My boolean drawFlag is being set to false in my code with nothing visible actually telling it to change value to false. This is preventing the code inside method mouseDragged(mouseEvent) to execute. If someone could point out what's making the flag become false so this would stop happening? Thanks.
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
public class DrawAndDrag {
public static void main(String[] args) throws InterruptedException {
GraphicsFrame window = new GraphicsFrame("Draw Rectangle");
window.init();
}
}
class GraphicsFrame extends JFrame {
public GraphicsFrame(String title) {
super(title);
}
public void init() {
Container pane = this.getContentPane();
pane.add(new GraphicsContent().init());
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.setSize(600, 600);
this.setVisible(true);
}
}
class GraphicsContent extends JPanel {
private int xStart, yStart;
private int width, height;
public JPanel init() {
this.setBackground(Color.WHITE);
this.addMouseListener(new MouseDrag());
this.addMouseMotionListener(new MouseDrag());
return this;
}
public void paintComponent(Graphics g) {
super.paintComponent(g);
g.setColor(Color.BLUE);
g.fillRect(xStart, yStart, width, height);
}
class MouseDrag implements MouseListener, MouseMotionListener {
private boolean drawFlag;
public void mousePressed(MouseEvent e) {
if(isOutside(e)) {
this.drawFlag = true;
xStart = e.getX();
yStart = e.getY();
width = 0; height = 0;
System.out.println(drawFlag);
}else {
// this.drawFlag = false;
}
}
public void mouseDragged(MouseEvent e) {
System.out.println(drawFlag);
if(drawFlag) {
width = e.getX() - xStart;
height = e.getY() - yStart;
repaint();
}
}
public boolean isOutside(MouseEvent e) {
int xMin = Math.min(xStart, xStart + width); int yMin = Math.min(yStart, yStart + height);
int xMax = Math.max(xStart, xStart + width); int yMax = Math.max(yStart, yStart + height);
if((e.getX() < xMin || e.getX() > xMax)
|| (e.getY() < yMin || e.getY() > yMax)) {
return true;
}else {
return false;
}
}
public void mouseEntered(MouseEvent e) {}
public void mouseExited(MouseEvent e) {}
public void mouseClicked(MouseEvent e) {}
public void mouseReleased(MouseEvent e) {}
public void mouseMoved(MouseEvent e) {}
}
}
Try to move drawFlag attribute from the inner class MouseDrag to the outer class GraphicsContent as follow
class GraphicsContent extends JPanel {
private int xStart, yStart;
private int width, height;
private volatile boolean drawFlag;
// other code
}
However as you drag, the value is constantly being reported as being false
You've got two listeners. One is a motion listener:
this.addMouseListener(new MouseDrag());
this.addMouseMotionListener(new MouseDrag());
mousePressed will not be called on a motion listener, so it will always be false in the drag event.
I expect what you meant is this:
MouseDrag listener = new MouseDrag();
this.addMouseListener(listener);
this.addMouseMotionListener(listener);
Are you sure you need two MouseDrag elements? I.e. using something like
public JPanel init() {
this.setBackground(Color.WHITE);
MouseDrag md = new MouseDrag();
this.addMouseListener(md);
this.addMouseMotionListener(md);
return this;
}
I can at least plot a blue square....
Related
I am making Conways Game of Life. In the mouse listener I want the cell to appear/disappear on the screen when I click once. I use a 40x40 boolean array (gameState) of 20x20 pixel cells. I want to paint the squares in my paint method using the co-ordinates of my mouse which i get in its clicked method. However, I am getting a null-pointer exception at line 71 and do not know what to do to solve it.
Main
import javax.swing.*;
import java.awt.*;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.image.BufferStrategy;
public class mainApplication extends JFrame implements Runnable, MouseListener {
private static final Dimension windowsize = new Dimension(80, 600);
private BufferStrategy strategy;
private Graphics offscreenGraphics;
private static boolean isGraphicsInitialised = false;
private static int rows = 40;
private static int columns = 40;
private static int height = windowsize.height;
private static int width = windowsize.width;
private static Cells cells;
private int xArrayElement,yArrayElement, xPosition, yPosition;
private static boolean gameState[][] = new boolean[rows][columns];
public mainApplication() {
System.out.println(System.getProperty("user.dir"));
setDefaultCloseOperation(EXIT_ON_CLOSE);
Dimension screensize = java.awt.Toolkit.getDefaultToolkit().getScreenSize();
int x = screensize.width / 2 - windowsize.width / 2;
int y = screensize.height / 2 - windowsize.height / 2;
setBounds(x, y, screensize.width, screensize.height);
setVisible(true);
createBufferStrategy(2);
strategy = getBufferStrategy();
offscreenGraphics = strategy.getDrawGraphics();
isGraphicsInitialised = true;
// MouseEvent mouseEvent = new MouseEvent();
addMouseListener(this);
// addMouseMotionListener(MouseEvent);
Thread t = new Thread(this);
t.start();
}
public void mousePressed(MouseEvent e) { }
public void mouseReleased(MouseEvent e) { }
public void mouseEntered(MouseEvent e) { }
public void mouseExited(MouseEvent e) { }
public void mouseClicked(MouseEvent e) {
if(e.getClickCount() == 1){
xPosition = e.getX();
yPosition = e.getY();
cells.setPosition(xPosition,yPosition);
xArrayElement = (xPosition/20);
yArrayElement = (yPosition/20);
if(gameState[xArrayElement][yArrayElement]){
gameState[xArrayElement][yArrayElement] = false;
}
else if (!gameState[xArrayElement][yArrayElement]) {
gameState[xArrayElement][yArrayElement] = true;
}
}
}
#Override
public void run() {
while (true) {
try { //threads entry point
Thread.sleep(20); //forces us to catch exception
}
catch (InterruptedException e) {
}
}
}
public void paint(Graphics g) {
if (isGraphicsInitialised) {
g = strategy.getDrawGraphics();
g.setColor(Color.BLACK);
g.fillRect(0, 0, 800, 800);
if (gameState[xArrayElement][yArrayElement]) {
g.setColor(Color.WHITE);
cells.paint(g);
}
else if (!gameState[xArrayElement][yArrayElement]) {
g.setColor(Color.BLACK);
g.fillRect(xPosition, yPosition, 20, 20);
}
strategy.show();
}
}
public static void main(String[]args){
mainApplication test = new mainApplication();
}
}
Cells class
import java.awt.*;
public class Cells {
int x;
int y;
public Cells(){
}
public void setPosition(int xi, int xj){
x = xi;
y = xi;
System.out.println(xi);
System.out.println("sjdkgffdjv" + y);
}
public boolean cellState(boolean visible){
return visible;
}
public void paint(Graphics g){
g.drawRect(x, y, 20,20);
}
}
It's because you haven't initialized your cells variable in Main class..
So try this
private static Cells cells = new Cells();
As #nullPointer has pointed out (sorry, dad joke) you're getting a NPE because you haven't initialized the class member Cells. There are also a few other points to make that might unrelated to the question.
Don't create that thread
Swing already uses a thread to handle UI events and drawing so creating another thread is dangerous.
Make Cells immutable
Cells should be immutable. At no point should you need to set the position of a cell. If you need to change where a Cell is at, just dispose of the object and create a new one at that position.
These are the specific instruction but they are kind of confusing to me (are the instructions confusing/ambiguous or am I just not getting it?)
write a method public static void draw shooter(Graphics g, Color c);
call draw shooter using the shooter color as the last parameter in drawAll(?)
test the program you should see a red disk centered near the bottom of the screen(?)
