Android BT LE advertisement start to fail when bluetooth is OFF

When we start a BT LE advertisement while bluetooth is OFF, the
advertisement should fail to start, and on the other hand when
bluetooth is switched back ON, starting the advertisement should
be possible again.

This commit adds offline/online check to the startAdvertising function.

In addition the creation of the advertiser is delayed until the first
advertisement request. This delaying is done for the case when the
bluetooth is OFF when the LE controller is created => we don't want the
creation of advertisement to fail once during construction and therefore
become unusable even if bluetooth is later switched ON.

For completeness it should be mentioned that Android documentation
mentions that the getBluetoothLeAdvertiser() returns 'null' if the
bluetooth is offline. However on all the devices I've tried this,
it returns a valid instance. This means that the creation delay of this
commit would not be strictly speaking necessary. But we shouldn't rely
on it: on some Android devices the advertiser might be returned as null
when bluetooth is offline, as documented.

Fixes: QTBUG-104106
Change-Id: Ia016e4534c29fac23f42785d68bc95d568c41def
Reviewed-by: Ivan Solovev <ivan.solovev@qt.io>
(cherry picked from commit 4292b32d57f7b6dc2f644ee75403ce8b26f9e1e5)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

1 files changed, 14 insertions, 7 deletions

diff --git a/src/android/bluetooth/src/org/qtproject/qt/android/bluetooth/QtBluetoothLEServer.java b/src/android/bluetooth/src/org/qtproject/qt/android/bluetooth/QtBluetoothLEServer.java
index 025c874b..f3cc3041 100644
--- a/src/android/bluetooth/src/org/qtproject/qt/android/bluetooth/QtBluetoothLEServer.java
+++ b/src/android/bluetooth/src/org/qtproject/qt/android/bluetooth/QtBluetoothLEServer.java
@@ -298,12 +298,7 @@ public class QtBluetoothLEServer {
             return;
         }
 
-        mLeAdvertiser = mBluetoothAdapter.getBluetoothLeAdvertiser();
-
-        if (!mBluetoothAdapter.isMultipleAdvertisementSupported())
-            Log.w(TAG, "Device does not support Bluetooth Low Energy advertisement.");
-        else
-            Log.w(TAG, "Let's do BTLE Peripheral.");
+        Log.w(TAG, "Let's do BTLE Peripheral.");
     }
 
     // The following functions are synchronized callback handlers. The callbacks
@@ -779,8 +774,20 @@ public class QtBluetoothLEServer {
                                     AdvertiseData scanResponse,
                                     AdvertiseSettings settings)
     {
-        if (mLeAdvertiser == null)
+        // Check that the bluetooth is on
+        if (mBluetoothAdapter == null || !mBluetoothAdapter.isEnabled()) {
+            Log.w(TAG, "StartAdvertising: Bluetooth not available or offline");
             return false;
+        }
+
+        // According to Android doc this check should always precede the advertiser creation
+        if (mLeAdvertiser == null && mBluetoothAdapter.isMultipleAdvertisementSupported())
+            mLeAdvertiser = mBluetoothAdapter.getBluetoothLeAdvertiser();
+
+        if (mLeAdvertiser == null) {
+            Log.w(TAG, "StartAdvertising: LE advertisement not supported");
+            return false;
+        }
 
         if (!connectServer()) {
             Log.w(TAG, "Server::startAdvertising: Cannot open GATT server");