flutter_blue_plus\FlutterBluePlusPlugin.java uses or overrides a deprecated API

[cvanbeek13]

When I run flutter build apk, I get the following warning:

Note: D:\Users\cvanbeek\installs\flutter\.pub-cache\hosted\pub.dartlang.org\flutter_blue_plus-1.1.3\android\src\main\java\com\boskokg\flutter_blue_plus\FlutterBluePlusPlugin.java uses or overrides a deprecated API.
Note: Recompile with -Xlint:deprecation for details.

Version Info:

flutter_blue_plus: 1.1.3

Flutter:

Flutter 2.10.4 • channel stable • https://github.com/flutter/flutter.git
Framework • revision c860cba910 (4 weeks ago) • 2022-03-25 00:23:12 -0500
Engine • revision 57d3bac3dd
Tools • Dart 2.16.2 • DevTools 2.9.2

[sqcsabbey]

It looks like this project is using Android's BluetoothAdapter startLeScan and stopLeScan methods, which are deprecated; here are the warnings with the deprecated linting enabled:

/Users/csabbey/homebrew/Caskroom/flutter/2.10.3/flutter/.pub-cache/hosted/pub.dartlang.org/flutter_blue_plus-1.1.3/android/src/main/java/com/boskokg/flutter_blue_plus/FlutterBluePlusPlugin.java:904: warning: [deprecation] startLeScan(UUID[],LeScanCallback) in BluetoothAdapter has been deprecated
    boolean success = mBluetoothAdapter.startLeScan(uuids, getScanCallback18());
                                       ^

/Users/csabbey/homebrew/Caskroom/flutter/2.10.3/flutter/.pub-cache/hosted/pub.dartlang.org/flutter_blue_plus-1.1.3/android/src/main/java/com/boskokg/flutter_blue_plus/FlutterBluePlusPlugin.java:909: warning: [deprecation] stopLeScan(LeScanCallback) in BluetoothAdapter has been deprecated
    mBluetoothAdapter.stopLeScan(getScanCallback18());
                     ^

This SO answer says to use BluetoothLeScanner instead, which is available since API level 21 (Android 5.0).

[MrCsabaToth]

Oh ok, currently my minSDK level is 19, so bumping that to 24 would exclude some of my users. Although I know that it could get rid of some spurious Bluetooth behavior if I'd support higher min SDK level. I wish support libraries would port back the newer scanner to 19. Although that's ancient, KitKat. Usually iOS users who really want my app dig up some dusty slow crappy old tablet from a bottom of a drawer and those sometimes are KitKat. PITA.

[MrCsabaToth]

It's a question though when will the currently used API deprecate. Having a plan to transition to BluetoothLeScanner. I accidentally wrote API level 24, I meant 21 and that's not so far from 19.

[MrCsabaToth]

Here is a way to use both: https://stackoverflow.com/a/39412791/292502

private BluetoothAdapter bluetoothAdapter;
private BluetoothAdapter.LeScanCallback leScanCallback;
private ScanCallback scanCallback;
private ScanSettings scanSetting;

// Check before call the function
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
    bluetoothAdapter.getBluetoothLeScanner().startScan(filterList, scanSetting, scanCallback);
} else {
    bluetoothAdapter.startLeScan(leScanCallback);
}

[boskokg]

Actually we are checking before call:

  if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
    startScan21(settings);
  } else {
    startScan18(settings);
  }

Thing is that we cannot write all that logic to single line and extracting to methods startScan21 and startScan18 makes this false-positive warning.

[MrCsabaToth]

Actually we are checking before call:

Oooh! That's great to know! Sorry for not checking the source code!