很简单,我声明了ActionBar,调用hide()并得到了一个nullpointer异常。这是一个常见问题,所以我将确保我提及自己尝试过的内容。
-确保AppTheme没有声明Theme.WithoutActionBar
。
-使用import android.support.v7.app.ActionBarActivity;扩展ActionBarActivity而不是Activity;
-确保我使用的最小SDK为> 11
编辑:当我将项目切换到Android Studio时,ActionBar返回null的整个混乱开始了
这是我在oncreate()里面的代码,在这里我弄乱了操作栏。
@Override
protected void onCreate(Bundle savedInstanceState) {
getWindow().requestFeature(Window.FEATURE_ACTION_BAR);
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_login);
ActionBar bar = getActionBar();
bar.hide();
这是我的logcat错误
Process: com.example.rafa.ideas, PID: 19806
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.rafa.ideas/com.example.rafa.ideas.LoginActivity}: java.lang.NullPointerException
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2413)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2471)
at android.app.ActivityThread.access$900(ActivityThread.java:175)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1308)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:146)
at android.app.ActivityThread.main(ActivityThread.java:5602)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1283)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1099)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
at com.example.rafa.ideas.LoginActivity.onCreate(LoginActivity.java:33)
at android.app.Activity.performCreate(Activity.java:5451)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1093)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2377)
编辑:这是我的清单
<application
android:name=".IdeasApplication"
android:allowBackup="true"
android:icon="@drawable/idea_logo"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name=".SignupActivity"
android:label="@string/app_name"
android:parentActivityName=".LoginActivity" >
</activity>
<activity
android:name=".MainActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name=".LoginActivity"
android:label="@string/app_name"
android:windowSoftInputMode="adjustResize|stateHidden" >
</activity>
<activity
android:name=".AddIdeaActivity"
android:label="@string/app_name" android:parentActivityName=".MainActivity">
</activity>
</application>
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
</manifest>
编辑:这是我在样式设置中的主题
<!--
Base application theme, dependent on API level. This theme is replaced
by AppBaseTheme from res/values-vXX/styles.xml on newer devices.
-->
<style name="AppBaseTheme" parent="Theme.AppCompat.Light">
<!--
Theme customizations available in newer API levels can go in
res/values-vXX/styles.xml, while customizations related to
backward-compatibility can go here.
-->
</style>
<!-- Application theme. -->
<style name="AppTheme" parent="AppBaseTheme">
<!-- All customizations that are NOT specific to a particular API-level can go here. -->
</style>
最佳答案
如果正在使用getSupportActionBar
,则应使用getActionBar
而不是ActionBarActivity
。 getActionBar
方法在ActionBarActivity
API中可用,因为它扩展了Activity
,但在使用支持活动时不应使用。
关于java - ActionBar返回NullPointerException,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/27663172/