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How to create a new object(rectangle) everytime when the button is clicked?

I want to create a shape Object(in my case the object is a rectangle). Each time I click a button. Currently, I'm able to make it appear just once. The idea would be that each time I click the button, a new rectangle Object is created, additional to the old one. Therefore, if I click the button 5 times, I should have 5 rectangles.
I tried to do it with an ArrayList, but still, there is just one rectangle appearing. Does someone know how to do it!
Thank you very much in advance!
This is the main class, FYI there is also a rectangle Class(not attached)
import controlP5.*;
ControlP5 cp5;
Rectangle rect; // rect begins as null
Button rc;
ArrayList<Rectangle> rectList;
void setup(){
size(1000, 1000);
rectList = new ArrayList<Rectangle>();
cp5 = new ControlP5(this);
rc = cp5.addButton("Rectangle").
setPosition(5, 4).
setColorBackground(color(52, 55, 76));
rc.onRelease(new CallbackListener() {
public void controlEvent(CallbackEvent theEvent) {
// only create the rectangle when the button is clicked
rect = new Rectangle(100, 100, 100, 100);
}
});
}
void draw(){
background(255);
// if the rect exists, draw it on the screen
if(rect != null) {
rect.displayRect();
showRect();
}
for(int i = 0; i < rectList.size(); i++){
//((Rectangle)rectList.get(i)).update();
((Rectangle)rectList.get(i)).displayRect();
}
}
public void showRect(){
for(Rectangle r: rectList){
r.displayRect();
rect(r.getXvalue(), r.getYvalue(), r.getWvalue(), r.getHvalue());
}
}

You have a list, but you never add anything to that list. The list remains empty.
Drop the member field rect, delete this line:
Rectangle rect; // rect begins as null
When you instantiate a new Rectangle, immediately add it to the list.
rc.onRelease( new CallbackListener() {
public void controlEvent(CallbackEvent theEvent) {
// When the button is clicked, instantiate a new rectangle and remember it by adding to our list of rectangles.
rectList.add(
new Rectangle( 100, 100, 100, 100 )
);
}
});
Some chiding: This was not a good Question for Stack Overflow. You could easily have found this bug by using a debugger to step through the code. You would have seen that the list remains empty. Before posting, do your own debugging exhaustively.

