即使具有位置权限，Android BLE startDiscovery() 回调也不会触发

该应用程序的目标版本为 22，最低版本为 18，并且在 Lollipop 上按预期运行。启动 Marshmallow 应用程序需要 BLE 的“精细”和“粗略”权限。我已经添加了它们，但回调没有被触发。

Android 清单：

...

<uses-feature android:name="android.hardware.bluetooth_le" android:required="true"/>

    <!-- ble -->
    <uses-permission android:name="android.permission.BLUETOOTH" />
    <uses-permission android:name="android.permission.BLUETOOTH_ADMIN" />
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
    <uses-permission android:name="android.permission.CHANGE_WIFI_STATE" />

    <!-- for Android M  BLE requires the following permissions too -->
    <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
    <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />

发现是通过 UUID 过滤完成的：

this.adapter.startLeScan(new UUID[]{this.serviceUUID}, this.discoveryListener);

打回来：

@Override
public void onLeScan(BluetoothDevice device, int rssi, byte[] scanRecord) {
    Log.d(TAG, "Bluetooth device found: " + device);
    foundBluetoothDevices.add(device);
}

我可以看到设备已找到，但回调未触发：

12-03 12:34:19.266    9003-9003/com.company.project D/FindCamerasTask﹕ Discovery started
12-03 12:34:19.266    9003-9003/com.company.project D/BluetoothAdapter﹕ startLeScan(): [Ljava.util.UUID;@dd832eb
12-03 12:34:19.268    9003-9003/com.company.project D/BluetoothAdapter﹕ STATE_ON
12-03 12:34:19.270    4362-4375/? D/BtGatt.GattService﹕ registerClient() - UUID=92d098d2-0da1-4908-8194-14c504680fae
12-03 12:34:19.271    4362-4382/? D/BtGatt.GattService﹕ onClientRegistered() - UUID=92d098d2-0da1-4908-8194-14c504680fae, clientIf=5
12-03 12:34:19.271    9003-9064/com.company.project D/BluetoothLeScanner﹕ onClientRegistered() - status=0 clientIf=5
12-03 12:34:19.271    4362-4401/? D/BtGatt.GattService﹕ start scan with filters
12-03 12:34:19.273    4362-4385/? D/BtGatt.ScanManager﹕ handling starting scan
12-03 12:34:19.288    4362-4382/? D/BtGatt.GattService﹕ onScanFilterEnableDisabled() - clientIf=5, status=0, action=1
12-03 12:34:19.288    4362-4382/? D/BtGatt.ScanManager﹕ callback done for clientIf - 5 status - 0
12-03 12:34:19.288    4362-4385/? D/BtGatt.ScanManager﹕ addFilterToController: 2
12-03 12:34:19.302    4362-4382/? D/BtGatt.GattService﹕ onScanFilterConfig() - clientIf=5, action = 0 status = 0, filterType=2, availableSpace=47
12-03 12:34:19.302    4362-4382/? D/BtGatt.ScanManager﹕ callback done for clientIf - 5 status - 0
12-03 12:34:19.302    4362-4385/? D/BtGatt.ScanManager﹕ configureFilterParamter 500 10000 1 0
12-03 12:34:19.316    4362-4382/? D/BtGatt.GattService﹕ onScanFilterParamsConfigured() - clientIf=5, status=0, action=0, availableSpace=15
12-03 12:34:19.316    4362-4382/? D/BtGatt.ScanManager﹕ callback done for clientIf - 5 status - 0
12-03 12:34:19.316    4362-4385/? D/BtGatt.ScanManager﹕ configureRegularScanParams() - queue=1
12-03 12:34:19.317    4362-4385/? D/BtGatt.ScanManager﹕ configureRegularScanParams() - ScanSetting Scan mode=2 mLastConfiguredScanSetting=-2147483648
12-03 12:34:19.317    4362-4385/? D/BtGatt.ScanManager﹕ configureRegularScanParams - scanInterval = 8000configureRegularScanParams - scanWindow = 8000
12-03 12:34:19.318    4362-4382/? D/BtGatt.GattService﹕ onScanParamSetupCompleted : 0
12-03 12:34:19.466    4362-4382/? D/bt_btif_gattc﹕ btif_gattc_update_properties BLE device name=Device-00W15380138 len=17 dev_type=2
12-03 12:34:19.701    4362-4382/? D/bt_btif_gattc﹕ btif_gattc_update_properties BLE device name=Device-20154300041 len=17 dev_type=2
12-03 12:34:21.021    4362-4382/? D/bt_btif_gattc﹕ btif_gattc_update_properties BLE device name=Device-20154300015 len=17 dev_type=2
12-03 12:34:39.278    9003-9003/com.company.project W/BleRpcConnectionFactory﹕ Discovery timeout fired (20000)
12-03 12:34:39.279    9003-9003/com.company.project D/BluetoothAdapter﹕ stopLeScan()
12-03 12:34:39.324    4362-4382/? D/BtGatt.GattService﹕ onScanFilterParamsConfigured() - clientIf=5, status=0, action=1, availableSpace=16
12-03 12:34:39.324    4362-4382/? D/BtGatt.ScanManager﹕ callback done for clientIf - 5 status - 0
12-03 12:34:39.324    4362-4385/? D/BtGatt.ScanManager﹕ configureRegularScanParams() - queue=0
12-03 12:34:39.324    4362-4385/? D/BtGatt.ScanManager﹕ configureRegularScanParams() - ScanSetting Scan mode=-2147483648 mLastConfiguredScanSetting=2
12-03 12:34:39.324    4362-4385/? D/BtGatt.ScanManager﹕ configureRegularScanParams() - queue emtpy, scan stopped

我已经检查了 Android > 设置 > 应用程序 > 权限中授予的“位置”权限。在 Nexus 9 上进行测试。 有什么想法吗？

附言。我尝试过 API 21adapter.getBluetoothLeScanner().startScan(filters, scanSettings, internalScanCallbackAPI21);仍然没有运气 - 类似的日志，但没有触发回调。

聚苯硫醚。如果设置报告延迟，我就让它工作了：

ScanSettings scanSettings = new ScanSettings.Builder()
            .setScanMode(ScanSettings.SCAN_MODE_LOW_LATENCY)
            .setReportDelay(discoveryDelay)  // 0 for immediate callback (not working for me), > 0 for batch mode
            .build();

如果设置0立即回调仍然没有让侦听器被解雇。

我必须设置报告延迟 = 1，因为 0 不会触发回调（立即回调）：

ScanSettings scanSettings = new ScanSettings.Builder()
                .setScanMode(ScanSettings.SCAN_MODE_LOW_LATENCY)
                .setReportDelay(1) // '0' or  not setting any value will lead to callback not fired!
                .build();

请随意提出更好的解决方案，而不是这个“肮脏的小黑客”。