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;
            }
        }
    }
}

int titleId = getResources().getIdentifier("action_bar_title", "id",
            "android");
    TextView yourTextView = (TextView) findViewById(titleId);
    yourTextView.setTextColor(getResources().getColor(R.color.black));
    yourTextView.setTypeface(face);

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);
        }
    }

    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);

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>

这是一个丑陋的黑客，但你可以这样做(因为action_bar_title是隐藏的):

    try {
        Integer titleId = (Integer) Class.forName("com.android.internal.R$id")
                .getField("action_bar_title").get(null);
        TextView title = (TextView) getWindow().findViewById(titleId);
        // check for null and manipulate the title as see fit
    } catch (Exception e) {
        Log.e(TAG, "Failed to obtain action bar title reference");
    }

这段代码适用于后姜饼设备，但也可以很容易地扩展到动作栏Sherlock

附注:基于@pjv评论，有一个更好的方法找到操作栏标题id

final int titleId = 
    Resources.getSystem().getIdentifier("action_bar_title", "id", "android");