App stürzt bei getWritableDatabase ab: NullPointerException

Question

Ich versuche eine App zu machen, die eine Datenbank beinhaltet. Ich verwende einen ContentProvider und stürzt in der Abfragemethode ab, wenn er versucht, die WiditableDatabase zu holen. Es gibt eine NullPointerException zurück. Ich weiß in der Tat, dass der Kontext nicht null ist, da dies der Hauptgrund für diese Art von Problem zu sein scheint.

Hier ist der Contentprovider Code:

package com.corvus.corvusenterprises.digimonapp; 

import android.content.ContentProvider; 
import android.content.ContentResolver; 
import android.content.ContentUris; 
import android.content.ContentValues; 
import android.content.Context; 
import android.content.UriMatcher; 
import android.database.Cursor; 
import android.database.SQLException; 
import android.database.sqlite.SQLiteDatabase; 
import android.database.sqlite.SQLiteQueryBuilder; 
import android.net.Uri; 
import android.text.TextUtils; 
import android.util.Log; 

import java.util.Arrays; 
import java.util.HashSet; 

import static com.corvus.corvusenterprises.digimonapp.DBHelper.presentDigimon; 

/** 
* Created by Jack on 01/05/2017. 
*/ 

public class DigimonContentProvider extends ContentProvider { 
    private static DigimonContentProvider instance; 
    private DBHelper dbHelper; 
    private SQLiteDatabase db; 

    private static final int DIGIMON = 10; 
    private static final int DIGIMON_ID = 20; 
    private static final int ATTACKS = 30; 
    private static final int ATTACKS_ID = 40; 
    private static final int EVOLUTIONS = 50; 
    private static final int EVOLUTIONS_ID = 60; 

    private static final String AUTHORITY = "com.corvus.corvusenterprises.digimonapp"; 

    private static final String BASE_PATH_DIGIMON = "digimon"; 
    private static final String BASE_PATH_ATTACKS = "attacks"; 
    private static final String BASE_PATH_EVOLUTIONS = "evolutions"; 

    public static final Uri CONTENT_URI_DIGIMON = Uri.parse("content://" + AUTHORITY + "/" + BASE_PATH_DIGIMON); 
    public static final Uri CONTENT_URI_ATTACKS = Uri.parse("content://" + AUTHORITY + "/" + BASE_PATH_ATTACKS); 
    public static final Uri CONTENT_URI_EVOLUTIONS = Uri.parse("content://" + AUTHORITY + "/" + BASE_PATH_EVOLUTIONS); 

    public static final String CONTENT_TYPE = ContentResolver.CURSOR_DIR_BASE_TYPE + "/digimon"; 
    public static final String CONTENT_ITEM_TYPE = ContentResolver.CURSOR_ITEM_BASE_TYPE + "/digimon"; 

    private static final UriMatcher sURIMatcher = new UriMatcher(UriMatcher.NO_MATCH); 

    static { 
     sURIMatcher.addURI(AUTHORITY, BASE_PATH_DIGIMON, DIGIMON); 
     sURIMatcher.addURI(AUTHORITY, BASE_PATH_DIGIMON + "/#", DIGIMON_ID); 
     sURIMatcher.addURI(AUTHORITY, BASE_PATH_ATTACKS, ATTACKS); 
     sURIMatcher.addURI(AUTHORITY, BASE_PATH_ATTACKS + "/#", ATTACKS_ID); 
     sURIMatcher.addURI(AUTHORITY, BASE_PATH_EVOLUTIONS, EVOLUTIONS); 
     sURIMatcher.addURI(AUTHORITY, BASE_PATH_EVOLUTIONS + "/#", EVOLUTIONS_ID); 
    } 

    private DigimonContentProvider() 
    { 

    } 
    public static DigimonContentProvider getInstance() { 
     if (instance == null) 
      instance = new DigimonContentProvider(); 
     return instance; 
    } 
    @Override 
    public boolean onCreate() { 
     Context ctx = MyApp.getContext(); 
     dbHelper = DBHelper.getInstance(ctx); 

