A Qt/Symbian app is something very close to a normal Qt-based application for desktop, but there are some little differences that can make you confused and some tips you may need, here are my advices for some pitfalls I’ve found.

Instead of showing widgets, add them to a QStackedWidget

(that’s the best solution I’ve found, but it seems to have other solutions)

In desktop Qt, you create a new QWidget and call show() to create a new window containing that widget. This won’t work with Symbian. When you do that, all you’ll get is a small, transparent widget at the corner of your screen.

The solution is to get the QMainWindow of your application, add a QStackedWidget as its central widget and add your new widgets into this QStackedWidget.

Every new widget must be added to QStackedWidget. It sounds painful, but Qt documentation tells us that when a widget is added to a QStackedWidget, the QStackedWidget becomes its parent.

When you create the first widget and add it to the stack, our QStackedWidget becomes its parent. So, to create a second widget and add it to the stack, you create your new widget as you do normally and asks the parent of the first widget – the QStackWidget! – to add it to the stack.

// Create your widget
QWidget *someWidget = new QWidget(parent());

// Get the reference to our QStackedWidget casting the widget parent
QStackedWidget *stackedWidget = (QStackedWidget*) parent();

// Add the widget
stackedWidget->addWidget(someWidget);
stackedWidget->setCurrentWidget(someWidget);

Creating menus and associating to positive and negative buttons

Nokia cell phones, even the cheaper ones, have options associated to the positive and negative buttons. Take a look on this picture of an old N70:

In the picture above, the positive action is Options, the negative option is Back. Creating options like these for your widget is quite simple.

In your widget’s source code, put the following lines in your constructor. Behold the lines where we use setSoftKeyRole to associate the action to a key. In my example, I have a “Back” shortcut and a “Details” shortcut, that access some slots.

// Register the negative action
QAction *backToMainScreenAction = new QAction("Back", this);
backToMainScreenAction->setSoftKeyRole(QAction::NegativeSoftKey);
connect(backToMainScreenAction, SIGNAL(triggered()), SLOT(removeWidget()));
addAction(backToMainScreenAction);

// Register the negative action
QAction *selectResultAction = new QAction("Details", this);
selectResultAction->setSoftKeyRole(QAction::PositiveSoftKey);
connect(selectResultAction, SIGNAL(triggered()), SLOT(showDetailsAboutTheCurrentItem()));
addAction(selectResultAction);

This code will register the action of each widget. But to make the options show in the screen, we must make the widget’s container – the QStackedWidget! – register these actions in the menu every time the widget is created. I put the following lines in the same file where’s my main window containing the QStackedWidget. First we create the following slot:

// This is a slot!
void MainWindow::updateActions() {
    QWidget *currentWidget = stackedWidget->currentWidget();
    menuBar()->clear();
    menuBar()->addActions(currentWidget->actions());
}

In the class’s constructor, we connect the stacked widget’s signals that are emmited when a widget is added or removed to the slot above:

connect(stackedWidget, SIGNAL(currentChanged(int)), SLOT(updateActions()));
connect(stackedWidget, SIGNAL(widgetRemoved(int)), SLOT(updateActions()));

Don’t believe the Nokia simulator

It’s still experimental. Sometimes you may think you made a mistake and have a bug, but you don’t. The simulator sometimes is confused with menus and soft buttons. If you get lost with your code and can’t find the causes of some obscure bug, try your application with a real device.

Good luck with the Remote Compiler

It’s still experimental too. When I tried to use it, I got some short error messages whose source I couldn’t discover. So, if you don’t use Windows (like me), prepare a virtual machine running Qt SDK on Windows.

The good surprise is that they sent me a Qt Ambassador kit: a t-shirt, some stickers and a Nokia C7 mobile phone. The pictures I took aren’t very good, but here they are:

The stickers are beautiful and I’m thinking of where I’ll put them. The most attractive item is, obviously, the Nokia C7. It runs Symbian^3, and it was the very first time I could use a device with it. My first impressions:

• The capactive touch screen is very good. I already test devices from Apple, Motorola, Sony Ericsson and HTC, and I can say that it’s very sensitive. It has support for pinch zoom on images.
• Symbian^3′s UI is way better than its predecessors. It’s like a mix of the old Symbian (since it’s still Symbian…), iOS and Android. You have non-intrusive alerts at the top of the screen (like a desktop) instead of the old ugly rectangles that older versions of Symbian used for their notifications. The menus still are a bit confusing, but are better than my old Nokia E71′s menus.
• The AMOLED display is very sharp, its colours are brilliant and the images look great. You have an ambient light detector that changes the display’s illumination, like my MacBook does.
• The stereo sound from its back outputs are clear and powerful. Nokia knows how to put a good sound into its devices.
• Its camera has 8.0MP, dual flash and face recognition. It can record videos in HD resolution, but I haven’t tested it yet.

