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// Copyright (C) 2026 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GFDL-1.3-no-invariants-only
/*!
\title Qt for HarmonyOS Restart Application Example
\example platform/harmonyrestartapp
\examplecategory {Mobile}
\meta tag {widgets,harmonyos,want}
\ingroup corelib_examples
\brief Restarts a Qt application on HarmonyOS and passes data to the new
instance in the parameters of its launch Want.
An application can ask the platform to restart it. The Want that it
passes becomes the launch Want of the new instance, so it decides what
the restarted application starts with. The example keeps a restart count
in a Want parameter of its own, \c org.qtproject.example.restartCount,
and shows the count of the running instance.
The example has a single window, so the process has a single
\c UIAbility instance, the default ability. The \c launchWant property
of that ability is the Want that the application was launched with. The
first button passes that Want object itself, so the new instance starts
with the same count. The second button passes a copy with the count
increased. The copy is built on the Qt thread as a QJsonObject and
mapped to a JS object on the JS thread:
\snippet platform/harmonyrestartapp/main.cpp 1
The restart itself is a call to \c restartApp() on the
\c ApplicationContext, which the task reaches from the default ability.
The task uses node-addon-api, the C++ wrapper for Node-API published by
the Node.js project, as we recommend for applications:
\snippet platform/harmonyrestartapp/main.cpp 0
If the platform accepts the request, the new instance replaces the
running one. If the platform refuses, for example because restarts were
requested too often, \c restartApp() throws synchronously.
node-addon-api turns the thrown error into a C++ exception, which the
example catches. The failure is then shown in the window, as is a
missing ability. The task posts the text to the Qt thread with
QNativeInterface::QHarmonyApplication::runOnQtThread(). It passes a
QPointer to the status label, which was created on the Qt thread. The
posted functor checks the QPointer before it updates the label:
\snippet platform/harmonyrestartapp/main.cpp 2
The example reads the launch Want once at startup, with
QNativeInterface::QHarmonyApplication::runOnJsThreadAndWait() and
QtHarmony::mapJsObjectToQJsonObject(). The count that the window shows
and the Want of the second button both come from it.
\section1 Running the Example
Press the second button. The application restarts and shows the count
increased by one. If you press the first button instead, the restarted
application shows the same count.
*/