Thread: need help understanding code

So I am studying how to build android apps by myself and I am stuck trying to understand some of the life of codes for this particular code:

package com.ebookfrenzy.javalayout;
 
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.Button;
import android.widget.RelativeLayout;
 
public class JavaLayoutActivity extends AppCompatActivity
{
    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        Button myButton = new Button(this);
        RelativeLayout myLayout = new RelativeLayout(this);
        myLayout.addView(myButton);
        setContentView(myLayout);
    }
}

This is to create a simple button. However, I do not under what "this" in:
Button myButton = new Button(this);
RelativeLayout myLayout = new RelativeLayout(this);

refers to, and the book does not say.

Ah, I see now. Thanks

--- Update ---

I have one more question (I don't want to create another thread since it is basically more on understanding the code)

This is the same code, but added more to create a background of blue and a yellow button that says "PRESS ME".

package com.ebookfrenzy.javalayout;
 
import android.annotation.SuppressLint;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.Button;
import android.widget.RelativeLayout;
import android.graphics.Color;
import android.widget.EditText;
import android.content.res.Resources;
import android.util.TypedValue;
 
public class JavaLayoutActivity extends AppCompatActivity
{
    @SuppressLint("ResourceType")
    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
 
        //sets button
        Button myButton = new Button(this);
        myButton.setText("Press Me");
        myButton.setBackgroundColor(Color.YELLOW);
 
        //sets background color
        RelativeLayout myLayout = new RelativeLayout(this);
        myLayout.setBackgroundColor(Color.BLUE);
 
        EditText myEditText = new EditText(this);
 
        myButton.setId(1);
        myEditText.setId(2);
 
        //sets location of the button relative to the screen
        RelativeLayout.LayoutParams buttonParams = new RelativeLayout.LayoutParams(
 
                RelativeLayout.LayoutParams.WRAP_CONTENT, RelativeLayout.LayoutParams.WRAP_CONTENT
        );
 
        RelativeLayout.LayoutParams textParams = new RelativeLayout.LayoutParams(
 
                RelativeLayout.LayoutParams.WRAP_CONTENT, RelativeLayout.LayoutParams.WRAP_CONTENT
        );
 
        textParams.addRule(RelativeLayout.ABOVE, myButton.getId());
 
        textParams.addRule(RelativeLayout.CENTER_HORIZONTAL);
        textParams.setMargins(0, 0, 0, 80);
 
        buttonParams.addRule(RelativeLayout.CENTER_HORIZONTAL);
        buttonParams.addRule(RelativeLayout.CENTER_VERTICAL);
 
        myLayout.addView(myButton, buttonParams);
        myLayout.addView(myEditText, textParams);
        setContentView(myLayout);
    }
}

My question is, for:
myButton.setId(1);
myEditText.setId(2);
there was an error, and automatically is created something called: @SuppressLint("ResourceType")
What does this mean? and why was there an error for the setId methods?