我花了几天时间寻找一个通用的解决方案。我的工具栏与android菜单和导航图标。

首先，您需要创建自定义工具栏类。这个类必须计算标题居中的位置(填充):

    class CenteredToolbar @JvmOverloads constructor(context: Context, attrs: AttributeSet? = null, defStyleAttr: Int = 0)
    : Toolbar(context, attrs, defStyleAttr) {

    init {
        addOnLayoutChangeListener(object : View.OnLayoutChangeListener {
            override fun onLayoutChange(v: View?, left: Int, top: Int, right: Int, bottom: Int, oldLeft: Int, oldTop: Int, oldRight: Int, oldBottom: Int) {
                val titleTextView = findViewById<TextView>(R.id.centerTitle)

                val x = titleTextView.x.toInt()
                val x2 = x + titleTextView.width

                val fullWidth = width
                val fullCenter = fullWidth / 2

                val offsetLeft = Math.abs(fullCenter - x)
                val offsetRight = Math.abs(x2 - fullCenter)
                val differOffset = Math.abs(offsetLeft - offsetRight)

                if (offsetLeft > offsetRight) {
                    titleTextView.setPadding(differOffset, 0, 0, 0)
                } else if (offsetRight > offsetLeft) {
                    titleTextView.setPadding(0, 0, differOffset, 0)
                }

                removeOnLayoutChangeListener(this)
            }
        })
    }

    override fun setTitle(resId: Int) = getTitleView().setText(resId)

    override fun setTitle(title: CharSequence?) = getTitleView().setText(title)

    fun getTitleView(): TextView = findViewById(R.id.centerTitle)

}

其次，你需要创建布局工具栏:

<CenteredToolbar xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/toolbar">

    <TextView
        android:id="@+id/centerTitle"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>

</CenteredToolbar>

这是所有

更新自@MrEngineer13的回答:要在任何情况下对齐标题中心，包括汉堡图标，选项菜单，你可以在工具栏中添加一个框架布局，像这样:

   <android.support.v7.widget.Toolbar
    android:id="@+id/toolbar_top"
    android:layout_height="wrap_content"
    android:layout_width="match_parent"
    android:minHeight="?attr/actionBarSize"
    android:background="@color/action_bar_bkgnd"
    app:theme="@style/ToolBarTheme" >

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

              <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" />

        </FrameLayout>

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

我用这个问题的解决方案:

 public static void applyFontForToolbarTitle(Activity a){
        Toolbar toolbar = (Toolbar) a.findViewById(R.id.app_bar);
        for(int i = 0; i < toolbar.getChildCount(); i++){
            View view = toolbar.getChildAt(i);
            if(view instanceof TextView){
                TextView tv = (TextView) view;
                if(tv.getText().equals(a.getTitle())){
                    tv.setTypeface(getRuneTypefaceBold(a));
                    break;
                }
            }
        }
    }

对于重心，我认为有必要将布局参数水平更改为match_parent，然后:

tv.setGravity(Gravity.CENTER);

我也遇到了同样的问题，通过在MainActivity中这样做来解决

Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
TextView mTitle = (TextView) toolbar.findViewById(R.id.toolbar_title);
setSupportActionBar(toolbar);
getSupportActionBar().setDisplayShowTitleEnabled(false);

碎片化

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    if (view == null) {
        // Inflate the layout for this fragment
        view = inflater.inflate(R.layout.fragment_example, container, false);
        init();
    }
    getActivity().setTitle("Choose Fragment");
    return view;
}

@Override
public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
    inflater.inflate(R.menu.example_menu, menu);
}

要在你的工具栏中使用自定义标题，你需要做的是记住，工具栏只是一个花哨的ViewGroup，所以你可以添加一个自定义标题，如下所示:

<android.support.v7.widget.Toolbar
    android:id="@+id/toolbar_top"
    android:layout_height="wrap_content"
    android:layout_width="match_parent"
    android:minHeight="?android:attr/actionBarSize"
    android:background="@color/action_bar_bkgnd"
    app:theme="@style/ToolBarTheme" >


     <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Toolbar Title"
        android:layout_gravity="center"
        android:id="@+id/toolbar_title" />


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

这意味着你可以样式的TextView，但你想，因为它只是一个常规的TextView。在你的activity中，你可以像这样访问标题:

Toolbar toolbarTop = (Toolbar) findViewById(R.id.toolbar_top);
TextView mTitle = (TextView) toolbarTop.findViewById(R.id.toolbar_title);

我使用这个解决方案:

static void centerToolbarTitle(@NonNull final Toolbar toolbar) {
    final CharSequence title = toolbar.getTitle();
    final ArrayList<View> outViews = new ArrayList<>(1);
    toolbar.findViewsWithText(outViews, title, View.FIND_VIEWS_WITH_TEXT);
    if (!outViews.isEmpty()) {
        final TextView titleView = (TextView) outViews.get(0);
        titleView.setGravity(Gravity.CENTER);
        final Toolbar.LayoutParams layoutParams = (Toolbar.LayoutParams) titleView.getLayoutParams();
        layoutParams.width = ViewGroup.LayoutParams.MATCH_PARENT;
        toolbar.requestLayout();
        //also you can use titleView for changing font: titleView.setTypeface(Typeface);
    }
}