无法用json在点之间绘制路径

Question

我对Android很新，我有这个项目，我正在努力。但是，我在这里遇到了一些挑战.. 该应用程序应该从用户的当前位置绘制一条线到选定的目的地。相反，当选择目标时，它会抛出此错误..

错误：

java.lang.NullPointerException: Attempt to invoke virtual method 'int java.lang.String.length()' on a null object reference

以下是代码块

public void onResponse(@NonNull Call<String> call, @NonNull Response<String> response) {
                    try {
                        JSONObject jsonObject = new JSONObject(response.body());
                        JSONArray jsonArray = jsonObject.getJSONArray("routes");

                        for(int i=0;i<jsonArray.length();i++)
                        {
                            JSONObject route = jsonArray.getJSONObject(i);
                            JSONObject poly = route.getJSONObject("overview_polyline");
                            String polyline = poly.getString("points");
                            polyLineList = decodePoly(polyline);

                        }

                        LatLngBounds.Builder builder = new LatLngBounds.Builder();
                        for(LatLng latLng:polyLineList)
                            builder.include(latLng);
                        LatLngBounds bounds = builder.build();
                        CameraUpdate mCameraUpdate = CameraUpdateFactory.newLatLngBounds(bounds,2);
                        mMap.animateCamera(mCameraUpdate);

                        polylineOptions = new PolylineOptions();
                        polylineOptions.color(Color.GRAY);
                        polylineOptions.width(5);
                        polylineOptions.startCap(new SquareCap());
                        polylineOptions.endCap(new SquareCap());
                        polylineOptions.jointType(JointType.ROUND);
                        polylineOptions.addAll(polyLineList);
                        greyPolyline = mMap.addPolyline(polylineOptions);


                        blackPolylineOptions = new PolylineOptions();
                        blackPolylineOptions.color(Color.BLACK);
                        blackPolylineOptions.width(5);
                        blackPolylineOptions.startCap(new SquareCap());
                        blackPolylineOptions.endCap(new SquareCap());
                        blackPolylineOptions.jointType(JointType.ROUND);
                        blackPolyline = mMap.addPolyline(blackPolylineOptions);

                        mMap.addMarker(new MarkerOptions()
                        .position(polyLineList.get(polyLineList.size()-1))
                        .title("Pick a location"));


                        //animations
                        ValueAnimator polyLineAnimator = ValueAnimator.ofInt(0,100);
                        polyLineAnimator.setDuration(2000);
                        polyLineAnimator.setInterpolator(new LinearInterpolator());
                        polyLineAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
                            @Override
                            public void onAnimationUpdate(ValueAnimator animation) {
                                List<LatLng> points = greyPolyline.getPoints();
                                int percentValue = (int)animation.getAnimatedValue();
                                int size = points.size();
                                int newPoints = (int) (size * (percentValue/100.0f));
                                List<LatLng> p = points.subList(0,newPoints);
                                blackPolyline.setPoints(p);

                            }
                        });

                        polyLineAnimator.start();

                        carMarker = mMap.addMarker(new MarkerOptions().position(currentPoint)
                        .flat(true)
                        .icon(BitmapDescriptorFactory.fromResource(R.drawable.car)));

                        handler = new Handler();
                        index =-1;
                        next=1;
                        handler.postDelayed(drawPathRunnable,3000);

                    }
                    catch (JSONException e)
                    {
                        e.printStackTrace();
                    }
                }