QThread 线程中使用 SQLite

基本的流程如下:

QThread: 线程与Sqlite绑定

生成实例前先把与 sqlquery 信号与槽 建立好，然后就线程开始，等待信号:

class SQLThread : public QObject
{
    Q_OBJECT
private:
    QThread workerThread;
public:
    explicit SQLThread(QObject *parent = nullptr);
    ~SQLThread();
private slots:
    void slot_res_select(int tid, bool res, QString msg, QList<QSqlRecord> data);
signals:
    void sig_initDB();      // 接收上层调用信号，然后去调用下层 SQLQuery 的slot功能函数
    void sig_select(int tid, QString sql);
    void sig_res_select(int tid, bool res, QString msg, QList<QSqlRecord> data);

SQLThread::SQLThread(QObject *parent) : QObject(parent)
{
    SQLQuery *sq = new SQLQuery;
    sq->moveToThread(&workerThread);
    connect(&workerThread, &QThread::finished, sq, &QObject::deleteLater);
    // Select SQL
    connect(this, &SQLThread::sig_selectSql, sq, &SQLQuery::slot_selectSql);
    connect(sq, &SQLQuery::sig_res_selectSql, this, &SQLThread::slot_res_selectSql);
    qDebug() << "workThread.start";
    workerThread.start();
}
SQLThread::~SQLThread()
{
    qDebug() << "workThread.quit and wait";
    workerThread.quit();
    workerThread.wait();
}
void SQLThread::slot_res_selectSql(int tid, bool res, QString msg, QList<QSqlRecord> data)
{
    emit sig_res_select(tid, res, msg, data);
}

SQLQuery: 正常的操作数据库:

class SQLQuery : public QObject
{
    Q_OBJECT
public slots:
    void slot_select(int tid, QString sql);    // select
signals:
    void sig_res_select(int tid, bool res, QString msg, QList<QSqlRecord> data);
};

void SQLQuery::slot_select(int tid, QString sql)
{
    QString msg;
    QList<QSqlRecord> data;
    QSqlDatabase mDB = QSqlDatabase::addDatabase("QSQLITE", "select"); // 添加数据库驱动
    mDB.setDatabaseName(mDBName);
    if (!mDB.open()) {
        qDebug("打开数据库失败");
        msg = "Open db file fail";
        emit sig_res_selectSql(tid, false, msg, data);
        return;
    }
    QSqlQuery query(mDB);
    if (!query.exec(sql)) {
        qDebug() << "insert sql fail:" << query.lastError().text();
        qDebug() << "sql: " << sql;
        msg = "insert fail, sql: " + sql;
        emit sig_res_selectSql(tid, false, msg, data);
        QSqlDatabase::removeDatabase(
                        QSqlDatabase::database().connectionName()
                        );
        return;
    }
    while (query.next()) {
        data.append(query.record());
    }
    qDebug() << "SQLQuery: select succ, count: " << data.count();
    emit sig_res_selectSql(tid, true, msg, data);
    QSqlDatabase::removeDatabase(QSqlDatabase::database().connectionName());
    return;
}

MainWindow:

class MainWindow : public QMainWindow
{
    Q_OBJECT
private slots:
    void slot_res_selectSql(int tid, bool res, QString msg, QList<QSqlRecord> data);
private:
    SQLThread *st;
}

MainWindow::Select()
{
    ...
    qRegisterMetaType<QList<QSqlRecord>>("QList<QSqlRecord>"); // 注册新类型
    st = new SQLThread;
    connect(st, &SQLThread::sig_res_select, this, &MainWindow::slot_res_select);
    QString sql = "SELECT * from accountTBL order by id asc";
    emit st->sig_selectSql(10001, sql);
}
void MainWindow::slot_res_select(int tid, bool res, QString msg, QList<QSqlRecord> data)
{
    if (tid != 10001) { ... }
    else {
        if (res) {
            for (int i=0; i<data.count(); i++) {
                int uid = data.at(i).value("id").toInt();
                QString email = data.at(i).value("email").toString();
            }
        }
    }
}