我正在阅读关于这个问题的stackoverflow，但我仍然没有找到解决方案。有时我的应用程序面临这个问题这是我的错误日志，
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)
这是在ContacGroupDbAdapter类中崩溃的方法，
/**
* 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;
}
并且它在行cursor.moveToFirst（）中崩溃并出现此错误。请帮我解决这个问题。
我使用单独的BaseDbAdapter类来关闭db，
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，并将其getInstance方法更改为synchronized as this answer但仍未解决问题。
/**
* 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;
}
答案 0 :(得分：1)
我认为问题在于synchronization。当多个线程访问时，对数据库的状态存在误解。
您应该避免使数据库成为实例变量，而是在辅助类中使其成为本地方法（最好是扩展SQLiteOpenHelper的方法）。获取数据库并对其进行处理的示例如下所示：
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 Database Tutorial
以下是一个如何干净利落地提出的示例：
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;
}
}
请在此处查看SQLiteOpenHelper.java：SQLiteOpenHelper.java 然后，您将了解如何通过getReadableDatabase（），getWritableDatabase（）和close（）等方法维护数据库（mDatabase）。
答案 1 :(得分：0)
public ArrayList<ContactGroup> getContactGroups() {
ArrayList<ContactGroup> list = null;
try {
// TODO Auto-generated method stub
SQLiteDatabase database = this.getWritableDatabase();
Cursor cursor = database.rawQuery("SELECT * FROM " + TABLE_NAME, null);
if (cursor != null && cursor.moveToFirst()) {
list = new ArrayList<ContactGroup>();
try {
while (cursor.moveToNext())
{
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) {
}
}
if (cursor != null)
{
cursor.close();
database.close();
}
} catch (Exception e) {
}
return list;
}
try this effort