Question

我试图关注this tutorial，但是当我在设备上运行时，我收到此错误消息：

   08-04 01:40:12.820  27896-27896/com.filipeferminiano.quiz E/AndroidRuntime﹕ FATAL EXCEPTION: main
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.filipeferminiano.quiz/com.filipeferminiano.quiz.MyActivity}: java.lang.IllegalStateException: attempt to re-open an already-closed object: SQLiteDatabase: /data/data/com.filipeferminiano.quiz/databases/triviaQuiz

我该如何解决这个问题？

Answer 1

跟踪已经告诉你它崩溃的原因： attempt to re-open an already-closed object: SQLiteDatabase

Answer 2

尝试更换此课程，希望这可以帮助您解决问题。

public class DbHelper extends SQLiteOpenHelper {

    private static final int DATABASE_VERSION = 1;
    // Database Name
    private static final String DATABASE_NAME = "triviaQuiz";
    // tasks table name
    private static final String TABLE_QUEST = "quest";
    // tasks Table Columns names
    private static final String KEY_ID = "id";
    private static final String KEY_QUES = "question";
    private static final String KEY_ANSWER = "answer"; //correct option
    private static final String KEY_OPTA= "opta"; //option a
    private static final String KEY_OPTB= "optb"; //option b
    private static final String KEY_OPTC= "optc"; //option c
    private SQLiteDatabase dbase;
    public DbHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }
    @Override
    public void onCreate(SQLiteDatabase db) {
        String sql = "CREATE TABLE IF NOT EXISTS " + TABLE_QUEST + " ( "
                + KEY_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " + KEY_QUES
                + " TEXT, " + KEY_ANSWER+ " TEXT, "+KEY_OPTA +" TEXT, "
                +KEY_OPTB +" TEXT, "+KEY_OPTC+" TEXT)";
        db.execSQL(sql);
        addQuestions(db);
    }
    private void addQuestions(SQLiteDatabase db)
    {
        Question q1=new Question("Which company is the largest manufacturer" +
                " of network equipment?","HP", "IBM", "CISCO", "C");
        this.addQuestion(q1,db);
        Question q2=new Question("Which of the following is NOT " +
                "an operating system?", "SuSe", "BIOS", "DOS", "B");
        this.addQuestion(q2,db);
        Question q3=new Question("Which of the following is the fastest" +
                " writable memory?","RAM", "FLASH","Register","C");
        this.addQuestion(q3,db);
        Question q4=new Question("Which of the following device" +
                " regulates internet traffic?",    "Router", "Bridge", "Hub","A");
        this.addQuestion(q4,db);
        Question q5=new Question("Which of the following is NOT an" +
                " interpreted language?","Ruby","Python","BASIC","C");
        this.addQuestion(q5,db);
    }
    @Override
    public void onUpgrade(SQLiteDatabase db, int oldV, int newV) {
        // Drop older table if existed
        db.execSQL("DROP TABLE IF EXISTS " + TABLE_QUEST);
        // Create tables again
        onCreate(db);
    }
    // Adding new question
    public void addQuestion(Question quest,SQLiteDatabase db) {
        ContentValues values = new ContentValues();
        values.put(KEY_QUES, quest.getQUESTION());
        values.put(KEY_ANSWER, quest.getANSWER());
        values.put(KEY_OPTA, quest.getOPTA());
        values.put(KEY_OPTB, quest.getOPTB());
        values.put(KEY_OPTC, quest.getOPTC());
        // Inserting Row
        db.insert(TABLE_QUEST, null, values);
    }
    public List<Question> getAllQuestions() {
        List<Question> quesList = new ArrayList<Question>();
        // Select All Query
        String selectQuery = "SELECT  * FROM " + TABLE_QUEST;
        dbase=this.getReadableDatabase();
        Cursor cursor = dbase.rawQuery(selectQuery, null);
        // looping through all rows and adding to list
        if (cursor.moveToFirst()) {
            do {
                Question quest = new Question();
                quest.setID(cursor.getInt(0));
                quest.setQUESTION(cursor.getString(1));
                quest.setANSWER(cursor.getString(2));
                quest.setOPTA(cursor.getString(3));
                quest.setOPTB(cursor.getString(4));
                quest.setOPTC(cursor.getString(5));
                quesList.add(quest);
            } while (cursor.moveToNext());
        }
// return quest list
        dbase.close();
        return quesList;
    }
    public int rowcount()
    {
        int row=0;
        String selectQuery = "SELECT  * FROM " + TABLE_QUEST;
        SQLiteDatabase db = this.getWritableDatabase();
        Cursor cursor = db.rawQuery(selectQuery, null);
        row=cursor.getCount();
        return row;
    }
}

Answer 3

检查你关闭的数据库对象，你的代码中的某些地方也检查教程中没有任何地方写db.close（）所以不要在你的例子中关闭你的数据库。多数民众赞成......

无法在设备中启动活动

3 个答案: