actionViewClass屬性使用

1.今天在開發的時候遇到了一個問題，menu裏面的actionViewClass裏面的控件找不到，佈局如下：

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    tools:context="com.liluo.epco.UI.activity.SeachTaskActivity">
    <item
        android:id="@+id/menu_seach"
        android:title=""
        android:icon="@mipmap/sousuo"
        android:actionViewClass="android.widget.SearchView"
        app:showAsAction="always" />
</menu>

咋一看是沒啥問題，當我們在java裏面使用時就會報:

 Caused by: java.lang.NullPointerException: Attempt to invoke interface method 'android.view.View android.view.MenuItem.getActionView()' on a null object reference
                                                                    at com.liluo.epco.UI.activity.SerachActivity.initView(SerachActivity.java:47)
                                                                    at com.liluo.epco.base.BaseActivity.init(BaseActivity.java:135)
                                                                    at com.liluo.epco.base.BaseActivity.onCreate(BaseActivity.java:44)
                                                                    at android.app.Activity.performCreate(Activity.java:5990)
                                                                    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106)
                                                                    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2278)
                                                                    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387) 
                                                                    at android.app.ActivityThread.access$800(ActivityThread.java:151) 
                                                                    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303) 
                                                                    at android.os.Handler.dispatchMessage(Handler.java:102) 
                                                                    at android.os.Looper.loop(Looper.java:135) 
                                                                    at android.app.ActivityThread.main(ActivityThread.java:5254) 
                                                                    at java.lang.reflect.Method.invoke(Native Method) 
                                                                    at java.lang.reflect.Method.invoke(Method.java:372)

解決方案其實很簡單,將android換爲app即可

app:actionViewClass="android.widget.SearchView"