利用golang和QML来开发Ubuntu应用

在前面的文章“使用golang来设计我们的Ubuntu Scope”中，我们已经介绍了如何利用golang来开发Ubuntu Scope。在今天的文章中，我们来简单介绍一下如何使用golang来开发QML应用。这对于一些熟悉golang语言的，但是不是很熟悉C++的开发这来说，无疑是一个好的选择。虽然我们大多数的QML应用只需要QML加上一些Javascript的脚本即可，但是我们可以使用Qt C++或Go语言来拓展它的功能，来做一些需要计算或特殊功能的部分。

首先，我们来查看我们中国开发者dawndiy所做的一个repository:

https://github.com/dawndiy/ubuntu-go-qml-template

这个repository是基于另外一个repository: https://github.com/go-qml/qml

首先就像dawndiy在它的github里描述的那样：

安装Ubuntu SDK

安装额外的包

$sudo apt-get install golang g++ qtdeclarative5-dev qtbase5-private-dev qtdeclarative5-private-dev libqt5opengl5-dev qtdeclarative5-qtquick2-plugin

设置chroots

$git clone https://github.com/nikwen/ubuntu-go-qml-template.git
$cd ubuntu-go-qml-template
$chroot-scripts/setup-chroot.sh

#!/bin/bash

DIR=$(dirname $(readlink -f "$0"))

echo "====================================="
echo "========== Creating chroot =========="
echo "====================================="
echo

sudo click chroot -a armhf -f ubuntu-sdk-14.10 -s utopic create
sudo click chroot -a armhf -f ubuntu-sdk-14.10 -s utopic upgrade

echo
echo "====================================="
echo "=== Installing packages in chroot ==="
echo "====================================="
echo

sudo click chroot -a armhf -f ubuntu-sdk-14.10 -s utopic maint apt-get install git qtdeclarative5-dev:armhf qtbase5-private-dev:armhf qtdeclarative5-private-dev:armhf libqt5opengl5-dev:armhf qtdeclarative5-qtquick2-plugin:armhf

GO_DIR=$DIR/../go-installation

mkdir -p $GO_DIR
cd $GO_DIR

$DIR/install-go-1-3-3.sh

在Desktop下运行应用

$./run.sh

应用中的qml文件可以在./share/ubuntu-go-qml-template/main.qml中找到：

main.qml

import QtQuick 2.0
import Ubuntu.Components 1.1

/*!
    \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: "ubuntu-go-qml-template.nikwen"

    /*
     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(100)
    height: units.gu(75)

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

        Column {
            spacing: units.gu(1)
            anchors {
                margins: units.gu(2)
                fill: parent
            }

            Label {
                id: label
                objectName: "label"

                text: ctrl.message
            }

            Button {
                objectName: "button"
                width: parent.width

                text: i18n.tr("Tap me!")

                onClicked: ctrl.hello()
            }
        }
    }
}

package main

import (
        "gopkg.in/qml.v1"
        "log"
)

func main() {
        err := qml.Run(run)
        if (err != nil) {
                log.Fatal(err)
        }
}

func run() error {
        engine := qml.NewEngine()
        component, err := engine.LoadFile("share/ubuntu-go-qml-template/main.qml")
        if err != nil {
                return err
        }

        ctrl := Control{Message: "Hello from Go!"}
        context := engine.Context()
        context.SetVar("ctrl", &ctrl)

        win := component.CreateWindow(nil)
        ctrl.Root = win.Root()

        win.Show()
        win.Wait()
        return nil
}

type Control struct {
	Root    qml.Object
	Message string
}

func (ctrl *Control) Hello() {
        go func() {
                if (ctrl.Message == "Hello from Go!") {
                        ctrl.Message = "Hello from Go Again!"
                } else {
                        ctrl.Message = "Hello from Go!"
                }
                qml.Changed(ctrl, &ctrl.Message)
        }()
}

部署到手机中

$./install-on-device.sh