Question

我希望在我的应用内部实施的Google地图中的两点之间找到方向。我使用过一个我在网上找到的简单课程。当我运行代码时，它会抛出此错误：日志文件：

02-27 19:33:52.819: E/AndroidRuntime(1871): java.lang.RuntimeException: Unable to start activity ComponentInfo{info.androidhive.googlemapsv2/info.androidhive.googlemapsv2.MainActivity}: java.lang.NullPointerException
02-27 19:33:52.819: E/AndroidRuntime(1871):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2211)
02-27 19:33:52.819: E/AndroidRuntime(1871):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261)
02-27 19:33:52.819: E/AndroidRuntime(1871):     at android.app.ActivityThread.access$600(ActivityThread.java:141)
02-27 19:33:52.819: E/AndroidRuntime(1871):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256)
02-27 19:33:52.819: E/AndroidRuntime(1871):     at android.os.Handler.dispatchMessage(Handler.java:99)
02-27 19:33:52.819: E/AndroidRuntime(1871):     at android.os.Looper.loop(Looper.java:137)
02-27 19:33:52.819: E/AndroidRuntime(1871):     at android.app.ActivityThread.main(ActivityThread.java:5103)
02-27 19:33:52.819: E/AndroidRuntime(1871):     at java.lang.reflect.Method.invokeNative(Native Method)
02-27 19:33:52.819: E/AndroidRuntime(1871):     at java.lang.reflect.Method.invoke(Method.java:525)
02-27 19:33:52.819: E/AndroidRuntime(1871):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
02-27 19:33:52.819: E/AndroidRuntime(1871):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
02-27 19:33:52.819: E/AndroidRuntime(1871):     at dalvik.system.NativeStart.main(Native Method)
02-27 19:33:52.819: E/AndroidRuntime(1871): Caused by: java.lang.NullPointerException
02-27 19:33:52.819: E/AndroidRuntime(1871):     at info.androidhive.googlemapsv2.GMapV2Direction.getDirection(GMapV2Direction.java:112)
02-27 19:33:52.819: E/AndroidRuntime(1871):     at info.androidhive.googlemapsv2.MainActivity.onCreate(MainActivity.java:34)
02-27 19:33:52.819: E/AndroidRuntime(1871):     at android.app.Activity.performCreate(Activity.java:5133)
02-27 19:33:52.819: E/AndroidRuntime(1871):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
02-27 19:33:52.819: E/AndroidRuntime(1871):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2175)
02-27 19:33:52.819: E/AndroidRuntime(1871):     ... 11 more

方向类：

public class GMapV2Direction {
    public final static String MODE_DRIVING = "driving";
    public final static String MODE_WALKING = "walking";

    public GMapV2Direction() {
    }

    public Document getDocument(LatLng start, LatLng end, String mode) {
        String url = "http://maps.googleapis.com/maps/api/directions/xml?"
                + "origin=" + start.latitude + "," + start.longitude
                + "&destination=" + end.latitude + "," + end.longitude
                + "&sensor=false&units=metric&mode=" + mode;

        try {
            HttpClient httpClient = new DefaultHttpClient();
            HttpContext localContext = new BasicHttpContext();
            HttpPost httpPost = new HttpPost(url);
            HttpResponse response = httpClient.execute(httpPost, localContext);
            InputStream in = response.getEntity().getContent();
            DocumentBuilder builder = DocumentBuilderFactory.newInstance()
                    .newDocumentBuilder();
            Document doc = builder.parse(in);
            return doc;
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

    public String getDurationText(Document doc) {
        NodeList nl1 = doc.getElementsByTagName("duration");
        Node node1 = nl1.item(nl1.getLength() - 1);
        NodeList nl2 = node1.getChildNodes();
        Node node2 = nl2.item(getNodeIndex(nl2, "text"));
        Log.i("DurationText", node2.getTextContent());
        return node2.getTextContent();
    }

    public int getDurationValue(Document doc) {
        NodeList nl1 = doc.getElementsByTagName("duration");
        Node node1 = nl1.item(nl1.getLength() - 1);
        NodeList nl2 = node1.getChildNodes();
        Node node2 = nl2.item(getNodeIndex(nl2, "value"));
        Log.i("DurationValue", node2.getTextContent());
        return Integer.parseInt(node2.getTextContent());
    }

