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Java LibGDX how to check if sprite stands on specific tile e.g. door?

I want to change the map (method changeMapToWinter()) when sprite stands on specific tile of specific map. I have no layers on map.
Currently I do something like that if(sprite.getX() > 100 && sprite.getX() < 200 && sprite.getY() > 100 && sprite.getY() < 200) but of course it works only on one map and do not look too good and I guess there is a better solution for that.
Texture img;
TiledMap tiledMap;
OrthographicCamera camera;
TiledMapRenderer tiledMapRenderer;
SpriteBatch sb;
Texture texture;
Sprite sprite;
private ShapeRenderer shapeRenderer;
private TiledMapTileLayer tileLayer;
private TiledMap winterMap;
#Override
public void create() {
float w = Gdx.graphics.getWidth();
float h = Gdx.graphics.getHeight();
camera = new OrthographicCamera();
camera.setToOrtho(false, w, h);
camera.update();
tiledMap = new TmxMapLoader().load("untitled.tmx");
winterMap = new TmxMapLoader().load("untitled2.tmx");
tiledMapRenderer = new OrthogonalTiledMapRenderer(tiledMap);
Gdx.input.setInputProcessor(this);
sb = new SpriteBatch();
texture = new Texture(Gdx.files.internal("bold_brown_blue-1.png"));
sprite = new Sprite(texture);
}
void changeMapToWinter() {
tiledMap.dispose();
winterMap = new TmxMapLoader().load("untitled2.tmx");
tiledMapRenderer = new OrthogonalTiledMapRenderer(winterMap);
}
#Override
public void render() {
Gdx.gl.glClearColor(1, 0, 0, 1);
Gdx.gl.glBlendFunc(GL20.GL_SRC_ALPHA, GL20.GL_ONE_MINUS_SRC_ALPHA);
Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);
camera.update();
tiledMapRenderer.setView(camera);
tiledMapRenderer.render();
sb.begin();
sb.draw(sprite, (int) (Gdx.app.getGraphics().getWidth() / 2) - (sprite.getWidth()), (int) (Gdx.app.getGraphics().getHeight() / 2) - (sprite.getHeight() / 2));
sb.end();
Vector3 click = new Vector3(Gdx.input.getX(), Gdx.input.getY(), 0);
TiledMapTileLayer layer = (TiledMapTileLayer)tiledMap.getLayers().get(0);
// WANT TO CHANGE IT
if(sprite.getX() > 100 && sprite.getX() < 200 && sprite.getY() > 100 && sprite.getY() < 200)
changeMapToWinter();
}

Solution you might use can be something like this:
Rectangle changePosition = new Rectangle(100,100,100,100);
if(sprite.getBoundingRectangle().overlaps(changePosition)) ...
Constructor for rectangle have this format Rectangle(float x, float y, float width, float height).
Also this will behave a bit differently from your code as you weren't taking into account size of the sprite, but this code does.
Btw LibGDX have usefull class for problems like this if you wouldn't be able to find appropriate function in Rectangle class or whatever shape you are using. It is called Intersector.

