Android Development Tutorial - 15 - Error

package com.bmsldev.thirdtest;

import android.content.Context;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.text.style.RelativeSizeSpan;
import android.util.AttributeSet;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.RelativeLayout;
import android.widget.Button;
import android.graphics.Color;
import android.view.View;
import android.widget.EditText;

public class MainActivity extends ActionBarActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        //Layout
        RelativeLayout testLayout = new RelativeLayout(this);
        testLayout.setBackgroundColor(Color.GREEN);

        //Button
        Button redButton = new Button(this);
        redButton.setText("Log In");
        redButton.setBackgroundColor(Color.RED);

        //Username input
        EditText username = new EditText(this);

        redButton.setId(1);
        username.setId(2);

        RelativeLayout.LayoutParams buttonDetails = new RelativeLayout.LayoutParams(
                RelativeLayout.LayoutParams.WRAP_CONTENT,
                RelativeLayout.LayoutParams.WRAP_CONTENT
        );
        RelativeLayout.LayoutParams usernameDetails = new RelativeLayout.LayoutParams(
                RelativeLayout.LayoutParams.WRAP_CONTENT,
                RelativeLayout.LayoutParams.WRAP_CONTENT
        );

        //Give rules to position widgets
        usernameDetails.addRule(RelativeLayout.ABOVE,redButton.getId(1));
        usernameDetails.addRule(RelativeLayout.CENTER_HORIZONTAL);
        usernameDetails.setMargins(0,0,0,50);

        buttonDetails.addRule(RelativeLayout.CENTER_HORIZONTAL);
        buttonDetails.addRule(RelativeLayout.CENTER_VERTICAL);

        //Add widget to layout (button is now a child of layout
        testLayout.addView(redButton, buttonDetails);
        testLayout.addView(username, usernameDetails);

        //Set this activity content/display to this view
        setContentView(testLayout);
        }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }
}