'我试图创建一个依赖spinner与数据从sqlite的android studio。但spinner不显示任何内容的预期。前缀是假设缩小选择的Lotno和最后显示种植园_名称基于数据库SmartSawit.db。请帮助：〉（it been days）

Spinner spinnerPrefix, spinnerLotno, spinnerPlantation_name;
Context context;
database Database;
String prefixValue, lotnoValue, nameValue;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_daftar_pokok);
    spinnerPrefix = findViewById(R.id.spinnerPrefix);
    spinnerLotno = findViewById(R.id.spinnerLotno);
    spinnerPlantation_name = findViewById(R.id.spinnerPlantation_name);
    context = this;

    Database = new database(this, "SmartSawit.db", 1);

    try {
        Database.CheckDB();
        fillSpinner(context,spinnerPrefix, "registered_plantation", "prefix", "");
        spinnerPrefix.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
            @Override
            public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
                prefixValue = parent.getItemAtPosition(position).toString();
                fillSpinner(context,spinnerLotno,"registered_plantation","lotno","where prefix = '"+prefixValue+"'");
            }

            @Override
            public void onNothingSelected(AdapterView<?> parent) {

            }
        });
        spinnerLotno.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
            @Override
            public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
                lotnoValue = parent.getItemAtPosition(position).toString();
                fillSpinner(context,spinnerPlantation_name,"registered_plantation","plantation_name","where prefix = '"+prefixValue+"' and lotno ='"+lotnoValue+"'");

            }

            @Override
            public void onNothingSelected(AdapterView<?> parent) {

            }
        });
    }catch(Exception e){
        e.printStackTrace();
    }


}

@SuppressLint("Range")

private void fillSpinner (Context context, Spinner mSpinner,String table, String column, String where) {

    SQLiteDatabase db = Database.OpenDatabase("registered_plantation.db");

    ArrayList<String> mArray = new ArrayList<>();
    Cursor cursor = db.rawQuery("Select distinct "+column+" from "+table+""+where, null);

    while (cursor.moveToNext()){
        mArray.add(cursor.getString(cursor.getColumnIndex(column)));
    }

    cursor.close();
    db.close();

    ArrayAdapter mAdapter = new ArrayAdapter(context, android.R.layout.simple_spinner_item,mArray);
    mAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
    mSpinner.setAdapter(mAdapter);

}

}

my databasehelper code:

private Context context;
private static final String DATABASE_NAME = "SmartSawit.db";
private static final int  DATABASE_VERSION = 1;

private static final String TABLE_NAME = "registered_plantation";

//private static final String COLUMN_NO = "_no";
private static final String COLUMN_NAME =  "plantation_name";
private static final String COLUMN_PREFIX = "prefix";
private static final String COLUMN_LOT_NUMBER = "lotno";

String DbPath;
Context mcontext;

String DbName;

public database(Context context, String name, int version) {
    super(context, DATABASE_NAME, null, version);
    this.context = context;
    this.mcontext = context;
    this.DbName = DATABASE_NAME;

    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) {
        this.DbPath = context.getFilesDir() + "/database/";
    }
}

@Override
public void onCreate(SQLiteDatabase db) {

    String query = "CREATE TABLE " + TABLE_NAME +
                    " (" + COLUMN_NAME + " TEXT PRIMARY KEY, " +
                    COLUMN_PREFIX + " TEXT, " +
                    COLUMN_LOT_NUMBER + " INTEGER);";

    db.execSQL(query);

}

@Override
public void onUpgrade(SQLiteDatabase db, int i, int i1) {

    db.execSQL("DROP TABLE IF EXISTS " + TABLE_NAME);
    onCreate(db);

}

public void CheckDB(){

    SQLiteDatabase checkDB = null;
    String filePath = DbPath + DbName;
    File file = new File(filePath);

    if(file.isFile() && file.exists()){
        Toast.makeText(mcontext, "already exist", Toast.LENGTH_SHORT).show();
    } else {
        CopyDatabase();
    }


}

private void CopyDatabase(){

    try {
        InputStream ios = mcontext.getAssets().open(DbName);
        File directory = new File(DbPath);

        if(!directory.exists()){
            directory.mkdirs();
        }

        OutputStream os = new FileOutputStream(DbPath + DbName);
        byte[] buffer = new byte[1024];
        int len;
        while((len = ios.read(buffer)) >0) {

            os.write(buffer,0, len);
        }

        os.flush();
        ios.close();
        os.close();
        Log.d("CopyDb", "Databse Copied");
    } catch (Exception e) {
        e.printStackTrace();
    }


}

void addLadang (String prefix, String namaLadang, int lotNo){

    SQLiteDatabase db = this.getWritableDatabase();
    ContentValues cv = new ContentValues();

    cv.put(COLUMN_PREFIX, prefix );
    cv.put(COLUMN_NAME, namaLadang );
    cv.put(COLUMN_LOT_NUMBER, lotNo );

    long result = db.insert(TABLE_NAME,null, cv);
    if (result == -1){

        Toast.makeText(context, "FAILED", Toast.LENGTH_SHORT).show();
    }
    else {

        Toast.makeText(context, "SUCCESSFULLY SAVED", Toast.LENGTH_SHORT).show();

    }

}

Cursor readAllData(){
        String query = "SELECT * FROM " + TABLE_NAME;
        SQLiteDatabase db = this.getReadableDatabase();

        Cursor cursor = null;
        if(db != null){
          cursor =   db.rawQuery(query, null);
        }
        return cursor;

}

public SQLiteDatabase OpenDatabase(String dbName){
    String filePath = DbPath + dbName;
    return SQLiteDatabase.openDatabase(filePath,null,0);

}

}