MapFragment - NullPointerException - Google Maps V

问题:

I'm getting an NullPointerException with the following code:

private ProjectionProxy proxy = new ProjectionProxy();
private GoogleMap mMap = null;
private Context context = this;

@Override
protected void onCreate(Bundle load) { 
    super.onCreate(load);

    setContentView(R.layout.fragment_ride_tracking);

    //mMap = ((MapFragment) getFragmentManager().findFragmentById(R.id.myMapView)).getMap();

    mMap = ((MapFragment) getFragmentManager().findFragmentById(R.id.map)).getMap();

    int result = GooglePlayServicesUtil.isGooglePlayServicesAvailable(context);

    mMap.setMapType(GoogleMap.MAP_TYPE_NORMAL);
    mMap.setMyLocationEnabled(true);

    //SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.myMapView);
    //mMap = mapFragment.getMap();

    Log.e("RideTracking", "Google Map VALUE:"+mMap);

    if (mMap != null) { 
        proxy.setProjection(mMap.getProjection());
    }

The line where the NullPointerException is happening is this line of code:

mMap = ((MapFragment) getFragmentManager().findFragmentById(R.id.map)).getMap();

I'm not initializing my mMap variable to null. What is my issue here?

回答1:

Try to check the MapFragment that you've created in the XML of the Activity. Check mine; it's working.

...

<fragment
        android:id="@+id/map"
        android:name="com.google.android.gms.maps.MapFragment"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1" />

...

Is yours different? Also, you checked if you put the correct permissions and metadata on the AndroidManifest.xml?

Here's the permission:

<uses-permission android:name="com.google.android.providers.gsf.permission.READ_GSERVICES" />

And here's the metadata section:

<application>

    ...

    <meta-data android:name="com.google.android.maps.v2.API_KEY"
               android:value="HERE GOES YOUR API KEY" />

</application>

I hope this helps you!

回答2:

MainActivity.xml :

<?xml version="1.0" encoding="utf-8"?>
<fragment
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/map"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:name="com.google.android.gms.maps.SupportMapFragment"/>

MainActivity.java :

private GoogleMap googleMap;
googleMap = ((SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map)).getMap();

回答3:

You may be missing this from manifest.xml
<meta-data android:name="com.google.android.gms.version" android:value="@integer/google_play_services_version"/>