Question

I need to show below two points (A and B) on a radar circle image that I have created using Canvas in Android. And those two points have latitude and longitude values. Suppose Point A has these values-

Latitude: 37.33774833333334
Longitude: -121.88670166666667

Point B has these values-

Latitude: 37.336453
Longitude: -121.884985

I need to show these two above points on a Canvas by doing some sort of calculations from the center point of a circle as shown in the below image. Below is the code that is creating radar circle in Android like below-

public class CircleCanvas extends View{

    Context context;
    int[] imageNames=new int[6];

    public CircleCanvas(Context mContext,int mUser,int mfirstDis,int msecondDis,int mthirdDis,int mfourDis,int bgMap) {
        super(mContext);
        context = mContext;
        imageNames[0]=mUser;
        imageNames[1]=mfirstDis;
        imageNames[2]=msecondDis;
        imageNames[3]=mthirdDis;
        imageNames[4]=mfourDis;
        imageNames[5]=bgMap;
    }
    protected void onDraw(Canvas canvas) { 
        super.onDraw(canvas); 
        Paint p = new Paint(); 
        p.setColor(Color.BLACK); //BLACK 
        p.setStyle(Style.STROKE);
        //canvas.drawColor(Color.BLACK); //WHITE

        WindowManager mWinMgr = (WindowManager)context.getSystemService(Context.WINDOW_SERVICE);
        @SuppressWarnings("deprecation")
        int displayWidth = mWinMgr.getDefaultDisplay().getWidth();
        @SuppressWarnings("deprecation")
        int displayHeight = mWinMgr.getDefaultDisplay().getHeight();

        canvas.drawBitmap(BitmapFactory.decodeResource(getResources(),imageNames[5]), 0, 0, null);

        int totalCircle=4;
        int radius=40;
        int centerimagesize=13;

        for (int i = 1; i <= totalCircle; i ++) { 
            canvas.drawCircle(displayWidth/2,displayHeight/4, i*radius, p); 
            canvas.drawBitmap(BitmapFactory.decodeResource(getResources(),imageNames[i]), ((displayWidth/2)+(i*radius)),(displayHeight/4), null);
        } 

        canvas.drawLine((displayWidth/2-(totalCircle*radius)), (displayHeight/4), (displayWidth/2+(totalCircle*radius)), (displayHeight/4), p);
        canvas.drawLine((displayWidth/2), (displayHeight/4-(totalCircle*radius)), (displayWidth/2), (displayHeight/totalCircle+(4*radius)), p);
        canvas.drawBitmap(BitmapFactory.decodeResource(getResources(),imageNames[0]), ((displayWidth/2)-(centerimagesize/2)),((displayHeight/4)-(centerimagesize/2)), null);

        invalidate(); 
    } 


}

And this is the image of the Canvas from the above code-

And I am passing all the images that I am showing currently on the Canvas from the onCreate method

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    FrameLayout main = (FrameLayout) findViewById(R.id.main_view);
    CircleCanvas circleCanvas=new CircleCanvas(this,R.drawable.current_user,R.drawable.tenm,R.drawable.twentym,R.drawable.thirtym,R.drawable.fourtym,R.drawable.bg_map);
    main.addView(circleCanvas);

   locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
   locationManager.requestLocationUpdates(
            LocationManager.GPS_PROVIDER,
            MINIMUM_TIME_BETWEEN_UPDATES,
            MINIMUM_DISTANCE_CHANGE_FOR_UPDATES,
            new MyLocationListener()
    ); 
}

And I am not sure, how can I show two points(A and B) on that radar circle image by doing calculations from the center point of the circle that I have created using Canvas. Is there some angle calculation that needs to be done? I have seperate images for two points A and B in my drawable folder in Android project

Answer 1

The easiest way to do this is to use OverlayItem and GeoPoint in a MapView. https://developers.google.com/maps/documentation/android/hello-mapview. You may be better make the radar an OverlayItem as well.