您可以使用自定义TypefaceSpan类来实现这一点。它优于上面提到的customView方法，因为它在使用其他操作栏元素(如展开操作视图)时不会中断。

这样一个类的使用应该是这样的:

SpannableString s = new SpannableString("My Title");
s.setSpan(new TypefaceSpan(this, "MyTypeface.otf"), 0, s.length(),
        Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);

// Update the action bar title with the TypefaceSpan instance
ActionBar actionBar = getActionBar();
actionBar.setTitle(s);

自定义TypefaceSpan类传递给您的Activity上下文和assets/fonts目录中的字体名称。它加载文件并在内存中缓存一个新的字体实例。TypefaceSpan的完整实现非常简单:

/**
 * Style a {@link Spannable} with a custom {@link Typeface}.
 * 
 * @author Tristan Waddington
 */
public class TypefaceSpan extends MetricAffectingSpan {
      /** An <code>LruCache</code> for previously loaded typefaces. */
    private static LruCache<String, Typeface> sTypefaceCache =
            new LruCache<String, Typeface>(12);

    private Typeface mTypeface;

    /**
     * Load the {@link Typeface} and apply to a {@link Spannable}.
     */
    public TypefaceSpan(Context context, String typefaceName) {
        mTypeface = sTypefaceCache.get(typefaceName);

        if (mTypeface == null) {
            mTypeface = Typeface.createFromAsset(context.getApplicationContext()
                    .getAssets(), String.format("fonts/%s", typefaceName));

            // Cache the loaded Typeface
            sTypefaceCache.put(typefaceName, mTypeface);
        }
    }

    @Override
    public void updateMeasureState(TextPaint p) {
        p.setTypeface(mTypeface);

        // Note: This flag is required for proper typeface rendering
        p.setFlags(p.getFlags() | Paint.SUBPIXEL_TEXT_FLAG);
    }

    @Override
    public void updateDrawState(TextPaint tp) {
        tp.setTypeface(mTypeface);

        // Note: This flag is required for proper typeface rendering
        tp.setFlags(tp.getFlags() | Paint.SUBPIXEL_TEXT_FLAG);
    }
}

简单地复制上面的类到你的项目中，并在你的活动的onCreate方法中实现它，如上所示。

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!!

更新正确答案。

首先:将标题设置为false，因为我们正在使用自定义视图

    actionBar.setDisplayShowTitleEnabled(false);

第二步:创建titleview.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
   android:layout_width="match_parent"
   android:layout_height="match_parent"
   android:background="@android:color/transparent" >

    <TextView
       android:id="@+id/title"
       android:layout_width="wrap_content"
       android:layout_height="wrap_content"
       android:layout_centerVertical="true"
       android:layout_marginLeft="10dp"
       android:textSize="20dp"
       android:maxLines="1"
       android:ellipsize="end"
       android:text="" />

</RelativeLayout>

最后:

//font file must be in the phone db so you have to create download file code
//check the code on the bottom part of the download file code.

   TypeFace font = Typeface.createFromFile("/storage/emulated/0/Android/data/"   
    + BuildConfig.APPLICATION_ID + "/files/" + "font name" + ".ttf");

    if(font != null) {
        LayoutInflater inflator = LayoutInflater.from(this);
        View v = inflator.inflate(R.layout.titleview, null);
        TextView titleTv = ((TextView) v.findViewById(R.id.title));
        titleTv.setText(title);
        titleTv.setTypeface(font);
        actionBar.setCustomView(v);
    } else {
        actionBar.setDisplayShowTitleEnabled(true);
        actionBar.setTitle("  " + title); // Need to add a title
    }

下载字体文件:因为我把文件存储到cloudinary，所以我有链接下载它。

/**downloadFile*/
public void downloadFile(){
    String DownloadUrl = //url here
    File file = new File("/storage/emulated/0/Android/data/" + BuildConfig.APPLICATION_ID + "/files/");
    File[] list = file.listFiles();
    if(list == null || list.length <= 0) {
        BroadcastReceiver onComplete = new BroadcastReceiver() {
            @Override
            public void onReceive(Context context, Intent intent) {
                try{
                    showContentFragment(false);
                } catch (Exception e){
                }
            }
        };

        registerReceiver(onComplete, new IntentFilter(DownloadManager.ACTION_DOWNLOAD_COMPLETE));
        DownloadManager.Request request = new DownloadManager.Request(Uri.parse(DownloadUrl));
        request.setVisibleInDownloadsUi(false);
        request.setDestinationInExternalFilesDir(this, null, ModelManager.getInstance().getCurrentApp().getRegular_font_name() + ".ttf");
        DownloadManager manager = (DownloadManager) getSystemService(Context.DOWNLOAD_SERVICE);
        manager.enqueue(request);
    } else {
        for (File files : list) {
            if (!files.getName().equals("font_name" + ".ttf")) {
                BroadcastReceiver onComplete = new BroadcastReceiver() {
                    @Override
                    public void onReceive(Context context, Intent intent) {
                        try{
                            showContentFragment(false);
                        } catch (Exception e){
                        }
                    }
                };

                registerReceiver(onComplete, new IntentFilter(DownloadManager.ACTION_DOWNLOAD_COMPLETE));
                DownloadManager.Request request = new DownloadManager.Request(Uri.parse(DownloadUrl));
                request.setVisibleInDownloadsUi(false);
                request.setDestinationInExternalFilesDir(this, null, "font_name" + ".ttf");
                DownloadManager manager = (DownloadManager) getSystemService(Context.DOWNLOAD_SERVICE);
                manager.enqueue(request);
            } else {
                showContentFragment(false);
                break;
            }
        }
    }
}

我只是在onCreate()函数中做了以下工作:

TypefaceSpan typefaceSpan = new TypefaceSpan("font_to_be_used");
SpannableString str = new SpannableString("toolbar_text");
str.setSpan(typefaceSpan,0, str.length(), Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
getSupportActionBar().setTitle(str);

我正在使用支持库，如果你不使用它们，我猜你应该切换到getActionBar()而不是getSupportActionBar()。

在Android Studio 3中，您可以按照以下说明添加自定义字体https://developer.android.com/guide/topics/ui/look-and-feel/fonts-in-xml.html，然后在“font_to_be_used”中使用您新添加的字体

试试这个

TextView headerText= new TextView(getApplicationContext());
RelativeLayout.LayoutParams lp = new RelativeLayout.LayoutParams(ActionBar.LayoutParams.WRAP_CONTENT, ActionBar.LayoutParams.WRAP_CONTENT);
headerText.setLayoutParams(lp);
headerText.setText("Welcome!");
headerText.setTextSize(20);
headerText.setTextColor(Color.parseColor("#FFFFFF"));
Typeface tf = Typeface.createFromAsset(getAssets(), "fonts/wesfy_regular.ttf");
headerText.setTypeface(tf);
getSupportActionBar().setDisplayOptions(ActionBar.DISPLAY_SHOW_CUSTOM);
getSupportActionBar().setCustomView(headerText);

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);
    }

}