You should post your Rectangle class to make it easier for others to test and help out.
As Basil pointed out (+1) you're only rendering a new rectangle for one frame when there's a click event.
The idea would be that each time I click the button, a new rectangle Object is created, additional to the old one. Therefore, if I click the button 5 times, I should have 5 rectangles.
This statement is a bit ambiguous. I get you'd like to render a rectangle per click, however in the click handler the rect has the exact same dimensions and coordinates. Even if you would make minor fixes, rendering 5 identical rectangles on top of each other will likely appear as if it's a single rectangle.
Regarding the code you posted, this stands out to me:
Rectangle rect; // rect begins as null: what is the purpose of the rect if you have this underneath: ArrayList<Rectangle> rectList; ?
showRect(); is called in draw(): it loops over rectList and not only calls displayRect() which I'd assume would render the current rect, but also re-renders the same data on the following line (rect(r.getXvalue(), r.getYvalue(), r.getWvalue(), r.getHvalue());)
underneath, there's a for loop over the same list calling displayRect() yet again. My guess is 2 out 3 calls to render rectangles are redundant. (Also the array list is typed therefore, no need to cast like this: (Rectangle)rectList.get(i)), rectList.get(i) should suffice)
The only other minor caveat I have is around naming: ideally you would want to stick to Java naming conventions in Processing. (For example getXValue() instead of getXvalue(), etc.)
Regarding the ControlP5 button you could use controlEvent() which is a bit simpler than setting a callback. Even simpler is to use this automatic variable plugging functionality. In short, if a function has the same name as a button's name it will be called automatically:
Automatic controller-event detection
ControlP5 offers a range of controllers that allow you to easily change and adjust values while your sketch is running. Each controller is identified by a unique name assigned when creating a controller. ControlP5 locates variables and functions inside your sketch and will link controllers to matching variables or functions automatically
(from controlP5 reference)
Here's a basic example that prints a message to console each time the button is clicked:
import controlP5.*;
ControlP5 cp5;
void setup() {
size(1000, 1000);
cp5 = new ControlP5(this);
cp5.addButton("rectangle").
setPosition(5, 4).
setColorBackground(color(52, 55, 76));
}
void draw(){
background(255);
}
void rectangle(){
println("rectangle button clicked");
}
(I've kept the name rectangle instead of Rectangle to keep in line with Java naming conventions. The text label is displayed in uppercase anyway)
Back to your main question, if you want to add new rectangle per button press and render them the code be as simple as:
import controlP5.*;
ControlP5 cp5;
ArrayList<Rectangle> rectList = new ArrayList<Rectangle>();
int x = 100;
int y = 100;
void setup() {
size(1000, 1000);
rectList = new ArrayList<Rectangle>();
cp5 = new ControlP5(this);
cp5.addButton("rectangle").
setPosition(5, 4).
setColorBackground(color(52, 55, 76));
}
void draw() {
background(255);
for (int i = 0; i < rectList.size(); i++) {
rectList.get(i).display();
}
}
void rectangle(){
rectList.add(new Rectangle(x, y, 100, 100));
// increment x, y to avoid superimposed rectangles
x += 50;
y += 50;
}
class Rectangle{
private int x, y, w, h;
Rectangle(int x, int y, int w, int h){
this.x = x;
this.y = y;
this.w = w;
this.h = h;
}
void display(){
rect(x, y, w, h);
}
// currently not used
public int getX(){
return x;
}
public int getY(){
return x;
}
public int getWidth(){
return x;
}
public int getHeight(){
return x;
}
}
Rectangle rect; stands out. If this was an OOP homework assignment or exercise perhaps the intention was to have a basic drawing app functionality where the user could have a rectangle drawing tool ?
If that's the case rect could be selection rectangle which could cloned into rectList so it persists.
You could implement rectangle selection like so:
when the mouse is pressed remember the coordinates: these are the starting point of the selection
as the mouse is dragged the end point coordinates are the current mouse coordinates, hence the selection rectangle dimensions are the difference between the current mouse coordinates and the previously stored mouse coordinates
