Null Objekt Referenz in Android sqlite

Question

Ich versuche, die Liste der Schulen von SQLite-Datenbank zu laden und es in AutoVervollständigen TextView in, dass ich bekomme ein Null-Objekt Fehler.Ich habe die SQLite Daten aus Asset-Ordner seit den Daten geladen sind zu hoch, ich habe es aus Assesse-Ordner geladen.

Code:

public class Profileeditpage extends AppCompatActivity implements GoogleApiClient.OnConnectionFailedListener, GoogleApiClient.ConnectionCallbacks{ 
    EditText name,email; 
    SQLiteDatabase db; 
    List<Schoolname> nameschool; 
    AutoCompleteTextView grade,location,schoolname; 
    Toolbar mtool; 
    private static final String LOG_TAG = "MainActivity"; 
    private static final int GOOGLE_API_CLIENT_ID = 0; 
    private GoogleApiClient mGoogleApiClient; 
    private PlaceArrayAdapter mPlaceArrayAdapter; 
    private static final LatLngBounds BOUNDS_MOUNTAIN_VIEW = new LatLngBounds(
      new LatLng(37.398160, -122.180831), new LatLng(37.430610, -121.972090)); 

    String[] grad={"Grade1","Grade2","Grade3","Grade4","Grade5","Grade6","Grade7"}; 
    private static final String TAG = Profileeditpage.class.getSimpleName(); 
    Schoolname currentq; 

    @Override 
    protected void onCreate(@Nullable Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.editprofile); 
     mtool=(Toolbar)findViewById(R.id.toolbar); 
     setSupportActionBar(mtool); 
     getSupportActionBar().setDisplayShowHomeEnabled(true); 

     init(); 
    } 

    private void init() { 
     SchoolDatabaseHelper db=new SchoolDatabaseHelper(this); 
     db.openDatabase(); 
     nameschool=getAllSchools(); 

     name = (EditText) findViewById(R.id.edtprofilename); 
     email = (EditText) findViewById(R.id.edtprofilemail); 
     location = (AutoCompleteTextView) findViewById(R.id.edtlocation); 
     schoolname = (AutoCompleteTextView) findViewById(R.id.tvschoolname); 
     grade = (AutoCompleteTextView) findViewById(R.id.tvgrade); 


     // schoolname.setThreshold(1); 
     ArrayAdapter<String> adapter = new ArrayAdapter<String> 
       (this,android.R.layout.select_dialog_item,grad); 
     grade.setThreshold(0); 
     grade.setDropDownWidth(-1); 

     grade.setDropDownVerticalOffset(5); 
     grade.setAdapter(adapter); 
     mGoogleApiClient = new GoogleApiClient.Builder(Profileeditpage.this) 
       .addApi(Places.GEO_DATA_API) 
       .enableAutoManage(this, GOOGLE_API_CLIENT_ID, this) 
       .addConnectionCallbacks(this) 
       .build(); 
     location.setThreshold(1); 
     location.setOnItemClickListener(mAutocompleteClickListener); 
     mPlaceArrayAdapter = new PlaceArrayAdapter(this, android.R.layout.simple_list_item_1, 
       BOUNDS_MOUNTAIN_VIEW, null); 
     location.setDropDownWidth(-1); 
     location.setAdapter(mPlaceArrayAdapter); 


    } 

    public List<Schoolname> getAllSchools() { 
     List<Schoolname>nameschool= new ArrayList<Schoolname>(); 
     // Select All Query 
     String selectQuery = "SELECT DISTINCT schoolname FROM schooldet ORDER BY schoolname ASC"; 
     //db = this.getReadableDatabase(); 
     Cursor cursor = db.rawQuery(selectQuery, null); 
     // looping through all rows and adding to list 
     if (cursor.moveToFirst()) { 
      do { 
       Schoolname quest = new Schoolname(); 
       quest.setNames(cursor.getString(0)); 
       nameschool.add(quest); 
      } while (cursor.moveToNext()); 
     } 
     // return quest list 

