如何动态地向选项卡中添加标签？

Question

我正在尝试使用下面的代码向选项卡组件添加一个新的选项卡。

运行时没有报错，但是没有显示出额外的选项卡。 我已经尝试过将tabs和tabs.__tabsModel都作为父级使用，但是没有显示出额外的选项卡。

import QtQuick 2.0
import QtQuick.LocalStorage 2.0
import Ubuntu.Components 0.1

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

    width: units.gu(100)
    height: units.gu(75)

    Tabs {
        id: tabs
        anchors.fill: parent

        Component.onCompleted: {
            mainView.initializeDB();
            mainView.saveFeed("BBC News","http://feeds.bbci.co.uk/news/rss.xml");
            mainView.saveFeed("Jono Bacon","http://www.jonobacon.org/?feed=rss2");
            mainView.saveFeed("The Register", "http://www.theregister.co.uk/headlines.atom");
            fillTabs();
        }

        tools: ToolbarActions {
            Action {
                objectName: "action"

                iconSource: Qt.resolvedUrl("avatar.png")
                text: i18n.tr("Tap me!")

                onTriggered: {
                    label.text = i18n.tr("Toolbar tapped")
                }
            }
        }

        // First tab begins here
        Tab {
            id: tabFrontPage
            objectName: "tabFrontPage"

            title: i18n.tr("Front Page")

            // Tab content begins here
            page: Page {
                Column {
                    anchors.centerIn: parent
                    Label {
                        id: labelFrontPage
                        text: i18n.tr("This will be the front page \n An aggregation of the top stories from each feed")
                    }
                }
            }
        }
    }

    function fillTabs() {
        var db = getDatabase();
        db.transaction(function(tx) {
            var rs = tx.executeSql('SELECT * FROM feeds;');
            if (rs.rows.length > 0) {
                for(var i = 0; i < rs.rows.length; i++) {
                    var feedTab = Qt.createQmlObject('import QtQuick 2.0;import Ubuntu.Components 0.1;Tab {anchors.fill: parent;objectName: "Tab";title: i18n.tr("Tab");page: Page {anchors.margins: units.gu(2);Column {anchors.centerIn: parent;Label {id: label;objectName: "label";text: i18n.tr("Tab");}}}}',tabs,"feedTab");
                }
            } else {
                res = "Unknown";
            }
        })
    }
    //Storage API
    function getDatabase() {
        return LocalStorage.openDatabaseSync("news-feed","1.0","StorageDatabase",10000)
    }

    //Initialise DB tables if not already existing
    function initializeDB() {
        var db = getDatabase();
        db.transaction(function(tx) {
            //Create settings table if not existing
            tx.executeSql('CREATE TABLE IF NOT EXISTS settings(setting TEXT UNIQUE, value TEXT)');
            tx.executeSql('CREATE TABLE IF NOT EXISTS feeds(feedName TEXT UNIQUE, feedURL TEXT UNIQUE)')
        });
    }

    //Write setting to DB
    function setSetting(setting,value){
        //setting: string - setting name (key)
        //value: string - value
        var db = getDatabase();
        var res = "";
        db.transaction(function(tx) {
            var rs = tx.executeSql('INSERT OR REPLACE INTO settings VALUES (?,?);',[setting,value]);
            //console.log(rs.rowsAffected)
            if(rs.rowsAffected > 0) {
                res = "OK";
            } else {
                res = "Error";
            }
        })
        return res;
    }

    //Read setting from DB
    function getSetting(setting) {
        var db = getDatabase();
        var res="";
        db.transaction(function(tx) {
            var rs = tx.executeSql('SELECT value FROM settings WHERE setting=?;', [setting]);
            if (rs.rows.length > 0) {
                res = rs.rows.item(0).value;
            } else {
                res = "Unknown";
            }
        })
        return res;
    }

    function saveFeed(feedName, feedURL) {
        var db = getDatabase();
        var res = "";
        db.transaction(function(tx){
            var rs = tx.executeSql('INSERT OR REPLACE INTO feeds VALUES (?,?)',[feedName,feedURL]);
            //console.log(rs.rowsAffected)
            if (rs.rowsAffected > 0) {
                res = "OK";
            } else {
                res = "Error";
            }
        })
        return res;
    }