import java.awt.*;
public class Project2{
public static final int PANEL_WIDTH = 300;
public static final int PANEL_HEIGHT = 300;
public static final int SLEEP_TIME = 50;
public static Color SHOOTER_COLOR = Color.RED;
public static Color BACKGROUND_COLOR = Color.WHITE;
public static final int SHOOTER_SIZE = 20; //diameter of the shooter
public static final int GUN_SIZE = 10; //length og the gun
public static final int SHOOTER_POSITION_Y = PANEL_HEIGHT - SHOOTER_SIZE;
public static final int SHOOTER_INITIAL_POSITION_X = 150;
int shooterPosition;
public static void initialize(){
int shooterPositionX = SHOOTER_INITIAL_POSITION_X;
}
public static void main(String[] args) {
DrawingPanel panel = new DrawingPanel(PANEL_WIDTH, PANEL_HEIGHT);
Graphics g = panel.getGraphics( );
initialize();
startGame(panel, g);
drawShooter(g, SHOOTER_COLOR);
}
public static void drawShooter(Graphics g, Color C){
g.setColor(Color);
g.fillOval(shooterPosition, SHOOTER_POSITION_Y, SHOOTER_SIZE, SHOOTER_SIZE);
}
public static void drawAll(Graphics g){
g.drawString("Project 2 by Jasmine Ramirez", 10, 15);
}
public static void startGame(DrawingPanel panel, Graphics g) {
for (int i = 0; i <= 10000; i++) {
panel.sleep(SLEEP_TIME);
drawAll(g);
}
}
}
this is my code I guessed that I needed to draw and color in a circle inside the method but I am getting errors with the g.setColor inside the method and I'm not sure what the second step means. Thanks just started learning to program.
Drawing Panel
import java.awt.*;
import java.awt.event.*;
import java.awt.image.*;
import javax.swing.*;
import javax.swing.event.*;
import java.util.ArrayList;
public class DrawingPanel implements ActionListener {
private static final String versionMessage =
"Drawing Panel version 1.1, January 25, 2015";
private static final int DELAY = 100; // delay between repaints in millis
private static final boolean PRETTY = false; // true to anti-alias
private static boolean showStatus = false;
private static final int MAX_KEY_BUF_SIZE = 10;
private int width, height; // dimensions of window frame
private JFrame frame; // overall window frame
private JPanel panel; // overall drawing surface
private BufferedImage image; // remembers drawing commands
private Graphics2D g2; // graphics context for painting
private JLabel statusBar; // status bar showing mouse position
private volatile MouseEvent click; // stores the last mouse click
private volatile boolean pressed; // true if the mouse is pressed
private volatile MouseEvent move; // stores the position of the mouse
private ArrayList<KeyInfo> keys;
// construct a drawing panel of given width and height enclosed in a window
public DrawingPanel(int width, int height) {
this.width = width;
this.height = height;
keys = new ArrayList<KeyInfo>();
image = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);
statusBar = new JLabel(" ");
statusBar.setBorder(BorderFactory.createLineBorder(Color.BLACK));
statusBar.setText(versionMessage);
panel = new JPanel(new FlowLayout(FlowLayout.CENTER, 0, 0));
panel.setBackground(Color.WHITE);
panel.setPreferredSize(new Dimension(width, height));
panel.add(new JLabel(new ImageIcon(image)));
click = null;
move = null;
pressed = false;
// listen to mouse movement
MouseInputAdapter listener = new MouseInputAdapter() {
public void mouseMoved(MouseEvent e) {
pressed = false;
move = e;
if (showStatus)
statusBar.setText("moved (" + e.getX() + ", " + e.getY() + ")");
}
public void mousePressed(MouseEvent e) {
pressed = true;
move = e;
if (showStatus)
statusBar.setText("pressed (" + e.getX() + ", " + e.getY() + ")");
}
public void mouseDragged(MouseEvent e) {
pressed = true;
move = e;
if (showStatus)
statusBar.setText("dragged (" + e.getX() + ", " + e.getY() + ")");
}
public void mouseReleased(MouseEvent e) {
click = e;
pressed = false;
if (showStatus)
statusBar.setText("released (" + e.getX() + ", " + e.getY() + ")");
}
public void mouseEntered(MouseEvent e) {
// System.out.println("mouse entered");
panel.requestFocus();
}
};
panel.addMouseListener(listener);
panel.addMouseMotionListener(listener);
new DrawingPanelKeyListener();
g2 = (Graphics2D)image.getGraphics();
g2.setColor(Color.BLACK);
if (PRETTY) {
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
g2.setStroke(new BasicStroke(1.1f));
}
frame = new JFrame("Drawing Panel");
frame.setResizable(false);
try {
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); // so that this works in an applet
} catch (Exception e) {}
frame.getContentPane().add(panel);
frame.getContentPane().add(statusBar, "South");
frame.pack();
frame.setVisible(true);
toFront();
frame.requestFocus();
// repaint timer so that the screen will update
new Timer(DELAY, this).start();
}
public void showMouseStatus(boolean f) {
showStatus = f;
}
public void addKeyListener(KeyListener listener) {
panel.addKeyListener(listener);
panel.requestFocus();
}
// used for an internal timer that keeps repainting
public void actionPerformed(ActionEvent e) {
panel.repaint();
}
// obtain the Graphics object to draw on the panel
public Graphics2D getGraphics() {
return g2;
}
// set the background color of the drawing panel
public void setBackground(Color c) {
panel.setBackground(c);
}
// show or hide the drawing panel on the screen
public void setVisible(boolean visible) {
frame.setVisible(visible);
}
// makes the program pause for the given amount of time,
// allowing for animation
public void sleep(int millis) {
panel.repaint();
try {
Thread.sleep(millis);
} catch (InterruptedException e) {}
}
// close the drawing panel
public void close() {
frame.dispose();
}
// makes drawing panel become the frontmost window on the screen
public void toFront() {
frame.toFront();
}
// return panel width
public int getWidth() {
return width;
}
// return panel height
public int getHeight() {
return height;
}
// return the X position of the mouse or -1
public int getMouseX() {
if (move == null) {
return -1;
} else {
return move.getX();
}
}
// return the Y position of the mouse or -1
public int getMouseY() {
if (move == null) {
return -1;
} else {
return move.getY();
}
}
// return the X position of the last click or -1
public int getClickX() {
if (click == null) {
return -1;
} else {
return click.getX();
}
}
// return the Y position of the last click or -1
public int getClickY() {
if (click == null) {
return -1;
} else {
return click.getY();
}
}
// return true if a mouse button is pressed
public boolean mousePressed() {
return pressed;
}
public synchronized int getKeyCode() {
if (keys.size() == 0)
return 0;
return keys.remove(0).keyCode;
}
public synchronized char getKeyChar() {
if (keys.size() == 0)
return 0;
return keys.remove(0).keyChar;
}
public synchronized int getKeysSize() {
return keys.size();
}
private synchronized void insertKeyData(char c, int code) {
keys.add(new KeyInfo(c,code));
if (keys.size() > MAX_KEY_BUF_SIZE) {
keys.remove(0);
// System.out.println("Dropped key");
}
}
private class KeyInfo {
public int keyCode;
public char keyChar;
public KeyInfo(char keyChar, int keyCode) {
this.keyCode = keyCode;
this.keyChar = keyChar;
}
}
private class DrawingPanelKeyListener implements KeyListener {
int repeatCount = 0;
public DrawingPanelKeyListener() {
panel.addKeyListener(this);
panel.requestFocus();
}
public void keyPressed(KeyEvent event) {
// System.out.println("key pressed");
repeatCount++;
if ((repeatCount == 1) || (getKeysSize() < 2))
insertKeyData(event.getKeyChar(),event.getKeyCode());
}
public void keyTyped(KeyEvent event) {
}
public void keyReleased(KeyEvent event) {
repeatCount = 0;
}
}
}
1st Error
In your drawShooter() method you do:
g.setColor(Color)
This is incorrect, since you need to pass an instance of the class Color not the class itself.
So instead use this:
g.setColor(C);
2nd Error
change the shooterPosition to static so that it can be accessed by a static method.
I assume that the method initialize() is also wrong because you are declaring a new shooterPosition int for no reason so do these changes:
int shooterPosition;
To:
public static int shooterPosition;
And
public static void initialize(){
int shooterPositionX = SHOOTER_INITIAL_POSITION_X;
}
To:
public static void initialize() {
shooterPosition = SHOOTER_INITIAL_POSITION_X;
}
3rd Error
In startGame() you are looping for 10000 times and each time you are waiting for a bit more than 1/20th of a second, which means that you will have to wait for almost 10 minutes until the red circle is drawn. So you have two options.
