Coordinator layout cannot be cast to android.support.v7.widget.Toolbar error crashes the app

Question

I am trying to build a navigation drawer activity and this error would show up whenever the main activity is to be displayed and crashes the app.

xml code:

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">

<android.support.design.widget.AppBarLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:theme="@style/AppTheme.AppBarOverlay">

    <android.support.v7.widget.Toolbar
        android:id="@+id/toolbar"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:background="?attr/colorPrimaryDark"
        app:popupTheme="@style/AppTheme.PopupOverlay" />

</android.support.design.widget.AppBarLayout>

<include layout="@layout/content_main" />

<android.support.design.widget.FloatingActionButton
    android:id="@+id/Button_sign_out"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentRight="true"
    android:layout_alignParentBottom="true"
    android:layout_gravity="bottom|end"
    android:layout_margin="@dimen/fab_margin"
    android:src="@drawable/ic_arrow_forward_black_24dp"
    />

</android.support.design.widget.CoordinatorLayout>

this is my java code:

package com.android.example.ithelpdesk;

import android.content.Intent;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.NavigationView;
import android.support.v4.view.GravityCompat;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.ActionBarDrawerToggle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ListView;

import java.util.ArrayList;

public class MainActivity extends AppCompatActivity
    implements NavigationView.OnNavigationItemSelectedListener {

public DrawerLayout drawer;
public Toolbar supportActionBar;
private boolean mToolBarNavigationListenerIsRegistered  = false;
ActionBarDrawerToggle toggle;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    populateTicketList();

   Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);
    getSupportActionBar().setDisplayShowTitleEnabled(false);
    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
            this,
            drawer, toolbar,
            R.string.navigation_drawer_open,
            R.string.navigation_drawer_close
    );

    drawer.addDrawerListener(toggle);
    drawer.setDrawerListener(toggle);
    toggle.syncState();

    NavigationView navigationView = (NavigationView) 
     findViewById(R.id.nav_view);
    navigationView.setNavigationItemSelectedListener(this);

    ListView listView = (ListView) findViewById(R.id.lvSubcategory);
    listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {

  @Override
        public void onItemClick(AdapterView<?> adapterView, View view, int 
       i, long l) {
       Intent intent = new Intent(MainActivity.this, ComplaintDetail.class);
                startActivity(intent);
        }
    });

}

@Override
public void onBackPressed() {
    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    if (drawer.isDrawerOpen(GravityCompat.START)) {
        drawer.closeDrawer(GravityCompat.START);
    } else {
        super.onBackPressed();
    }
}

/*private void signOut() {
    mGoogleSignInClient.signOut()
            .addOnCompleteListener(this, new OnCompleteListener<Void>() {
                @Override
                public void onComplete(@NonNull Task<Void> task) {
                    // ...
                }
            });
}*/

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

public void setSupportActionBar(Toolbar supportActionBar) {
    this.supportActionBar = supportActionBar;
}


private void populateTicketList() {
    ArrayList<Ticket> arrayOfTicket = Ticket.getTicket();

    TicketAdapter adapter = new TicketAdapter(this, arrayOfTicket);
    ListView listView = (ListView) findViewById(R.id.lvTicket);
    listView.setAdapter(adapter);

}

@SuppressWarnings("StatementWithEmptyBody")
 @Override
public boolean onNavigationItemSelected(MenuItem item) {
    // Handle navigation view item clicks here.
    int id = item.getItemId();

    if (id == R.id.nav_complaint) {
        Intent intent = new Intent(MainActivity.this, TicketCategory.class);
        startActivity(intent);
    }
    else if (id == R.id.nav_profile) {
        Intent intent = new Intent(this, MainActivity.class);
        startActivity(intent);
    }// else if (id == R.id.nav_slideshow) {

     //  } else if (id == R.id.nav_manage) {

   // }
    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    drawer.closeDrawer(GravityCompat.START);
    return true;
}

}

the crash from the log cat:

pls help. I am a beginner so I would appreciate an explanation regarding this problem too as to what is the issue and how can i avoid it in the future.

Here is the logcat:

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.android.example.ithelpdesk/com.android.example.ithelpdesk.MainActivity}: java.lang.ClassCastException: android.support.design.widget.CoordinatorLayout cannot be cast to android.support.v7.widget.Toolbar at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2455) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2515) at android.app.ActivityThread.access$1000(ActivityThread.java:154) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1379) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:157) at android.app.ActivityThread.main(ActivityThread.java:5571) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:745) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:635) Caused by: java.lang.ClassCastException: android.support.design.widget.Coor dinatorLayout cannot be cast to android.support.v7.widget.Toolbar at com.android.example.ithelpdesk.MainActivity.onCreate(MainActivity.java:35) at android.app.Activity.performCreate(Activity.java:6357) at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1108) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2408) ... 9 more

Answer 1

You have not implemented DrawerLayout and NavigationView Layout in xml code yet. If you are not known to this layout, then try below link

How to create a custom navigation drawer in android