[JAVA] [Android] Two ways to get a Bluetooth Adapter

Thing you want to do

――I want to get a Bluetooth Adapter to do various things with Bluetooth

The first way

--Use Bluetooth Manager

//API Level 23 or higher
BluetoothManager bluetoothManager = Context.getSystemService(BluetoothManager.class)
//API Level 1 or higher
BluetoothManager bluetoothManager = (BluetoothManager) getApplicationContext().getSystemService(Context.BLUETOOTH_SERVICE);

BluetoothAdapter bluetoothAdapter = bluetoothManager.getAdapter();

The second way

--Use the static method of BluetoothAdapter

//Null may be returned
BluetoothAdapter bluetoothAdapter = BluetoothAdapter.getDefaultAdapter();

Which one is better?

If you look at the Official Reference,

To get a BluetoothAdapter representing the local Bluetooth adapter, call the getAdapter() function on BluetoothManager. On JELLY_BEAN_MR1 and below you will need to use the static getDefaultAdapter() method instead.

Basically the first way, JELLY_BEAN_MR1 or less, that is, Android 4.2.2 or less, let's do it in the second way.