AnnotatedUrl: handle adapter state

Extend the AnnotatedUrl example application to handle adapter state
changes. This allows to correctly handle NFC enabling and disabling,
while the application is running.

Task-number: QTBUG-94033
Pick-to: 6.2
Change-Id: I9978436b98a772db256e12cfd41072c3b6286b88
Reviewed-by: Alex Blasche <alexander.blasche@qt.io>

6 files changed, 43 insertions, 5 deletions

diff --git a/examples/nfc/annotatedurl/annotatedurl.cpp b/examples/nfc/annotatedurl/annotatedurl.cpp
index 5bb602e5..c1945083 100644
--- a/examples/nfc/annotatedurl/annotatedurl.cpp
+++ b/examples/nfc/annotatedurl/annotatedurl.cpp
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2017 The Qt Company Ltd.
+** Copyright (C) 2021 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the QtNfc module.
@@ -72,6 +72,8 @@ AnnotatedUrl::AnnotatedUrl(QObject *parent)
             this, &AnnotatedUrl::targetDetected);
     connect(manager, &QNearFieldManager::targetLost,
             this, &AnnotatedUrl::targetLost);
+    connect(manager, &QNearFieldManager::adapterStateChanged,
+            this, &AnnotatedUrl::handleAdapterStateChange);
 }
 
 AnnotatedUrl::~AnnotatedUrl()
@@ -83,10 +85,12 @@ void AnnotatedUrl::startDetection()
 {
     if (!manager->isEnabled()) {
         qWarning() << "NFC not enabled";
+        emit nfcStateChanged(false);
         return;
     }
 
-    manager->startTargetDetection(QNearFieldTarget::NdefAccess);
+    if (manager->startTargetDetection(QNearFieldTarget::NdefAccess))
+        emit nfcStateChanged(true);
 }
 
 void AnnotatedUrl::targetDetected(QNearFieldTarget *target)
@@ -111,6 +115,18 @@ void AnnotatedUrl::handlePolledNdefMessage(QNdefMessage message)
     handleMessage(message, target);
 }
 
+//! [handleAdapterState]
+void AnnotatedUrl::handleAdapterStateChange(QNearFieldManager::AdapterState state)
+{
+    if (state == QNearFieldManager::AdapterState::Online) {
+        startDetection();
+    } else if (state == QNearFieldManager::AdapterState::Offline) {
+        manager->stopTargetDetection();
+        emit nfcStateChanged(false);
+    }
+}
+//! [handleAdapterState]
+
 //! [handleMessage 1]
 void AnnotatedUrl::handleMessage(const QNdefMessage &message, QNearFieldTarget *target)
 {
diff --git a/examples/nfc/annotatedurl/annotatedurl.h b/examples/nfc/annotatedurl/annotatedurl.h
index 59ada47a..4c0bdbe0 100644
--- a/examples/nfc/annotatedurl/annotatedurl.h
+++ b/examples/nfc/annotatedurl/annotatedurl.h
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2017 The Qt Company Ltd.
+** Copyright (C) 2021 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the QtNfc module.
@@ -52,12 +52,12 @@
 #define ANNOTATEDURL_H
 
 #include <QtNfc/QNdefMessage>
+#include <QtNfc/QNearFieldManager>
 
 #include <QtCore/QObject>
 #include <QtCore/QUrl>
 
 QT_FORWARD_DECLARE_CLASS(QPixmap)
-QT_FORWARD_DECLARE_CLASS(QNearFieldManager)
 QT_FORWARD_DECLARE_CLASS(QNearFieldTarget)
 
 //! [0]
@@ -73,12 +73,15 @@ public:
 
 signals:
     void annotatedUrl(const QUrl &url, const QString &title, const QPixmap &pixmap);
+    void nfcStateChanged(bool enabled);
 
 public slots:
     void targetDetected(QNearFieldTarget *target);
     void targetLost(QNearFieldTarget *target);
     void handleMessage(const QNdefMessage &message, QNearFieldTarget *target);
     void handlePolledNdefMessage(QNdefMessage message);
+    void handleAdapterStateChange(QNearFieldManager::AdapterState state);
+
 private:
     QNearFieldManager *manager;
 };
diff --git a/examples/nfc/annotatedurl/doc/src/annotatedurl.qdoc b/examples/nfc/annotatedurl/doc/src/annotatedurl.qdoc
index c3c3d525..b2004839 100644
--- a/examples/nfc/annotatedurl/doc/src/annotatedurl.qdoc
+++ b/examples/nfc/annotatedurl/doc/src/annotatedurl.qdoc
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2017 The Qt Company Ltd.
+** Copyright (C) 2021 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the documentation of the Qt local connectivty modules.
@@ -82,6 +82,16 @@ corresponding signal is emitted so that the UI can handle it.
 
 \snippet annotatedurl/annotatedurl.cpp handleMessage 4
 
+\section1 Adapter State Handling
+
+On Android the adapter state changes can be detected by connecting to the
+\l QNearFieldManager::adapterStateChanged() signal. This allows stopping the
+detection when the NFC adapter is disabled, and restarting it when the adapter
+is enabled again. This approach is implemented in the
+\c {AnnotatedUrl::handleAdapterStateChange} slot.
+
+\snippet annotatedurl/annotatedurl.cpp handleAdapterState
+
 \section1 Automatic Application Startup
 
 Android supports automatic application startup when the NDEF tag is touched.
diff --git a/examples/nfc/annotatedurl/main.cpp b/examples/nfc/annotatedurl/main.cpp
index d0f68eb2..8134b002 100644
--- a/examples/nfc/annotatedurl/main.cpp
+++ b/examples/nfc/annotatedurl/main.cpp
@@ -66,6 +66,8 @@ int main(int argc, char *argv[])
 
     QObject::connect(&annotatedUrl, &AnnotatedUrl::annotatedUrl,
                      &mainWindow, &MainWindow::displayAnnotatedUrl);
+    QObject::connect(&annotatedUrl, &AnnotatedUrl::nfcStateChanged,
+                     &mainWindow, &MainWindow::nfcStateChanged);
 
     annotatedUrl.startDetection();
     mainWindow.show();
diff --git a/examples/nfc/annotatedurl/mainwindow.cpp b/examples/nfc/annotatedurl/mainwindow.cpp
index 707c03eb..03f4ee09 100644
--- a/examples/nfc/annotatedurl/mainwindow.cpp
+++ b/examples/nfc/annotatedurl/mainwindow.cpp
@@ -75,6 +75,12 @@ void MainWindow::displayAnnotatedUrl(const QUrl &url, const QString &title, cons
     ui->m_image->setPixmap(pixmap);
 }
 
+void MainWindow::nfcStateChanged(bool enabled)
+{
+    const QString text = enabled ? "Touch a tag" : "Enable NFC";
+    ui->m_help->setText(text);
+}
+
 void MainWindow::mouseReleaseEvent(QMouseEvent *event)
 {
     if (ui->centralWidget->rect().contains(event->pos()))
diff --git a/examples/nfc/annotatedurl/mainwindow.h b/examples/nfc/annotatedurl/mainwindow.h
index 36ad9944..28962977 100644
--- a/examples/nfc/annotatedurl/mainwindow.h
+++ b/examples/nfc/annotatedurl/mainwindow.h
@@ -75,6 +75,7 @@ public:
 
 public slots:
     void displayAnnotatedUrl(const QUrl &url, const QString &title, const QPixmap &pixmap);
+    void nfcStateChanged(bool enabled);
 
 protected:
     void mouseReleaseEvent(QMouseEvent *event) override;