     dbHelper.insertDigimon("Guilmon", "Guilmon", "Child/Rookie", "Virus", "Dinosaur", "TRUE","R.mipmap.guilmon.jpg"); 
     dbHelper.insertDigimon("Growmon", "Growlmon", "Adult/Champion", "Virus", "Bigger Dinosaur", "FALSE","R.mipmap.growmon.jpg"); 
     dbHelper.insertDigimon("Terriermon", "terriermon", "Child/Rookie", "Vaccine", "Dogbunny", "FALSE","R.mipmap.terriermon.jpg"); 
     dbHelper.insertDigimon("Galgomon", "Gargomon", "Adult/Champion", "Vaccine", "Gunbunny", "FALSE","R.mipmap.galgomon.jpg"); 
     dbHelper.insertDigimon("Kyubimon", "Kyubimon", "Adult/Champion", "Data", "9-Tailed Fox", "FALSE","R.mipmap.kyubimon.jpg"); 
     dbHelper.insertDigimon("Taomon", "Taomon", "Perfect/Ultimate", "Data", "Kitsune Miko", "FALSE","R.mipmap.taomon.jpg"); 
     dbHelper.insertDigimon("Impmon", "Impmon", "Child/Rookie", "Virus", "Kid in a purple onesie", "FALSE","R.mipmap.impmon.jpg"); 
     dbHelper.insertDigimon("Beelzebumon", "Beelzemon", "Ultimate/Mega", "Virus", "Demon Lord of Gluttony", "FALSE","R.mipmap.beelzebumon.jpg"); 

     presentDigimon[460] = true; presentDigimon[454] = true; 
     presentDigimon[1019] = true; presentDigimon[374] = true; 
     presentDigimon[572] = true; presentDigimon[1013] = true; 
     presentDigimon[507] = true; presentDigimon[100] = true; 

     dbHelper.insertEvolution("Guilmon", "Growmon", ""); 
     dbHelper.insertEvolution("Terriermon", "Galgomon",""); 
     dbHelper.insertEvolution("Kyubimon", "Taomon",""); 
     dbHelper.insertEvolution("Impmon", "Beelzebumon", "(Warp Evolution)"); 

     dbHelper.insertAttack("Fireball", "Pyro Sphere", "Guilmon", "Explosive Fireball"); 
     dbHelper.insertAttack("Rock Breaker", "Rock Breaker", "Guilmon", "Claw Swipe"); 
     dbHelper.insertAttack("Exhaust Flame", "Pyro Blaster", "Growmon", "Fire Laser"); 
     dbHelper.insertAttack("Plasma Blade", "Dragon Slash", "Growmon", "Forearm Blades"); 
     dbHelper.insertAttack("Blazing Fire", "Bunny Blast", "Terriermon", "Energy Blast"); 
     dbHelper.insertAttack("Petit Twister", "Terrier Tornado", "Terriermon", "Throws Tornado"); 
     dbHelper.insertAttack("Gatling Arm", "Gargo Laser", "Galgomon", "Fires Guns"); 
     dbHelper.insertAttack("Dum Dum Upper", "Bunny Pummel", "Galgomon", "Fires Guns While Punching"); 
     dbHelper.insertAttack("Koenryu", "Dragon Wheel", "Kyubimon", "Fire Dragon"); 
     dbHelper.insertAttack("Onibidama", "Fox-Tail Inferno", "Kyubimon", "Fireballs from the tails"); 
     dbHelper.insertAttack("Bonhitsusen", "Talisman of Light", "Taomon", "Energy Seal Laser"); 
     dbHelper.insertAttack("Oṃ", "Talisman Spell", "Taomon", "Makes a dome shield"); 
     dbHelper.insertAttack("Night of Fire", "Badaboom", "Impmon", "Mini-Fireballs"); 
     dbHelper.insertAttack("Pillar of Fire", "", "Impmon", "Wall of Flames"); 
     dbHelper.insertAttack("Double Impact", "Double Impact", "Beelzebumon", "Fires two bullets"); 
     dbHelper.insertAttack("Darkness Claw", "", "Beelzebumon", "Kills Leomon"); 
     db = dbHelper.getWritableDatabase(); 
     return false; 
    } 

    @Override 
    public Uri insert(Uri uri, ContentValues values) { 
     Uri _uri = null; 
     switch (sURIMatcher.match(uri)) { 
      case DIGIMON: 
       long _ID1 = db.insert(DigimonTable.DIGIMON_TABLE_NAME, "", values); 
       if (_ID1 > 0) { 
        _uri = ContentUris.withAppendedId(CONTENT_URI_DIGIMON, _ID1); 
        MyApp.getContext().getContentResolver().notifyChange(_uri, null); 
       } 
       break; 
      case ATTACKS: 
       long _ID2 = db.insert(AttacksTable.ATTACKS_TABLE_NAME, "", values); 
       if (_ID2 > 0) { 
        _uri = ContentUris.withAppendedId(CONTENT_URI_ATTACKS, _ID2); 
        MyApp.getContext().getContentResolver().notifyChange(_uri, null); 
       } 
       break; 
      case EVOLUTIONS: 
       long _ID3 = db.insert(EvolutionsTable.EVOLUTIONS_TABLE_NAME, "", values); 
       if (_ID3 > 0) { 
        _uri = ContentUris.withAppendedId(CONTENT_URI_EVOLUTIONS, _ID3); 
        MyApp.getContext().getContentResolver().notifyChange(_uri, null); 
       } 
       break; 
      default: 
       throw new SQLException("Failed to insert row into " + uri); 
     } 
     MyApp.getContext().getContentResolver().notifyChange(uri, null); 
     return _uri; 
    } 

    @Override 
    public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) { 
     SQLiteQueryBuilder queryBuilder = new SQLiteQueryBuilder(); 

     int uriType = sURIMatcher.match(uri); 

     checkColumns(projection, uriType); 

     queryBuilder.setTables(DigimonTable.DIGIMON_TABLE_NAME + ", " + EvolutionsTable.EVOLUTIONS_TABLE_NAME + ", " + AttacksTable.ATTACKS_TABLE_NAME); 

     switch (uriType) { 
      case DIGIMON: 
       break; 
      case DIGIMON_ID: 
       queryBuilder.appendWhere(DigimonTable.DIGIMON_COLUMN_ID+"="+uri.getLastPathSegment()); 
      case ATTACKS: 
       break; 
      case ATTACKS_ID: 
       queryBuilder.appendWhere(AttacksTable.ATTACKS_COLUMN_ID+"="+uri.getLastPathSegment()); 
      case EVOLUTIONS: 
       break; 
      case EVOLUTIONS_ID: 
       queryBuilder.appendWhere(EvolutionsTable.EVOLUTIONS_COLUMN_ID+"="+uri.getLastPathSegment()); 
      default: 
       throw new IllegalArgumentException("Unknown URI: "+ uri); 
     } 
     Cursor cursor = queryBuilder.query(db, projection, selection, selectionArgs, null, null, sortOrder); 
     cursor.setNotificationUri(MyApp.getContext().getContentResolver(), uri); 

     return cursor; 
    } 

    @Override 
    public String getType(Uri uri) { 
     return null; 
    } 

    @Override 
    public int delete(Uri uri, String selection, String[] selectionArgs) { 
     int uriType = sURIMatcher.match(uri); 
     int rowsDeleted = 0; 
     switch (uriType) { 
      case DIGIMON: 
       rowsDeleted = db.delete(DigimonTable.DIGIMON_TABLE_NAME, selection, selectionArgs); 
       break; 
      case DIGIMON_ID: 
       String id1 = uri.getLastPathSegment(); 
       if (TextUtils.isEmpty(selection)) { 
        rowsDeleted = db.delete(
          DigimonTable.DIGIMON_TABLE_NAME, 
          DigimonTable.DIGIMON_COLUMN_ID + "=" + id1, 
          null); 
       } else { 
        rowsDeleted = db.delete(
          DigimonTable.DIGIMON_TABLE_NAME, 
          DigimonTable.DIGIMON_COLUMN_ID + "=" + id1 
            + " and " + selection, 
          selectionArgs); 
       } 
       break; 
      case ATTACKS: 
       rowsDeleted = db.delete(AttacksTable.ATTACKS_TABLE_NAME, selection, selectionArgs); 
       break; 
      case ATTACKS_ID: 
       String id2 = uri.getLastPathSegment(); 
       if (TextUtils.isEmpty(selection)) { 
        rowsDeleted = db.delete(
          AttacksTable.ATTACKS_TABLE_NAME, 
          AttacksTable.ATTACKS_COLUMN_ID + "=" + id2, 
          null); 
       } else { 
        rowsDeleted = db.delete(
          AttacksTable.ATTACKS_TABLE_NAME, 
          AttacksTable.ATTACKS_COLUMN_ID + "=" + id2 
            + " and " + selection, 
          selectionArgs); 
       } 
       break; 
      case EVOLUTIONS: 
       rowsDeleted = db.delete(EvolutionsTable.EVOLUTIONS_TABLE_NAME, selection, selectionArgs); 
       break; 
      case EVOLUTIONS_ID: 
       String id3 = uri.getLastPathSegment(); 
       if (TextUtils.isEmpty(selection)) { 
        rowsDeleted = db.delete(
          EvolutionsTable.EVOLUTIONS_TABLE_NAME, 
          EvolutionsTable.EVOLUTIONS_COLUMN_ID + "=" + id3, 
          null); 
       } else { 
        rowsDeleted = db.delete(
          EvolutionsTable.EVOLUTIONS_TABLE_NAME, 
          EvolutionsTable.EVOLUTIONS_COLUMN_ID + "=" + id3 
            + " and " + selection, 
          selectionArgs); 
       } 
       break; 
      default: 
       throw new IllegalArgumentException("Unknown URI: " + uri); 
     } 
     MyApp.getContext().getContentResolver().notifyChange(uri, null); 
     return rowsDeleted; 
    } 

