我有一个代码模块,它实现了带有导航抽屉的Viewpager,但是,当我运行代码时,我得到以下错误
01-26 09:20:02.958: D/AndroidRuntime(18779): Shutting down VM
01-26 09:20:02.959: E/AndroidRuntime(18779): FATAL EXCEPTION: main
01-26 09:20:02.959: E/AndroidRuntime(18779): Process: com.example.tabwithslidingdrawer, PID: 18779
01-26 09:20:02.959: E/AndroidRuntime(18779): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.tabwithslidingdrawer/com.example.tabwithslidingdrawer.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.ActionBar.setDisplayHomeAsUpEnabled(boolean)' on a null object reference
01-26 09:20:02.959: E/AndroidRuntime(18779): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2314)
01-26 09:20:02.959: E/AndroidRuntime(18779): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2388)
01-26 09:20:02.959: E/AndroidRuntime(18779): at android.app.ActivityThread.access$800(ActivityThread.java:148)
01-26 09:20:02.959: E/AndroidRuntime(18779): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1292)
01-26 09:20:02.959: E/AndroidRuntime(18779): at android.os.Handler.dispatchMessage(Handler.java:102)
01-26 09:20:02.959: E/AndroidRuntime(18779): at android.os.Looper.loop(Looper.java:135)
01-26 09:20:02.959: E/AndroidRuntime(18779): at android.app.ActivityThread.main(ActivityThread.java:5312)
01-26 09:20:02.959: E/AndroidRuntime(18779): at java.lang.reflect.Method.invoke(Native Method)
01-26 09:20:02.959: E/AndroidRuntime(18779): at java.lang.reflect.Method.invoke(Method.java:372)
01-26 09:20:02.959: E/AndroidRuntime(18779): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:901)
01-26 09:20:02.959: E/AndroidRuntime(18779): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:696)
01-26 09:20:02.959: E/AndroidRuntime(18779): Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.ActionBar.setDisplayHomeAsUpEnabled(boolean)' on a null object reference
01-26 09:20:02.959: E/AndroidRuntime(18779): at com.example.tabwithslidingdrawer.MainActivity.onCreate(MainActivity.java:95)
01-26 09:20:02.959: E/AndroidRuntime(18779): at android.app.Activity.performCreate(Activity.java:5953)
01-26 09:20:02.959: E/AndroidRuntime(18779): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1128)
01-26 09:20:02.959: E/AndroidRuntime(18779): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2267)
01-26 09:20:02.959: E/AndroidRuntime(18779): ... 10 more
09:20:02.959: E/AndroidRuntime(18779): Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.ActionBar.setDisplayHomeAsUpEnabled(boolean)' on a null object reference 01-26 09:20:02.959: E/AndroidRuntime(18779): at com.example.tabwithslidingdrawer.MainActivity.onCreate(MainActivity.java:95)
指向这条线
// enabling action bar app icon and behaving it as a toggle button
getActionBar().setDisplayHomeAsUpEnabled(true);
getActionBar().setHomeButtonEnabled(true);
entire code 100
我的舱单
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.tabwithslidingdrawer"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="19" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/Theme.Tabwithpager" >
<activity
android:name="com.example.tabwithslidingdrawer.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>
</application>
</manifest>
android:theme="@style/Theme.Tabwithpager"
密码
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我从中学到了什么
每当发生此类错误时
1. Check what kind of Activity is being used, is it a simple android.app Activity or an AppCompatActivity or an ActionBarActivity and so on.
2. Check if your activity type which is extended falls under the compat category
例如android.基于应用程序的活动/片段是非appCompat类型,
如果它属于appCompat,我们使用getSupportActionBar()
3. Check the theme applied to the activity in question in the manifest file
例子:
但如果 list 中的活动主题如下