Exception raised during Rendering: android.support.design.widget.CoordinatorLayout cannot be cast to android.view.ViewGroup

Question

Although i was getting preview before, i have not made any changes in the files. As a matter of fact there is not much to change in my code, its just a OK button in app. Just to tell, i deleted the toolbar from my design in activity_main.xml file.But undo the changes afterwards as i can see it in MainActivity.java file. I am a newbie to android studio, any help would be useful. Here's my java file.

package com.learning.pehlaapp;

import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.View;
import android.view.Menu;
import android.view.MenuItem;

public class SampleActivity extends AppCompatActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_sample);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

    FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
    fab.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                    .setAction("Action", null).show();
        }
    });
}

@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_sample, 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);
}
}

Answer 1

Exception raised during Rendering:    
android.support.design.widget.CoordinatorLayout cannot be cast to 
android.view.ViewGroup 

As error said coordinatorLayout can not br cast to ViewGroup Please check your   
XML view as you uses FloatingActionButton which are define under  
CoordinatorLayout and that layout treated as ViewGroup in Activty  thus this 
exception arised