Kinect & Processing: Passing skeleton hand data to mouse position

I've been working on this a while and feel so close! Should be easy, but I'm still new to this.
The skeleton hand data is being passed in as joints[KinectPV2.JointType_HandLeft] and can be accessed through joint.getX() and joint.getY(). I want to pass this data into the update function to replace mouseX and mouseY. I'm guessing I have to create global variables to access it within the update function or maybe I have to pass the skeleton data as parameters into the update function? How can I replace the mouse position data with the hand position?
import KinectPV2.*;
KinectPV2 kinect;
private class MyFluidData implements DwFluid2D.FluidData{
// update() is called during the fluid-simulation update step.
#Override
public void update(DwFluid2D fluid) {
float px, py, vx, vy, radius, vscale, temperature;
radius = 15;
vscale = 10;
px = width/2;
py = 50;
vx = 1 * +vscale;
vy = 1 * vscale;
radius = 40;
temperature = 1f;
fluid.addDensity(px, py, radius, 0.2f, 0.3f, 0.5f, 1.0f);
fluid.addTemperature(px, py, radius, temperature);
particles.spawn(fluid, px, py, radius, 100);
boolean mouse_input = mousePressed;
// add impulse: density + velocity, particles
if(mouse_input && mouseButton == LEFT){
radius = 15;
vscale = 15;
px = mouseX;
py = height-mouseY;
vx = (mouseX - pmouseX) * +vscale;
vy = (mouseY - pmouseY) * -vscale;
fluid.addDensity (px, py, radius, 0.25f, 0.0f, 0.1f, 1.0f);
fluid.addVelocity(px, py, radius, vx, vy);
particles.spawn(fluid, px, py, radius*2, 300);
}
// add impulse: density + temperature, particles
if(mouse_input && mouseButton == CENTER){
radius = 15;
vscale = 15;
px = mouseX;
py = height-mouseY;
temperature = 2f;
fluid.addDensity(px, py, radius, 0.25f, 0.0f, 0.1f, 1.0f);
fluid.addTemperature(px, py, radius, temperature);
particles.spawn(fluid, px, py, radius, 100);
}
// particles
if(mouse_input && mouseButton == RIGHT){
px = mouseX;
py = height - 1 - mouseY; // invert
radius = 50;
particles.spawn(fluid, px, py, radius, 300);
}
}
}
int viewport_w = 1280;
int viewport_h = 720;
int viewport_x = 230;
int viewport_y = 0;
int gui_w = 200;
int gui_x = 20;
int gui_y = 20;
int fluidgrid_scale = 3;
DwFluid2D fluid;
// render targets
PGraphics2D pg_fluid;
//texture-buffer, for adding obstacles
PGraphics2D pg_obstacles;
// custom particle system
MyParticleSystem particles;
// some state variables for the GUI/display
int BACKGROUND_COLOR = 0;
boolean UPDATE_FLUID = true;
boolean DISPLAY_FLUID_TEXTURES = false;
boolean DISPLAY_FLUID_VECTORS = false;
int DISPLAY_fluid_texture_mode = 0;
boolean DISPLAY_PARTICLES = true;
public void settings() {
size(viewport_w, viewport_h, P2D);
smooth(4);
}
public void setup() {
surface.setLocation(viewport_x, viewport_y);
// main library context
DwPixelFlow context = new DwPixelFlow(this);
context.print();
context.printGL();
// fluid simulation
fluid = new DwFluid2D(context, viewport_w, viewport_h, fluidgrid_scale);
// set some simulation parameters
fluid.param.dissipation_density = 0.999f;
fluid.param.dissipation_velocity = 0.99f;
fluid.param.dissipation_temperature = 0.80f;
fluid.param.vorticity = 0.10f;
fluid.param.timestep = 0.25f;
fluid.param.gridscale = 8f;
// interface for adding data to the fluid simulation
MyFluidData cb_fluid_data = new MyFluidData();
fluid.addCallback_FluiData(cb_fluid_data);
// pgraphics for fluid
pg_fluid = (PGraphics2D) createGraphics(viewport_w, viewport_h, P2D);
pg_fluid.smooth(4);
pg_fluid.beginDraw();
pg_fluid.background(BACKGROUND_COLOR);
pg_fluid.endDraw();
// pgraphics for obstacles
pg_obstacles = (PGraphics2D) createGraphics(viewport_w, viewport_h, P2D);
pg_obstacles.smooth(4);
pg_obstacles.beginDraw();
pg_obstacles.clear();
float radius;
radius = 200;
pg_obstacles.stroke(64);
pg_obstacles.strokeWeight(1);
pg_obstacles.fill(0);
pg_obstacles.rect(1*width/2f, 1*height/4f, radius, radius/2, 10);
pg_obstacles.stroke(64);
pg_obstacles.strokeWeight(1);
pg_obstacles.fill(0);
pg_obstacles.rect(1*width/3.5f, 1*height/2.5f, radius, radius/2, 10);
//// border-obstacle
//pg_obstacles.strokeWeight(20);
//pg_obstacles.stroke(64);
//pg_obstacles.noFill();
//pg_obstacles.rect(0, 0, pg_obstacles.width, pg_obstacles.height);
pg_obstacles.endDraw();
fluid.addObstacles(pg_obstacles);
// custom particle object
particles = new MyParticleSystem(context, 1024 * 1024);
kinect = new KinectPV2(this);
//Enables depth and Body tracking (mask image)
kinect.enableDepthMaskImg(true);
kinect.enableSkeletonDepthMap(true);
kinect.init();
background(0);
frameRate(60);
}
public void draw() {
PImage imgC = kinect.getDepthMaskImage();
image(imgC, 0, 0, 320, 240);
//get the skeletons as an Arraylist of KSkeletons
ArrayList<KSkeleton> skeletonArray = kinect.getSkeletonDepthMap();
//individual joints
for (int i = 0; i < skeletonArray.size(); i++) {
KSkeleton skeleton = (KSkeleton) skeletonArray.get(i);
//if the skeleton is being tracked compute the skleton joints
if (skeleton.isTracked()) {
KJoint[] joints = skeleton.getJoints();
color col = skeleton.getIndexColor();
fill(col);
stroke(col);
drawHandState(joints[KinectPV2.JointType_HandRight]);
drawHandState(joints[KinectPV2.JointType_HandLeft]);
}
}
// update simulation
if(UPDATE_FLUID){
fluid.addObstacles(pg_obstacles);
fluid.update();
particles.update(fluid);
}
// clear render target
pg_fluid.beginDraw();
pg_fluid.background(BACKGROUND_COLOR);
pg_fluid.endDraw();
// render fluid stuff
if(DISPLAY_FLUID_TEXTURES){
// render: density (0), temperature (1), pressure (2), velocity (3)
fluid.renderFluidTextures(pg_fluid, DISPLAY_fluid_texture_mode);
}
if(DISPLAY_FLUID_VECTORS){
// render: velocity vector field
fluid.renderFluidVectors(pg_fluid, 10);
}
if( DISPLAY_PARTICLES){
// render: particles; 0 ... points, 1 ...sprite texture, 2 ... dynamic points
particles.render(pg_fluid, BACKGROUND_COLOR);
}
// display
image(pg_fluid , 320, 0);
image(pg_obstacles, 320, 0);
// display number of particles as text
//String txt_num_particles = String.format("Particles %,d", particles.ALIVE_PARTICLES);
//fill(0, 0, 0, 220);
//noStroke();
//rect(10, height-10, 160, -30);
//fill(255,128,0);
//text(txt_num_particles, 20, height-20);
// info
//String txt_fps = String.format(getClass().getName()+ " [size %d/%d] [frame %d] [fps %6.2f]", fluid.fluid_w, fluid.fluid_h, fluid.simulation_step, frameRate);
//surface.setTitle(txt_fps);
}
//draw a ellipse depending on the hand state
void drawHandState(KJoint joint) {
noStroke();
handState(joint.getState());
//println(joint.getState());
pushMatrix();
translate(joint.getX(), joint.getY(), joint.getZ());
//println(joint.getX(), joint.getY(), joint.getZ());
ellipse(joint.getX(), joint.getY(), 70, 70);
popMatrix();
}
/*
Different hand state
KinectPV2.HandState_Open
KinectPV2.HandState_Closed
KinectPV2.HandState_Lasso
KinectPV2.HandState_NotTracked
*/
//Depending on the hand state change the color
void handState(int handState) {
switch(handState) {
case KinectPV2.HandState_Open:
fill(0, 255, 0);
break;
case KinectPV2.HandState_Closed:
fill(255, 0, 0);
break;
case KinectPV2.HandState_Lasso:
fill(0, 0, 255);
break;
case KinectPV2.HandState_NotTracked:
fill(100, 100, 100);
break;
}
}

I'm guessing I have to create global variables to access it within the update function or maybe I have to pass the skeleton data as parameters into the update function?
What happened when you tried those approaches?
Either approach sounds fine. You could store the variables in a sketch-level variable, set those variables from the kinect code, then use those variables in your drawing code. Or you could pass the variables as a parameter to the drawing code. Either should work fine. I'd probably go for the first approach because it sounds easier to me, but that's just my personal preference.
I suggest working in smaller chunks. Create a separate program that ignores the kinect for now. Create a hard-coded sketch-level variable that holds the same type of information you'd get from the kinect. Then write drawing code that uses that hard-coded variable to draw the frame. Get that working perfectly before you try adding the kinect code back in.
Then if you get stuck on a specific step, you can post a MCVE and we can go from there. Good luck.

libgdx won't draw sprite or animation

it seems as though i cannot get the draw method to work???
it seems as though the bullet.draw(batcher)
does not work and i cannot understand why as the bullet is a sprite.
i have made a Sprite[] and added them as animation.
could that be it?
i tried
batcher.draw(AssetLoader.bulletAnimation.getKeyFrame(runTime), bullet.getX(), bullet.getY(), bullet.getOriginX() / 2, bullet.getOriginY() / 2, bullet.getWidth(), bullet.getHeight(), 1, 1, bullet.getRotation());
but that dont work, the only way it draws is this
batcher.draw(AssetLoader.bulletAnimation.getKeyFrame(runTime), bullet.getX(), bullet.getY());
below is the code.
// this is in a Asset Class
texture = new Texture(Gdx.files.internal("SpriteN1.png"));
texture.setFilter(TextureFilter.Nearest, TextureFilter.Nearest);
bullet1 = new Sprite(texture, 380, 350, 45, 20);
bullet1.flip(false, true);
bullet2 = new Sprite(texture, 425, 350, 45, 20);
bullet2.flip(false, true);
Sprite[] bullets = { bullet1, bullet2 };
bulletAnimation = new Animation(0.06f, bullets);
bulletAnimation.setPlayMode(Animation.PlayMode.LOOP);
// this is the GameRender class
public class GameRender() {
private Bullet bullet;
private Ball ball;
public GameRenderer(GameWorld world) {
myWorld = world;
cam = new OrthographicCamera();
cam.setToOrtho(true, 480, 320);
batcher = new SpriteBatch();
// Attach batcher to camera
batcher.setProjectionMatrix(cam.combined);
shapeRenderer = new ShapeRenderer();
shapeRenderer.setProjectionMatrix(cam.combined);
// Call helper methods to initialize instance variables
initGameObjects();
initAssets();
}
private void initGameObjects() {
ball = GameWorld.getBall();
bullet = myWorld.getBullet();
scroller = myWorld.getScroller();
}
private void initAssets() {
ballAnimation = AssetLoader.ballAnimation;
bulletAnimation = AssetLoader.bulletAnimation;
}
public void render(float runTime) {
Gdx.gl.glClearColor(0, 0, 0, 1);
Gdx.gl.glClear(GL30.GL_COLOR_BUFFER_BIT);
batcher.begin();
// Disable transparency
// This is good for performance when drawing images that do not require
// transparency.
batcher.disableBlending();
// The ball needs transparency, so we enable that again.
batcher.enableBlending();
batcher.draw(AssetLoader.ballAnimation.getKeyFrame(runTime), ball.getX(), ball.getY(), ball.getWidth(), ball.getHeight());
batcher.draw(AssetLoader.bulletAnimation.getKeyFrame(runTime), bullet.getX(), bullet.getY());
// End SpriteBatch
batcher.end();
}
}
// this is the gameworld class
public class GameWorld {
public static Ball ball;
private Bullet bullet;
private ScrollHandler scroller;
public GameWorld() {
ball = new Ball(480, 273, 32, 32);
bullet = new Bullet(10, 10);
scroller = new ScrollHandler(0);
}
public void update(float delta) {
ball.update(delta);
bullet.update(delta);
scroller.update(delta);
}
public static Ball getBall() {
return ball;
}
public ScrollHandler getScroller() {
return scroller;
}
public Bullet getBullet() {
return bullet;
}
}
is there anyway so make the sprite work?
i am adding the bullet class to see if there could be something wrong there.
public class Bullet extends Sprite {
public static final float BULLET_HOMING = 6000;
public static final float BULLET_SPEED = 300;
private Vector2 velocity;
private float lifetime;
public Bullet(float x, float y) {
velocity = new Vector2(0, 0);
setPosition(x, y);
}
public void update(float delta) {
float targetX = GameWorld.getBall().getX();
float targetY = GameWorld.getBall().getY();
float dx = targetX - getX();
float dy = targetY - getY();
float distToTarget = (float) Math.sqrt(dx * dx + dy * dy);
dx /= distToTarget;
dy /= distToTarget;
dx *= BULLET_HOMING;
dy *= BULLET_HOMING;
velocity.x += dx * delta;
velocity.y += dy * delta;
float vMag = (float) Math.sqrt(velocity.x * velocity.x + velocity.y * velocity.y);
velocity.x /= vMag;
velocity.y /= vMag;
velocity.x *= BULLET_SPEED;
velocity.y *= BULLET_SPEED;
Vector2 v = velocity.cpy().scl(delta);
setPosition(getX() + v.x, getY() + v.y);
setOriginCenter();
setRotation(velocity.angle());
lifetime += delta;
setRegion(AssetLoader.bulletAnimation.getKeyFrame(lifetime));
}
}