Nokia C7 has a very powerful hardware. Its software is pretty cool and as friendly as Android IMHO (unfortunately Nokia will use Windows Phone instead of Symbian in some time…). The mobile phone was given to me with a short letter asking to develop for it, so that’s what I’ll do. I’ll try to write some Qt application for Symbian, and I’ll report any progress here.

I tried to find a set of useful and free (as in “free beer” and/or as in “free speech”) tools to make my work easier. They are:

Classic Shell Setup

I don’t know why Microsoft removed the toolbar from Windows Explorer since Windows Vista, but this application tries to put it back there. It also allows you to get some customisation of Start Menu, and get a simple, fast and useful menu like the Windows 9x/ME/2000 times.

Notepad++

I like gedit and kate, and the native alternative for Windows is Notepad++: a good editor for plain text files, like source code.

Pidgin

With support for MSN/Live/whatever network, Google Talk, ICQ, etc. Pidgin is one of the best chat clients. I’d rather use it than the fancy MSN Live Messenger.

Winamp

Why use iTunes or the suffering Windows Media Player if you can use Winamp? It has a clean interface, a good way to organise library (although it’s a little bit iTunesy) and a simple playlist, everything in the same screen. I really love the good and old Winamp.

VLC

Winamp can play some videos, but I think VLC is a better tool for this job. Besides, it has a great support for a huge range  of video formats and features for users with any needs and all experience levels.

Nice, isn’t it? So, I downloaded the new beta for Linux, and it looks like the screenshot below. I had to set the tabs to be on top; Windows version brings this for default (at least the one that I installed using Wine).

Compare. The screenshot below is Firefox 3.6.4.

It’s a little far from the mockups of Firefox for Linux at Mozilla’s site. I hope I can see it soon.

www.youtube.com/watch?v=rJcqZ2SVTK0

If you want to reproduce this problem, you can download its source code as a Qt Creator project. Please keep in mind that it’s the source code with errors!  But there’s a workaround to this problem:

1. In the class where you create the Phonon::AudioOutput whose volume is handled by the VolumeSlider, put this:

connect(audioOutput, SIGNAL(mutedChanged(bool)), this, SLOT(handleMute(bool)));
connect(audioOutput, SIGNAL(volumeChanged(qreal)), this, SLOT(handleVolume(qreal)));

2. Create the slots you used above using the following code:

void MainWindow::handleMute(bool mute) {
    if (!mute) {
        audioOutput->setVolume(outputVolume);
    }
}
void MainWindow::handleVolume(qreal volume) {
    outputVolume = volume;
}

3. Declare the slots and the outputVolume variable in your header file:

private:
    qreal outputVolume;

private slots:
    void handleMute(bool mute);
    void handleVolume(qreal volume);

You can download the fixed source code. I don’t know if this behaviour is the expected in Qt, but I filed a bug for it.

It was fixed changing the SVN interface from JavaHL to SVNKit in Eclipse preferences (click to zoom):

So I googled a way to fix for this problem, and found the fix at Arch Linux forums. You’ll need to create a file called .fonts.conf in your home directory with this content:

<?xml version='1.0'?>
<!DOCTYPE fontconfig SYSTEM 'fonts.dtd'>
<fontconfig>
   <match target="font" >
      <edit mode="assign" name="rgba" >
         <const>rgb</const>
      </edit>
   </match>
   <match target="font" >
      <edit mode="assign" name="hinting" >
         <bool>true</bool>
      </edit>
   </match>
   <match target="font" >
      <edit mode="assign" name="hintstyle" >
         <const>hintslight</const>
      </edit>
   </match>
   <match target="font" >
      <edit mode="assign" name="antialias" >
         <bool>true</bool>
      </edit>
   </match>
</fontconfig>

I closed Qt Creator and reopened it. The result was this:

But I read a little about Qt and, after talking with some friends about the pros and cons of GTK and Qt, I decided to do with Qt the same things that I’ve already done with GTK up to that point. So I would know what choice was better for me. Notice that I’m not saying that Qt is better for everybody and that GTK must die, but that Qt looked better for me and my personal project. After this disclaimer, and can tell my reasons:

• Look & feel. I’m a look&feel fanatic, and sometimes I move from GNOME to KDE only to check its new features. But I hate how GTK applications look in KDE. You can use gtk-qt-engine, but you’ll still notice the differences. You can set GTK to use the excellent QtCurve theme, that have identical versions to Qt and GTK, but you’ll get tied to a theme. But look what you have if you run a Qt application in GNOME (gedit is a GTK-based application and Picard is a Qt-based application):
  
