我无法写入数据库

Question

我想在地图上长按一下就保存坐标信息。我有错误的两个类：

 mMapView = (MapView) v.findViewById(R.id.mapView);
    mMapView.onCreate(savedInstanceState);
    mMapView.getMapAsync(new OnMapReadyCallback() {
        @Override
        public void onMapReady(GoogleMap googleMap)
        {
            mGoogleMap = googleMap;

            if(mGoogleMap == null)
            {return;}
            else {
                mGoogleMap.setOnMapLongClickListener(new GoogleMap.OnMapLongClickListener() {
                    @Override
                    public void onMapLongClick(LatLng latLng) {
                        mGoogleMap.addMarker(new MarkerOptions().position(latLng).title("Sei qui").snippet(coordinateList));
                        ContentValues contentValues = new ContentValues();
                        coordinateList = latLng.latitude + ", " + latLng.longitude;
                        contentValues.put("coordinate", coordinateList);
                       dbManager.setProvider(contentValues);

                    }
                });

                mGoogleMap.setOnMarkerClickListener(new GoogleMap.OnMarkerClickListener() {
                    @Override
                    public boolean onMarkerClick(Marker marker)
                    {

                        /*String id = marker.getId();
                        String position = marker.getPosition().toString();
                        marker.setSnippet(id + "-" + position);
                        marker.showInfoWindow();*/
                        marker.getId();
                        marker.getTitle();
                        marker.getSnippet();
                        marker.showInfoWindow();
                        return false;
                    }
                });


                mGoogleMap.setInfoWindowAdapter(new GoogleMap.InfoWindowAdapter() {
                    @Override
                    public View getInfoWindow(Marker marker) {
                        return null;
                    }

                    @Override
                    public View getInfoContents(final Marker marker) {

                        View v = getLayoutInflater(bundle).from(getActivity()).inflate(R.layout.snipper_layout, null);

                        TextView id = (TextView) v.findViewById(R.id.id);
                        TextView descrizione = (TextView) v.findViewById(R.id.descrizione);
                        TextView title = (TextView) v.findViewById(R.id.title);

                        title.setText(marker.getTitle());
                        descrizione.setText(marker.getSnippet());
                        id.setText("ID: " + marker.getId());

                        return v; //inflate e inserimento dati
                    }
                });

                mGoogleMap.setOnInfoWindowLongClickListener(new GoogleMap.OnInfoWindowLongClickListener()
                {
                    @Override
                    public void onInfoWindowLongClick(Marker marker)
                    {
                        mostraToast("hai toccato l'ID: " + marker.getId());
                        openDialog(marker);
                    }
                });
            }
        }
    });

给我错误的行：

       contentValues.put("coordinate", coordinateList);

和

public class DbManager

{     private DbHelper helper = null;

public DbManager(Context context)
{
    helper=new DbHelper(context);
}

public void setProvider(ContentValues contentValues)
{
    SQLiteDatabase db = helper.getWritableDatabase();
    db.insert("tab", null, contentValues);
}

public List<String> getProviderss()
{
    SQLiteDatabase db=helper.getReadableDatabase();
    Cursor crs=db.query("tab", null, null, null, null, null, null);

    List<String> res;
    res = new ArrayList<String>();

    while(crs.moveToNext())
    {
        String cord = crs.getString(crs.getColumnIndex("coordinate"));
        //String altezzaPal = crs.getString(crs.getColumnIndex("altezzapalo"));
        //String paloTipo = crs.getString(crs.getColumnIndex("palotipo"));
        res.add(cord /*+ altezzaPal + paloTipo*/);
    }
    return res;
}

}

我的SQLiteDatabase类：

public class DbHelper extends SQLiteOpenHelper

{

public DbHelper(Context context)
{
    super(context, "Providerss", null, 1);
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion)
{ }

@Override
public void onCreate(SQLiteDatabase db)
{
    String query = "CREATE TABLE tab " +
            "(" +
            "_id integer primary key autoincrement, " +
            "coordinate text " + // manca ,
            //"palotipo text, " +
            //"altezzapalo text" +
            ")";

    db.execSQL(query);
    inizialzza(db);
}

public void inizialzza(SQLiteDatabase db)
{
    ContentValues contentValues = new ContentValues();
    contentValues.put("coordinate", "ciao");
    db.insert("tab", null, contentValues);
}

}

，例外是：

E/AndroidRuntime: FATAL EXCEPTION: main
              Process: com.example.mattia.provaconfragment, PID: 7045
              java.lang.NullPointerException: Attempt to invoke virtual method 'android.database.sqlite.SQLiteDatabase android.content.Context.openOrCreateDatabase(java.lang.String, int, android.database.sqlite.SQLiteDatabase$CursorFactory, android.database.DatabaseErrorHandler)' on a null object reference
                  at android.database.sqlite.SQLiteOpenHelper.getDatabaseLocked(SQLiteOpenHelper.java:223)
                  at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:163)
                  at com.example.mattia.provaconfragment.Database.DbManager.setProvider(DbManager.java:26)
                  at com.example.mattia.provaconfragment.PrimoFragment$3$1.onMapLongClick(PrimoFragment.java:107)
                  at com.google.android.gms.maps.GoogleMap$24.onMapLongClick(Unknown Source)
                  at com.google.android.gms.maps.internal.zzs$zza.onTransact(Unknown Source)
                  at android.os.Binder.transact(Binder.java:387)
                  at zr.a(:com.google.android.gms.DynamiteModulesB:93)
                  at maps.D.p$2.a(Unknown Source)
                  at maps.V.u.f(Unknown Source)
                  at maps.V.P.onLongPress(Unknown Source)
                  at maps.z.e$b.onLongPress(Unknown Source)
                  at maps.z.c.c(Unknown Source)
                  at maps.z.c$a.handleMessage(Unknown Source)
                  at android.os.Handler.dispatchMessage(Handler.java:102)
                  at android.os.Looper.loop(Looper.java:148)
                  at android.app.ActivityThread.main(ActivityThread.java:5417)
                  at java.lang.reflect.Method.invoke(Native Method)
                  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
                  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)