android - 如何使用 Intent 中的附加功能

Question

我正在学习如何在 android 上使用蓝牙，并且我为 BluetoothAdapter.ACTION_STATE_CHANGED 注册了一个 BroadCastReceiver。 在文档中，它说

Broadcast Action: The state of the local Bluetooth adapter has been changed. For example, Bluetooth has been turned on or off. Always contains the extra fields EXTRA_STATE and EXTRA_PREVIOUS_STATE
containing the new and old states respectively.

现在，我如何使用 EXTRA_STATE 和 EXTRA_PREVIOUS_STATE？

Answer 1

来自 here :

private final BroadcastReceiver mReceiver = new BroadcastReceiver() {
@Override
public void onReceive(Context context, Intent intent) {
    final String action = intent.getAction();

    if (action.equals(BluetoothAdapter.ACTION_STATE_CHANGED)) {
        final int state = intent.getIntExtra(BluetoothAdapter.EXTRA_STATE,
                                             BluetoothAdapter.ERROR);
        switch (state) {
        case BluetoothAdapter.STATE_OFF:
            //Bluetooth off
            break;
        case BluetoothAdapter.STATE_TURNING_OFF:
            //Turning Bluetooth off...
            break;
        case BluetoothAdapter.STATE_ON:
            //Bluetooth on
            break;
        case BluetoothAdapter.STATE_TURNING_ON:
            //Turning Bluetooth on...
            break;
        }
    }
}

};