as the mouse is released, reset the selection rectangle (so it no longer displays)
Here's a basic example sketch:
Rectangle selection = new Rectangle(0, 0, 0, 0);
void setup(){
size(1000, 1000);
}
void draw(){
background(255);
selection.display();
}
void mousePressed(){
// store selection start
selection.x = mouseX;
selection.y = mouseY;
}
void mouseDragged(){
// update selection dimension as the difference between the current mouse coordinates and the previous ones (selection x, y)
selection.w = mouseX - selection.x;
selection.h = mouseY - selection.y;
}
void mouseReleased(){
selection.w = selection.h = selection.x = selection.y = 0;
}
class Rectangle{
private int x, y, w, h;
Rectangle(int x, int y, int w, int h){
this.x = x;
this.y = y;
this.w = w;
this.h = h;
}
void display(){
rect(x, y, w, h);
}
}
Resetting the Rectangle properties to 0 could be nicely encapsulated into a method:
void reset(){
x = y = w = h = 0;
}
The release handler would also be useful to add a new rectangle to rectList which has the same properties (x, y, w, h) as the selection, but before the selection is reset. something like:
void mouseReleased(){
// add a copy of the selection to rectList
rectList.add(new Rectangle(selection.x, selection.y, selection.w, selection.h));
// reset selection
selection.reset();
}
Again, the copy functionality is something that could be nicely encapsulated as a method as well:
Rectangle copy(){
return new Rectangle(x, y, w, h);
}
Putting it all together would look like this:
import controlP5.*;
ControlP5 cp5;
ArrayList<Rectangle> rectList = new ArrayList<Rectangle>();
Rectangle selection = new Rectangle(0, 0, 0, 0);
void setup() {
size(1000, 1000);
rectList = new ArrayList<Rectangle>();
cp5 = new ControlP5(this);
cp5.addButton("rectangle").
setPosition(5, 4).
setColorBackground(color(52, 55, 76));
}
void draw() {
background(255);
// draw previous rectangles (black)
stroke(0);
for (int i = 0; i < rectList.size(); i++) {
rectList.get(i).display();
}
// draw current selection (green)
stroke(0, 192, 0);
selection.display();
}
void rectangle(){
println("selected drawing tool is rectangle");
}
void mousePressed(){
// store selection start
selection.x = mouseX;
selection.y = mouseY;
}
void mouseDragged(){
// update selection dimension as the difference between the current mouse coordinates and the previous ones (selection x, y)
selection.w = mouseX - selection.x;
selection.h = mouseY - selection.y;
}
void mouseReleased(){
// add a new rectangle to the list: a copy of the selection
rectList.add(selection.copy());
// reset selection
selection.reset();
}
class Rectangle{
private int x, y, w, h;
Rectangle(int x, int y, int w, int h){
this.x = x;
this.y = y;
this.w = w;
this.h = h;
}
void display(){
rect(x, y, w, h);
}
Rectangle copy(){
return new Rectangle(x, y, w, h);
}
void reset(){
x = y = w = h = 0;
}
}
At this stage the button is a bit redundant, however it could useful in the future if other shapes are required (e.g. an Ellipse would be an obviously simple one to implement since ellipse() has the same parameters as rect(), just need to ensure ellipseMode(CORNER) is set to use the same selection x,y coordinates the rectangle does)
Hopefully this is useful. The initial code, as mentioned before looks a bit messy, as if it's put together in a haste before a deadline.
(I assume this because it reminds me of my code as a student :))
I'd recommend taking a short walk away from the computer, remembering what the task is and pen on paper breaking the task into small, clear, easy to implement subtasks. Once that is as clear as it can be, implement one subtask at a time in isolation. Initially the code may break or get messy, but eventually it will work (and it will be easier to write compared to the whole drawing program). Once that works, cleanup the code so that all unnecessary code is removed and it's easy to move the code to another sketch and run it without errors. Repeat the process for each subtask which should result in multiple minimal sketches solving one single problem. Once all parts are solved in isolation you can start putting the code together into one main sketch, however I recommend adding one subtask code as a time and testing first. When mixing code from multiple sketches conflicts/errors may arise and it will far easier to tackle merging two sketches a time than all of the subtask sketches in one go. Best of luck !

