开发GPS追踪器应用程序。我在这个应用程序中使用了片段找到我自己我放了一个mylocation按钮，将我重定向到MapFragment文件。但是我在moveCamera（cameraUpdate）上得到了NullPointerException
我的错误如下：
java.lang.NullPointerException: Attempt to invoke virtual method 'void com.google.android.gms.maps.GoogleMap.moveCamera(com.google.android.gms.maps.CameraUpdate)' on a null object reference
at aark.co.in.locateme.fragments.MapFragment.onCreateView(MapFragment.java:217)
at android.support.v4.app.Fragment.performCreateView(Fragment.java:2074)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1104)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1286)
at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:758)
at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1671)
at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:532)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5441)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:738)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:628)
和这里是mapFragment.java代码。
public View onCreateView (LayoutInflater inflater, ViewGroup container, Bundle
savedInstanceState){
View rootview = inflater.inflate(R.layout.fragment_map, container, false);
// Getting a reference to the AutoCompleteTextView
mMapView = (MapView) rootview.findViewById(R.id.maps);
mMapView.getMapAsync(onMapReadyCallback);
mMapView.onCreate(savedInstanceState);
dbHelper = new SQLiteHandler(getActivity());
// MapView mapView;
// ((SupportMapFragment) getActivity().getSupportFragmentManager().findFragmentById(R.id.mapToday)).getMapAsync(onMapReadyCallback);
// SupportMapFragment mapFragment ;
// ((SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map)).getMapAsync(onMapReadyCallback);
// ((MapView) getSupportFragmentManager().findFragmentById(R.id.maps))
// MapsInitializer.initialize(getActivity().getApplicationContext());
FloatingActionButton fab = (FloatingActionButton) rootview.findViewById(R.id.fabChat);
fab.setOnClickListener(new View.OnClickListener() {
// @Contract("_, null -> null") — method returns null if its second argument is null @Contract("_, null -> null; _, !null -> !null") — method returns null if its second argument is null and not-null otherwise @Contract("true -> fail") — a typical assertFalse method which throws an exception if true is passed to it
@Override
public void onClick(View view) {
Intent intent = new Intent(getActivity(), AddUserMapActivity.class);
startActivity(intent);
}
});
// FloatingActionButton fabnav= (FloatingActionButton) rootview.findViewById(R.id.fabNav);
// fabnav.setOnClickListener(new View.OnClickListener() {
// @Override
// public void onClick(View v) {
// showDistance();
// }
// });
mMapView.onResume();// needed to get the map to display immediately
// try {
// MapsInitializer.initialize(getActivity().getApplicationContext());
// } catch (Exception e) {
// e.printStackTrace();
// }
// latitude and longitude
//Getting Current Location Here
GPSTracker mGPS = new GPSTracker(getActivity());
if (!mGPS.canGetLocation()) {
mGPS.showSettingsAlert();
} else {
latitude = mGPS.getLatitude();
longitude = mGPS.getLongitude();
}
if (latitude != 0.0 && longitude != 0.0) {
// create marker
MarkerOptions marker = new MarkerOptions().position(
new LatLng(latitude, longitude)).title("You");
marker.icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_ROSE));
if (marker != null) {
// adding marker
mGoogleMap.addMarker(marker);
}
// Changing marker icon
}
//Setting camera position
//CameraPosition cameraPosition = new Builder()
// .target(new LatLng(latitude, longitude)).zoom(17).build();
LatLng latLng = new LatLng(latitude, longitude);
CameraUpdate cameraUpdate = CameraUpdateFactory.newLatLngZoom(latLng,17);
mGoogleMap.moveCamera(cameraUpdate);
MainActivity.java代码如下
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//Setting Start Navigation
aController = (AppController) getApplicationContext();
mToolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(mToolbar);
getSupportActionBar().setDisplayShowHomeEnabled(true);
drawerFragment = (FragmentDrawer)
getSupportFragmentManager().findFragmentById(R.id.fragment_navigation_drawer);
drawerFragment.setUp(R.id.fragment_navigation_drawer, (DrawerLayout) findViewById(R.id.drawer_layout), mToolbar);
drawerFragment.setDrawerListener(this);
// display the first navigation drawer view on app launch
displayView(0);
