我在以前的文章中，讲述了如何使用U1db及SQLite offline storage API来存储应用的一些状态。在这篇文章中，我将介绍如何使用Qt.labs.settings来存储应用的状态。更加详细的介绍，请参阅链接。

首先，我们创建一个最简单的“App with Simple UI”模版应用，并修改文件“main.qml”如下：

import QtQuick 2.0
import Ubuntu.Components 1.1
import Qt.labs.settings 1.0

/*!
    \brief MainView with a Label and Button elements.
*/

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"

    /*
     This property enables the application to change orientation
     when the device is rotated. The default is false.
    */
    //automaticOrientation: true

    // Removes the old toolbar and enables new features of the new header.
    useDeprecatedToolbar: false

    width: units.gu(50)
    height: units.gu(75)

    Page {
        title: i18n.tr("Simple")

        Column {
            anchors.fill: parent
            anchors.centerIn: parent
            anchors.horizontalCenter: parent.center


            Label {
                text: "Please input a string below:"
                fontSize: "large"
            }

            TextField {
                id: myTextField
                text: settings.input
                placeholderText: "please input a string"

                onTextChanged: {
                    settings.input = text
                }
            }

            Button {
                text: "Get category"
                onClicked: {
                    console.log("settings category:" + settings.category);
                }
            }
        }

        Settings {
            id: settings
            property string input: "unknown"
        }

        Component.onDestruction: {
            settings.input = myTextField.text
        }
    }
}

<span style="font-family: Arial, Helvetica, sans-serif; background-color: rgb(255, 255, 255);">记得这里我们一定要加入“</span><span style="font-family: Arial, Helvetica, sans-serif; background-color: rgb(255, 255, 255);">Qt.labs.settings</span><span style="font-family: Arial, Helvetica, sans-serif; background-color: rgb(255, 255, 255);">”。我们首先绑定myTextField的值为settings中的input。在程序退出的时候，我们通过如下的方式进行存储：</span>

        Component.onDestruction: {
            settings.input = myTextField.text
        }

            TextField {
                id: myTextField
                text: settings.input
                placeholderText: "please input a string"

                onTextChanged: {
                    settings.input = text
                }
            }

运行我们的应用，我们会发现，当我们修改myTextField中的值，并退出后。下次启动时，可以看到，上次输入的值被读取，并存放于myTextField中。

整个测试的源码在　bzr branch lp:~liu-xiao-guo/debiantrial/settingsqml

使用Qt.labs.settings来存储应用的设置