understanding difficulties java swing

im trying to paint random (not yet) circles on a JPanel through click on a JMenu.
Im using a JTextField (and have to keep this) for some output.
Here is my Class:
class RandomDrawer extends JPanel implements ActionListener {
#Override
public void actionPerformed(ActionEvent e) {
//double x = Math.random();
//double y = Math.random();
Random generator = new Random();
int x = generator.nextInt(100)+1;
int y = generator.nextInt(100)+1;
//System.out.printf("x = %d y = %d\n", x, y);
status.setText(String.format("rnd draw x: %d y: %d", x, y));
Graphics2D gg = (Graphics2D) canvas.getGraphics();
gg.setColor(Color.BLACK);
gg.drawOval(50, 50, 50, 50);
}
}
As long i let the line
status.setText(String.format("rnd draw x: %d y: %d", x, y));
stay in there i get nothing drawn. Without it i get my circle, im not sure what the problem is. I cant figure out why nothing is drawn.
Thanks a lot
EDIT:
Hello, i tried to understand the given informations.
Sadly I have to draw using the Graphics2D class, so i guess i can not draw using shapes. So i tried this, sadly it wont draw yet, can u give me some tips?
I tried to create a new class DrawShape, my thought was that i could keep track with those objects.
In my understanding there should be a drawn oval right now
gg.drawOval(100,100,100,100);
Thank you.
class DrawShape {
public DrawShape(String string) {
// TODO Auto-generated constructor stub
}
}
class RandomDrawer extends JPanel implements ActionListener {
/* (non-Javadoc)
* #see java.awt.event.ActionListener#actionPerformed(java.awt.event.ActionEvent)
*/
private List<DrawShape> shapes = new ArrayList<DrawShape>();
public void addShape(DrawShape s) {
shapes.add(s);
repaint();
}
#Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
final Graphics2D gg = (Graphics2D) g;
gg.setColor(Color.BLACK);
gg.drawOval(100, 100, 100, 100);
}
#Override
public void actionPerformed(ActionEvent e) {
Random generator = new Random();
int x = generator.nextInt(100)+100;
int y = generator.nextInt(100)+100;
if (e.getActionCommand()==("Draw RandomCircle")) {
System.out.printf("x = %d y = %d\n", x, y);
status.setText(String.format("rnd draw x:%d y:%d ", x, y));
DrawShape circle = new DrawShape("Circle");
addShape(circle);
int count = shapes.size();
System.out.printf("objects in array: %d\n", count);
}
else if (e.getActionCommand()==("Draw RandomRectangle")) {
System.out.printf("x = %d y = %d\n", x, y);
//status.setText(String.format("rnd draw x: y: "));
//Graphics2D gg = (Graphics2D) canvas.getGraphics();
//gg.setColor(Color.BLACK);
//gg.drawRect(x, y, generator.nextInt(x), generator.nextInt(y));
}
}
}

Painting and such happens event-driven. If a a piece of a component needs to be redrawn its paintComponent method is called.
This means you need a component that nows how to draw by for instance:
public class DrawShape {
public final String text;
public final Color color;
public final Shape shape;
public DrawShape(String text, Color color, Shape shape) {
this.text = text;
this.color = color;
this.shape = shape;
}
}
public class CanvasWithShapes extends JPanel {
private List<DrawShape> shapes = new ArrayList<>();
public void addShape(DrawShape shape) {
shapes.add(shape);
}
#Override
public void paintComponent(Graphics g) {
final Graphics2D gg = (Graphics2D) g;
// Java 8: shapes.stream().forEach((shape) -> gg.draw(shape));
for (DrawShape drawShape : shapes) {
gg.setColor(drawShape.color);
gg.draw(drawShape.shape);
Rectangle bounds = shape.getBounds();
gg.drawString(shape.text, bounds.x+ 10, bounds.y + 20);
}
}
}
And then just add shapes to be redrawn a bit later.
Shape oval = ...;
c.add(oval);
c.repaint(50L); // A bit later
More detailed
A Shape has many implementations of interest like rectangle and oval.
Graphics2D can draw and fill a Shape. So in your case it would be ideal to add such a Shape. Maybe together with color and text. So I took your DrawShape class to hold these properties.
Random generator = new Random();
int x = generator.nextInt(100)+100;
int y = generator.nextInt(100)+100;
if (e.getActionCommand().equals("Draw RandomCircle")) {
System.out.printf("x = %d y = %d\n", x, y);
status.setText(String.format("rnd draw x:%d y:%d ", x, y));
int w = generator.nextInt(100) + 10;
int h = w;
Shape circle = new Ellipse2D.Double(x, y, w, h);
addShape(new DrawShape(text, Color.BLACK, circle));
int count = shapes.size();
System.out.printf("objects in array: %d\n", count);
} else if (e.getActionCommand().equals("Draw RandomRectangle")) {
System.out.printf("x = %d y = %d\n", x, y);
generator.nextInt(y));
int w = generator.nextInt(100) + 10;
int h = generator.nextInt(100) + 10;
Shape rect = Rectangle2D.Double(x, y, w, h)
addShape(new DrawShape(text, Color.BLACK, rect));
}

Graphics2D gg = (Graphics2D) canvas.getGraphics();
Don't use the getGraphics() method to do painting. The painting is temporary. It will be lost if you resize the frame for example.
Instead you need to override the paintComponent() method of your panel.
If you want to paint multiple objects then you need to keep track of each object. Check out Custom Painting Approaches for the two common ways to do this:
keep of List of Objects to paint and then iterate through the List each time the component is repainted.
paint the Object directly to a BufferedImage and then just paint the BufferedImage.
The example paints Rectangles. Basically you need a method like the addRectangle(...) method to add a new object to paint. So every time you click your button you add the new random shape.

