javascript - 如何决定 SQLite 文件在 QML LocalStorage 中的存储位置

Question

我有这个代码:

import QtQuick 2.6
import QtQuick.Controls 2.1
import QtQuick.LocalStorage 2.0

ApplicationWindow {
visible: true
width: 640
height: 480
title: qsTr("Hello World")

property var db // the database of this application
property string dbIdentifier: '/Users/cedo/desktop/test/DatabaseApplicationDB.db'
property string dbVersion: '1.0'
property string dbDescription: 'DatabaseApplicationDB'
property int dbEstimatedSize: 1000000

Component.onCompleted: {
    db = LocalStorage.openDatabaseSync(dbIdentifier, dbVersion, dbDescription, dbEstimatedSize);

    db.transaction(function(tx) {
        var sql = "create table if not exists mytable(id integer)";
        tx.executeSql(sql);
    });

}
}

dbIdentifier 在创建数据库时起作用，但当我在桌面中搜索 db 文件时，该文件不存在。它在哪里？或者如何决定把它放在哪里？

Answer 1

根据openDatabaseSync()方法documentation ，函数原型(prototype)为:

object openDatabaseSync(string name, string version, string description, int estimated_size, jsobject callback(db))

name is the database name

version is the database version

description is the database display name

estimated_size is the database's estimated size, in bytes

callback is an optional parameter, which is invoked if the database has not yet been created.

所以没有文件名参数。再次，根据documentations :

These databases are user-specific and QML-specific, but accessible to all QML applications. They are stored in the Databases subdirectory of QQmlEngine::offlineStoragePath(), currently as SQLite databases.

为了能够将数据库文件放入某个自定义目录中，您应该使用 QQmlEngine 或 QQmlApplicationEngine 的 setOfflineStoragePath(const QString &dir) 函数强>实例。

要查看数据库文件当前所在的位置，请使用以下 C++ 代码:

QQmlApplicationEngine engine;
engine.load(QUrl(QStringLiteral("qrc:/main.qml")));
qDebug() << engine.offlineStoragePath();

更多信息here和 here