1st option: decrease the amount of iterations or even better remove the loop.
public static void startGame(DrawingPanel panel, Graphics g) {
for (int i = 0; i <= 10000; i++) {
panel.sleep(SLEEP_TIME);
drawAll(g);
}
}
To:
public static void startGame(DrawingPanel panel, Graphics g) {
for (int i = 0; i <= 1; i++) {
panel.sleep(SLEEP_TIME);
drawAll(g);
}
}
or
public static void startGame(DrawingPanel panel, Graphics g) {
panel.sleep(SLEEP_TIME);
drawAll(g);
}
2nd option: execute the drawShooter() method before the startGame() method or don't execute the startGame() at all.
startGame(panel, g); drawShooter(g, SHOOTER_COLOR);
To:
drawShooter(g, SHOOTER_COLOR);
startGame(panel, g);
or
drawShooter(g, SHOOTER_COLOR);
Didn't you ask this same question or something similar to it yesterday? And you're passing in the class name to g.setColor(Color) method and need to pass in the parameter which holds the object: g.setColor(C)
Your use of Graphics is not good, as you shouldn't use a Graphics obtained from a component via getGraphics(), but I'm guessing that it's because that's what your instructor told you to do. Same for use of a while (true) loop. Instead you should use a Swing Timer.
Like stated before g.setcolor(c) is required
check your error msgs since it allows you to gather that error and the shooterPosition error(its not public so cant be used inside a method)
I try to do make when we click the frame, it shows the coordinates of the click point. And i did this:
public void mouseClicked(MouseEvent e) {
int x = e.getX();
int y = e.getY();
j1.setLocation(x, y);
j1.setText("(" + x + ", " + y + ")");
}
public void mousePressed(MouseEvent e) {
int x = e.getX();
int y = e.getY();
j1.setLocation(x, y);
j1.setText("(" + x + ", " + y + ")");
}
public void mouseDragged(MouseEvent e) {}
public void mouseMoved(MouseEvent e) {}
public void mouseEntered(MouseEvent e) {}
public void mouseExited(MouseEvent e) {}
public void mouseReleased(MouseEvent e) {}
But when i click it shows the coordinates first at the center then the click point, 2 times. But i just want only one and at the click point. Where did i mistake, what shoul i do?
Just use mousePressed and that's it. When you click the mouse, 3 methods are often called -- mousePressed, mouseReleased and if the mouse does not move between press and release, mouseClicked. You want to respond to just one of these methods.
So change to:
public void mouseClicked(MouseEvent e) {} // leave this empty
public void mousePressed(MouseEvent e) {
int x = e.getX();
int y = e.getY();
j1.setLocation(x, y);
j1.setText("(" + x + ", " + y + ")");
// also be sure to tell your container to re-position components
revalidate();
repaint();
}
As a side recommendation, note that rather than having a class implement MouseListener, you could have it extend MouseAdapter, and that way your class wouldn't have to have all those empty MouseListener interface methods.
For example:
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import javax.swing.*;
#SuppressWarnings("serial")
public class MousePosition extends JPanel {
private static final int PREF_W = 600;
private static final int PREF_H = PREF_W;
// format String for display String
protected static final String FORMAT = "(%d, %d)";
private int xPos = -40;
private int yPos = -40;
private String displayText = "";
public MousePosition() {
addMouseListener(new MouseAdapter() {
#Override
public void mousePressed(MouseEvent e) {
xPos = e.getX();
yPos = e.getY();
// use FORMAT String to create our display text
displayText = String.format(FORMAT, xPos, yPos);
repaint();
}
});
}
#Override
public Dimension getPreferredSize() {
if (isPreferredSizeSet()) {
return super.getPreferredSize();
}
return new Dimension(PREF_W, PREF_H);
}
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
g.drawString(displayText, xPos, yPos);
}
private static void createAndShowGui() {
MousePosition mainPanel = new MousePosition();
JFrame frame = new JFrame("MousePosition");
frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
frame.getContentPane().add(mainPanel);
frame.pack();
frame.setLocationByPlatform(true);
frame.setVisible(true);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGui();
}
});
}
}
Here i have a code which draws a rectangle on the mouseClicked position using the paintComponent.I can get the output message but anything related to graphics and .draw() wont work.