    @Override 
    public int update(Uri uri, ContentValues values, String selection, 
         String[] selectionArgs) { 

     int uriType = sURIMatcher.match(uri); 
     int rowsUpdated = 0; 
     switch (uriType) { 
      case DIGIMON: 
       rowsUpdated = db.update(DigimonTable.DIGIMON_TABLE_NAME, 
         values, 
         selection, 
         selectionArgs); 
       break; 
      case DIGIMON_ID: 
       String id1 = uri.getLastPathSegment(); 
       if (TextUtils.isEmpty(selection)) { 
        rowsUpdated = db.update(DigimonTable.DIGIMON_TABLE_NAME, 
          values, 
          DigimonTable.DIGIMON_COLUMN_ID + "=" + id1, 
          null); 
       } else { 
        rowsUpdated = db.update(DigimonTable.DIGIMON_TABLE_NAME, 
          values, 
          DigimonTable.DIGIMON_COLUMN_ID + "=" + id1 
            + " and " 
            + selection, 
          selectionArgs); 
       } 
       break; 
      case ATTACKS: 
       rowsUpdated = db.update(AttacksTable.ATTACKS_TABLE_NAME, 
         values, 
         selection, 
         selectionArgs); 
       break; 
      case ATTACKS_ID: 
       String id2 = uri.getLastPathSegment(); 
       if (TextUtils.isEmpty(selection)) { 
        rowsUpdated = db.update(AttacksTable.ATTACKS_TABLE_NAME, 
          values, 
          AttacksTable.ATTACKS_COLUMN_ID + "=" + id2, 
          null); 
       } else { 
        rowsUpdated = db.update(AttacksTable.ATTACKS_TABLE_NAME, 
          values, 
          AttacksTable.ATTACKS_COLUMN_ID + "=" + id2 
            + " and " 
            + selection, 
          selectionArgs); 
       } 
       break; 
      case EVOLUTIONS: 
       rowsUpdated = db.update(EvolutionsTable.EVOLUTIONS_TABLE_NAME, 
         values, 
         selection, 
         selectionArgs); 
       break; 
      case EVOLUTIONS_ID: 
       String id3 = uri.getLastPathSegment(); 
       if (TextUtils.isEmpty(selection)) { 
        rowsUpdated = db.update(EvolutionsTable.EVOLUTIONS_TABLE_NAME, 
          values, 
          EvolutionsTable.EVOLUTIONS_COLUMN_ID + "=" + id3, 
          null); 
       } else { 
        rowsUpdated = db.update(EvolutionsTable.EVOLUTIONS_TABLE_NAME, 
          values, 
          EvolutionsTable.EVOLUTIONS_COLUMN_ID + "=" + id3 
            + " and " 
            + selection, 
          selectionArgs); 
       } 
       break; 
      default: 
       throw new IllegalArgumentException("Unknown URI: " + uri); 
     } 
     MyApp.getContext().getContentResolver().notifyChange(uri, null); 
     return rowsUpdated; 
    } 
    private void checkColumns(String[] projection, int uri) { 
     HashSet<String> availableColumns; 
     String[] availableDigimon = { DigimonTable.DIGIMON_COLUMN_ID, 
       DigimonTable.DIGIMON_COLUMN_NAME, DigimonTable.DIGIMON_COLUMN_DUB_NAME, 
       DigimonTable.DIGIMON_COLUMN_LEVEL, DigimonTable.DIGIMON_COLUMN_ATTRIBUTE, 
       DigimonTable.DIGIMON_COLUMN_DESCRIPTION, DigimonTable.DIGIMON_COLUMN_FAVOURITE, 
       DigimonTable.DIGIMON_COLUMN_PATH}; 
     String[] availableAttacks = {AttacksTable.ATTACKS_COLUMN_ID, AttacksTable.ATTACKS_COLUMN_NAME, 
       AttacksTable.ATTACKS_COLUMN_DUB_NAME, AttacksTable.ATTACKS_COLUMN_DIGIMON, 
       AttacksTable.ATTACKS_COLUMN_DESCRIPTION}; 
     String[] availableEvolutions = {EvolutionsTable.EVOLUTIONS_COLUMN_ID,EvolutionsTable.EVOLUTIONS_COLUMN_FROM, 
       EvolutionsTable.EVOLUTIONS_COLUMN_TO, EvolutionsTable.EVOLUTIONS_COLUMN_CONDITIONS}; 
     if (projection != null) { 
      HashSet<String> requestedColumns = new HashSet<String>(
        Arrays.asList(projection)); 
      switch(uri){ 
       case DIGIMON: 
       case DIGIMON_ID: availableColumns = new HashSet<String>(Arrays.asList(availableDigimon)); 
        break; 
       case ATTACKS: 
       case ATTACKS_ID: availableColumns = new HashSet<String>(Arrays.asList(availableAttacks)); 
        break; 
       case EVOLUTIONS: 
       case EVOLUTIONS_ID: availableColumns = new HashSet<String>(Arrays.asList(availableEvolutions)); 
        break; 
       default: availableColumns = new HashSet<String>(Arrays.asList(availableDigimon)); 
      } 
      // check if all columns which are requested are available 
      if (!availableColumns.containsAll(requestedColumns)) { 
       throw new IllegalArgumentException(
         "Unknown columns in projection"); 
      } 
     } 
    } 

