Android：查询sqlite打开数据库时的FC

Question

Android 系统会自动关闭一个打开的 SQLite 数据库吗？我已经实现了一个用于访问数据的单例类，有时那里的方法需要在工作线程上运行。我有一个在后台运行的查询的同步功能，代码如下：

public ArrayList<ActualCall> getUnsentCalls(boolean forUnsentSignature) {
    ArrayList<ActualCall> calls = new ArrayList<ActualCall>();

    Cursor c;
    open();

    if (forUnsentSignature)
        c = db.rawQuery("SELECT * FROM " + TXN_ACTUAL_CALL_COMPONENT
                + " WHERE sentFlag=1 and sigSentFlag=?", new String[] {"0"});
    else
        c = db.rawQuery("SELECT * FROM " + TXN_ACTUAL_CALL_COMPONENT
                + " WHERE sentFlag=? AND signature != ''", new String[] {"0"});

    if (c.moveToFirst()) {
        do {
            if (!db.isOpen())
                open();
            ActualCall call = new ActualCall();

            call.setAcpComponentId(c.getString(c.getColumnIndex("acpComponentId")));
            call.setAcpDate(c.getString(c.getColumnIndex("acpDate")));
            call.setAcpId(c.getString(c.getColumnIndex("acpId")));
            call.setCallEndTime(c.getString(c.getColumnIndex("callEndTime")));
            call.setCallStartTime(c.getString(c.getColumnIndex("callStartTime")));
            call.setCoordinates(c.getString(c.getColumnIndex("coordinates")));
            call.setDeviceTimestamp(c.getString(c.getColumnIndex("deviceTimestamp")));
            call.setDoctorId(c.getString(c.getColumnIndex("doctorId")));
            call.setSignature(c.getString(c.getColumnIndex("signature")));
            call.setSigSentFlag(c.getString(c.getColumnIndex("sigSentFlag")));
            call.setTimeSpent(c.getString(c.getColumnIndex("timeSpent")));
            call.setSentFlag(c.getString(c.getColumnIndex("sentFlag")));
            call.setCoordinates(c.getString(c.getColumnIndex("coordinates")));

            calls.add(call);

        } while (c.moveToNext());
    }

    c.close();
    db.close();

    return calls;
}

如您所见，我已经在最初的几行中调用了 open()，但我收到了一个错误，表明我的数据库已经关闭。这是堆栈跟踪：

 java.lang.IllegalStateException: database    
 /data/data/com.***.****/databases/****.db (conn# 0) already closed
 at android.database.sqlite.SQLiteDatabase.verifyDbIsOpen(SQLiteDatabase.java:2123)
 at android.database.sqlite.SQLiteDatabase.lock(SQLiteDatabase.java:398)
 at android.database.sqlite.SQLiteDatabase.lock(SQLiteDatabase.java:390)
 at android.database.sqlite.SQLiteQuery.fillWindow(SQLiteQuery.java:74)
 at android.database.sqlite.SQLiteCursor.fillWindow(SQLiteCursor.java:311)
 at android.database.sqlite.SQLiteCursor.getCount(SQLiteCursor.java:292)
 at android.database.AbstractCursor.moveToPosition(AbstractCursor.java:156)
 at android.database.AbstractCursor.moveToFirst(AbstractCursor.java:233)
 at com.***.****.datalayer.ESCAndroidDataLayer.getUnsentCalls(ESCAndroidDataLayer.java:5340)
 at com.***.****.synchall.SynchAll$UnsentSignatureSender.run(SynchAll.java:1750)

再一次，上面的方法是在一个 Thread 类上调用的，如果有帮助的话。我找到了一个关于自动关闭 SQLite 的链接，但我不明白他的解决方案：http://darutk-oboegaki.blogspot.com/2011/03/sqlitedatabase-is-closed-automatically.html

Answer 1

尝试在 c.moveToFirst() 之前调用 db.acquireReference()

    db.acquireReference();

    if (c.moveToFirst()) {

或者只需将 db.close() 与 "if (db.isOpen())" 括起来就足够了。

    if (db.isOpen())
    {
        db.close();
    }

我不太确定，但这些会改变一些事情。