Add support for ble scanning to speed up reconnection

app/src/main/AndroidManifest.xml

@@ -343,6 +343,13 @@
                 <action android:name="android.bluetooth.adapter.action.STATE_CHANGED" />
             </intent-filter>
         </receiver>
+        <receiver
+            android:name=".externalevents.BluetoothScanCallbackReceiver"
+            android:exported="false">
+            <intent-filter>
+                <action android:name="nodomain.freeyourgadget.gadgetbridge.blescancallback" />
+            </intent-filter>
+        </receiver>
         <receiver
             android:name=".service.receivers.GBMusicControlReceiver"
             android:exported="false">

app/src/main/java/nodomain/freeyourgadget/gadgetbridge/externalevents/BluetoothScanCallbackReceiver.java

@@ -0,0 +1,80 @@
+/*  Copyright (C) 2019 Andreas Böhler
+
+    This file is part of Gadgetbridge.
+
+    Gadgetbridge is free software: you can redistribute it and/or modify
+    it under the terms of the GNU Affero General Public License as published
+    by the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    Gadgetbridge is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU Affero General Public License for more details.
+
+    You should have received a copy of the GNU Affero General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>. */
+package nodomain.freeyourgadget.gadgetbridge.externalevents;
+
+import android.annotation.TargetApi;
+import android.app.PendingIntent;
+import android.bluetooth.BluetoothAdapter;
+import android.bluetooth.BluetoothDevice;
+import android.bluetooth.le.BluetoothLeScanner;
+import android.bluetooth.le.ScanResult;
+import android.content.BroadcastReceiver;
+import android.content.Context;
+import android.content.Intent;
+import android.os.Build;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.ArrayList;
+
+
+import nodomain.freeyourgadget.gadgetbridge.GBApplication;
+import nodomain.freeyourgadget.gadgetbridge.util.DeviceHelper;
+
+public class BluetoothScanCallbackReceiver extends BroadcastReceiver {
+
+    private static final Logger LOG = LoggerFactory.getLogger(BluetoothScanCallbackReceiver.class);
+    private String mSeenScanCallbackUUID = "";
+
+    @TargetApi(Build.VERSION_CODES.O)
+    @Override
+    public void onReceive(Context context, Intent intent) {
+        String action = intent.getAction();
+        if(!action.equals("nodomain.freeyourgadget.gadgetbridge.blescancallback") || !intent.hasExtra("address") || !intent.hasExtra("uuid")) {
+            return;
+        }
+
+        String wantedAddress = intent.getExtras().getString("address");
+        String uuid = intent.getExtras().getString("uuid");
+
+        int bleCallbackType = intent.getIntExtra(BluetoothLeScanner.EXTRA_CALLBACK_TYPE, -1);
+        if(bleCallbackType != -1) {
+            //LOG.debug("Passive background scan callback type: " + bleCallbackType);
+            ArrayList<ScanResult> scanResults = intent.getParcelableArrayListExtra(BluetoothLeScanner.EXTRA_LIST_SCAN_RESULT);
+            for(ScanResult result: scanResults) {
+                BluetoothDevice device = result.getDevice();
+                if(device.getAddress().equals(wantedAddress) && !mSeenScanCallbackUUID.equals(uuid)) {
+                    mSeenScanCallbackUUID = uuid;
+                    LOG.info("ScanCallbackReceiver has found " + device.getAddress() + "(" + device.getName() + ")");
+                    BluetoothAdapter.getDefaultAdapter().getBluetoothLeScanner().stopScan(getScanCallbackIntent(GBApplication.getContext(), wantedAddress, uuid));
+                    GBApplication.deviceService().connect(DeviceHelper.getInstance().toSupportedDevice(device));
+
+                }
+            }
+        }
+    }
+
+    @TargetApi(Build.VERSION_CODES.O)
+    public static PendingIntent getScanCallbackIntent(Context context, String address, String uuid) {
+        Intent intent = new Intent(context, BluetoothScanCallbackReceiver.class);
+        intent.setAction("nodomain.freeyourgadget.gadgetbridge.blescancallback");
+        intent.putExtra("address", address);
+        intent.putExtra("uuid", uuid);
+        return PendingIntent.getBroadcast(context, 0, intent, PendingIntent.FLAG_UPDATE_CURRENT);
+    }
+}

app/src/main/java/nodomain/freeyourgadget/gadgetbridge/service/btle/AbstractBTLEDeviceSupport.java

@@ -34,11 +34,13 @@
 import java.util.Set;
 import java.util.UUID;
 
+import nodomain.freeyourgadget.gadgetbridge.GBApplication;
 import nodomain.freeyourgadget.gadgetbridge.Logging;
 import nodomain.freeyourgadget.gadgetbridge.impl.GBDevice;
 import nodomain.freeyourgadget.gadgetbridge.service.AbstractDeviceSupport;
 import nodomain.freeyourgadget.gadgetbridge.service.btle.actions.CheckInitializedAction;
 import nodomain.freeyourgadget.gadgetbridge.service.btle.profiles.AbstractBleProfile;
+import nodomain.freeyourgadget.gadgetbridge.util.GBPrefs;
 
 /**
  * Abstract base class for all devices connected through Bluetooth Low Energy (LE) aka
@@ -74,6 +76,14 @@ public boolean connect() {
         if (mQueue == null) {
             mQueue = new BtLEQueue(getBluetoothAdapter(), getDevice(), this, this, getContext(), mSupportedServerServices);
             mQueue.setAutoReconnect(getAutoReconnect());
+            GBPrefs prefs = GBApplication.getGBPrefs();
+            boolean autoReconnectScan = GBPrefs.AUTO_RECONNECT_SCAN_DEFAULT;
+            if (prefs != null) {
+                autoReconnectScan = prefs.getAutoReconnectScan();
+            }
+            // Override the user preference if required by the device
+            autoReconnectScan = autoReconnectScan || useBleScannerForReconnect();
+            mQueue.setBleScannerForReconnect(autoReconnectScan);
         }
         return mQueue.connect();
     }
@@ -385,4 +395,8 @@ public boolean onDescriptorReadRequest(BluetoothDevice device, int requestId, in
     public boolean onDescriptorWriteRequest(BluetoothDevice device, int requestId, BluetoothGattDescriptor descriptor, boolean preparedWrite, boolean responseNeeded, int offset, byte[] value) {
         return false;
     }
+
+    public boolean useBleScannerForReconnect() {
+        return false;
+    }
 }