     String[] stockArr = new String[nameschool.size()]; 
     stockArr = nameschool.toArray(stockArr); 
     ArrayAdapter<String> sadapter = new ArrayAdapter<String> 
       (this,android.R.layout.select_dialog_item,stockArr); 
     schoolname.setAdapter(sadapter); 

     return nameschool; 
    } 
    private AdapterView.OnItemClickListener mAutocompleteClickListener 
      = new AdapterView.OnItemClickListener() { 
     @Override 
     public void onItemClick(AdapterView<?> parent, View view, int position, long id) { 
      final PlaceArrayAdapter.PlaceAutocomplete item = mPlaceArrayAdapter.getItem(position); 
      final String placeId = String.valueOf(item.placeId); 
      Log.i(LOG_TAG, "Selected: " + item.description); 
      PendingResult<PlaceBuffer> placeResult = Places.GeoDataApi 
        .getPlaceById(mGoogleApiClient, placeId); 
      placeResult.setResultCallback(mUpdatePlaceDetailsCallback); 
      Log.i(LOG_TAG, "Fetching details for ID: " + item.placeId); 
     } 
    }; 
    private ResultCallback<PlaceBuffer> mUpdatePlaceDetailsCallback 
      = new ResultCallback<PlaceBuffer>() { 
     @Override 
     public void onResult(PlaceBuffer places) { 
      if (!places.getStatus().isSuccess()) { 
       Log.e(LOG_TAG, "Place query did not complete. Error: " + 
         places.getStatus().toString()); 
       return; 
      } 
      // Selecting the first object buffer. 
      final Place place = places.get(0); 
      CharSequence attributions = places.getAttributions(); 


     } 
    }; 
    @Override 
    public void onConnected(Bundle bundle) { 
     mPlaceArrayAdapter.setGoogleApiClient(mGoogleApiClient); 
     Log.i(LOG_TAG, "Google Places API connected."); 

    } 

    @Override 
    public void onConnectionFailed(ConnectionResult connectionResult) { 
     Log.e(LOG_TAG, "Google Places API connection failed with error code: " 
       + connectionResult.getErrorCode()); 

     Toast.makeText(this, 
       "Google Places API connection failed with error code:" + 
         connectionResult.getErrorCode(), 
       Toast.LENGTH_LONG).show(); 
    } 

    @Override 
    public void onConnectionSuspended(int i) { 
     mPlaceArrayAdapter.setGoogleApiClient(null); 
     Log.e(LOG_TAG, "Google Places API connection suspended."); 
} 

Datenbank:

public class SchoolDatabaseHelper extends Activity{ 
    private static final String DB_NAME = "school.sqlite"; 

    private Context context; 

    public SchoolDatabaseHelper(Context context) { 
     this.context = context; 
    } 

    public SQLiteDatabase openDatabase() { 
     File dbFile = context.getDatabasePath(DB_NAME); 

     if (!dbFile.exists()) { 
      try { 
       SQLiteDatabase checkDB = context.openOrCreateDatabase(DB_NAME, context.MODE_PRIVATE, null); 
       if(checkDB != null){ 

        checkDB.close(); 

       } 
       copyDatabase(dbFile); 
      } catch (IOException e) { 
       throw new RuntimeException("Error creating source database", e); 
      } 
     } 

     return SQLiteDatabase.openDatabase(dbFile.getPath(), null, SQLiteDatabase.OPEN_READONLY); 
    } 

    private void copyDatabase(File dbFile) throws IOException { 
     InputStream is = context.getAssets().open(DB_NAME); 
     OutputStream os = new FileOutputStream(dbFile); 

     byte[] buffer = new byte[1024]; 
     while (is.read(buffer) > 0) { 
      os.write(buffer); 
     } 

     os.flush(); 
     os.close(); 
     is.close(); 
    } 
} 

Fehler:

Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.database.Cursor android.database.sqlite.SQLiteDatabase.rawQuery(java.lang.String, java.lang.String[])' on a null object reference 
     at nidhinkumar.gridcam.logindetails.Profileeditpage.getAllSchools(Profileeditpage.java:104) 
     at nidhinkumar.gridcam.logindetails.Profileeditpage.onCreate(Profileeditpage.java:63) 
     at android.app.Activity.performCreate(Activity.java:6092) 
     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1112) 
     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2468) 

Answer 1

Die Membervariable db ist nicht initialisiert. In Ihrem init-Methode erstellen Sie eine lokale Variable, die aus dem Verfahren nicht zugänglich ist getAllSchools()

So etwas wie dies versuchen:

SchoolDatabaseHelper db =new SchoolDatabaseHelper(this); 
this.db = db.getReadableDatabase(); 
nameschool=getAllSchools();