code: public void cancelDiscovery() {
          mHandler.removeCallbacks(scanTimeoutCallback);
  
          if (mScanning) {
              Log.i(TAG, "Cancelling discovery process");
              BluetoothAdapter.getDefaultAdapter().stopLeScan(mCallback);
              mScanning = false;
              boolean success = mHandler.post(new Runnable() {
                  @Override
                  public void run() {
                      mListener.onDiscoveryComplete();
                  }
              });
              if (!success) {
                  Log.e(TAG, "Failed to post Discovery Complete callback!");
              }
          } else {
              Log.e(TAG, "No discovery in progress");
          }
      }
docs: Cancel a scan currently in progress. If no scan is in progress, this method does nothing.