BtChat: fix crash when no adapter is found

The example was assuming that QBluetoothLocalDevice::allDevices() always
returns a non-empty list.
This is not true for the cases when desktop has no bluetooth adapters,
as well as for WinRT implementation (it always returns empty list for now).

This patch fixes the crash and provides some information messages to the
console. Note that WinRT implementation has an extended warning, because
it returns an empty list even if the adapter actually exists.

Fixes: QTBUG-98323
Change-Id: Iaa81465cf6be2febf20526c11909667fd60728b3
Reviewed-by: Juha Vuolle <juha.vuolle@insta.fi>
Reviewed-by: Alex Blasche <alexander.blasche@qt.io>
(cherry picked from commit adcfc156f437b766b7a922d0350d7f03da5c36bd)
Reviewed-by: Andreas Buhr <andreas.buhr@qt.io>

1 files changed, 12 insertions, 2 deletions

diff --git a/examples/bluetooth/btchat/chat.cpp b/examples/bluetooth/btchat/chat.cpp
index 5df2ed67..c3846319 100644
--- a/examples/bluetooth/btchat/chat.cpp
+++ b/examples/bluetooth/btchat/chat.cpp
@@ -91,8 +91,18 @@ Chat::Chat(QWidget *parent)
     }
 
     // make discoverable
-    QBluetoothLocalDevice adapter(localAdapters.at(0).address());
-    adapter.setHostMode(QBluetoothLocalDevice::HostDiscoverable);
+    if (!localAdapters.isEmpty()) {
+        QBluetoothLocalDevice adapter(localAdapters.at(0).address());
+        adapter.setHostMode(QBluetoothLocalDevice::HostDiscoverable);
+    } else {
+        qWarning("Local adapter is not found! The application might work incorrectly.");
+#ifdef Q_OS_WIN
+        // WinRT implementation does not support adapter information yet. So it
+        // will always return an empty list.
+        qWarning("If the adapter exists, make sure to pair the devices manually before launching"
+                 " the chat.");
+#endif
+    }
 
     //! [Create Chat Server]
     server = new ChatServer(this);