Detecting virtual keyboard open and close events in Symbian^3

Article Metadata

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Code Example

Source file: Media:Vkbstatetest qtmobility symbian3.zip

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Article

Created: treinio (09 Dec 2010)

Last edited: hamishwillee (11 Oct 2012)

Applications running on Symbian touch devices may want to react to software input panel (virtual keyboard) state events; for example, to improve user experience by immediately processing the input after virtual keyboard is dismissed. Qt provides QEvent::CloseSoftwareInputPanel event, but it's sent only after the target widget has lost focus.

This code snippet uses QValueSpaceSubscriber to detect virtual keyboard state changes. The code depends on a Publish and Subscribe key that is only available on Symbian^3 platform.

Warning: The following code implements a Qt class whose functionality is neither cross-platform nor future-proof. It only works on Symbian^3 platform with the default virtual keyboard in use (no signals are emitted when running on earlier S60 devices or other platforms).

Usage

#include <QValueSpaceSubscriber> 
 
    QValueSpaceSubscriber* vkbState = new QValueSpaceSubscriber("/vkb/state", this);
    QObject::connect(vkbState, SIGNAL(contentsChanged()), this, SLOT(handleStateChanged()));

Declaring /vkb/state value state path

Create a new .qcrml file, with following content:

<?xml version="1.0" encoding="UTF-8"?>
<repository target="RProperty" version="" uidName="KPSUidAknFep" uidValue="0x100056de">
    <key ref="/vkb/state" int="0x00000004"/>
</repository>

Changes to .pro file

Add the following definitions to .pro file:

CONFIG += mobility
MOBILITY += publishsubscribe
 
symbian: {
crml.pkg_postrules = "\"pskeydefs.qcrml\" - \"c:/resource/qt/crml/pskeydefs_$${TARGET}.qcrml\""
DEPLOYMENT += crml
}

Warning: While this article shows how the Publish and Subscribe API can be used to access keys defined and populated by other applications, creating such a *.qcrml file raises the deployment problem. In Symbian each file can be owned and deployed by only one package, so if two applications are using this solution and attempt to install the pskeydefs.qcrml file, the second app will always fail. The uninstall sequence is also problematic, since one of the apps could remove the file while other installed apps still need it.

Above solution tries to avoid these problems by modifying the deployed .qcrml filename to include also the name of the application (TARGET), thus making it unique.

Example project

File:Vkbstatetest qtmobility symbian3.zip (can be self-signed, doesn't use any capabilities)