    //Return a single feed
    function getFeed(feedName) {
        var db = getDatabase();
        var res = "";
        db.transaction(function(tx) {
            var rs = tx.executeSql('SELECT feedURL FROM feeds WHERE feedName=?;', [feedName]);
            if (rs.rows.length > 0) {
                res = rs.rows.item(0).feedURL;
            } else {
                res = "Unknown";
            }

        })
        return res;
    }

    //Return all feeds and urls
    function getFeeds() {
        var db = getDatabase();
        var res = "";
        db.transaction(function(tx) {
            var rs = tx.executeSql('SELECT * FROM feeds;');
            if (rs.rows.length > 0) {
                return rs;
            } else {
                res = "Unknown";
            }
        })
        return res;
    }
}

- Morchuboo

---

这个问题可能与本地话题稍有偏离。我建议你在StackOverflow上提问，以获得更快速和更好的回答。 - lordqwerty

这个问题完全符合主题。我们一直以来都非常成功地在Ask Ubuntu上提问关于应用开发的问题。 - David Planella

另外，这个问题可能特别与Ubuntu组件有关。 - Morchuboo

不小心误操作了关闭投票，非常抱歉朋友们。 - Raja G

Answer 1

很抱歉，目前无法动态添加选项卡。

SDK团队告诉我，这是VisualItemModel类型（Tabs组件使用的类型）的限制，它不允许动态添加子元素。

有一个bug用于跟踪此问题。

- David Planella

---

还有一些工作要做；-) - NilsB

有没���可以追踪的票？ - payload

我早就料到了。 我通过在一个JavaScript函数中创建整个选项卡容器组件和所有包含的选项卡组件，然后将其作为主视图的父级添加进去来解决了这个问题。 虽然有点糟糕的hack方法，但是它能正常工作 :P - Morchuboo

@payload，现在没有一个bug来跟踪这个问题，但是请随时打开一个bug供SDK团队查看：https://bugs.launchpad.net/ubuntu-ui-toolkit/+filebug - David Planella

@payload，有人已经提交了此问题的票据：https://bugs.launchpad.net/ubuntu-ui-toolkit/+bug/1124071。我的解决方法是使用Qt.createQmlObject函数与标签集合和所有子元素。可以在这里看到：http://pastebin.com/dmyPkyyX。它确实不太优雅，并且字符串很快就变得难以管理，但是有效。请查看fillTabs（）函数。 - Morchuboo

@Morchuboo，谢谢，我已经更新了答案并附上了错误报告。你可能也想将你的解决方案代码片段作为额外的答案发布。我相信其他尝试做同样事情的人会从你的工作中受益。 - David Planella

Answer 2

这是一个示例的解决方法。

这种方法几乎将所有的图形用户界面都指定为字符串，并且很快变得混乱，但在上游实现追加到VisualItemModel的功能之前，它可以工作。

这是我正在调试的一个RSS阅读器的开头。如果你将它粘贴到一个空的qml文件中，它应该能正常运行。（你可能需要安装libqt5sql5-sqlite和qtdeclarative5-localstorage-plugin。它们在手机镜像上，但没有与SDK安装一起安装）。

import QtQuick 2.0
import QtQuick.LocalStorage 2.0
import Ubuntu.Components 0.1

/*!
    \brief MainView with Tabs element.
       First Tab has a single Label and
       second Tab has a single ToolbarAction.
*/

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

    width: units.gu(100)
    height: units.gu(75)

    tools: ToolbarActions {
    Action {
        objectName: "action"

        iconSource: Qt.resolvedUrl("avatar.png")
        text: i18n.tr("Tap me!")

        onTriggered: {
            label.text = i18n.tr("Toolbar tapped")
        }
    }
    }

    Component.onCompleted: {
    mainView.initializeDB();
    mainView.saveFeed("BBC News","http://feeds.bbci.co.uk/news/rss.xml");
    mainView.saveFeed("Jono Bacon","http://www.jonobacon.org/?feed=rss2");
    mainView.saveFeed("The Register", "http://www.theregister.co.uk/headlines.atom");
    fillTabs();
    }

    Tabs {
    id: initialtabs
    anchors.fill: parent

    tools: ToolbarActions {
        Action {
            objectName: "action"

            iconSource: Qt.resolvedUrl("avatar.png")
            text: i18n.tr("Tap me!")

            onTriggered: {
                label.text = i18n.tr("Toolbar tapped")
            }
        }
    }

