Android ActionBar NullPointerException

概述我想启用 Android ActionBar,但它对我不起作用. 这是我的MainActivity： public void onCreate(Bundle savedInstanceState) { this.requestWindowFeature(Window.FEATURE_NO_TITLE); super.onCreate(savedInstance 我想启用 Android Actionbar,但它对我不起作用.

这是我的MainActivity：

public voID onCreate(Bundle savedInstanceState) {        this.requestwindowFeature(Window.FEATURE_NO_Title);        super.onCreate(savedInstanceState);        setContentVIEw(R.layout.login);        Actionbar actionbar = getActionbar();        actionbar.show();        //more code............

这是logcat：

03-04 16:31:09.423: E/AndroIDRuntime(1441): FATAL EXCEPTION: main03-04 16:31:09.423: E/AndroIDRuntime(1441): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.salebook/com.example.salebook.MainActivity}: java.lang.NullPointerException03-04 16:31:09.423: E/AndroIDRuntime(1441):     at androID.app.ActivityThread.performlaunchActivity(ActivityThread.java:2180)03-04 16:31:09.423: E/AndroIDRuntime(1441):     at androID.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)03-04 16:31:09.423: E/AndroIDRuntime(1441):     at androID.app.ActivityThread.access0(ActivityThread.java:141)03-04 16:31:09.423: E/AndroIDRuntime(1441):     at androID.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)03-04 16:31:09.423: E/AndroIDRuntime(1441):     at androID.os.Handler.dispatchMessage(Handler.java:99)03-04 16:31:09.423: E/AndroIDRuntime(1441):     at androID.os.Looper.loop(Looper.java:137)03-04 16:31:09.423: E/AndroIDRuntime(1441):     at androID.app.ActivityThread.main(ActivityThread.java:5041)03-04 16:31:09.423: E/AndroIDRuntime(1441):     at java.lang.reflect.Method.invokeNative(Native Method)03-04 16:31:09.423: E/AndroIDRuntime(1441):     at java.lang.reflect.Method.invoke(Method.java:511)03-04 16:31:09.423: E/AndroIDRuntime(1441):     at com.androID.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)03-04 16:31:09.423: E/AndroIDRuntime(1441):     at com.androID.internal.os.ZygoteInit.main(ZygoteInit.java:560)03-04 16:31:09.423: E/AndroIDRuntime(1441):     at dalvik.system.NativeStart.main(Native Method)03-04 16:31:09.423: E/AndroIDRuntime(1441): Caused by: java.lang.NullPointerException03-04 16:31:09.423: E/AndroIDRuntime(1441):     at com.example.salebook.MainActivity.onCreate(MainActivity.java:130)03-04 16:31:09.423: E/AndroIDRuntime(1441):     at androID.app.Activity.performCreate(Activity.java:5104)03-04 16:31:09.423: E/AndroIDRuntime(1441):     at androID.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)03-04 16:31:09.423: E/AndroIDRuntime(1441):     at androID.app.ActivityThread.performlaunchActivity(ActivityThread.java:2144)03-04 16:31:09.423: E/AndroIDRuntime(1441):     ... 11 more

第130行是anctionbar.show(),我在res / menu / menu.xml中：

<menu xmlns:androID="http://schemas.androID.com/apk/res/androID">    <item androID:ID="@+ID/itemID_0"        androID:title="Action Item 0"        androID:icon="@drawable/ic_launcher"        androID:orderIncategory="0"        androID:showAsAction="ifRoom|withText" />    <item androID:ID="@+ID/itemID_1"        androID:title="Action Item 1"        androID:orderIncategory="0" />    <item androID:ID="@+ID/itemID_2"        androID:title="Action Item 2"        androID:orderIncategory="0" />    <item androID:ID="@+ID/itemID_3"        androID:title="Action Item 3"        androID:orderIncategory="0" /></menu>

我没有发现问题.希望有人帮助我.

谢谢.

另外,在appThem风格：

<style name="Apptheme" parent="AppBasetheme">        <item name="androID:windowActionbar">true</item>        <!-- All customizations that are NOT specific to a particular API-level can go here. -->    </style>

解决方法 您的Actionbar返回null,因为您没有 *** 作栏但是您正在请求使用getActionbar()

确保您具有显示 *** 作栏的窗口功能,这是 *** 作栏显示所必需的.有关详细信息,请查看以下链接.
…检查此问题getActionBar returns null并查看此链接以获取有关您的问题http://blog.perpetumdesign.com/2011/08/strange-case-of-dr-action-and-mr-bar.html的更多信息

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