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。

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;
            }
        }
    }
}

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。

    ActionBar actionBar = getSupportActionBar();
    TextView tv = new TextView(getApplicationContext());
    Typeface typeface = ResourcesCompat.getFont(this, R.font.monotype_corsiva);
    RelativeLayout.LayoutParams lp = new RelativeLayout.LayoutParams(
            RelativeLayout.LayoutParams.MATCH_PARENT, // Width of TextView
            RelativeLayout.LayoutParams.WRAP_CONTENT); // Height of TextView
    tv.setLayoutParams(lp);
    tv.setText("Your Text"); // ActionBar title text
    tv.setTextSize(25);
    tv.setTextColor(Color.WHITE);
    tv.setTypeface(typeface, typeface.ITALIC);
    actionBar.setDisplayOptions(ActionBar.DISPLAY_SHOW_CUSTOM);
    actionBar.setCustomView(tv);

试试这个

public void findAndSetFont(){
        getActionBar().setTitle("SOME TEST TEXT");
        scanForTextViewWithText(this,"SOME TEST TEXT",new SearchTextViewInterface(){

            @Override
            public void found(TextView title) {

            } 
        });
    }

public static void scanForTextViewWithText(Activity activity,String searchText, SearchTextViewInterface searchTextViewInterface){
    if(activity == null|| searchText == null || searchTextViewInterface == null)
        return;
    View view = activity.findViewById(android.R.id.content).getRootView();
    searchForTextViewWithTitle(view, searchText, searchTextViewInterface);
}

private static void searchForTextViewWithTitle(View view, String searchText, SearchTextViewInterface searchTextViewInterface)
{
    if (view instanceof ViewGroup)
    {
        ViewGroup g = (ViewGroup) view;
        int count = g.getChildCount();
        for (int i = 0; i < count; i++)
            searchForTextViewWithTitle(g.getChildAt(i), searchText, searchTextViewInterface);
    }
    else if (view instanceof TextView)
    {
        TextView textView = (TextView) view;
        if(textView.getText().toString().equals(searchText))
            if(searchTextViewInterface!=null)
                searchTextViewInterface.found(textView);
    }
}
public interface SearchTextViewInterface {
    void found(TextView title);
}

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) {
        }
    }