Dot game failed , cannot identify and draw dots around image correctly

Question

What i am trying to achieve is to draw dot at the exact same location as black dot already present in image , but there are problem that i have to face regarding image:

1. Image can change its densities in multiple screens(so no fixed size)
2. Given image can be of any size , i have to convert it to appropriate size to show on custom View.
3. and How to show image in custom view so its density remain the same ?

Now problems regarding dots drawing:

1. How can i identify black dots x,y axis dynamically to draw at the same exact black dot drawn in image of custom view.
2. Is there a good way to achieve question 1 dynamically or i should hard code dots.

What i have done so far:

1. I have moved all images to drawable folder and done layout_width = wrap_content and height the same as width.

   <com.jutt.dotbot.ConnectDotsView
   android:id="@+id/gfxImage"
   android:layout_width="500dpi"
   android:layout_height="600dpi"
   android:layout_marginTop="100dip"
   android:layout_centerHorizontal="true"/>
   

2. I've look hard coded points by Toast the point on each ACTION_DOWN in onTouchEvent and then noted then and given to the class ConnectDotsView .

   switch (event.getAction()) {
   case MotionEvent.ACTION_DOWN:
       touch_start(x, y);
       invalidate();
       L.s(getContext(), "x = "+x+"y = "+y);
       break;
   

3. After i've noted all points drawn , i am giving this class back that same points to draw , by calling:

   public void setPoints(List<Point> points) {
       this.mPoints = points;
   }
   

4. Now Biggest problem [which i think still persist] , (x,y) on screen 1152w*720h may not be same on 480w*600h , so what i've done is who a function to actually convert those points.

   private static final int OLDSCREENX = 1152;
   private static final int OLDSCREENY = 720;
   
   private int[] makeDimentionGeneric(float oldScreenX, float oldScreenY,
           float oldX, float oldY) {
       // get screen size
       DisplayMetrics displaymetrics = new DisplayMetrics();
       getWindowManager().getDefaultDisplay().getMetrics(displaymetrics);
       final float y = displaymetrics.heightPixels;
       final float x = displaymetrics.widthPixels;
       int[] i = new int[] { (int) ((oldX / oldScreenX) * x),
               (int) ((oldY / oldScreenY) * y) };
       return i;
   }
   

and i am calling this while setting the points like makeDimentionGeneric(OLDSCREENX, OLDSCREENY, p.x, p.y); when p.x and p.y are hardcoded stored value from screen.

Now what happens when i try to run it in different devices.

When am i doing it wrong and how can i achieve it correctly ? please guys i've worked hard studied but can't seems to find a better approach than i've mentioned.

[Update] as requested(21 jul 2015):

private int[] makeDimentionGeneric(float oldScreenX, float oldScreenY,
        float oldX, float oldY) {
    // convert all px to dp
    oldScreenY = convertPixelsToDp(oldScreenY, this);
    oldScreenX = convertPixelsToDp(oldScreenX,this);
    oldX = convertPixelsToDp(oldX,this);
    oldY = convertPixelsToDp(oldY,this);

    // get screen size
    DisplayMetrics displaymetrics = new DisplayMetrics();
    getWindowManager().getDefaultDisplay().getMetrics(displaymetrics);
    final float y = convertPixelsToDp(displaymetrics.heightPixels, this);
    final float x = convertPixelsToDp(displaymetrics.widthPixels, this);

    int[] i = new int[] { (int)((oldX / oldScreenX) * x),
            (int) ((oldY / oldScreenY) * y) };

    return i;

}

Answer 1

Since your image differs depending on DPI your pixel calculations must also differ depending on DPI. Consider the following question:

Converting pixels to dp

In your case (copied from answer in above question) you probably want to use this method:

/**
 * This method converts device specific pixels to density independent pixels.
 *
 * @param px A value in px (pixels) unit. Which we need to convert into db
 * @param context Context to get resources and device specific display metrics
 * @return A float value to represent dp equivalent to px value
 */
public static float convertPixelsToDp(float px, Context context){
    Resources resources = context.getResources();
    DisplayMetrics metrics = resources.getDisplayMetrics();
    float dp = px / (metrics.densityDpi / 160f);
    return dp;
}