    public String getDistanceText(Document doc) {
        NodeList nl1 = doc.getElementsByTagName("distance");
        Node node1 = nl1.item(nl1.getLength() - 1);
        NodeList nl2 = node1.getChildNodes();
        Node node2 = nl2.item(getNodeIndex(nl2, "text"));
        Log.i("DistanceText", node2.getTextContent());
        return node2.getTextContent();
    }

    public int getDistanceValue(Document doc) {
        NodeList nl1 = doc.getElementsByTagName("distance");
        Node node1 = nl1.item(nl1.getLength() - 1);
        NodeList nl2 = node1.getChildNodes();
        Node node2 = nl2.item(getNodeIndex(nl2, "value"));
        Log.i("DistanceValue", node2.getTextContent());
        return Integer.parseInt(node2.getTextContent());
    }

    public String getStartAddress(Document doc) {
        NodeList nl1 = doc.getElementsByTagName("start_address");
        Node node1 = nl1.item(0);
        Log.i("StartAddress", node1.getTextContent());
        return node1.getTextContent();
    }

    public String getEndAddress(Document doc) {
        NodeList nl1 = doc.getElementsByTagName("end_address");
        Node node1 = nl1.item(0);
        Log.i("StartAddress", node1.getTextContent());
        return node1.getTextContent();
    }

    public String getCopyRights(Document doc) {
        NodeList nl1 = doc.getElementsByTagName("copyrights");
        Node node1 = nl1.item(0);
        Log.i("CopyRights", node1.getTextContent());
        return node1.getTextContent();
    }

    public ArrayList<LatLng> getDirection(Document doc) {
        NodeList nl1, nl2, nl3;
        ArrayList<LatLng> listGeopoints = new ArrayList<LatLng>();
        nl1 = doc.getElementsByTagName("step");
        if (nl1.getLength() > 0) {
            for (int i = 0; i < nl1.getLength(); i++) {
                Node node1 = nl1.item(i);
                nl2 = node1.getChildNodes();

                Node locationNode = nl2
                        .item(getNodeIndex(nl2, "start_location"));
                nl3 = locationNode.getChildNodes();
                Node latNode = nl3.item(getNodeIndex(nl3, "lat"));
                double lat = Double.parseDouble(latNode.getTextContent());
                Node lngNode = nl3.item(getNodeIndex(nl3, "lng"));
                double lng = Double.parseDouble(lngNode.getTextContent());
                listGeopoints.add(new LatLng(lat, lng));

                locationNode = nl2.item(getNodeIndex(nl2, "polyline"));
                nl3 = locationNode.getChildNodes();
                latNode = nl3.item(getNodeIndex(nl3, "points"));
                ArrayList<LatLng> arr = decodePoly(latNode.getTextContent());
                for (int j = 0; j < arr.size(); j++) {
                    listGeopoints.add(new LatLng(arr.get(j).latitude, arr
                            .get(j).longitude));
                }

                locationNode = nl2.item(getNodeIndex(nl2, "end_location"));
                nl3 = locationNode.getChildNodes();
                latNode = nl3.item(getNodeIndex(nl3, "lat"));
                lat = Double.parseDouble(latNode.getTextContent());
                lngNode = nl3.item(getNodeIndex(nl3, "lng"));
                lng = Double.parseDouble(lngNode.getTextContent());
                listGeopoints.add(new LatLng(lat, lng));
            }
        }

        return listGeopoints;
    }

    private int getNodeIndex(NodeList nl, String nodename) {
        for (int i = 0; i < nl.getLength(); i++) {
            if (nl.item(i).getNodeName().equals(nodename))
                return i;
        }
        return -1;
    }

    private ArrayList<LatLng> decodePoly(String encoded) {
        ArrayList<LatLng> poly = new ArrayList<LatLng>();
        int index = 0, len = encoded.length();
        int lat = 0, lng = 0;
        while (index < len) {
            int b, shift = 0, result = 0;
            do {
                b = encoded.charAt(index++) - 63;
                result |= (b & 0x1f) << shift;
                shift += 5;
            } while (b >= 0x20);
            int dlat = ((result & 1) != 0 ? ~(result >> 1) : (result >> 1));
            lat += dlat;
            shift = 0;
            result = 0;
            do {
                b = encoded.charAt(index++) - 63;
                result |= (b & 0x1f) << shift;
                shift += 5;
            } while (b >= 0x20);
            int dlng = ((result & 1) != 0 ? ~(result >> 1) : (result >> 1));
            lng += dlng;

