Calculate path between two points on the screen in Android

Problem seemed very simple to me at first but now I am stuck.

Scenario I want to move a image on the screen, on a certain path I create. Moving this image is being made on a thread, something like:

@Override
    public void run() {
        Canvas c;
        while (run) {
            c = null;
开发者_StackOverflow            try {
                c = panel.getHolder().lockCanvas(null);
                  synchronized (panel.getHolder()) {

                    panel.updateImageCoordinates();
                    panel.onDraw(c);


                }
            } finally {
                if (c != null) {
                    panel.getHolder().unlockCanvasAndPost(c);
                }
            }
        }

for the Image I want to move I have a List with main points where it should go. Each coordinate has:

 public class Coordinates {
        private int x = 0;
        private int y = 0;
        private int speedX=0;
        private int speedY=0;
}

For example, my first point is -5;-30 and I need to get to second point 50.50. The calculation of next coordinates to draw the image is made on updateImageCoordinates(). My problem is that I don't know how to calculate speedX and speedY so that I get from point A to point B on a straight line. Basically for each execution of updateImageCoorindates() I need to do:

image.currentX= image.currentX+speedX;
image.currentY= image.currentY+speedY
//Check if I reached the B point. if so, move to next point.

I don't know based on knowing the coordinates, how I can calculate the speed on x and Y directions.

I attach a image for exemplification. Any help is appreciated.

I'm not shure if I've understood your question clearly...

If you are looking for function which will translate PointA into point on line A-B.

Line containing both points will have equation:

-30 = -5*a + b and 50 = 50*a + b so b = -250/11 a = 16/11

so to find next point you have to:

check if x of next point is at left (-1) or right (+1) of the destination point

and calculate next point by:

image.currentX= image.currentX+((-1 or +1)*movement_speed);
image.currentY= image.currentY+16/11*(-1 or +1)*movement_speed + (-250/11)

You'll find the API Demos for Animation useful I think. In particular, check out Custom Evaluator.