Presumably, your problem arises from the setText() invocation modifying the Graphics object in some unexpected way. It is rarely appropriate to use getGraphics() in your own code. Instead, paint with the Graphics that is given to you.
Your approach is anyway flawed. If you manage to draw on a GUI component only once, as you are trying to do, then whatever you have drawn will disappear when the component is next repainted. Repainting can happen for a wide variety of reasons, many of them unrelated to the program's own behavior.
What you need to do is store some kind of data that the component's paintComponent() method will rely upon to do your custom painting every time. It follows that you will need to override the paintComponent() method of the component on which you want the circles to be drawn. For example, you might create a class that records all the needed drawing details for one circle, and give RandomDrawer a List of those objects as a member variable. The action listener manipulates that list appropriately and schedules a repainting, and paintComponent() is overridden to perform the actual painting.

Multiple cameras and ScissorStack?

I'm currently trying to make a game, and I'm still novice with using cameras, and I'm thinking that two OrthographicCameras may be necessary, but I'm not sure if that's the most efficient way, or even how to do so.
Basically, I want this to be the layout for it:
The Main Area is where the main stuff is, which is a Server Interface. The Game Level is where the actual game part is in. I am currently using a ScissorStack to cut the region, but with this demo, results make me question how to do this:
public class TestScissorStackAndCamera extends ApplicationAdapter {
private SpriteBatch batch;
private OrthographicCamera camera;
private Sprite sprite;
private int width, height;
#Override
public void create() {
Gdx.gl.glClearColor(0, 0, 0, 0);
width = Gdx.graphics.getWidth();
height = Gdx.graphics.getHeight();
batch = new SpriteBatch();
camera = new OrthographicCamera(width, height);
camera.position.set(width / 2, height / 2, 0);
camera.update();
createSprite();
}
private void createSprite() {
Pixmap map = new Pixmap(width, height, Format.RGBA8888);
map.setColor(Color.RED);
map.fillRectangle(0, 0, width, height);
map.setColor(Color.BLUE);
map.drawLine(width / 2, 0, width / 2, height);
map.drawLine(0, height / 2, width, height / 2);
Texture texture = new Texture(map);
sprite = new Sprite(texture);
}
#Override
public void render() {
Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);
batch.setProjectionMatrix(camera.combined); // The Question!
batch.begin();
{
Rectangle scissors = new Rectangle();
Rectangle area = new Rectangle(10, 10, width - 20, height - 20);
ScissorStack.calculateScissors(camera, batch.getTransformMatrix(), area, scissors);
ScissorStack.pushScissors(scissors);
batch.draw(sprite, 0, 0);
batch.flush();
ScissorStack.popScissors();
}
batch.end();
}
public static void main(String[] args) {
LwjglApplicationConfiguration config = new LwjglApplicationConfiguration();
config.title = "ScissorStack & Camera Test";
config.resizable = false;
new LwjglApplication(new TestScissorStackAndCamera(), config);
}
}
Questioning batch.setProjectionMatrix(camera.combined)
I marked a line in the code with a comment, The Question!, which is what is affecting the results. If I don't have it, using the camera.translate(...) method, the image is drawn at (0, 0) but what it does is it moves what part is viewed. If I do have that line, when I use the camera.translate(...) method, the image is drawn respectively to the position of the camera.
In respect to the game that I'm currently developing, it behaves awkwardly without the projectionMatrix not being set, but when I do set it, it messes up the positioning of the rest of the game. I even added some testing features, and it's not rendering inside of the correct ScissorStack
How could I go about setting up two cameras, or what could I do to set up what I'm trying to correctly and efficiently?
With my actual game (not the mock-up) this is what it is doing. It should be rendering inside of the red lines, but it's not:
If you'd like to see my current code for my GameLevel that is handling the ScissorStack and OrthographicCamera:
public GameLevel(int x, int y, int displayWidth, int displayHeight) {
this.x = x; // x = 10
this.y = y; // y = 10
this.displayWidth = displayWidth; // displayWidth = Gdx.graphics.getWidth() - x - 10
this.displayHeight = displayHeight; // displayHeight = Gdx.graphics.getHeight() - y - 120
camera = new OrthographicCamera(Gdx.graphics.getWidth(), Gdx.graphics.getHeight());
camera.position.set(displayWidth / 2, displayHeight / 2, 0);
// FBLAGame.batch.setProjectionMatrix(camera.combined);
camera.update();
init();
}
...
#Override
public void render() {
Rectangle area = new Rectangle(x, y, displayWidth, displayHeight);
Rectangle scissor = new Rectangle();
Matrix4 matrix = FBLAGame.batch.getTransformMatrix();
ScissorStack.calculateScissors(camera, matrix, area, scissor);
ScissorStack.pushScissors(scissor);
renderLevel();
FBLAGame.batch.flush();
ScissorStack.popScissors();
Pixmap map = new Pixmap(Gdx.graphics.getWidth(), Gdx.graphics.getHeight(), Format.RGBA8888);
map.setColor(Color.RED);
map.drawRectangle((int) area.x, (int) area.y, (int) area.width, (int) area.height);
Texture t = new Texture(map);
map.dispose();
FBLAGame.batch.draw(t, 0, 0);
}

