Android SQLite问题“无法执行此操作，因为连接池已关闭”

Question

 Caused by: java.lang.IllegalStateException: Cannot perform this operation because the connection pool has been closed.

public List<contacts> getAllcontacts() {
List<contacts> contactsl = new LinkedList<contacts>();

// 1. build the query
String query = "SELECT  * FROM contacts";

// 2. get reference to writable DB
SQLiteDatabase db = this.getWritableDatabase();
Cursor cursor = db.rawQuery(query, null);

// 3. go over each row, build a contact and add it to list
contacts contact = null;
if (cursor.moveToFirst()) {
    do {
        contact = new contacts();

        contact.setName(cursor.getString(1));
        contact.setNumero(cursor.getString(3));
        contact.setProfil(cursor.getString(2));
        contact.setShow(cursor.getString(5));
        contact.setBlocked(cursor.getString(4));
        contact.setObjectid(cursor.getString(6));
        contactsl.add(contact);
    } while (cursor.moveToNext());
}

return contactsl;
}

private static sql sInstance;

private static final int DATABASE_VERSION = 1;

private static final String DATABASE_NAME = "Contact";

public static sql getInstance(Context context) {

// Use the application context, which will ensure that you
// don't accidentally leak an Activity's context.
if (sInstance == null) {
    sInstance = new sql(context.getApplicationContext());
}
return sInstance;
}

public sql(Context context) {
    super(context, DATABASE_NAME, null, DATABASE_VERSION);
}

@Override
public void onCreate(SQLiteDatabase db) {

    String CREATETABLE = "CREATE TABLE contacts ( " +
            "id INTEGER PRIMARY KEY AUTOINCREMENT, " +
            "name TEXT, "+
            "profil TEXT, "+
            "phone TEXT UNIQUE ,"+
            "blocked TEXT, "+
            "show TEXT , "+
            "objectid TEXT )";

    db.execSQL(CREATETABLE);
}




@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int `newVersion) {`
    // TODO Auto-generated method stub
    db.execSQL("DROP TABLE IF EXISTS contacts");

    this.onCreate(db);
}

Answer 1

如果过早关闭DBHelper，则可能会出现此错误。如果关闭帮助程序并将其关闭，请搜索代码，看看是否仍遇到此错误。

否则，可以尝试这个模板来实例化您的DBHelper。

public class MyDBHelper extends SQLiteOpenHelper {

    private static final String DATABASE_NAME = "myDatabase.db";
    private static final int SCHEMA = 1;
    private static volatile MyDBHelper sInstance;


    private MyDBHelper(Context context) {
        super(context, DATABASE_NAME, null, SCHEMA);
    }

    public static MyDBHelper getInstance(Context context) {
        if (sInstance == null) {
            synchronized (MyDBHelper.class) {
                if (sInstance == null) {
                    sInstance = new MyDBHelper(context.getApplicationContext());
                }
            }
        }
        return sInstance;
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        // create your tables here
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        // handle db upgrade or leave blank
    }
}

作为对您评论的回答，您仍然可以在实例完成时关闭数据库

@Override
public void finalize() throws Throwable {
    sInstance.close();
    super.finalize();
}