Getting Marker coordinates from JSON to Android phone

Question

I have this code:

public class MainActivity extends FragmentActivity {
    private static final String LOG_TAG = "ExampleApp";

    private static final String SERVICE_URL = "http://heimerdinger.pe.hu/getjson.php";

    protected GoogleMap map;

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

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

    private void setUpMapIfNeeded() {
        if (map == null) {
            map = ((SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map))
                    .getMap();
            if (map != null) {
                setUpMap();
            }
        }
    }

    private void setUpMap() {
        // Retrieve the city data from the web service
        // In a worker thread since it's a network operation.
        new Thread(new Runnable() {
            public void run() {
                try {
                    retrieveAndAddCities();
                } catch (IOException e) {
                    Log.e(LOG_TAG, "Cannot retrive cities", e);
                    return;
                }
            }
        }).start();
    }

    protected void retrieveAndAddCities() throws IOException {
        HttpURLConnection conn = null;
        final StringBuilder json = new StringBuilder();
        try {
            // Connect to the web service
            URL url = new URL(SERVICE_URL);
            conn = (HttpURLConnection) url.openConnection();
            InputStreamReader in = new InputStreamReader(conn.getInputStream());

            // Read the JSON data into the StringBuilder
            int read;
            char[] buff = new char[1024];
            while ((read = in.read(buff)) != -1) {
                json.append(buff, 0, read);
            }
        } catch (IOException e) {
            Log.e(LOG_TAG, "Error connecting to service", e);
            throw new IOException("Error connecting to service", e);
        } finally {
            if (conn != null) {
                conn.disconnect();
            }
        }

        // Create markers for the city data.
        // Must run this on the UI thread since it's a UI operation.
        runOnUiThread(new Runnable() {
            public void run() {
                try {
                    createMarkersFromJson(json.toString());
                } catch (JSONException e) {
                    Log.e(LOG_TAG, "Error processing JSON", e);
                }
            }
        });
    }

    void createMarkersFromJson(String json) throws JSONException {
        // De-serialize the JSON string into an array of city objects
        JSONArray jsonArray = new JSONArray(json);
        for (int i = 0; i < jsonArray.length(); i++) {
            // Create a marker for each city in the JSON data.
            JSONObject jsonObj = jsonArray.getJSONObject(i);
            map.addMarker(new MarkerOptions()
                                .title(jsonObj.getString("nosaukums"))
                                .snippet(Integer.toString(jsonObj.getInt("")))
                                .position(new LatLng(jsonObj.getDouble("latCo"),jsonObj.getDouble("longCo"))));
        }
    }
}

The main idea is to get variable from JSON and to create markers in android. When i launch my application it accidentally crashes and gives me message in LogCat:

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.girts.trymap/com.example.girts.trymap.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'com.google.android.gms.maps.GoogleMap com.google.android.gms.maps.SupportMapFragment.getMap()' on a null object reference
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2298)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
    at android.app.ActivityThread.access$800(ActivityThread.java:144)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
    at android.os.Handler.dispatchMessage(Handler.java:102)
    at android.os.Looper.loop(Looper.java:135)
    at android.app.ActivityThread.main(ActivityThread.java:5221)
    at java.lang.reflect.Method.invoke(Native Method)
    at java.lang.reflect.Method.invoke(Method.java:372)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'com.google.android.gms.maps.GoogleMap com.google.android.gms.maps.SupportMapFragment.getMap()' on a null object reference
    at com.example.girts.trymap.MainActivity.setUpMapIfNeeded(MainActivity.java:48)
    at com.example.girts.trymap.MainActivity.onCreate(MainActivity.java:36)
    at android.app.Activity.performCreate(Activity.java:5937)
    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105)
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2251)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
    at android.app.ActivityThread.access$800(ActivityThread.java:144)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
    at android.os.Handler.dispatchMessage(Handler.java:102)
    at android.os.Looper.loop(Looper.java:135)
    at android.app.ActivityThread.main(ActivityThread.java:5221)
    at java.lang.reflect.Method.invoke(Native Method)
    at java.lang.reflect.Method.invoke(Method.java:372)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)

I dont know where the error is i read the whole code and everything there seems just right json in json can anyone help me what is happening?

xml:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
    android:layout_height="match_parent" android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:paddingBottom="@dimen/activity_vertical_margin" tools:context=".MainActivity">

    <com.google.android.gms.maps.MapView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:id="@+id/map" />
</RelativeLayout>

new LogCat:

org.json.JSONException: No value for
    at org.json.JSONObject.get(JSONObject.java:389)
    at org.json.JSONObject.getInt(JSONObject.java:478)
    at com.example.girts.trymap.MainActivity.createMarkersFromJson(MainActivity.java:115)
    at com.example.girts.trymap.MainActivity$2.run(MainActivity.java:99)
    at android.os.Handler.handleCallback(Handler.java:739)
    at android.os.Handler.dispatchMessage(Handler.java:95)
    at android.os.Looper.loop(Looper.java:135)
    at android.app.ActivityThread.main(ActivityThread.java:5221)
    at java.lang.reflect.Method.invoke(Native Method)
    at java.lang.reflect.Method.invoke(Method.java:372)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)

Answer 1

i think you have to use below code for map,

<fragment
    android:id="@+id/map"
    android:layout_width="match_parent"
    android:layout_height="0dip"
    android:layout_weight="7"
    class="com.google.android.gms.maps.SupportMapFragment" />

instead of this,

<com.google.android.gms.maps.MapView
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/map" />