    public Cursor defaultMainMenu() 
    { 
     Cursor cursor = MyApp.getContext().getContentResolver().query(CONTENT_URI_DIGIMON, new String[]{DigimonTable.DIGIMON_COLUMN_NAME, DigimonTable.DIGIMON_COLUMN_FAVOURITE}, null, null, DigimonTable.DIGIMON_COLUMN_NAME + " ASC"); 
     int dummy = cursor.getCount(); 
     return cursor; 

    } 
    public Cursor searchMenuQuery(String search) 
    { 
     Cursor cursor = MyApp.getContext().getContentResolver().query(CONTENT_URI_DIGIMON,new String[] {DigimonTable.DIGIMON_COLUMN_NAME,DigimonTable.DIGIMON_COLUMN_FAVOURITE},DigimonTable.DIGIMON_COLUMN_NAME+" = '?'",new String[]{search},DigimonTable.DIGIMON_COLUMN_NAME+" ASC"); 
     int dummy = cursor.getCount(); 
     return cursor; 
    } 
    public Cursor favouritesMenuQuery() 
    { 
     Cursor cursor = MyApp.getContext().getContentResolver().query(CONTENT_URI_DIGIMON,new String[] {DigimonTable.DIGIMON_COLUMN_NAME},DigimonTable.DIGIMON_COLUMN_FAVOURITE+" = true",null,DigimonTable.DIGIMON_COLUMN_NAME+" ASC"); 
     int dummy = cursor.getCount(); 
     return cursor; 
    } 
    public Cursor digimonProfileQuery(String name) 
    { 
     Cursor cursor = MyApp.getContext().getContentResolver().query(CONTENT_URI_DIGIMON,null,DigimonTable.DIGIMON_COLUMN_NAME+" = '?'",new String[]{name},null); 
     int dummy = cursor.getCount(); 
     return cursor; 
    } 
    public Cursor digimonAttacksQuery(String name) 
    { 
     Cursor cursor = MyApp.getContext().getContentResolver().query(CONTENT_URI_ATTACKS,null,AttacksTable.ATTACKS_COLUMN_DIGIMON+" = '?'",new String[]{name},null); 
     int dummy = cursor.getCount(); 
     return cursor; 
    } 
    public Cursor digimonEvolutionFromQuery(String name) 
    { 
     Cursor cursor = MyApp.getContext().getContentResolver().query(CONTENT_URI_EVOLUTIONS,null,EvolutionsTable.EVOLUTIONS_COLUMN_FROM+" = '?'",new String[]{name},null); 
     int dummy = cursor.getCount(); 
     return cursor; 
    } 
    public Cursor digimonEvolutionToQuery(String name) 
    { 
     Cursor cursor = MyApp.getContext().getContentResolver().query(CONTENT_URI_EVOLUTIONS,null,EvolutionsTable.EVOLUTIONS_COLUMN_TO+" = '?'",new String[]{name},null); 
     int dummy = cursor.getCount(); 
     return cursor; 
    } 
} 

Und hier ist die Logcat Ergebnisse:

Process: com.corvus.corvusenterprises.digimonapp, PID: 12198 
       java.lang.RuntimeException: Unable to get provider com.corvus.corvusenterprises.digimonapp.DigimonContentProvider: java.lang.NullPointerException 
        at android.app.ActivityThread.installProvider(ActivityThread.java:5084) 
        at android.app.ActivityThread.installContentProviders(ActivityThread.java:4673) 
        at android.app.ActivityThread.handleBindApplication(ActivityThread.java:4613) 
        at android.app.ActivityThread.access$1800(ActivityThread.java:141) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1298) 
        at android.os.Handler.dispatchMessage(Handler.java:102) 
        at android.os.Looper.loop(Looper.java:136) 
        at android.app.ActivityThread.main(ActivityThread.java:5333) 
        at java.lang.reflect.Method.invokeNative(Native Method) 
        at java.lang.reflect.Method.invoke(Method.java:515) 
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:895) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:711) 
        at dalvik.system.NativeStart.main(Native Method) 
       Caused by: java.lang.NullPointerException 
        at android.database.sqlite.SQLiteOpenHelper.getDatabaseLocked(SQLiteOpenHelper.java:224) 
        at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:164) 
        at com.corvus.corvusenterprises.digimonapp.DigimonContentProvider.onCreate(DigimonContentProvider.java:62) 
        at android.content.ContentProvider.attachInfo(ContentProvider.java:1616) 
        at android.content.ContentProvider.attachInfo(ContentProvider.java:1587) 
        at android.app.ActivityThread.installProvider(ActivityThread.java:5081) 
        at android.app.ActivityThread.installContentProviders(ActivityThread.java:4673) 
        at android.app.ActivityThread.handleBindApplication(ActivityThread.java:4613) 
        at android.app.ActivityThread.access$1800(ActivityThread.java:141) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1298) 
        at android.os.Handler.dispatchMessage(Handler.java:102) 
        at android.os.Looper.loop(Looper.java:136) 
        at android.app.ActivityThread.main(ActivityThread.java:5333) 
        at java.lang.reflect.Method.invokeNative(Native Method) 
        at java.lang.reflect.Method.invoke(Method.java:515) 
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:895) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:711) 
        at dalvik.system.NativeStart.main(Native Method) 

Hier ist der DBHelper Code, es hilft bei:

package com.corvus.corvusenterprises.digimonapp; 

    import android.content.ContentValues; 
    import android.content.Context; 
    import android.database.sqlite.SQLiteDatabase; 
    import android.database.sqlite.SQLiteOpenHelper; 

    import static com.corvus.corvusenterprises.digimonapp.DigimonContentProvider.CONTENT_URI_ATTACKS; 
    import static com.corvus.corvusenterprises.digimonapp.DigimonContentProvider.CONTENT_URI_DIGIMON; 
    import static com.corvus.corvusenterprises.digimonapp.DigimonContentProvider.CONTENT_URI_EVOLUTIONS; 

