Toolbar image centered

Toolbar is just a ViewGroup, you can customize is as much as you want.

Try this :

<android.support.v7.widget.Toolbar
   style="@style/ToolBarStyle"
   xmlns:android="http://schemas.android.com/apk/res/android"
   android:layout_width="match_parent"
   android:layout_height="wrap_content"
   android:background="?attr/colorPrimary"
   android:minHeight="@dimen/abc_action_bar_default_height_material">

    <ImageView
        android:layout_width="wrap_content"
        android:contentDescription="@string/logo"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:src="@drawable/ic_launcher"/>

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

This should bring your imageView in center of toolbar.

This is not the best solution but it's a work around that works even when you have up button or menu item.

try

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

    <android.support.v7.widget.Toolbar
       style="@style/ToolBarStyle"
       xmlns:android="http://schemas.android.com/apk/res/android"
       android:layout_width="match_parent"
       android:layout_height="wrap_content"
       android:background="?attr/colorPrimary"
       android:minHeight="@dimen/abc_action_bar_default_height_material"/>

    <ImageView
        android:layout_width="wrap_content"
        android:contentDescription="@string/logo"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:src="@drawable/ic_launcher"/>

</FrameLayout>

I like the approach given by Ruben Yoo's answer because of its simplicity. It is explicit, easy to follow, and keeps all the code changes together.

Here's an updated version with some minor improvements:

<android.support.design.widget.AppBarLayout
    android:id="@+id/layout_app_bar"
    android:layout_width="match_parent"
    android:layout_height="wrap_content">

    <FrameLayout
        android:layout_width="match_parent"
        android:layout_height="?attr/actionBarSize">

        <android.support.v7.widget.Toolbar
            android:id="@+id/toolbar"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize">
        </android.support.v7.widget.Toolbar>

        <ImageView
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:contentDescription="@string/app_name"
            android:scaleType="centerInside"
            android:src="@mipmap/ic_launcher"/>
    </FrameLayout>

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

---

Changes:

1. introduced AppBarLayout parent
2. explicit size ?attr/actionBarSize provided to frame & toolbar
3. ImageView matches parent dimensions in width & height
4. logo resized to centerInside

If you have any views and can't quite get the logo centered, it will be because the centering is based on remaining space, not the entire toolbar.

To guarantee the logo being centered, try using a layer-list as a background of your toolbar instead of trying to use an image as a view.

toolbar.xml

<android.support.v7.widget.Toolbar
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/toolbar"
    android:layout_width="match_parent"
    android:layout_height="?attr/actionBarSize"
    android:background="@drawable/toolbar_background"
    android:theme="@style/ThemeOverlay.AppCompat.Dark"
    app:popupTheme="@style/ThemeOverlay.AppCompat.Light"
    app:layout_scrollFlags="scroll|enterAlways"
    app:layout_collapseMode="pin">
</android.support.v7.widget.Toolbar>

toolbar_background.xml

<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
  <item>
    <shape android:shape="rectangle">
      <solid android:color="@color/colorPrimary" />
    </shape>
  </item>
  <item>
    <bitmap android:src="@drawable/logo" android:gravity="center" />
  </item>
</layer-list>

That should ensure a centered logo, with a specific background colour.