Point Collision & add custom views instead of default circles (SOLUTIONS)

[omerxhaferi]

package ng.dat.ar;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.location.Location;
import android.opengl.Matrix;
import android.widget.LinearLayout;
import android.widget.RelativeLayout;
import android.widget.TextView;

import java.util.ArrayList;
import java.util.List;

import ng.dat.ar.helper.LocationHelper;
import ng.dat.ar.model.ARPoint;

/**

• Created by ntdat on 1/13/17.
  */

public class AROverlayView extends RelativeLayout {

private Context context;
private float[] rotatedProjectionMatrix = new float[16];
private Location currentLocation;
private final List<ARPoint> arPoints;
private final List<TextView> textViews;

public AROverlayView(Context context) {
    super(context);

    textViews = new ArrayList<>();

    this.context = context;
    this.setWillNotDraw(false);
    //Demo points
    arPoints = new ArrayList<ARPoint>() {{
        add(new ARPoint("New York", 40.7128, 74.0060, 50));
        add(new ARPoint("London", 51.5074, 0.1278, 100));
        add(new ARPoint("Frankfurn", 50.1109, 8.6821, 150));
        add(new ARPoint("Sydney", 33.8688, 151.2093, 200));
        add(new ARPoint("Rome", 41.9028, 12.4964, 250));
        add(new ARPoint("Athens", 37.9838, 23.7275, 300));
    }};


    for (int i = 0; i < arPoints.size(); i++) {

        textViews.add(new TextView(context));
        textViews.get(i).setTextSize(40);
        textViews.get(i).setBackgroundColor(Color.RED);
        this.addView(textViews.get(i));
    }
}


public void updateRotatedProjectionMatrix(float[] rotatedProjectionMatrix) {
    this.rotatedProjectionMatrix = rotatedProjectionMatrix;
    this.invalidate();
}

public void updateCurrentLocation(Location currentLocation) {
    this.currentLocation = currentLocation;
    this.invalidate();
}

@Override
protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);

    if (currentLocation == null) {
        return;
    }

    for (int i = 0; i < arPoints.size(); i++) {
        float[] currentLocationInECEF = LocationHelper.WSG84toECEF(currentLocation);
        float[] pointInECEF = LocationHelper.WSG84toECEF(arPoints.get(i).getLocation());
        float[] pointInENU = LocationHelper.ECEFtoENU(currentLocation, currentLocationInECEF, pointInECEF);

        float[] cameraCoordinateVector = new float[4];
        Matrix.multiplyMV(cameraCoordinateVector, 0, rotatedProjectionMatrix, 0, pointInENU, 0);

        // cameraCoordinateVector[2] is z, that always less than 0 to display on right position
        // if z > 0, the point will display on the opposite
        if (cameraCoordinateVector[2] < 0) {
            float x = (0.5f + cameraCoordinateVector[0] / cameraCoordinateVector[3]) * getWidth();
            float y = (0.5f - cameraCoordinateVector[1] / cameraCoordinateVector[3]) * getHeight();

            textViews.get(i).setX(x);
            textViews.get(i).setY(y);
            textViews.get(i).setText(arPoints.get(i).getName());
        }
    }
}

}

[SmartToolFactory]

Why Matrix.multiplyMV(cameraCoordinateVector, 0, rotatedProjectionMatrix, 0, pointInENU, 0); is required? What does it do?