    /** 
    * Created by Jack on 01/05/2017. 
    */ 

    public class DBHelper extends SQLiteOpenHelper { 
     public static final String[]digimonArray = { 
       "Gigantic array of names"}; 
     private static final String DATABASE_NAME = "DigimonDatabase.db"; 
    private static final int version = 1; 
    private static DBHelper instance; 
    public static boolean[]presentDigimon = new boolean[digimonArray.length]; 
    private DBHelper(Context context) { 
     super(context, DATABASE_NAME, null, version); 
    } 
    public static DBHelper getInstance(Context ctx) { 
     if (instance == null) 
      instance = new DBHelper(ctx); 
     return instance; 
    } 
    @Override 
    public void onCreate(SQLiteDatabase db) { 
     DigimonTable.onCreate(db); 
     AttacksTable.onCreate(db); 
     EvolutionsTable.onCreate(db); 
    } 
    public void onUpgrade(SQLiteDatabase db, int oldver, int newVer) 
    { 
     DigimonTable.onUpgrade(db,oldver,newVer); 
     AttacksTable.onUpgrade(db,oldver,newVer); 
     EvolutionsTable.onUpgrade(db,oldver,newVer); 
    } 
    public void insertDigimon(String name, String dub_name, String level, String attribute, String description, String favourite, String path) 
    { 
     DigimonContentProvider dcp = DigimonContentProvider.getInstance(); 
     ContentValues values = new ContentValues(); 
     values.put(DigimonTable.DIGIMON_COLUMN_NAME,name); 
     values.put(DigimonTable.DIGIMON_COLUMN_DUB_NAME,dub_name); 
     values.put(DigimonTable.DIGIMON_COLUMN_LEVEL,level); 
     values.put(DigimonTable.DIGIMON_COLUMN_ATTRIBUTE,attribute); 
     values.put(DigimonTable.DIGIMON_COLUMN_DESCRIPTION,description); 
     values.put(DigimonTable.DIGIMON_COLUMN_FAVOURITE, favourite); 
     values.put(DigimonTable.DIGIMON_COLUMN_PATH,path); 
     dcp.insert(CONTENT_URI_DIGIMON, values); 
    } 
    public void insertAttack(String name, String dub_name, String digimon, String description) 
    { 
     DigimonContentProvider dcp = DigimonContentProvider.getInstance(); 
     ContentValues values = new ContentValues(); 
     values.put(AttacksTable.ATTACKS_COLUMN_NAME, name); 
     values.put(AttacksTable.ATTACKS_COLUMN_DUB_NAME,dub_name); 
     values.put(AttacksTable.ATTACKS_COLUMN_DIGIMON, digimon); 
     values.put(AttacksTable.ATTACKS_COLUMN_DESCRIPTION, description); 
     dcp.insert(CONTENT_URI_ATTACKS, values); 
    } 
    public void insertEvolution(String from, String to, String conditions) 
    { 
     DigimonContentProvider dcp = DigimonContentProvider.getInstance(); 
     ContentValues values = new ContentValues(); 
     values.put(EvolutionsTable.EVOLUTIONS_COLUMN_TO,to); 
     values.put(EvolutionsTable.EVOLUTIONS_COLUMN_FROM,from); 
     values.put(EvolutionsTable.EVOLUTIONS_COLUMN_CONDITIONS,conditions); 
     dcp.insert(CONTENT_URI_EVOLUTIONS, values); 
    } 
} 

irgendwelche und alle Hilfe geschätzt. Wenn Sie weitere Informationen benötigen, lassen Sie es mich wissen. (EDITED): Neue Version wird bearbeitet. Code aktualisiert (EDITED 2): Ein mögliches Problem mit rekursiven Aufrufen wurde behoben.

Answer 1

ich für eine Tatsache, dass der Kontext

Wie wissen Sie, dass nicht null ist? MyApp.getContext() sieht mir komisch aus.

Versuchen Sie, den Kontext zu dem Contentprovider

private Context mContext; 

private DigimonContentProvider(Context context) 
{ 
    this.mContext = context; 
} 

private DigimonContentProvider() { } 


public static DigimonContentProvider getInstance(Context context) { 
    if (instance == null) 
     instance = new DigimonContentProvider(context); 
    return instance; 
} 

@Override 
public boolean onCreate() { 
    dbHelper = DBHelper.getInstance(this.mContext); 

jedoch geben, müssen Sie eine Contentprovider nicht benötigen eine Datenbank zu haben, so versuchen, die Datenbank, ohne es zu arbeiten bekommen.

Answer 2

Es wirft eine NullPointerException, weil Sie versuchen, auf Ihre ContentProvider Methoden direkt zugreifen, anstatt eine ContentResolver für die gleiche zu verwenden.

Sie können den Code, den Sie in ContentProvider geschrieben haben, abstrahieren, um in einer anderen Klasse darauf zuzugreifen. Und diesmal verwenden Sie eine ContentResolver Instanz für die gleiche.

Edit:
Vielleicht ist Ihr Problem ist, dass Ihr dbHelper nicht Singleton ist und Sie eine weitere Instanzen davon durch dbHelper.getInstance(getContext) in insert() Methode erstellen.
Versuchen Sie, eine neue Instanz von dbHelper nur in onCreate() Methode und nicht in anderen Methoden.

können Sie dieses Beispiel verwenden: MoviesContentProvider.java