Code:
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public final class testclass extends JFrame {
static JPanel p;
Timer t;
int x = 1;
int y = 1;
int xspeed = 1;
int yspeed = 1;
public testclass() {
initComponents();
this.setBounds(100, 300, 500, 500);
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
t.start();
this.add(p);
}
public void initComponents() {
final ActionListener action = new ActionListener() {
public void actionPerformed(ActionEvent evt) {
System.out.println("Hello!");
p.repaint();
}
};
t = new Timer(50, action);
p = new JPanel() {
public void paintComponent(Graphics g) {
super.paintComponent(g);
final Graphics2D gD = (Graphics2D) g;
moveBALL();
gD.drawOval(x, y, 25, 25);
p.addMouseListener(new MouseListener() {
#Override
public void mouseReleased(MouseEvent e) {
System.out.println("a");
}
#Override
public void mousePressed(MouseEvent e) {
System.out.println("b");
}
#Override
public void mouseExited(MouseEvent e) {
System.out.println("c");
}
#Override
public void mouseEntered(MouseEvent e) {
System.out.println("d");
}
#Override
public void mouseClicked(MouseEvent e) {
gD.drawRect(e.getX(), e.getY(), 10, 60);
gD.setColor(Color.green);
System.out.println("clicked");
}
});
}
void moveBALL() {
x = x + xspeed;
y = y + yspeed;
if (x < 0) {
x = 0;
xspeed = -xspeed;
} else if (x > p.getWidth() - 20) {
x = p.getWidth() - 20;
xspeed = -xspeed;
}
if (y < 0) {
y = 0;
yspeed = -yspeed;
} else if (y > p.getHeight() - 20) {
y = p.getHeight() - 20;
yspeed = -yspeed;
}
}
};
}
public static void main(String args[]) {
EventQueue.invokeLater(new Runnable() {
public void run() {
new testclass().setVisible(true);
p.setBackground(Color.WHITE);
}
});
}
}
What is the proper way to implement a mouseListener() in this program?
Thanks.
Some suggestions on current code:
Watch class naming scheme i.e testclass should be TestClass or even better Test (but thats nit picking). All class names begin with capital letter and each new word thereafter is capitalized.
Dont extend JFrame unnecessarily.
Dont call setBounds on JFrame rather use appropriate LayoutManager and/or override getPreferredSize() of JPanel and return dimensions which fits its content.
Always call pack() on JFrame before setting it visible (taking above into consideration).
Use MouseAdapter vs MouseListener
Dont call moveBall() in paintComponent rather call it in your Timer which repaints the screen, not only slightly better design but we also should not do possibly long running tasks in paint methods.
As for your problem I think your logic is a bit skewed.
One approach would see the Rectangle (or Rectangle2D) get replaced by its own custom class (which will allow us to store attributes like color etc). Your ball would also have its own class which has the method moveBall() and its attributes like x and y position etc. On every repaint() your JPanel would call the method to move the ball, the JPanel itself could wrap the moveBall() in its own public method which we could than call from the timer which repaints the screen.