Your keyframes are kept in an array called bullets, but when you call the Animation constructor you pass something called 'aims' as the second argument. You should try instead passing 'bullets', as in:
bulletAnimation = new Animation(0.06f,bullets);
You shouldn't have a problem with using a Sprite[] as the Sprite class extends TextureRegion I think.
------ OP fixed the typo and still didn't work------
I think the problem will be with the origin arguments of the batcher.draw()call. The position of the Sprite is relative to the origin of the SpriteBatch's co-ordinate system, and the origin of the Sprite is relative to this position (i.e. the bottom-left corner of the Sprite rectangle). To get an origin in the center of the Sprite, i think originX should be width/2 and originY should be height/2. So try:
batcher.draw(AssetLoader.bulletAnimation.getKeyFrame(runTime),bullet.getX(),bullet.getY(), bullet.getWidth()/2,bullet.getHeight()/2,bullet.getWidth(),bullet.getHeight(),1,1,bullet.getRotation());
Because if your getOriginX/Y methods return origins relative to the SpriteBatcher's co-ordinate system(the screen co-ordinates), then your Sprites could be rotating and scaling around some ridiculous origin and end up being drawn off-screen.
I hope I'm right and it's problem solved.
----- OP posted further code, the 'bullet' class-----
When you call bullet.getWidth() and bullet.getHeight() in your draw method, these will return 0.0f because you haven't specified values for them. Remember the Sprites you are actually drawing are bullet1 and bullet2 from your AssetLoader class. Try setting bullet's width and height with:
setSize(AssetLoader.bullet1.getWidth(), AssetLoader.bullet1.getHeight());
in your bullet constructor.
I don't think you need to use setRegion() in your bullet class either, again, because the Sprites you're actually drawing are bullet1 and 2.
fingers crossed.

try and change the update method to this
Vector2 target = new Vector2(GameWorld.getBall().getX(), GameWorld.getBall().getY());
target.sub(getX(), getY());
target.nor().scl(BULLET_HOMING);
velocity.add(target.scl(delta));
velocity.nor().scl(BULLET_SPEED);
Vector2 v = velocity.cpy().scl(delta);
translate(v.x, v.y);
setOriginCenter();
setRotation(velocity.angle());
that should clean your code a little