//Setting End Navigation
//Setting Font in Calibri
font_calibri = Typeface.createFromAsset(getAssets(), "calibri_bold.ttf");
txtUserName = (TextView) findViewById(R.id.txt_profile_name);
//Intent i=getIntent();
sharedPreferences = getSharedPreferences(MyPREFERENCES, Context.MODE_PRIVATE);
editor = sharedPreferences.edit();
icprofile = (ImageView) findViewById(R.id.ic_profile);
String stringpath = sharedPreferences.getString("key_profile_pic", "Null Value");
String stringname = sharedPreferences.getString("key_profile_name", "Null Value");
String stringnumber = sharedPreferences.getString("key_mobile", "Null Value");
txtUserName.setText(stringname);
File imgFile = new File(stringpath);
if (imgFile.exists()) {
Bitmap bmp = BitmapFactory.decodeFile(imgFile.getAbsolutePath());
Bitmap circleImage = Bitmap.createBitmap(bmp.getWidth(), bmp.getHeight(), Bitmap.Config.ARGB_8888);
BitmapShader shader = new BitmapShader(bmp, Shader.TileMode.CLAMP, Shader.TileMode.CLAMP);
Paint paint = new Paint();
paint.setShader(shader);
paint.setAntiAlias(true);
Canvas c = new Canvas(circleImage);
c.drawCircle(bmp.getWidth() / 2, bmp.getHeight() / 2, bmp.getWidth() / 2, paint);
icprofile.setImageBitmap(circleImage);
}
icprofile.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent intent = new Intent(getApplicationContext(), ProfileActivity.class);
startActivity(intent);
///Now set this bitmap on imageview
}
});
if (name != null && email != null) {
name = stringname;
email = stringnumber;
}
//Checking For GPS Enabled Or Disabled
LocationManager locationManager = (LocationManager) getSystemService(LOCATION_SERVICE);
if (locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER)) {
// showGPSDisabledAlertToUser();
} else {
showGPSDisabledAlertToUser();
}
//For Fragment Stack
//Checking Google Play Services
name = stringname;
email = stringnumber;
// Make sure the device has the proper dependencies.
GCMRegistrar.checkDevice(this);
// Make sure the manifest was properly set - comment out this line
// while developing the app, then uncomment it when it's ready.
GCMRegistrar.checkManifest(this);
registerReceiver(mHandleMessageReceiver, new IntentFilter(
DISPLAY_MESSAGE_ACTION));
// Get GCM registration id
final String regId = GCMRegistrar.getRegistrationId(this);
// Check if regid already presents
if (regId.equals("")) {
// Registration is not present, register now with GCM
GCMRegistrar.register(this, SENDER_ID);
} else {
// Device is already registered on GCM
if (GCMRegistrar.isRegisteredOnServer(this)) {
// Skips registration.
Toast.makeText(getApplicationContext(), "Already registered with GCM", Toast.LENGTH_LONG).show();
} else {
// Try to register again, but not in the UI thread.
// It's also necessary to cancel the thread onDestroy(),
// hence the use of AsyncTask instead of a raw thread.
final Context context = this;
mRegisterTask = new AsyncTask<Void, Void, Void>() {
@Override
protected Void doInBackground(Void... params) {
// Register on our server
// On server creates a new user
ServerUtilities.register(context, name, email, regId);
return null;
}
@Override
protected void onPostExecute(Void result) {
mRegisterTask = null;
}
};
mRegisterTask.execute(null, null, null);
}
}
// ATTENTION: This was auto-generated to implement the App Indexing API.
// See https://g.co/AppIndexing/AndroidStudio for more information.
client = new GoogleApiClient.Builder(this).addApi(AppIndex.API).build();
}
@Override
public void onDrawerItemSelected(View view, int position) {
displayView(position);
}
private void displayView(int position) {
Fragment fragment = null;
String title = getString(R.string.app_name);
switch (position) {
case 0:
fragment = new HomeFragment();
title = getString(R.string.title_home);
break;
case 1:
fragment = new FriendsFragment();
title = getString(R.string.title_friends);
isExit = false;
break;
case 2:
fragment = new MessageFragment();
title = getString(R.string.title_messages);
isExit = false;
break;
case 3:
fragment = new MapFragment();
title = getString(R.string.title_map);
isExit = false;
break;
case 4:
fragment = new SettingFragment();
title = getString(R.string.title_setting);
isExit = false;
break;
case 5:
fragment = new AboutFragment();
title = getString(R.string.title_about);
isExit = false;
break;
default:
break;
}如果有的话，请你找到解决方案。 谢谢你花了宝贵的时间..