Android Studio 3.6 - how use layouts in Design Palette? - android-studio

Question

I am new to Android development and Android studio. I'm using Android Studio 3.6.1 . I'm having trouble understanding the "Layouts" options in the Design Palette. First, I don't see a "RelativeLayout" option. I realize many feel this is superceded by the ConstraintLayout, but it seems to me it should be a choice. Second, I don't see how to even use these layout options. If I drag one to an existing design, nothing happens. I thought maybe it would replace the root layout, but doesn't seem to. It doesn't create a child layout (if such a thing is possible). My code is just a simple "MainActivity" class with "setContentView(R.layout.activity_main);" in the onCreate() method. I have been tinkering with the activity_main.xml file to learn UI concepts. I can type in manual changes to change the layout to RelativeLayout, but it wasn't obvious what the classpath of the RelativeLayout class was, it is not in the same package as the ConstraintLayout class. I'm trying to use the power of the Android Studio IDE to discover options and build code, but I'm not finding how to use it for Layout options. I tried emptying the "activity_main.xml" file and then dragging a Layout from the palette, but nothing happens. I can delete the "activity_main.xml" file and create a new one, but when it prompts for a layout, there is no discovery to help choose one, it seems you have to know the package.
How can these Layouts in the Design Palette actually be used in the IDE? Can RelativeLayout be added to the list? Are there other missing Layouts?
package com.example.test;
import android.os.Bundle;
import com.google.android.material.floatingactionbutton.FloatingActionButton;
import com.google.android.material.snackbar.Snackbar;
import androidx.appcompat.app.AppCompatActivity;
import androidx.appcompat.widget.Toolbar;
import android.view.View;
import android.view.Menu;
import android.view.MenuItem;
public class MainActivity extends AppCompatActivity
{
#Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
}
<?xml version="1.0" encoding="utf-8"?>
<android.widget.RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:id="#+id/textView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="TextView" />
</android.widget.RelativeLayout>

Answer 1

Something changed and I can now right-click a Layout and "add to design" or drag it to the design. I can also right-click the Layout in the component tree and convert to another layout, including RelativeLayout. I had added a Calendar component to my design for the heck of it and built and run in the emulator. After that, I deleted the Calendar and found I was able to now drag the layout components or convert the root component. So I'm comfortable with use of Layouts in the Palette. I am still unclear how to discover Layouts when creating a new layout XML file when it asks for "root tag". But I realize you don't need a full path, just the class name it seems, apparently the IDE finds the class. The glue behind the scenes I'll need to learn more about.