double(100,80);
Point2D endPoint = new Point2D.Double(200, 200);
Point2D[] points = new Point2D[] {startPoint,middlePoint,endPoint};
QuadCurveWithMiddlePoint curve;
private Point2D movingPoint;
private boolean dragIt = false;
private boolean showControls = false;
JCheckBox useNewMethod;
JSlider resolution;
public CurvePanel() {
setPreferredSize(new Dimension(300,300));
addMouseListener(this);
addMouseMotionListener(this);
curve = new QuadCurveWithMiddlePoint();
useNewMethod = new JCheckBox("Use new \"contains\" method");
resolution = new JSlider(JSlider.HORIZONTAL,1,10,1);
useNewMethod.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
resolution.setEnabled(useNewMethod.isSelected());
}
});
useNewMethod.setSelected(false);
resolution.setEnabled(false);
setCurve();
}
private void setCurve() {
curve.setCurveWithMiddlePoint(startPoint, middlePoint, endPoint);
}
public static void main(String[] args) {
JFrame f = new JFrame("Test");
CurvePanel panel = new CurvePanel();
f.getContentPane().setLayout(new BorderLayout());
f.getContentPane().add(panel.useNewMethod,BorderLayout.NORTH);
f.getContentPane().add(panel,BorderLayout.CENTER);
f.getContentPane().add(panel.resolution,BorderLayout.SOUTH);
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.pack();
f.setVisible(true);
}
#Override
public void mouseClicked(MouseEvent e) {}
#Override
public void mouseEntered(MouseEvent e) {}
#Override
public void mouseExited(MouseEvent e) {}
#Override
public void mousePressed(MouseEvent e) {
for (Point2D point : points) {
if (e.getPoint().distance(point) <= 2) {
movingPoint = point;
dragIt = true;
}
}
}
#Override
public void mouseReleased(MouseEvent e) {
dragIt = false;
}
#Override
public void mouseDragged(MouseEvent e) {
if (dragIt) {
movingPoint.setLocation(e.getPoint());
setCurve();
repaint();
}
}
#Override
public void mouseMoved(MouseEvent e) {
if (useNewMethod.isSelected())
showControls = curve.pointOnCurve(e.getPoint(), 2, resolution.getValue()/100.0);
else
showControls = curve.intersects(e.getX()-2, e.getY()-2, 4, 4);
repaint();
}
#Override
public void paintComponent(Graphics g) {
Graphics2D g2 = (Graphics2D)g;
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
g2.setPaint(Color.white);
g2.fillRect(0, 0, getWidth(), getHeight());
g2.setPaint(Color.black);
g2.draw(curve);
if (showControls)
for (Point2D point : points) {
g2.setPaint(Color.black);
g2.drawOval((int)point.getX()-2, (int)point.getY()-2, 4, 4);
g2.setPaint(Color.red);
g2.fillOval((int)point.getX()-2, (int)point.getY()-2, 4, 4);
}
}
}
And also :
import java.awt.geom.Point2D;
import java.awt.geom.QuadCurve2D.Double;
#SuppressWarnings("serial")
public class QuadCurveWithMiddlePoint extends Double {
private Point2D middlePoint = new Point2D.Double();
private final double L = 0.5;
public QuadCurveWithMiddlePoint(double x1,double y1, double xm, double ym, double x2, double y2) {
super(x1,y1,xm,ym,x2,y2);
setMiddlePoint(xm, ym);
}
public QuadCurveWithMiddlePoint() {
this(0,0,0,0,0,0);
}
public Point2D getMiddlePoint() {
calculateMiddlePoint();
return middlePoint;
}
public void setMiddlePoint(double middleX, double middleY) {
setCurve(getP1(), getControlPointByMiddle(middleX, middleY), getP2());
calculateMiddlePoint();
}
public void setMiddlePoint(Point2D middle) {
setMiddlePoint(middle.getX(),middle.getY());
}
private Point2D getControlPointByMiddle(double middleX,double middleY) {
double cpx = (middleX-(L*L-2*L+1)*x1-(L*L)*x2)/(-2*L*L+2*L);
double cpy = (middleY-(L*L-2*L+1)*y1-(L*L)*y2)/(-2*L*L+2*L);
return new Point2D.Double(cpx,cpy);
}
private Point2D calculatePoint(double position) {
if (position<0 || position>1)
return null;
double middlex = (position*position-2*position+1)*x1+(-2*position*position+2*position)*ctrlx+(position*position)*x2;
double middley = (position*position-2*position+1)*y1+(-2*position*position+2*position)*ctrly+(position*position)*y2;
return new Point2D.Double(middlex,middley);
}
public void calculateMiddlePoint() {
middlePoint.setLocation(calculatePoint(L));
}
public void setCurveWithMiddlePoint(double xx1,double yy1, double xxm, double yym, double xx2, double yy2) {
setCurve(xx1, yy1, xxm, yym, xx2, yy2);
setMiddlePoint(xxm,yym);
}
public void setCurveWithMiddlePoint(Point2D start, Point2D middle, Point2D end) {
setCurveWithMiddlePoint(start.getX(),start.getY(),middle.getX(),middle.getY(),end.getX(),end.getY());
}
public boolean pointOnCurve(Point2D point, double accuracy, double step) {
if (accuracy<=0)
return false;
if (step<=0 || step >1)
return false;
boolean oncurve = false;
double current = 0;
while (!oncurve && current <= 1) {
if (calculatePoint(current).distance(point)<accuracy)
oncurve = true;
current += step;
}
return oncurve;
}
}
If you want to know how i made the class, do a search for basic linear algebra and also search Wikipedia for Bézier curves.