backendless.jar Disappearing When Attempting to Compile

I put the backendless.jar into my libs folder but whenever I try to build/run the project the .jar disappears and gives me errors only where I’ve used method associated with Objects from the .jar.



import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;

import com.backendless.Backendless;
import com.backendless.Persistence;

public class CloudTestActivity extends AppCompatActivity
{

    final String YOUR_APP_ID = "A008628F-CA21-B27B-FFB9-3F872AB77900";
    final String YOUR_SECRET_KEY = "A2C5C06C-9C3D-03A5-FF23-8BD591629C00";
    final String appVersion = "v1";
    final Button mSaveThePostButton = (Button) findViewById(R.id.savePost);

    public void saveNewPost(View view)
    {
        Post testPost = new Post();
        testPost.testString("The Post.");

        Post savedPost =  Backendless.Persistence.save(testPost);

    }


    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_cloud_test);
        Backendless.initApp( this, YOUR_APP_ID, YOUR_SECRET_KEY, appVersion );

        mSaveThePostButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {

                saveNewPost(null);

            }
        });


    }

}

This must be something with the development environment setup. Please contact the developer of the IDE (say if it is Android Studio, consider posting to the google’s forum for the product).

Regards,
Mark