android toolbar效果3

Title居中，只有一个右边按钮

activity_main.xml:

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout 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="com.homelink.testtoolbar7.MainActivity">

    <android.support.v7.widget.Toolbar
        style="style/toolbarStyle"
        android:id="@+id/my_toolbar"
        xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:background="?attr/colorPrimary"
        android:minHeight="?attr/actionBarSize"
        app:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
        app:popupTheme="@style/ThemeOverlay.AppCompat.Light">

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Toolbar Title"
            android:layout_gravity="center"
            style="@style/TextAppearance.AppCompat.Widget.ActionBar.Title"
            android:id="@+id/toolbar_title" />

        <ImageView
            android:id="@+id/bluetoothState"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:src="@drawable/fm_detailitem_walk"
            android:contentDescription="content_description_bluetooth_status"
            android:padding="8dp"
            android:layout_marginRight="10dp"
            android:layout_gravity="right"/>
    </android.support.v7.widget.Toolbar>

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</android.support.constraint.ConstraintLayout>

MainActivity.java

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

         Toolbar myToolbar = (Toolbar) findViewById(R.id.my_toolbar);
         TextView mTitle = (TextView) myToolbar.findViewById(R.id.toolbar_title);
         setSupportActionBar(myToolbar);

         mTitle.setText(myToolbar.getTitle());

         getSupportActionBar().setDisplayShowTitleEnabled(false);
         getSupportActionBar().setDisplayHomeAsUpEnabled(true);
     }

styles.xml:

<resources>

    <!-- Base application theme. -->
    <style name="AppTheme" parent="Theme.AppCompat.Light.NoActionBar">
        <!-- Customize your theme here. -->
        <item name="colorPrimary">@color/colorPrimary</item>
        <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
        <item name="colorAccent">@color/colorAccent</item>

        <!-- Toolbar styles -->
        <item name="toolbarStyle">@style/Widget.AppCompat.Toolbar</item>
    </style>

</resources>