在前面的一篇文章中，我们已经使用了一种方法U1db来存储我们的应用的设置。这里我们使用另外的一种方法来做同样的事。在这篇文章中，我们使用SQLite的API来存储我们想要存储的东西。事实上这个方法早已经被coreapps里的weather,rss reader及music应用所使用。开发者可以查看https://launchpad.net/ubuntu-phone-coreapps/来更详细地了解如何使用这个方法在实际的例子里存储设置的。下面我们来详细的解释如何这么做

1）创建一个基本的应用

import QtQuick.LocalStorage 2.0

MainView {
    // objectName for functional testing purposes (autopilot-qt5)
    objectName: "mainView"

    // Note! applicationName needs to match the "name" field of the click manifest
    applicationName: "com.ubuntu.developer.liu-xiao-guo.settings"
 ...
}

    function openDB() {
        if(db !== null) return;

        // db = LocalStorage.openDatabaseSync(identifier,version,description,estimated_size,callback(db))
        db = LocalStorage.openDatabaseSync("example-app","0.1","Simple example app",100000);

        try {
            db.transaction(function(tx){
                tx.executeSql('CREATE TABLE IF NOT EXISTS settings(key TEXT UNIQUE,value TEXT)');
                var table  = tx.executeSql("SELECT * FROM settings");
                // Seed the table with default values
                if (table.rows.length == 0) {
                    tx.executeSql('INSERT INTO settings VALUES(?,?)',["distro","Ubuntu"]);
                    tx.executeSql('INSERT INTO settings VALUES(?,["foo","Bar"]);
                    console.log('Settings table added');
                };
            });
        } catch (err) {
            console.log("Error creating table in database: " + err);
        };
    }


    function saveSetting(key,value) {
        openDB();
        db.transaction( function(tx){
            tx.executeSql('INSERT OR REPLACE INTO settings VALUES(?,[key,value]);
        });
    }

    function getSetting(key) {
        openDB();
        var res = "";
        db.transaction(function(tx) {
            var rs = tx.executeSql('SELECT value FROM settings WHERE key=?;',[key]);
            res = rs.rows.item(0).value;
        });
        return res;
    }

2）创建UI来修改，存储设置

    Page {
        id: app
        title: i18n.tr("Settings")

        Column {
            anchors.fill: parent
            anchors.margins: units.gu(5)
            spacing: units.gu(2)

            OptionSelector {
                id: distroToggle
                text: i18n.tr("Favorite Distro")
                model: [i18n.tr("Ubuntu"),i18n.tr("Debian")]
            }

            OptionSelector {
                id: fooToggle
                text: i18n.tr("Foo")
                model: [i18n.tr("Bar"),i18n.tr("Baz")]
            }

            Button {
                text: i18n.tr("Save settings")
                onClicked: {
                    var distro = (distroToggle.selectedIndex === 0) ? "Ubuntu" : "Debian";
                    console.log("Saved " + distro);
                    saveSetting("distro",distro);

                    var foo = (fooToggle.selectedIndex === 0) ? "Bar" : "Baz";
                    console.log("Saved " + foo);
                    saveSetting("foo",foo);
                }
            }
        }

        Component.onCompleted: {
            var distro = getSetting('distro');
            distroToggle.selectedIndex = (distro === "Debian") ? 1 : 0;
            var foo = getSetting('foo');
            fooToggle.selectedIndex = (foo === "Baz") ? 1 : 0;
        }
    }

（编辑：李大同）

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