Developing MeeGo apps with Python and QML

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2025-02-27 0 0 851.31KB 28 页 5.9玖币

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Developing MeeGo apps

with Python and QML

by Thomas Perl <m@thp.io>

http://thp.io/2010/meego-python/

Table of Contents

Introduction.....................................................................................................3

Why should I use Python to develop MeeGo apps?......................................3

Links.............................................................................................................3

Setting up the environment.............................................................................3

Getting the build scripts...............................................................................4

Building PySide and installing into $HOME...................................................4

Setting up environment variables................................................................5

Testing the installations...............................................................................5

Basic QML tutorial examples............................................................................6

Hello World...................................................................................................6

The Python source (HelloMeeGo.py).........................................................6

The QML UI file (HelloMeeGo.qml)............................................................8

Displaying HTML content in a QML WebView...............................................9

The Python source code (WebKitView.py).................................................9

The QML content (WebKitView.qml).......................................................11

The HTML page (WebKitView.html).........................................................11

Writing a new QML UI for existing apps for MeeGo........................................13

A QML UI for gPodder.................................................................................13

The glue layer in Python (gpodder-qml.py)............................................14

The QML main UI file (gpodder-qml.qml)................................................18

The QML file for displaying a list of podcasts (PodcastList.qml).............21

The QML file for displaying a list of episodes (EpisodeList.qml).............24

Packaging a Python application for MeeGo....................................................25

Installing the required dependencies.........................................................25

Creating the required metadata files.........................................................25

The desktop entry: gpodder-qml.desktop...............................................25

The icon for the app menu: gpodder-qml.png........................................25

The Spectacle YAML file: gpodder-qml.yaml...........................................26

The Python distutils file: setup.py..........................................................26

Changes in the gpodder-qml.py script.......................................................26

Creating the RPM sources..........................................................................27

Building the RPM package from source......................................................27

Installing and testing the RPM package.....................................................27

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

we'll create a QML UI for an existing application (gPodder) that can be used on

MeeGo Netbook and MeeGo Handset.

Why should I use 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 especially important 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, you just 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 GUI 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-python/

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 1.0 release), it's a good idea to build 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 your

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 do it, 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

QtGui” to check if the QtGui 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 QML content.

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摘要：

DevelopingMeeGoappswithPythonandQMLbyThomasPerlhttp://thp.io/2010/meego-python/TableofContentsIntroduction.....................................................................................................3WhyshouldIusePythontodevelopMeeGoapps?......................................3Links.............

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