The first tips you’ll need before start programming for Symbian using Qt

Last weekend I made my first Qt/Symbian mobile application. It was a very simple project, and its only purpose was to learn how to program for Symbian platform. I made a small application to search information about movies in TheMovieDb, and its source code is available at my github profile.

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</pre>
<pre>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);
[/sourcecode]</pre>
<pre>
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 <strong>QStackedWidget</strong>! – 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:</pre>
<pre>
// 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 Qt Ambassador Kit and my first impressions of Nokia C7

A few months ago, I submitted my personal audio player project Audactile to the Nokia’s Qt Ambassador program. They seem to have liked it and I was accepted into the program.

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:

Qt Ambassador Kit

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. :)

Cortando strings muito longas no Android

Eu estava fazendo uma aplicação para Android quando me deparei com um problema: cortar strings muito longas. Um bom exemplo é a string da figura aí de baixo.

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:

Frozen Bubble para Symbian

Hoje foi meu primeiro dia com um Nokia E71. Procurando aplicações pra instalar no brinquedo novo, me deparei com o Frozen Bubble pra Symbian! Para o E71, baixei a versão na resolução 320×240.

O Frozen Bubble, para quem não sabe, é um jogo simples e viciante para Linux.

Lista de celulares com Linux

Tenho feito uma pesquisa de smartphones por aí, já que pretendo adquirir um celular um pouco melhor nas próximas semanas. Acabei me deparando com uma seção do site Linux for Devices apenas com telefones celulares equipados com Linux. A lista, que parece ser atualizada com frequência, contém fotos e reviews de cada aparelho, como o Nokia N900 (com Maemo) e Motorola Droid (com Android).