在Android中打开SQLite数据库时出现非法状态异常

Question

因此，我有一个名为DatabaseHandler的类继承SQLiteOpenHelper。这个班负责管理将数据从联机数据库复制到手机的数据库。现在，问题在于，当我调用它的getQuestionsCount()方法时，它正如名称所示，计算项目的数量，它会崩溃。它在调用其getReadableDatabase()方法的线路上崩溃。它告诉我它有一个IllegalStateException。这是怎么回事？

关于崩溃活动的代码。检查是否已经存储的使用问题：

DatabaseHandler db = new DatabaseHandler(getApplicationContext()); 

if(db.getQuestionsCount() == 0) 
    if(!isNetworkAvailable() || !canConnectToServer()) 
     return -2; 
else 
    if(!isNetworkAvailable() || !canConnectToServer()) 
     return -3; 

部分我的数据库处理器类：在的onCreate（

public class DatabaseHandler extends SQLiteOpenHelper 
{ 
... 
    public DatabaseHandler(Context context) 
    { 
     super(context, DATABASE_NAME, null, DATABASE_VERSION); 
    } 
    ... 

    @Override 
    public void onCreate(SQLiteDatabase db) 
    { 
     String CREATE_QUESTIONS_TABLE = "CREATE TABLE IF NOT EXISTS " + TABLE_QUESTIONS + "(" 
      + KEY_ID + " INTEGER PRIMARY KEY," + KEY_QUESTION + " TEXT NOT NULL," 
      + KEY_CATEGORY + " INTEGER NOT NULL," + KEY_ANSWER_1 + " TEXT NOT NULL," 
      + KEY_ANSWER_2 + " TEXT NOT NULL," + KEY_ANSWER_3 + " TEXT NOT NULL," 
      + KEY_ANSWER_4 + " TEXT NOT NULL," + KEY_DATE_POSTED + " TEXT NOT NULL)"; 
     db.execSQL(CREATE_QUESTIONS_TABLE); 

     db.close(); 
    } 
    ... 

    public int getQuestionsCount() 
    { 
     String countQuery = "SELECT * FROM " + TABLE_QUESTIONS; 
     SQLiteDatabase db = this.getReadableDatabase(); //<-- ERROR ON THIS LINE 
     Cursor cursor = db.rawQuery(countQuery, null); 
     int count = cursor.getCount(); 
     cursor.close(); 

     // return count 
     return count; 
    } 
} 

Answer 1

删除db.close）

@Override 
public void onCreate(SQLiteDatabase db) 
{ 
    String CREATE_QUESTIONS_TABLE = "CREATE TABLE IF NOT EXISTS " + TABLE_QUESTIONS + "(" 
     + KEY_ID + " INTEGER PRIMARY KEY," + KEY_QUESTION + " TEXT NOT NULL," 
     + KEY_CATEGORY + " INTEGER NOT NULL," + KEY_ANSWER_1 + " TEXT NOT NULL," 
     + KEY_ANSWER_2 + " TEXT NOT NULL," + KEY_ANSWER_3 + " TEXT NOT NULL," 
     + KEY_ANSWER_4 + " TEXT NOT NULL," + KEY_DATE_POSTED + " TEXT NOT NULL)"; 
    db.execSQL(CREATE_QUESTIONS_TABLE); 
} 

你的光标之前关闭返回

public int getQuestionsCount() 
{ 
    String countQuery = "SELECT * FROM " + TABLE_QUESTIONS; 
    SQLiteDatabase db = this.getReadableDatabase(); 
    Cursor cursor = db.rawQuery(countQuery, null); 
    int count = cursor.getCount(); 
    cursor.close(); 

    return count; 
}