  Thanks to QGtkStyle, Qt applications detect if you are in GNOME and your Qt application gets an almost perfect GTK look & feel. And yeah, it includes open and save dialogs.
• Documentation. Qt has a very, very rich and well-organised documentation, with tutorials, API references, and examples. gtkmm also have all these items, but they didn’t look very friendly to me. And the documentation of Qt 4.7, still in development, will be even better.
• A simple, but good IDE. A good programmer must not be dependent on IDEs, but they really help you. I tried to use Anjuta (unstable sometimes), MonoDevelop (very good for .NET platform, but not a good IDE for C/C++ development) and Netbeans as IDE when I was using gtkmm, and I was not satisfied with them. But Qt has its official IDE, Qt Creator:
  
  Qt Creator is clean, simple, and complete. It has quick access to documentation, breakpoints, project configuration, native support for CVS, Subversion and Git, good code completion, a good GUI designer (like the GTK’s Glade), among other features.
• Runs well on many platforms. Qt is smart enough to run well – and with native look & feel, I really like this – in Linux, Mac, Windows, and others.

But Qt still has some cons:

• Users should have it installed to run Qt applications, and this is not very usual in Linux environments based on GNOME, neither on Windows systems.
• Qt is free only if you’re using it in a free project. For commercial applications, you must obtain a commercial Qt licence. Update: this is not exactly a con. You still can use Qt under LGPL in commercial applications, but if you make any change to Qt you must publish them or purchase a commercial Qt licence (thanks, krok, for the comment).

If you’re beginning to learn to program for graphical environments or you’re looking for a good graphical library to use in your project, you really should give Qt a try, implement some examples and feel which option is better for you.

]]> http://www.esdrasbeleza.com/2010/05/13/why-i-chose-qt/feed/ 5 http://www.esdrasbeleza.com/2010/04/24/conectando-o-php-ao-oracle/ http://www.esdrasbeleza.com/2010/04/24/conectando-o-php-ao-oracle/#comments Sat, 24 Apr 2010 19:02:15 +0000 Esdras Beleza http://www.esdrasbeleza.com/?p=132 Nota: fiz esse tutorial há 3 anos, não garanto que ele continue funcionando!

Depois de muito apanhar, aprendi uma maneira fácil de pôr o PHP pra se comunicar com o Oracle. A maioria das soluções que achei envolvia recompilar o PHP, mudar variáveis de ambiente, scripts de inicialização etc. Uma delas até deu certo, mas mudar as variáveis de ambiente fez o suporte a LDAP do PHP parar de funcionar, por razões que desconheço.

A solução que explico abaixo faz a mesma coisa, mas sem recompilar pacotes ou fazer gambiarras. Deu certo milagrosamente, após juntar a solução proposta por vários sites. O máximo que será feito é compilar a extensão oci8 para o PHP do Debian ou Ubuntu, que é feito automaticamente e em poucos segundos. A parte chata é baixar os arquivos do site do Oracle, que exige criação de conta.

Todos os comandos abaixo são executados como root. Boa sorte!

1. No site de downloads do Oracle para Linux, baixe os arquivos instantclient-basic-linux32-10.2.0.3-20061115.zip e instantclient-sdk-linux32-10.2.0.3-20061115.zip. Você vai precisar criar uma conta no site da Oracle para isso. Após o download, extraia-os para o diretório /usr/local/oracle.
2. Em /usr/local/oracle, crie o seguinte link: # ln -s libclntsh.so.10.1 libclntsh.so
3. Instale os pacotes php5-dev e php5-pear pelo apt-get ou aptitude (aptitude install php5-dev php5-pear). Caso não exista o php5-pear, procure por php-pear.
4. Agora execute (lembre-se: sempre como root): # pecl install oci8
5. Surgirá um prompt perguntando onde estão as bibliotecas do Oracle. Sua resposta será instantclient,/usr/local/oracle , como no exemplo:Please provide the path to ORACLE_HOME dir. Use ”instantclient,/path/to/instant/client/lib” if you”re compiling against Oracle Instant Client [autodetect] : instantclient,/usr/local/oracle
6. No diretório /etc/php5/conf.d , crie um arquivo oci8.ini, com o seguinte conteúdo:extension=oci8.so
7. O PHP deverá estar com suporte a Oracle (extensão oci8). Reinicie o seu servidor web (caso seja o Apache, apache2ctl restart).

Fontes: Installing PHP and the Oracle 10g Instant Client for Linux and Windows; How to: Installing Oracle XE on Ubuntu with PHP

Essa é a string na qual vamos nos basear. Ela é gerada pelo código

<TextView
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:text="@string/hello"
    android:textSize="20px"/>

Há duas maneiras de corrigir o problema. Uma delas é o seguinte código:

<TextView
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:text="@string/hello"
    android:textSize="20px"
    android:singleLine="true"/>

Porém, a diretiva android:singleLine é descrita na IDE como em desuso (deprecated). Um código que surte o mesmo efeito é

<TextView
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:text="@string/hello"
    android:textSize="22px"
    android:ellipsize="end"
    android:scrollHorizontally="true"
    android:lines="1"/>

O resultado é este: