从Android支持库v26 + Android Studio 3.0起，这个过程变得简单如轻弹!!

按照以下步骤更改工具栏标题的字体:

Read Downloadable Fonts & select any font from the list (my recommendation) or load a custom font to res > font as per Fonts in XML In res > values > styles, paste the following (use your imagination here!) <style name="TitleBarTextAppearance" parent="android:TextAppearance"> <item name="android:fontFamily">@font/your_desired_font</item> <item name="android:textSize">23sp</item> <item name="android:textStyle">bold</item> <item name="android:textColor">@android:color/white</item> </style> Insert a new line in your Toolbar properties app:titleTextAppearance="@style/TextAppearance.TabsFont" as shown below <android.support.v7.widget.Toolbar android:id="@+id/toolbar" android:layout_width="match_parent" android:layout_height="?attr/actionBarSize" android:background="?attr/colorPrimary" app:titleTextAppearance="@style/TitleBarTextAppearance" app:popupTheme="@style/AppTheme.PopupOverlay"/> Enjoy Custom Actionbar Title font styling!!

为了补充@Sam_D的答案，我必须这样做才能使它工作:

this.setTitle("my title!");
((TextView)v.findViewById(R.id.title)).setText(this.getTitle());
TextView title = ((TextView)v.findViewById(R.id.title));
title.setEllipsize(TextUtils.TruncateAt.MARQUEE);
title.setMarqueeRepeatLimit(1);
// in order to start strolling, it has to be focusable and focused
title.setFocusable(true);
title.setSingleLine(true);
title.setFocusableInTouchMode(true);
title.requestFocus();

这似乎有点过分-两次引用v.f entviewbyid (R.id.title)) -但这是唯一的方法，它会让我这样做。

没有自定义的文本视图是必需的!

首先，在你的java代码中禁用工具栏中的标题: getSupportActionBar () .setDisplayShowTitleEnabled(假);

然后，只需在工具栏内添加一个TextView:

<android.support.v7.widget.Toolbar
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:background="?attr/colorPrimary"
    app:popupTheme="@style/AppTheme.PopupOverlay">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/app_name"
        android:textSize="18sp"
        android:fontFamily="@font/roboto" />

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

以下代码将适用于所有版本。我确实在gingerbread设备和JellyBean设备上检查了这一点

 private void actionBarIdForAll()
    {
        int titleId = 0;

        if(Build.VERSION.SDK_INT>=Build.VERSION_CODES.HONEYCOMB)
        {
            titleId = getResources().getIdentifier("action_bar_title", "id", "android");
        }
        else
        {
          // This is the id is from your app's generated R class when ActionBarActivity is used for SupportActionBar

            titleId = R.id.action_bar_title;
        }

        if(titleId>0)
        {
            // Do whatever you want ? It will work for all the versions.

            // 1. Customize your fonts
            // 2. Infact, customize your whole title TextView

            TextView titleView = (TextView)findViewById(titleId);
            titleView.setText("RedoApp");
            titleView.setTextColor(Color.CYAN);
        }
    }

我们需要使用反射来实现这一点

final int titleId = activity.getResources().getIdentifier("action_bar_title", "id", "android");

    final TextView title;
    if (activity.findViewById(titleId) != null) {
        title = (TextView) activity.findViewById(titleId);
        title.setTextColor(Color.BLACK);
        title.setTextColor(configs().getColor(ColorKey.GENERAL_TEXT));
        title.setTypeface(configs().getTypeface());
    } else {
        try {
            Field f = bar.getClass().getDeclaredField("mTitleTextView");
            f.setAccessible(true);
            title = (TextView) f.get(bar);
            title.setTextColor(Color.BLACK);
            title.setTypeface(configs().getTypeface());
        } catch (NoSuchFieldException e) {
        } catch (IllegalAccessException e) {
        }
    }

使用新的工具栏在支持库设计你自己的动作栏或使用下面的代码

膨胀的Textview不是一个好的选择，尝试可扩展的字符串生成器

Typeface font2 = Typeface.createFromAsset(getAssets(), "fonts/<your font in assets folder>");   
SpannableStringBuilder SS = new SpannableStringBuilder("MY Actionbar Tittle");
SS.setSpan (new CustomTypefaceSpan("", font2), 0, SS.length(),Spanned.SPAN_EXCLUSIVE_INCLUSIVE);
actionBar.setTitle(ss);

复制以下类

public class CustomTypefaceSpan extends TypefaceSpan{

    private final Typeface newType;

    public CustomTypefaceSpan(String family, Typeface type) {
        super(family);
        newType = type;
    }

    @Override
    public void updateDrawState(TextPaint ds) {
        applyCustomTypeFace(ds, newType);
    }

    @Override
    public void updateMeasureState(TextPaint paint) {
        applyCustomTypeFace(paint, newType);
    }

    private static void applyCustomTypeFace(Paint paint, Typeface tf) {
        int oldStyle;
        Typeface old = paint.getTypeface();
        if (old == null) {
            oldStyle = 0;
        } else {
            oldStyle = old.getStyle();
        }

        int fake = oldStyle & ~tf.getStyle();
        if ((fake & Typeface.BOLD) != 0) {
            paint.setFakeBoldText(true);
        }

        if ((fake & Typeface.ITALIC) != 0) {
            paint.setTextSkewX(-0.25f);
        }

        paint.setTypeface(tf);
    }

}