How to move marker along polyline using google map

Question

I am trying to move the marker according to the polyline and with animation. Similar to the below image:

Mapbox is already giving this kind of demo. But I w

Answer 1

You can use for your task your approach based on custom marker animation: animate separately car movement and car turns throughout all direction points. For this You need 2 kinds of animation:

1) animation for car movement;

2) animation for car turn;

which calls each other on its end (car movement animation on end calls car turn animation and vice versa: car turn animation on its end calls car movement animation and so for all points of car path).

For example on fig.:

1) animation for car movement from P0 to P1;

2) animation for car turn on P1;

3) animation for car movement from P1 to P2

and so on.

Car movement animation can be implemented by method like this:

private void animateCarMove(final Marker marker, final LatLng beginLatLng, final LatLng endLatLng, final long duration) {
        final Handler handler = new Handler();
        final long startTime = SystemClock.uptimeMillis();

        final Interpolator interpolator = new LinearInterpolator();

        // set car bearing for current part of path
        float angleDeg = (float)(180 * getAngle(beginLatLng, endLatLng) / Math.PI);
        Matrix matrix = new Matrix();
        matrix.postRotate(angleDeg);
        marker.setIcon(BitmapDescriptorFactory.fromBitmap(Bitmap.createBitmap(mMarkerIcon, 0, 0, mMarkerIcon.getWidth(), mMarkerIcon.getHeight(), matrix, true)));

        handler.post(new Runnable() {
            @Override
            public void run() {
                // calculate phase of animation
                long elapsed = SystemClock.uptimeMillis() - startTime;
                float t = interpolator.getInterpolation((float) elapsed / duration);
                // calculate new position for marker
                double lat = (endLatLng.latitude - beginLatLng.latitude) * t + beginLatLng.latitude;
                double lngDelta = endLatLng.longitude - beginLatLng.longitude;

                if (Math.abs(lngDelta) > 180) {
                    lngDelta -= Math.signum(lngDelta) * 360;
                }
                double lng = lngDelta * t + beginLatLng.longitude;

                marker.setPosition(new LatLng(lat, lng));

                // if not end of line segment of path 
                if (t < 1.0) {
                    // call next marker position
                    handler.postDelayed(this, 16);
                } else {
                    // call turn animation
                    nextTurnAnimation();
                }
            }
        });
    }

where

mMarkerIcon is:

Bitmap mMarkerIcon;
...
mMarkerIcon = BitmapFactory.decodeResource(getResources(), R.drawable.the_car);  // for your car icon in file the_car.png in drawable folder

and car icon should be North oriented:

for correct rotation apply

nextTurnAnimation() - method called on end of car movement animation to start car turn animation:

private void nextTurnAnimation() {
        mIndexCurrentPoint++;

        if (mIndexCurrentPoint < mPathPolygonPoints.size() - 1) {
            LatLng prevLatLng = mPathPolygonPoints.get(mIndexCurrentPoint - 1);
            LatLng currLatLng = mPathPolygonPoints.get(mIndexCurrentPoint);
            LatLng nextLatLng = mPathPolygonPoints.get(mIndexCurrentPoint + 1);

            float beginAngle = (float)(180 * getAngle(prevLatLng, currLatLng) / Math.PI);
            float endAngle = (float)(180 * getAngle(currLatLng, nextLatLng) / Math.PI);

            animateCarTurn(mCarMarker, beginAngle, endAngle, TURN_ANIMATION_DURATION);
        }
    }

In its turn car turn animation method can be like this:

private void animateCarTurn(final Marker marker, final float startAngle, final float endAngle, final long duration) {
        final Handler handler = new Handler();
        final long startTime = SystemClock.uptimeMillis();
        final Interpolator interpolator = new LinearInterpolator();

        final float dAndgle = endAngle - startAngle;

        Matrix matrix = new Matrix();
        matrix.postRotate(startAngle);
        Bitmap rotatedBitmap = Bitmap.createBitmap(mMarkerIcon, 0, 0, mMarkerIcon.getWidth(), mMarkerIcon.getHeight(), matrix, true);
        marker.setIcon(BitmapDescriptorFactory.fromBitmap(rotatedBitmap));

        handler.post(new Runnable() {
            @Override
            public void run() {

                long elapsed = SystemClock.uptimeMillis() - startTime;
                float t = interpolator.getInterpolation((float) elapsed / duration);

                Matrix m = new Matrix();
                m.postRotate(startAngle + dAndgle * t);
                marker.setIcon(BitmapDescriptorFactory.fromBitmap(Bitmap.createBitmap(mMarkerIcon, 0, 0, mMarkerIcon.getWidth(), mMarkerIcon.getHeight(), m, true)));

                if (t < 1.0) {
                    handler.postDelayed(this, 16);
                } else {
                    nextMoveAnimation();
                }
            }
        });
    }

where nextMoveAnimation() is:

private void nextMoveAnimation() {
        if (mIndexCurrentPoint <  mPathPolygonPoints.size() - 1) {
            animateCarMove(mCarMarker, mPathPolygonPoints.get(mIndexCurrentPoint), mPathPolygonPoints.get(mIndexCurrentPoint+1), MOVE_ANIMATION_DURATION);
        }
    }

The mPathPolygonPoints (geopoints of car trip) is:

private List mPathPolygonPoints;

And the mIndexCurrentPoint variable is index of current point on path (it should be 0 at start of animation and incremented on each turn of path in nextTurnAnimation() method).

TURN_ANIMATION_DURATION - duration (in ms) animation for car turn on path geopoint;

MOVE_ANIMATION_DURATION - duration (in ms) animation for car movement along line segment of path;

To get bearing You can use method like that:

private double getAngle(LatLng beginLatLng, LatLng endLatLng) {
        double f1 = Math.PI * beginLatLng.latitude / 180;
        double f2 = Math.PI * endLatLng.latitude / 180;
        double dl = Math.PI * (endLatLng.longitude - beginLatLng.longitude) / 180;
        return Math.atan2(Math.sin(dl) * Math.cos(f2) , Math.cos(f1) * Math.sin(f2) - Math.sin(f1) * Math.cos(f2) * Math.cos(dl));;
    }

Finally You can start all animations by call animateCarMove() once:

animateCarMove(mCarMarker, mPathPolygonPoints.get(0), mPathPolygonPoints.get(1), MOVE_ANIMATION_DURATION);

other steps of animation will be called automatically for each point of car path.

And You should take into account some "special cases" like:

1) changing sign of of turn angle (e.g. bearing changes from -120 to 150 degrees);

2) possibilities for interrupt of animation by user;

3) calculate animation duration on path segment length (e.g. 1 sec for 1 km of segment length instead of fixed MOVE_ANIMATION_DURATION)

4) probably tune value 16 in handler.postDelayed(this, 16); line for better performance;

5) and so on.