Android SQLiteOpenHelper：不調用onCreate（）方法

Question

此代碼發生NullPointException。我認爲onCreate方法不會在null中調用'db'。 但我不能找到錯誤spot.ease看看下面的代碼，並給我任何建議。任何幫助將不勝感激。

public class DBManager { 
    private static DBManager instance; 

    public static DBManager getInstance() { 
     if (instance == null) { 
      instance = new DBManager(); 
     } 
     return instance; 
    } 

    DBHelper openHelper; 

    private DBManager() { 
     openHelper = new DBHelper(MyApplication.getContext()); 
    } 

    public void insertPerson(PersonData person) { 
     SQLiteDatabase db = openHelper.getWritableDatabase(); 
     ContentValues values = new ContentValues(); 
     values.put(PersonTable.NAME, person.name); 
     values.put(PersonTable.COMMENT, person.comment); 
     values.put(PersonTable.PHONE_NUM,person.phoneNum); 
     values.put(PersonTable.TYPE,person.type); 
     values.put(PersonTable.PROFILE_IMG,person.resId); 

     db.insert(PersonTable.TABLE_NAME, null, values); 
     db.close(); 
    } 

public class DBHelper extends SQLiteOpenHelper { 

     private final static String DB_NAME = "kakao.db"; 
     private final static int DB_VERSION = 1; 

     public DBHelper(Context context) { 
      super(context, DB_NAME, null, DB_VERSION); 

     } 

     @Override 
     public void onCreate(SQLiteDatabase db) { 
      String sql = "CREATE TABLE "+ PersonTable.TABLE_NAME + "(" 
        + PersonTable._ID 
        + " integer PRIMARY KEY autoincrement , " 
        + PersonTable.NAME + " text, " 
        + PersonTable.PHONE_NUM + " text, " 
        + PersonTable.PROFILE_IMG + " text, " 
        + PersonTable.COMMENT + " text, " 
        + PersonTable.TYPE + " text);"; 
      db.execSQL(sql); 
     } 

線29是 'SQLiteDatabase分貝= openHelper.getWritableDatabase（）;'

FATAL EXCEPTION: main 
java.lang.NullPointerException 
at android.database.sqlite.SQLiteOpenHelper.getDatabaseLocked(SQLiteOpenHelper.java:224) 
at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:164) 
at taca.yongseong.kakaomessanger.DBManager.insertPerson(DBManager.java:29) 
at taca.yongseong.kakaomessanger.Friend.getContact(Friend.java:137) 
at taca.yongseong.kakaomessanger.Friend.setData(Friend.java:106) 
at taca.yongseong.kakaomessanger.Friend.onCreateView(Friend.java:51) 

Answer 1

的Context你傳遞給SQLiteOpenHelper構造是null。