Apply pixel Coordinates to Screen Coordinates

I'm trying to make an object appear where the person last touched. However when I try to do so it appears in the wrong place. I assume this is because of the fact the coordinates that the input returns is different to the display coordinates, my code is as follows:
public class Core implements ApplicationListener, InputProcessor
{ //Has to be here otherwise the code formatting becomes buggy
private Mesh squareMesh;
private PerspectiveCamera camera;
private Texture texture;
private SpriteBatch spriteBatch;
Sprite sprite;
float moveX = 0;
private final Matrix4 viewMatrix = new Matrix4();
private final Matrix4 transformMatrix = new Matrix4();
#Override
public void create()
{
Gdx.input.setInputProcessor(this);
texture = new Texture(Gdx.files.internal("door.png"));
spriteBatch = new SpriteBatch();
sprite = new Sprite(texture);
sprite.setPosition(0, 0);
viewMatrix.setToOrtho2D(0, 0, 480, 320);
float x = 0;
float y = 0;
}
#Override
public void dispose()
{
}
#Override
public void pause()
{
}
#Override
public void render()
{
viewMatrix.setToOrtho2D(0, 0, 480, 320);
spriteBatch.setProjectionMatrix(viewMatrix);
spriteBatch.setTransformMatrix(transformMatrix);
spriteBatch.begin();
spriteBatch.disableBlending();
spriteBatch.setColor(Color.WHITE);
Gdx.gl.glClear(GL10.GL_COLOR_BUFFER_BIT);
//spriteBatch.draw(texture, 0, 0, 1, 1, 0, 0, texture.getWidth(),
// texture.getHeight(), false, false);
sprite.draw(spriteBatch);
spriteBatch.end();
update();
}
#Override
public void resize(int width, int height)
{
float aspectRatio = (float) width / (float) height;
camera = new PerspectiveCamera(67, 2f * aspectRatio, 2f);
}
#Override
public void resume()
{
}
public void update()
{
float delta = Gdx.graphics.getDeltaTime();
if(Gdx.input.isTouched())
{
Vector3 worldCoordinates = new Vector3(sprite.getX(), sprite.getY(), 0);
camera.unproject(worldCoordinates);
sprite.setPosition(Gdx.input.getX(), Gdx.input.getY());
float moveX = 0;
float moveY = 0;
}
}
I cropped this code for sake of simplicty.
I also made a video demonstrating the bug:
http://www.youtube.com/watch?v=m89LpwMkneI

Camera.unproject converts screen coordinates to world coordinates.
Vector3 pos = new Vector3(Gdx.input.getX(), Gdx.input.getY(), 0);
camera.unproject(pos);
sprite.setPosition(pos.x, pos.y);

Firstly, Gdx.input.getX() and Gdx.input.getY() return "screen coordinates". You want to transform these to your "camera coordinates". Screen coordinates typically have (0,0) in the top left corner of the window. I think your camera coordinates have (0,0) at the bottom left corner (either libgdx or opengl are doing that). Your video seems to suggest that this true. So you will need to multiply the Y value by -1. Secondly, I suspect the scale of the screen is different from the scale of the camera. I think you can fix the scale by multiplying by (world/screen).
Let's say your screen has width=800, height=600 and your world has width=480 height=320. Then your new X,Y for your sprite should be:
X = Gdx.input.getX()*(480/800)
Y = Gdx.input.getY()*(320/600)*-1

you should check your touch cordinates.
Gdx.app.log("", "hello x"+touchx);
Gdx.app.log("", "hello x"+touchy);
here touchx and touchy are your input x and input y variables
then do calculation where touch should work
like if u touched x=100,y=100
and touchx is coming 120
and touch y is coming 120
soo in your update method do this
sprite.setPosition(Gdx.input.getX()-20, Gdx.input.getY()-20);
i think this will help

I figured out the screen size/ game ratio and multiplied it to the current screen size:
rect.x=((((1024/Gdx.graphics.getWidth()))* Gdx.graphics.getWidth())
for a screen width of 1024 pixels
There must be an easier way however this works for me.

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.