如何设置在动作条自定义视图中的Andr​​oid？

我想用在动作条的应用程序标题，但每次我收到了同样的错误（空指针异常）自定义字体和我的应用程序说我说不幸的是****已停止。我寻觅了很多，并试图使用它们。但是没有什么工作。同样的错误不断发生。我创建了一个简单的布局与一个TextView，并试图通过这条线将其插入到动作条

I want to use a custom font in actionbar app title but Every time I am getting the same error (nullpointer exception) and my app says me that "Unfortunately **** has stopped ". I have searched a lot and tried to use them. But nothings working. The same error keeps happening. I have created a simple layout with a TextView and trying to insert it in the actionbar by this line

ActionBar actionBar = getActionBar();
actionBar.setCustomView(R.layout.custom_actionbar);

无论我做什么，在 setCustomView 发送我的空指针错误。我想，如果我可以设置在动作条的布局将是容易改变TextView的字体。这里是我的全code。

Whatever I do, the setCustomView sends me the nullpointer error. I am thinking that if I can set the layout in actionbar it will be easy to change the TextView font. Here is my full code.

public class MainActivity extends ActionBarActivity {
    @TargetApi(Build.VERSION_CODES.HONEYCOMB)
    @Override
    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        ViewPager viewPager = (ViewPager) findViewById(R.id.pager);
        viewPager.setAdapter(new ViewPagerAdapter(getSupportFragmentManager()));
        ActionBar actionBar = getActionBar();
        actionBar.setCustomView(R.layout.custom_actionbar);

    }
}

和布局

<?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/App_title"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerVertical="true"
        android:layout_marginLeft="10dp"
        android:textSize="40dp"
        android:maxLines="2"
        android:ellipsize="end"
        android:text="Prime" />
</RelativeLayout>

和错误：

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.tushar.primeplay2/com.example.tushar.primeplay2.MainActivity}: java.lang.NullPointerException
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2306)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2358)
            at android.app.ActivityThread.access$600(ActivityThread.java:156)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1340)
            at android.os.Handler.dispatchMessage(Handler.java:99)
            at android.os.Looper.loop(Looper.java:153)
            at android.app.ActivityThread.main(ActivityThread.java:5297)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:511)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:833)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:600)
            at dalvik.system.NativeStart.main(Native Method)
     Caused by: java.lang.NullPointerException
            at com.example.tushar.primeplay2.MainActivity.onCreate(MainActivity.java:22)
            at android.app.Activity.performCreate(Activity.java:5122)
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1081)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2270)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2358)
            at android.app.ActivityThread.access$600(ActivityThread.java:156)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1340)
            at android.os.Handler.dispatchMessage(Handler.java:99)
            at android.os.Looper.loop(Looper.java:153)
            at android.app.ActivityThread.main(ActivityThread.java:5297)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:511)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:833)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:600)
            at dalvik.system.NativeStart.main(Native Method)

我使用的机器人工作室。

I am using android studio.