Android ROS Message

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I'm unsure where to turn to get help for my question, so I might try my luck here.

I am trying to send a message to a ROS via an Android Application. The message is the string "Hello World". I tried to do some research and found out that I could use a MessageFactory object but I am unsure what else to do. Can someone point me in the right direction?

I am also aware that my node object has not been initialized. I tried doing some research into but haven't got found any information that can help. Any help here also would be appreciated. It is denoted by the comment "known error here".

I will post my code below, along with the packages I included.

//packages included

import org.ros.android.BitmapFromCompressedImage;
import org.ros.android.view.RosImageView;
import org.ros.android.view.VirtualJoystickView;
import org.ros.message.MessageFactory;
import org.ros.namespace.NameResolver;
import org.ros.node.Node;
import org.ros.node.NodeConfiguration;
import org.ros.node.NodeMainExecutor;


  public void executeCommand(NodeMainExecutor nodeMainExecutor){
      Node node;

      try{
          java.net.Socket socket = new java.net.Socket(getMasterUri().getHost(), getMasterUri().getPort());
          java.net.InetAddress local_network_address = socket.getLocalAddress();
          socket.close();
          NodeConfiguration nodeConfiguration = NodeConfiguration.newPublic(local_network_address.getHostAddress(), getMasterUri());

          String craneTopic = "/rosout";

          NameResolver appNameSpace = getMasterNameSpace();
          craneTopic = appNameSpace.resolve(craneTopic).toString();

          MessageFactory factory = node.getTopicMessageFactory();// known error here
          std_msgs.String m = factory.newFromType(std_msgs.String._TYPE);

         //nodeMainExecutor.execute(, nodeConfiguration.setNodeName("android/follow_crane")); // unknown what to put here

      }catch (IOException e) {
          Toast.makeText(getApplicationContext(), "Unable to execute command",Toast.LENGTH_SHORT).show();
      }  
  }