Drawing on Canvas and refreshing

I'm new to Android programming and now I'm trying to make a simple Sea Battle game for one person. Ships are places, player hits the field and see whether the shot hit or not.
Basically, the field looks like this:
The code is:
public void onDraw(Canvas canvas) {
if (getWidth() > getHeight()) {
rebro = getHeight();
} else {
rebro = getWidth(); // the smaller size of screen is "rebro"
}
rebro_piece = rebro / 10; // divide the screen by 10 (to get 10x10 field)
Paint background = new Paint();
background.setColor(getResources().getColor(R.color.game_background));
canvas.drawRect(0, 0, rebro, rebro, background); // draw background
Paint divider = new Paint();
divider.setColor(getResources().getColor(R.color.divider_black));
// drawing divider lines
for (int i=0; i<11; i++) {
canvas.drawLine(0, i*rebro_piece, rebro, i*rebro_piece, divider); // horizontal
canvas.drawLine(i*rebro_piece, 0, i*rebro_piece, rebro, divider); // vertical
}
canvas.drawLine(rebro-1, 0, rebro-1, rebro, divider);
}
That's how I make the "field."
In another class I have a method that collects numbers x and y of a 10×10 array that represents where the ships are placed. For debugging, I need to draw them on my field. Ship coordinates are retrieved in a cycle.
So I wrote a drawShip(int x, int y) method.
On Stack Overflow I've founded a question about "Why I can't paint outside onDraw()?" and I've changed my method to this:
public void drawShip(int x, int y) {
myX = x; //global
myY = y; //global
needToPaintShip = true; //boolean
invalidate(); // refreshing?
needToPaintShip = false;
}
Here needToPaintShip decides whether the redrawing of canvas is needed or not.
Also I've edited the onDraw(Canvas canvas) method:
if(needToPaintShip == true) {
Paint ship = new Paint();
ship.setColor(getResources().getColor(R.color.ship_color));
Log.d(TAG, "onDraw(): rebro_piece = " + rebro_piece + " , myX = "+ myX + " , myY = " + myY); // I only get the last coordinates!
Rect r = new Rect(myX*(rebro_piece),myY*rebro_piece, myX*(rebro_piece+1), myY*(rebro_piece+1));
canvas.drawRect(r, ship);
}
but the result is awful:
Guys, I'm desperate. How can I fix this and make "ships" be drawn on the field?