Here is an example of your code with above fixes implemented (please analyze it and if you have any questions let me know):
import java.awt.*;
import java.awt.event.*;
import java.awt.geom.Ellipse2D;
import java.awt.geom.Rectangle2D;
import java.util.ArrayList;
import javax.swing.*;
public class Test {
private MyPanel p;
private Timer t;
public Test() {
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
initComponents();
frame.add(p);
frame.pack();
frame.setVisible(true);
t.start();
}
private void initComponents() {
final ActionListener action = new ActionListener() {
#Override
public void actionPerformed(ActionEvent evt) {
p.moveEntities();//moves ball etc
p.repaint();
}
};
t = new Timer(50, action);
p = new MyPanel();
p.addMouseListener(new MouseAdapter() {
#Override
public void mouseClicked(MouseEvent e) {
p.addEntity(e.getX(), e.getY(), 10, 50, Color.GREEN);
System.out.println("clicked");
}
});
p.setBackground(Color.WHITE);
}
public static void main(String args[]) {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
new Test();
}
});
}
}
class MyPanel extends JPanel {
int width = 300, height = 300;
ArrayList<MyRectangle> entities = new ArrayList<>();
MyBall ball = new MyBall(10, 10, 25, 25, Color.RED, width, height);
void addEntity(int x, int y, int w, int h, Color c) {
entities.add(new MyRectangle(x, y, w, h, c));
}
void moveEntities() {
ball.moveBALL();
}
#Override
protected void paintComponent(Graphics grphcs) {
super.paintComponent(grphcs);
Graphics2D g2d = (Graphics2D) grphcs;
g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
g2d.setColor(ball.getColor());
g2d.fillOval((int) ball.x, (int) ball.y, (int) ball.width, (int) ball.height);
for (MyRectangle entity : entities) {
g2d.setColor(entity.getColor());
g2d.fillRect((int) entity.x, (int) entity.y, (int) entity.width, (int) entity.height);
}
}
#Override
public Dimension getPreferredSize() {
return new Dimension(width, height);
}
}
class MyRectangle extends Rectangle2D.Double {
Color color;
public MyRectangle(double x, double y, double w, double h, Color c) {
super(x, y, w, h);
color = c;
}
public void setColor(Color color) {
this.color = color;
}
public Color getColor() {
return color;
}
}
class MyBall extends Ellipse2D.Double {
int xspeed = 1;
int yspeed = 1;
Color color;
private final int maxWidth;
private final int maxHeight;
public MyBall(double x, double y, double w, double h, Color c, int maxWidth, int maxHeight) {
super(x, y, w, h);
color = c;
this.width = w;//set width and height of Rectangle2D
this.height = h;
//set max width and height ball can move
this.maxWidth = maxWidth;
this.maxHeight = maxHeight;
}
public void setColor(Color color) {
this.color = color;
}
public Color getColor() {
return color;
}
void moveBALL() {
x = x + xspeed;
y = y + yspeed;
if (x < 0) {
x = 0;
xspeed = -xspeed;
} else if (x > maxWidth - ((int) getWidth() / 2)) {// i dont like hard coding values its not good oractice and resuaibilty is diminshed
x = maxWidth - ((int) getWidth() / 2);
xspeed = -xspeed;
}
if (y < 0) {
y = 0;
yspeed = -yspeed;
} else if (y > maxHeight - ((int) getHeight() / 2)) {
y = maxHeight - ((int) getHeight() / 2);
yspeed = -yspeed;
}
}
}
First of all the paint component is called every time swing needs to redraw the component.
And you are adding a new instance of mouse listener to the panel every time the paint is called.
Just move the line
p.addMouseListener(new MouseListener() {...}
out of the paint component, preferably after the initialization of the panel.
default template is
JPanel p = new JPanel(){
#Override
public void paintComponent(Graphics g) {
}
};
p.addMouseListener(new MouseListener() or new MouseAdapter()
//Your overridden methods
});
Hope this helps.
I'm attempting to implement the dragging functionality of shapes on a canvas. My Shape class inherits from JPanel.
Absolutely nothing happens when I click on a shape, drag it and let go of the mouse button. It just remains where it was originally. Any ideas?
You need a few basic things:
A field for the shape itself (you already had)
Fields to keep track of the offset of the click within the shape (already had)
A field to keep track of if you're dragging
Overwrite the paintComponent method to paint your shape
A MouseListener and MouseMotionListener added to the Panel (MouseAdapter does both of these)
Here's a basic working example.
