IllegalStateException：无法执行此操作，因为连接池已关闭

Question

12-31 10:58:28.025: E/AndroidRuntime(16322): FATAL EXCEPTION: Timer-0
12-31 10:58:28.025: E/AndroidRuntime(16322): java.lang.IllegalStateException: Cannot perform this operation because the connection pool has been closed.
12-31 10:58:28.025: E/AndroidRuntime(16322):    at android.database.sqlite.SQLiteConnectionPool.throwIfClosedLocked(SQLiteConnectionPool.java:1031)
12-31 10:58:28.025: E/AndroidRuntime(16322):    at android.database.sqlite.SQLiteConnectionPool.waitForConnection(SQLiteConnectionPool.java:746)
12-31 10:58:28.025: E/AndroidRuntime(16322):    at android.database.sqlite.SQLiteConnectionPool.acquireConnection(SQLiteConnectionPool.java:400)
12-31 10:58:28.025: E/AndroidRuntime(16322):    at android.database.sqlite.SQLiteSession.acquireConnection(SQLiteSession.java:905)
12-31 10:58:28.025: E/AndroidRuntime(16322):    at android.database.sqlite.SQLiteSession.executeForCursorWindow(SQLiteSession.java:834)
12-31 10:58:28.025: E/AndroidRuntime(16322):    at android.database.sqlite.SQLiteQuery.fillWindow(SQLiteQuery.java:62)
12-31 10:58:28.025: E/AndroidRuntime(16322):    at android.database.sqlite.SQLiteCursor.fillWindow(SQLiteCursor.java:144)
12-31 10:58:28.025: E/AndroidRuntime(16322):    at android.database.sqlite.SQLiteCursor.getCount(SQLiteCursor.java:133)
12-31 10:58:28.025: E/AndroidRuntime(16322):    at android.database.AbstractCursor.moveToPosition(AbstractCursor.java:197)
12-31 10:58:28.025: E/AndroidRuntime(16322):    at android.database.AbstractCursor.moveToFirst(AbstractCursor.java:237)
12-31 10:58:28.025: E/AndroidRuntime(16322):    at com.eyepax.horseapp.data.dbadapters.ContactGroupDbAdapter.getContactGroups(ContactGroupDbAdapter.java:138)
12-31 10:58:28.025: E/AndroidRuntime(16322):    at com.eyepax.horseapp.data.DataManager.getGroups(DataManager.java:1548)
12-31 10:58:28.025: E/AndroidRuntime(16322):    at com.eyepax.horseapp.sync.ContactSync.contactGroupSync(ContactSync.java:43)
12-31 10:58:28.025: E/AndroidRuntime(16322):    at com.eyepax.horseapp.service.SynchingService.callSync(SynchingService.java:77)
12-31 10:58:28.025: E/AndroidRuntime(16322):    at com.eyepax.horseapp.service.SynchingService.access$0(SynchingService.java:70)
12-31 10:58:28.025: E/AndroidRuntime(16322):    at com.eyepax.horseapp.service.SynchingService$1.run(SynchingService.java:57)

/**
 * Returns ContactGroup.
 * 
 * @return ArrayList<ContactGroup>
 */
public ArrayList<ContactGroup> getContactGroups() {

    this.open();
    Cursor cursor = database.rawQuery("SELECT * FROM " + TABLE_NAME, null);
    ArrayList<ContactGroup> list = null;

    if (cursor != null && cursor.moveToFirst()) {
        list = new ArrayList<ContactGroup>();

        do {
            try {
                ContactGroup contactGroup = new ContactGroup();
                contactGroup.setGroupId(cursor.getString(cursor.getColumnIndex(GROUP_ID)));
                contactGroup.setGroupName(cursor.getString(cursor.getColumnIndex(GROUP_NAME)));
                contactGroup.setIsDeleted(cursor.getInt(cursor.getColumnIndex(GROUP_IS_DELETED)));
                contactGroup.setUpdatedDate(cursor.getString(cursor.getColumnIndex(GROUP_UPDATE_DATE)));
                contactGroup.setIsSync(cursor.getInt(cursor.getColumnIndex(GROUP_IS_SYNC)));

                list.add(contactGroup);
            } catch (Exception e) {

            }
        } while (cursor.moveToNext());

    }

    if (cursor != null)
        cursor.close();
    return list;
}

public class BaseDbAdapter {

/**
 * Application context.
 */
protected Context context;

/**
 * Database.
 */
protected SQLiteDatabase database;

/**
 * Database helper class.
 */
protected SQLiteDataBaseHelper dbHelper;

/**
 * StringBuilder
 */
protected StringBuilder stringBuilder;

public static final String CREATE_TABLE_PRE_TEXT = "create table if not exists ";
/**
 * Returns StringBuilder object.
 * 
 * @return
 */
protected StringBuilder getStringBuilder() {
    if (stringBuilder == null) {
        stringBuilder = new StringBuilder();
    }

    return stringBuilder;
}

/**
 * Opens a connection to the database.
 * 
 * @throws SQLException
 */
public synchronized void open() throws SQLException {
    dbHelper = SQLiteDataBaseHelper.getInstance(context);
    database = dbHelper.getWritableDatabase();
}

/**
 * Closes the connection.
 */
public synchronized void close() {
    database.close();
}

public static String getDeleteTableStatement(String tableName) {
    return "DELETE TABLE " + tableName;
}

我使用了SQLiteDataBaseHelper类，其getInstance方法更改为synchronize.
作为此答案，但仍然存在问题not fixed。

 /**
 * Get an instance of SQLiteDataBaseHelper.
 * 
 * @param context
 * @return SQLiteDataBaseHelper
 */
public static synchronized SQLiteDataBaseHelper getInstance(Context context) {

    // if(dbName == null) {
    // dbName = DataManager.getSQLiteDatabaseName(context);
    // }

    if (instance == null) {
        instance = new SQLiteDataBaseHelper(context);

    }

    return instance;
}

Answer 1

我认为问题出在同步上。当多个线程访问时，会对数据库的状态产生误解。

您应该避免将数据库设置为实例变量，而应将其设置为帮助器类（最好是扩展SQLiteOpenHelper的类）中的本地方法。下面展示了获取数据库并对其进行操作的示例：

public void addContact(Contact contact) {
    SQLiteDatabase db = this.getWritableDatabase();

    ContentValues values = new ContentValues();
    values.put(KEY_NAME, contact.getName()); // Contact Name
    values.put(KEY_PH_NO, contact.getPhoneNumber()); // Contact Phone Number

    // Inserting Row
    db.insert(TABLE_CONTACTS, null, values);
    db.close(); // Closing database connection
}

请查看本教程：Android SQLite数据库教程

public class DatabaseHelper extends SQLiteOpenHelper {

    ......

    // no need to synchronize
    public Cursor getBookList(){
        SQLiteDatabase db = getReadableDatabase(); // or getWritableDatabase()
        Cursor c = db.query(BookEntry.TABLE_NAME, null, null, null, null, null, BookEntry.COLUMN_NAME + " ASC");
        return c;
    }

    // no need to override close method, because that one is very well coded already
    // SQLiteOpenHelper will close any opened database, with its service close method.
}

public class SomeAdapter{


    // no need to synchronize, as all DatabaseHelper instances are method local
    public int getBookCount(){
        DatabaseHelper dbHelper = new DatabaseHelper(context);
        Cursor c = dbHelper.getBookList();
        int rowCount = c.getCount();
        c.close();  // close the cursor once used.
        dbHelper.close(); // ask the helper to close any open database.
        return rowCount;

    }

}