"Error:R cannot be resolved to a variable"

Question

Tried everything like cleaning the project,installing SDK build tools,checking for errors in XML layout files. Still no way I can get rid of this "unexpected R error".

Below is the code for First.java

package com.example.wctm;



    import android.os.Bundle;
    import android.app.Activity;
    import android.content.DialogInterface;
    import android.content.DialogInterface.OnClickListener;
    import android.content.Intent;
    import android.view.Menu;
    import android.view.View;
    import android.widget.Button;
    import android.widget.EditText;

    public class First extends Activity implements OnClickListener {

        EditText name;
        EditText pass;
        Button   submit;


        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_first);        
            name=(EditText)findViewById(R.id.editText1);
            pass=(EditText)findViewById(R.id.editText2);
            submit=(Button)findViewById(R.id.button1);
            submit.setOnClickListener((android.view.View.OnClickListener) this);
        }



    public void onClick(View v)
    {
        String na=name.getText().toString();
        String pa=pass.getText().toString();

        switch (v.getId()) {
        case R.id.button1:
            if(na.equals("wctm") && (pa.equals("wctm")))
            {
                Intent i=new Intent(this,Second.class);
                startActivity(i);
            }


            break;

        default:
            break;
        }

    }

        enter code here

    @Override
    public void onClick(DialogInterface arg0, int arg1) {

    }

}