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class DrawTest extends JPanel{
//Shape doesn't have a location field - you'd have to keep track of
//this yourself if you're set on using the shape interface
private Rectangle shape = new Rectangle(100, 100);
// The location within the shape you clicked
private int xOffset = 0;
private int yOffset = 0;
// To indicate dragging is happening
boolean isDragging = false;
public DrawTest(){
MouseAdapter listener = new MouseAdapter() {
#Override
public void mousePressed(MouseEvent e) {
// Starts dragging and calculates offset
if(shape.contains(e.getPoint())){
isDragging = true;
xOffset = e.getPoint().x - shape.x;
yOffset = e.getPoint().y - shape.y;
}
}
#Override
public void mouseReleased(MouseEvent e) {
// Ends dragging
isDragging = false;
}
#Override
public void mouseDragged(MouseEvent e) {
// Moves the shape - doesn't actually need to be a method
// but is because you had it as one
if(isDragging){
moveShape(e);
}
}
private void moveShape(MouseEvent e) {
Point newLocation = e.getPoint();
newLocation.x -= xOffset;
newLocation.y -= yOffset;
shape.setLocation(newLocation);
repaint();
}
};
//Add a mouse mostion listener (for dragging) and regular listener (for clicking)
addMouseListener(listener);
addMouseMotionListener(listener);
}
// So we have a play area to work with
public Dimension getPreferredSize(){
return new Dimension(400,300);
}
//Paints the shape
public void paintComponent(Graphics g){
super.paintComponent(g);
g.clearRect(0,0,getWidth(), getHeight());
g.fillRect(shape.x, shape.y, shape.width, shape.height);
}
public static void main(String[] args)
{
final JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(new DrawTest());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
}
Tried a small simple example
Dragging the rectangle will make it move with the cursor it also checks the bounds so the rectangle cannot be dragged off screen:
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Rectangle;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
public class ShapeMover {
public ShapeMover() {
JFrame frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setTitle("Shape Mover");
initComponents(frame);
frame.pack();
frame.setVisible(true);
}
public static void main(String s[]) {
SwingUtilities.invokeLater(new Runnable() {
#Override
public void run() {
new ShapeMover();
}
});
}
private void initComponents(JFrame frame) {
frame.getContentPane().add(new DragPanel());
}
}
class DragPanel extends JPanel {
Rectangle rect = new Rectangle(0, 0, 100, 50);
int preX, preY;
boolean isFirstTime = true;
Rectangle area;
boolean pressOut = false;
private Dimension dim = new Dimension(400, 300);
public DragPanel() {
setBackground(Color.white);
addMouseMotionListener(new MyMouseAdapter());
addMouseListener(new MyMouseAdapter());
}
#Override
public Dimension getPreferredSize() {
return dim;
}
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g;
if (isFirstTime) {
area = new Rectangle(dim);
rect.setLocation(50, 50);
isFirstTime = false;
}
g2d.setColor(Color.black);
g2d.fill(rect);
}
boolean checkRect() {
if (area == null) {
return false;
}
if (area.contains(rect.x, rect.y, 100, 50)) {
return true;
}
int new_x = rect.x;
int new_y = rect.y;
if ((rect.x + 100) > area.getWidth()) {
new_x = (int) area.getWidth() - 99;
}
if (rect.x < 0) {
new_x = -1;
}
if ((rect.y + 50) > area.getHeight()) {
new_y = (int) area.getHeight() - 49;
}
if (rect.y < 0) {
new_y = -1;
}
rect.setLocation(new_x, new_y);
return false;
}
private class MyMouseAdapter extends MouseAdapter {
#Override
public void mousePressed(MouseEvent e) {
preX = rect.x - e.getX();
preY = rect.y - e.getY();
if (rect.contains(e.getX(), e.getY())) {
updateLocation(e);
} else {
pressOut = true;
}
}
#Override
public void mouseDragged(MouseEvent e) {
if (!pressOut) {
updateLocation(e);
} else {
}
}
#Override
public void mouseReleased(MouseEvent e) {
if (rect.contains(e.getX(), e.getY())) {
updateLocation(e);
} else {
pressOut = false;
}
}
public void updateLocation(MouseEvent e) {
rect.setLocation(preX + e.getX(), preY + e.getY());
checkRect();
repaint();
}
}
}
Reference:
http://www.java2s.com/Code/Java/Event/MoveShapewithmouse.htm