            LatLng position = new LatLng((double) lat / 1E5, (double) lng / 1E5);
            poly.add(position);
        }
        return poly;
    }
}

主要活动类例如：

public class MainActivity extends Activity {

    private GoogleMap googleMap;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        LatLng fromPosition = new LatLng(13.687140112679154, 100.53525868803263);
        LatLng toPosition = new LatLng(13.683660045847258, 100.53900808095932);

        initilizeMap();
        GMapV2Direction md = new GMapV2Direction();

        Document doc = md.getDocument(fromPosition, toPosition,
                GMapV2Direction.MODE_DRIVING);
        ArrayList<LatLng> directionPoint = md.getDirection(doc);
        PolylineOptions rectLine = new PolylineOptions().width(3).color(
                Color.RED);

        for (int i = 0; i < directionPoint.size(); i++) {
            rectLine.add(directionPoint.get(i));
        }

        googleMap.addPolyline(rectLine);

    }

    @Override
    protected void onResume() {
        super.onResume();
        initilizeMap();
    }

    /**
     * function to load map If map is not created it will create it for you
     * */
    private void initilizeMap() {
        if (googleMap == null) {
            googleMap = ((MapFragment) getFragmentManager().findFragmentById(
                    R.id.map)).getMap();

            if (googleMap == null) {
                Toast.makeText(getApplicationContext(),
                        "Sorry! unable to create maps", Toast.LENGTH_SHORT)
                        .show();
            }
        }
    }

Answer 1

如果您想获得方向，则需要设置AsyncTask以获取数据格式的Google服务，示例代码如下：

class GetDirections extends AsyncTask<String, String, String>{
        @Override
        protected String doInBackground(String... params) {
            String startAddress =  params[0];
            startAddress = startAddress.replaceAll(" ", "%20");
            getLatLng(startAddress, false);

            String endingAddress = params[1];
            endingAddress = endingAddress.replaceAll(" ", "%20");
            getLatLng(endingAddress, true);
            return null;
        }

        @Override
        protected void onPostExecute(String s) {
            super.onPostExecute(s);
            String geoUriString = "http://maps.google.com/maps?addr=" +
                    addressPos.latitude + "," +
                    addressPos.longitude + "&daddr=" +
                    finalAddressPos.latitude + "," +
                    finalAddressPos.longitude;

            Intent mapCall = new Intent(Intent.ACTION_VIEW, Uri.parse(geoUriString));
            startActivity(mapCall);
        }
    }

    protected void getLatLng(String address, boolean setDestination) {
        String uri = "http://maps.google.com/maps/api/geocode/json?address="
                + address + "&sensor=false";

        HttpGet httpGet = new HttpGet(uri);

        HttpClient client = new DefaultHttpClient();
        HttpResponse response;
        StringBuilder stringBuilder = new StringBuilder();

        try {
            response = client.execute(httpGet);
            HttpEntity entity = response.getEntity();

            InputStream stream = entity.getContent();

            int byteData;
            while ((byteData = stream.read()) != -1) {
                stringBuilder.append((char) byteData);
            }

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

        double lat = 0.0, lng = 0.0;

        JSONObject jsonObject;
        try {
            jsonObject = new JSONObject(stringBuilder.toString());
            lng = ((JSONArray) jsonObject.get("results")).getJSONObject(0)
                    .getJSONObject("geometry").getJSONObject("location")
                    .getDouble("lng");
            lat = ((JSONArray) jsonObject.get("results")).getJSONObject(0)
                    .getJSONObject("geometry").getJSONObject("location")
                    .getDouble("lat");

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

        if (setDestination) {
            finalAddressPos = new LatLng(lat, lng);
        } else {
            addressPos = new LatLng(lat, lng);
        }

    }

然后获取start and end address表单editText并在用户click get direction button时执行AsyncTask：

public void getDirections(View view) {

        String startingAddress = et_address.getText().toString();
        String finalAddress = et_finalAddress.getText().toString();

        if ((startingAddress.equals("")) || finalAddress.equals("")) {
            Toast.makeText(this, "Enter a starting and Ending address", Toast.LENGTH_SHORT).show();
        } else {
            new GetDirections().execute(startingAddress, finalAddress);
        }
    }

您可以获取我的Github here的所有源代码。

enter image description here

Android之间两点简单方向

1 个答案: