Developing MeeGo apps with Python and QML



Introduction

This tutorial will guide you through how to set up a PySide environment on your MeeGo Netbook and then show you some basics through examples, and finally well create a QML UI for an existing application (gPodder) that can be used on MeeGo Netbook and MeeGo Handset.

Why should Iuse Python to develop MeeGo apps?

Low barrier to entry: Python is a very easy to learn language, so you can get quickly up to speed- independent of whether or not you are already familiar with other languages

Garbage collection:You don't have to manually manage the memory of the objects you create-the Python garbage collector takes care of removing no longer needed objects

No compiling: Python is an interpreted language, so you can run your application right after saving the source in an editor. No need to wait for code to compile. This is especiallyimportant on low-powered netbooks. Full access to the Qt libraries: PySide bindings allow access to all modules of Qt. And because it uses the native Qt libraries, library functions run at native (compiled) speed.

Shorter code: In my experience, C++ applications using Qt have about 3 times as much lines of code as the equivalent Python applications-using the same libraries and Qt classes!

Prototyping: Even if you plan on writing a C++ Qt application, Python and PySide are a great combination for quickly prototyping your ideas.This could be useful to prototype a C++ backend of your QML application. Later on, youjust exchange the Python backend with a C++ backend and can reuse the QML files from the Python app.

Development on the go: As Python is an interpreted language, the runtime already contains all the necessary tools to develop applications, so you don't have to install a compiler, development libraries and header files just to create apps-it's instant, and some people even develop Python GUl apps directly on handset devices like the N900.

Links

PySide Homepage: http://www.pyside.org/ MeeGo

Homepage: http://www.meego.com/

PySide Wiki: http/developer.qt.nokia.com/wiki/PySide

Tutorial homepage: http://thp.io/2010/meego-pythonl

Setting up the environment

First, make sure to have MeeGo Netbook installed-either directly on your netbook or in a virtual machine. How to do this is out of scope for this document, so please refer to the MeeGo Wiki.

As you probably want to start developing with PySide right now, and given the agile state of PySide at this moment (lots of bugfixes being integrated before the 1.0release), it's a good idea tobuild PySide from source. This will not be necessary in the future (when PySide packages are hopefully integrated into MeeGo), but you might nevertheless use an up-to-date version for development.

Getting the build scripts

I've created a set of build scripts that will automate the building of PySide from the Git repositories, including installing required build dependencies, so you can get up to speed quickly.

1. Click on the red"Applications" icon on MeeGo

2. Search for"Terminal" and start the application

3. Install Git via"sudo zypper install git"

4. Create a"pyside" folder in your $HOME with"mkdir pyside"

5. Change into the"pyside" folder: "cd pyside"

6. Check out the source:"git clone git://gitorious.org/pyside/buildscripts.git"

7. Change into the"buildscripts" folder:"cd buildscripts"

8. Fetch the sources:"git submodule init"and"git submodule update"

9.Fetching the sources will take a while-grab a coffee or a tea:)

After the buildscripts have been downloaded, you can use them to build PySide for MeeGo Netbook.

Building PySide and installing into $HOME

Now that you have gotten all the sources, you can build PySide for your netbook and install it into your home directory so that it does not conflict with any system-wide installations you might have in place. That's a safe way to install PySide from Git, as you can always just remove it from $HOME or reinstall it as often as you wish without cluttering up your system directories.

1. Open another Terminal (or use the one you still have open from the

previous step)

2. Go into the PySide buildscripts folder:"cd～/pyside/buildscripts"

3.Install the build dependencies:"sudo ./dependencies.meego.sh"

4.Before the next step, make sure to close down any other apps you might

have running-building PySide takes a lot of RAM. If you have problems building PySide, consider adding some RAM or adding a swapfile

5.(started 14;28) Build and install everything using"./build and install"

6.This will take about 2.5 hours (on an Atom single-core netbook)-yes,

that's a lot, but the upside of using Python for development on vour MeeGo netbook is that your applications do not have to be compiled, so instead of a develop-compile-run cycle, your have a develop-run cycle. This is especially nice on low-powered netbooks and saves you time and battery power on the go.

Setting up environment variables

Because we installed PySide into your $HOME, you have to set up some environment variables for that PySide version to become the active one for Python to use. Luckily, the"environment.sh" script in the PySide buildscripts takes care of that. You can either use.

source~/pyside/buildscripts/environment.sh

every time you want to do PySide development, or add this command to your～/.bashrc file, so it gets executed every time you open a shell or terminal window(that's the recommended way to doit, so you don't forget to source the"environment.sh" file when trying out the examples).

Testing the installations

Before we can start to write great PySide apps for MeeGo, let's see if

everything was installed correctly. Fire up another terminal window and enter"python"to start the interactive Python shell. Now, enter"from PySide import OtGui"to checkif the OtGui module was correctly installed. After that, try"from PySide import QtDeclarative"to check if the QtDeclarative module is working. We need the QtGui for basic UI classes (non-QML), and QtDeclarative for loading and displaying OML content.

Basic QML tutorial examples

This section should give you a short overview with code examples on how to do simple things with PySide and OML, More examples can be found on the homepage of this tutorial on http://thp.io/2010/meego-python/

【下载地址】

链接：https://pan.baidu.com/s/1Mi9gtmC7kwKIQZD5ZR2Snw

提取码：8om8