我发现:
if(mBluetoothAdapter.getScanMode() != BluetoothAdapter.SCAN_MODE_CONNECTABLE_disCOVERABLE)
{
Intent intent = new Intent(BluetoothAdapter.ACTION_REQUEST_disCOVERABLE);
intent.putExtra(BluetoothAdapter.EXTRA_disCOVERABLE_DURATION,30);
startActivityForResult(intent,idBluetoothdiscoveryRequest);
}