Android image with clickable areas

Question

I need an advice how to achieve the following functionality under Android:

• I need an image that represents something like a graph (from discrete math), with ve

Answer 1

I was bored, so I coded up this crude example... It assumes straight edges between points.

public class App extends Activity
{
    PlotView plot;
    @Override
    public void onCreate(Bundle sis)
    {
        super.onCreate(sis);
        plot = new PlotView(this);
        setContentView(plot);
    }

    public class PlotView extends View
    {
        Paint paint1 = new Paint();
        Paint paint2 = new Paint();
        Point[] points = new Point[10];

        public PlotView(Context context)
        {
            super(context);
            paint1.setColor(Color.RED);
            paint2.setColor(Color.BLUE);
            for (int i = 0; i < points.length; i++)
            {
                points[i] = new Point();
                points[i].x = (float) (Math.random() * 320);
                points[i].y = (float) (Math.random() * 480);
            }
            Arrays.sort(points);
        }

        @Override
        protected void onDraw(Canvas canvas)
        {
            canvas.drawColor(Color.WHITE);
            for (int i = 0; i < points.length; i++)
            {
                if (i < points.length - 1)
                {
                    canvas.drawLine(points[i].x, points[i].y, points[i + 1].x, points[i + 1].y, paint2);
                }
                canvas.drawCircle(points[i].x, points[i].y, 5, paint1);             
            }
            super.onDraw(canvas);
        }

        @Override
        public boolean onTouchEvent(MotionEvent event)
        {
            switch(event.getAction())
            {
                case MotionEvent.ACTION_DOWN:
                {
                    float x = event.getX();
                    float y = event.getY();

                    int hitPoint = -1;
                    int closestLeft = -1;
                    int closestRight = -1;

                    for (int i = 0; i < points.length; i++)
                    {
                        float dx = x - points[i].x;
                        float dy = y - points[i].y;

                        if(i < points.length - 1)
                        {
                            if(points[i].x < x && x < points[i + 1].x)
                            {
                                closestLeft = i;
                                closestRight = i + 1;
                            }
                        }

                        if (Math.abs(dx) <= 16.0f && Math.abs(dy) <= 16.0f)
                        {
                            hitPoint = i;
                            break;
                        }
                    }
                    if (hitPoint != -1)
                    {
                        Toast.makeText(getContext(), "Hit Point: " + hitPoint, Toast.LENGTH_SHORT).show();                      
                    }
                    else                        
                    if(closestLeft != -1 && closestRight != -1)
                    {
                        float dx = points[closestLeft].x - points[closestRight].x;
                        float dy = points[closestLeft].y - points[closestRight].y;

                        final float u = ((x - points[closestLeft].x) * dx + (y - points[closestLeft].y) * dy) / (dx * dx + dy * dy);

                        float px = points[closestLeft].x + u * dx;
                        float py = points[closestLeft].y + u * dy;

                        if (Math.abs(x - px) <= 16.0f && Math.abs(y - py) <= 16.0f)
                        {
                            Toast.makeText(getContext(), "Hit Line Between: " + closestLeft + " & " + closestRight, Toast.LENGTH_SHORT).show();
                        }
                    }                   
                }
            }
            return super.onTouchEvent(event);
        }

        public class Point implements Comparable
        {
            float x;
            float y;
            @Override
            public int compareTo(Point other)
            {
                if (x < other.x) return -1;
                if (x > other.x) return 1;
                return 0;
            }
        }       
    }
}