How to cast AppBarLayout to CoordinatorLayout in Android Studio?

Question

So the gradle build went successful but my app is currently force closing due to the line: Caused by: java.lang.ClassCastException: android.support.design.widget.AppBarLayout cannot be cast to android.support.design.widget.CoordinatorLayout

I tried to remove the AppBarLayout tag from activity_home.xml:

<android.support.design.widget.AppBarLayout
xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:theme="@style/AppTheme.AppBarOverlay"
    android:id="@+id/home_Layout">

and thought to move it and create a separate App_Bar.xml in layout directory but the error about CoordinatorLayout casting to AppBarLayout still persists, anyone can help me find the real problem behind this?

Here's my HomeActivity.java (MainActivity.java)

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_home);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    homeLayout = (CoordinatorLayout) findViewById(R.id.home_Layout);
    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();
        }
    });
    // ATTENTION: This was auto-generated to implement the App Indexing API.
    // See https://g.co/AppIndexing/AndroidStudio for more information.
    client = new GoogleApiClient.Builder(this).addApi(AppIndex.API).build();
}

@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_home, 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.
    switch (item.getItemId()){

    //noinspection SimplifiableIfStatement
    case R.id.action_checkbox1:
    if (item.isChecked()) item.setChecked(false);
    else item.setChecked(true);
        homeLayout.getResources().getColor(R.color.colorPrimary);
    return true;

    case R.id.action_checkbox2:
    if (item.isChecked()) item.setChecked(false);
    else item.setChecked(true);
        homeLayout.getResources().getColor(R.color.colorPrimary);
    return true;

    case action_checkbox3:
    if (item.isChecked()) item.setChecked(false);
    else item.setChecked(true);
        homeLayout.getResources().getColor(R.color.colorPrimary);
    return true;
    default:
    return super.onOptionsItemSelected(item);
}

}

@Override
public void onStart() {
    super.onStart();

    // ATTENTION: This was auto-generated to implement the App Indexing API.
    // See https://g.co/AppIndexing/AndroidStudio for more information.
    client.connect();
    Action viewAction = Action.newAction(
            Action.TYPE_VIEW, // TODO: choose an action type.
            "Home Page", // TODO: Define a title for the content shown.
            // TODO: If you have web page content that matches this app activity's content,
            // make sure this auto-generated web page URL is correct.
            // Otherwise, set the URL to null.
            Uri.parse("http://host/path"),
            // TODO: Make sure this auto-generated app deep link URI is correct.
            Uri.parse("android-app://com.example.jovie.canteen/http/host/path")
    );
    AppIndex.AppIndexApi.start(client, viewAction);
}

@Override
public void onStop() {
    super.onStop();

    // ATTENTION: This was auto-generated to implement the App Indexing API.
    // See https://g.co/AppIndexing/AndroidStudio for more information.
    Action viewAction = Action.newAction(
            Action.TYPE_VIEW, // TODO: choose an action type.
            "Home Page", // TODO: Define a title for the content shown.
            // TODO: If you have web page content that matches this app activity's content,
            // make sure this auto-generated web page URL is correct.
            // Otherwise, set the URL to null.
            Uri.parse("http://host/path"),
            // TODO: Make sure this auto-generated app deep link URI is correct.
            Uri.parse("android-app://com.example.jovie.canteen/http/host/path")
    );
    AppIndex.AppIndexApi.end(client, viewAction);
    client.disconnect();
}

}

activity_home.xml (activity_main.xml)

<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"
android:fitsSystemWindows="true"
tools:context="com.example.jovie.canteen.HomeActivity">

<android.support.design.widget.AppBarLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:theme="@style/AppTheme.AppBarOverlay"
    android:id="@+id/home_Layout">
</android.support.design.widget.AppBarLayout>

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

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

<android.support.design.widget.FloatingActionButton
    android:id="@+id/fab"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_gravity="bottom|end"
    android:layout_margin="@dimen/fab_margin"
    app:backgroundTint="@color/colorFAB"
    android:src="@drawable/ic_search_black_24px" />

content_home.xxml (content_main.xml)

<RelativeLayout 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"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
app:layout_behavior="@string/appbar_scrolling_view_behavior"
tools:context="com.example.jovie.canteen.HomeActivity"
tools:showIn="@layout/activity_home">

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Hello World!" />

Answer 1

You cannot cast AppBarLayout to CoordinatorLayout, these are two different classes. If you want to use CoordinatorLayout, you have to set an id on it in the XML file and use this id in findViewById().