我不知道appcompat库中是否有任何变化，但这是相当微不足道的，不需要反射。

Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);

// loop through all toolbar children right after setting support 
// action bar because the text view has no id assigned

// also make sure that the activity has some title here
// because calling setText() with an empty string actually
// removes the text view from the toolbar

TextView toolbarTitle = null;
for (int i = 0; i < toolbar.getChildCount(); ++i) {
    View child = toolbar.getChildAt(i);

    // assuming that the title is the first instance of TextView
    // you can also check if the title string matches
    if (child instanceof TextView) {
        toolbarTitle = (TextView)child;
        break;
    }
}

你只需要在你的工具栏布局中添加以下一行:

app:contentInsetStart="0dp"

布局:

<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" >

     <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Toolbar Title"
        android:layout_gravity="center"
        android:gravity="center"
        android:id="@+id/toolbar_title" />
</android.support.v7.widget.Toolbar>

代码:

    Toolbar mToolbar = parent.findViewById(R.id.toolbar_top);
    TextView mToolbarCustomTitle = parent.findViewById(R.id.toolbar_title);

    //setup width of custom title to match in parent toolbar
    mToolbar.postDelayed(new Runnable()
    {
        @Override
        public void run ()
        {
            int maxWidth = mToolbar.getWidth();
            int titleWidth = mToolbarCustomTitle.getWidth();
            int iconWidth = maxWidth - titleWidth;

            if (iconWidth > 0)
            {
                //icons (drawer, menu) are on left and right side
                int width = maxWidth - iconWidth * 2;
                mToolbarCustomTitle.setMinimumWidth(width);
                mToolbarCustomTitle.getLayoutParams().width = width;
            }
        }
    }, 0);

工具栏标题是可设置样式的。你所做的任何定制都必须在主题中进行。我给你们举个例子。

工具栏布局:

<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.Toolbar
    style="@style/ToolBarStyle.Event"
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/toolbar"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:background="?attr/colorPrimary"
    android:minHeight="@dimen/abc_action_bar_default_height_material" />

风格:

<style name="ToolBarStyle" parent="ToolBarStyle.Base"/>

<style name="ToolBarStyle.Base" parent="">
    <item name="popupTheme">@style/ThemeOverlay.AppCompat.Light</item>
    <item name="theme">@style/ThemeOverlay.AppCompat.Dark.ActionBar</item>
</style>

<style name="ToolBarStyle.Event" parent="ToolBarStyle">
    <item name="titleTextAppearance">@style/TextAppearance.Widget.Event.Toolbar.Title</item>
</style>

<style name="TextAppearance.Widget.Event.Toolbar.Title" parent="TextAppearance.Widget.AppCompat.Toolbar.Title">
    <!--Any text styling can be done here-->
    <item name="android:textStyle">normal</item>
    <item name="android:textSize">@dimen/event_title_text_size</item>
</style>

  @Composable
    fun topAppBar() {
        CenterAlignedTopAppBar(
            title = {
                Text(
                    "Top App Bar"
                )
            },
            navigationIcon = {
                IconButton(onClick = { /*TODO*/ }) {
                    Icon(
                        imageVector = Icons.Default.ArrowBack,
                        contentDescription = "Back"
                    )
                }
            },
            actions = {
                IconButton(onClick = { /*TODO*/ }) {
                    Icon(
                        imageVector = Icons.Default.MoreVert,
                        contentDescription = "More",
                    )
                }
            },
            colors = TopAppBarDefaults.smallTopAppBarColors(
                containerColor = MaterialTheme.colorScheme.secondaryContainer
            )
        )
    }
}

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);