Estou tentando adicionar um botão ao lado de HealthyApp, mas sem sorte.

Este é o meu código e imagem iniciais

  final ActionBar actionBar = getSupportActionBar();
    actionBar.setDisplayHomeAsUpEnabled(true);

Desejo adicionar um botão de exclusão ao lado do HealthyApp, mas o título do HealthyApp desapareceu.

 final ActionBar actionBar = getSupportActionBar();
        actionBar.setDisplayHomeAsUpEnabled(true);
        actionBar.setDisplayShowHomeEnabled(false);
        actionBar.setDisplayShowTitleEnabled(false);
        LayoutInflater mInflater = LayoutInflater.from(this);
        View mCustomView = mInflater.inflate(R.layout.header_button, null);
        Button mTitleTextView = (Button) mCustomView.findViewById(R.id.title_text);
        mTitleTextView.setText("Delete");
        actionBar.setCustomView(mCustomView);
        actionBar.setDisplayShowCustomEnabled(true);

delete_task

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    tools:context=".MainActivity">

    <android.support.v7.widget.Toolbar
        android:id="@+id/toolbar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="#d9d9d9"
        android:minHeight="?attr/actionBarSize">
        <LinearLayout
            android:layout_width="match_parent"
            android:gravity="right"
            android:layout_height="wrap_content">

            <Button
                android:text="Delete"
                android:layout_width="wrap_content"
                android:background="#000"
                android:textColor="#fff"
                android:layout_height="wrap_content"
                android:textSize="16dp" />
        </LinearLayout>

    </android.support.v7.widget.Toolbar>

    <ImageView
        android:src="@mipmap/to_do"
        android:layout_marginTop="50dp"
        android:layout_width="130dp"
        android:layout_height="210dp"
        android:id="@+id/imageView"
        android:gravity="center"
        android:layout_centerHorizontal="true"/>

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="20dp"
        android:text="No List Found"
        android:textSize="15dp"
        android:textColor="@color/btn_login"
        android:gravity="center"
        android:id="@+id/NoData"
        android:layout_centerHorizontal="true"
        android:layout_below="@+id/imageView"/>

    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <ListView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/list_todo"
            android:layout_weight="1"
            android:layout_alignParentLeft="true" />

    </RelativeLayout>

</RelativeLayout>