Why do you set needToPaintShip = false; after calling invalidate()? Don't you need to draw the ship again in subsequent frames?
Also, it seems like this item:
Rect r = new Rect(myX*(rebro_piece),myY*rebro_piece, myX*(rebro_piece+1), myY*(rebro_piece+1));
should probably be:
Rect r = new Rect(myX*(rebro_piece),myY*rebro_piece, (myX+1)*rebro_piece, (myY+1)*rebro_piece));
As for why the ship always appears in the bottom right corner, that depends on what you pass to drawShip(x,y), which isn't shown. Is it possible that you are passing pixel coordinates instead of something in the range [0-10)?

How can I efficiently draw many pixels on a Canvas?

I'm making my first game using Java on Android. I need to draw a lot of pixels which together should create a line. My first approach was to make a large array of booleans, create a loop, and draw a pixel when the associated boolean was true.
It wasn't a good idea of course (the array is about 200x300). Now I remember only the position of the first pixel of the line, and every next pixel has to remember his follower. It works pretty well, but when the line gets longer (but still not very long), the efficiency is bad (<20 fps after 4000 frames).
This is the function that I use to draw a line (only one for now). Can anybody help me improve its efficiency?
public void drawLine(Canvas canvas, int beginx, int beginy) {
Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
paint.setColor(Color.RED);
paint.setStrokeWidth(3);
int x = beginx;
int y = beginy;
while(C.mGrid[x][y].nx != -1) {
//canvas.drawLine(x, y, C.mGrid[x][y].nx, C.mGrid[x][y].ny, paint);
canvas.drawPoint(x, y, paint);
Grid temp = C.mGrid[x][y];
if ((C.mGrid[x][y].nx == x) && (C.mGrid[x][y].ny == y)) break;
x = temp.nx;
y = temp.ny;
}
}
and Grid.java:
package com.qwak.achtung;
public float x = 0,y = 0;
public int px = -1, py = -1, nx = -1, ny = -1;
public Grid(float x, float y) {
this.x = x;
this.y = y;
}
public void set(int px, int py, int nx, int ny) {
this.px = px;
this.py = py;
this.nx = nx;
this.ny = ny;
}
public void setp(int px, int py) {
this.px = px;
this.py = py;
}
public void setn(int nx, int ny) {
this.nx = nx;
this.ny = ny;
}
PS: It looks like this http://c.wrzuta.pl/wi10559/11f7d10b00110e504e25ebd3/0/andek 14 is fps (on my phone (samsung Spica) it run better - 40 but after a while it decreases to 20 and even less) and 983 is number of frames at all.

There is a drawLine method in the canvas object.
Use the example here: How to draw a line in android
canvas.drawLine(0, 0, 20, 20, paint);
If you want to draw a curve. Find the function of the curve. A Parabola for example is x=y^2. You can get points from the curve: 1 = 1, 2 = 4, 3 = 9, 4 = 16... etc.. If your drawing pixel by pixel you can plug in your x and get your y and draw it.
Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
paint.setColor(Color.RED);
paint.setStrokeWidth(3);
for(int i = beginx; i < CanvasWidth; i++)
{
int x = i;
int y = i * i; //x=y^2
canvas.drawPoint(x, y, paint);
}
To keep a record of points that were visited you could do the following:
class Point
{
int x;
int y;
}
List<Point> points = new List<Point>();
onMove(int newX, int newY)
{
Point p = new Point();
p.x = newX;
p.y = newY;
points.add(p);
}
onDraw()
{
for(Point p : points)
{
canvas.drawPoint(p.x, p.y, paint);
}
}

You want to look into the bresenham algorithm. A bresenham algorithm is a method to draw or rasterize a line. It's a bit different from the subdivision of a grid in a certain angle for example a morton-curve. It's a bit like compute the scalar product for every angle like recall here Traversing a 2D array in an angle.