    // First tab begins here
    Tab {
        id: tabFrontPage
        objectName: "tabFrontPage"

        title: i18n.tr("Front Page")

        // Tab content begins here
        page: Page {
            Column {
                anchors.centerIn: parent
                Label {
                    id: labelFrontPage
                    text: i18n.tr("This will be the front page \n An aggregation of the top stories from each feed")
                }
            }
        }
    }
    }


    function fillTabs() {
    initialtabs.destroy();
    var objStr = "import QtQuick 2.0;import Ubuntu.Components 0.1;import QtQuick.XmlListModel 2.0;Tabs{id:tabs;anchors.fill:parent;"
    var db = getDatabase();
    db.transaction(function(tx) {
        var rs = tx.executeSql('SELECT * FROM feeds;');
        if (rs.rows.length > 0) {
            for(var i = 0; i < rs.rows.length; i++) {
                objStr += "Tab {id:tab" + i + ";anchors.fill:parent;title:'" + rs.rows.item(i).feedName + "';property string source: '" + rs.rows.item(i).feedURL + "';page: Page {anchors.margins: units.gu(2);Column {anchors.centerIn: parent;Label{text:tab" + i + ".source;}}}}";
            }
            objStr += "}";
            var cmpTabs = Qt.createQmlObject(objStr,mainView,"tabsfile");
        } else {
            res = "Unknown";
        }
    })
    }

    //Create tabs for each feed
    function createTabs() {
    var feeds = getFeeds();
    for (var i = 0; i < feeds.length; i++){
        //Add tab for each feed.
        //Cannot be done with existing API

    }
    }

    //Storage API
    function getDatabase() {

    return LocalStorage.openDatabaseSync("news-feed","1.0","StorageDatabase",10000)
    }

    //Initialise DB tables if not already existing
    function initializeDB() {
    var db = getDatabase();
    db.transaction(function(tx) {
        //Create settings table if not existing
        tx.executeSql('CREATE TABLE IF NOT EXISTS settings(setting TEXT UNIQUE, value TEXT)');
        tx.executeSql('CREATE TABLE IF NOT EXISTS feeds(feedName TEXT UNIQUE, feedURL TEXT UNIQUE)')
    });
    }

    //Write setting to DB
    function setSetting(setting,value){
    //setting: string - setting name (key)
    //value: string - value
    var db = getDatabase();
    var res = "";
    db.transaction(function(tx) {
        var rs = tx.executeSql('INSERT OR REPLACE INTO settings VALUES (?,?);',[setting,value]);
        //console.log(rs.rowsAffected)
        if(rs.rowsAffected > 0) {
            res = "OK";
        } else {
            res = "Error";
        }
    })
    return res;
    }

    //Read setting from DB
    function getSetting(setting) {
       var db = getDatabase();
       var res="";
       db.transaction(function(tx) {
     var rs = tx.executeSql('SELECT value FROM settings WHERE setting=?;', [setting]);
     if (rs.rows.length > 0) {
          res = rs.rows.item(0).value;
     } else {
         res = "Unknown";
     }
      })
      // The function returns “Unknown” if the setting was not found in the database
      // For more advanced projects, this should probably be handled through error codes
      return res;
    }

    function saveFeed(feedName, feedURL) {
    var db = getDatabase();
    var res = "";
    db.transaction(function(tx){
        var rs = tx.executeSql('INSERT OR REPLACE INTO feeds VALUES (?,?)',[feedName,feedURL]);
        //console.log(rs.rowsAffected)
        if (rs.rowsAffected > 0) {
            res = "OK";
        } else {
            res = "Error";
        }
    })
    return res;
    }

    //Return a single feed
    function getFeed(feedName) {
    var db = getDatabase();
    var res = "";
    db.transaction(function(tx) {
        var rs = tx.executeSql('SELECT feedURL FROM feeds WHERE feedName=?;', [feedName]);
        if (rs.rows.length > 0) {
            res = rs.rows.item(0).feedURL;
        } else {
            res = "Unknown";
        }

    })
    return res;
    }

    //Return all feeds and urls
    function getFeeds() {
    var db = getDatabase();
    var res = "";
    db.transaction(function(tx) {
        var rs = tx.executeSql('SELECT * FROM feeds;');
        if (rs.rows.length > 0) {
            return rs;
        } else {
            res = "Unknown";
        }
        })
    return res;
    }
}

- Morchuboo