在 android 中创建侧边栏导航时出现空指针异常

Question

我正在尝试在 android 中创建侧边栏导航，但有一个问题我 facing.I 在 Whosebug 上经历了这么多 post 但它并没有解决我的问题

我正在按照完全提到的教程进行操作 here

但是当我运行我的应用程序出现错误时

   Process: com.example.deepak.myapplication, PID: 26704
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.deepak.myapplication/com.example.deepak.myapplication.Naviagtion}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v7.app.ActionBar.setDisplayHomeAsUpEnabled(boolean)' on a null object reference
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2721)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2782)
    at android.app.ActivityThread.-wrap12(ActivityThread.java)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1521)
    at android.os.Handler.dispatchMessage(Handler.java:102)
    at android.os.Looper.loop(Looper.java:163)
    at android.app.ActivityThread.main(ActivityThread.java:6228)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:904)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:794)
 Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v7.app.ActionBar.setDisplayHomeAsUpEnabled(boolean)' on a null object reference
    at com.example.deepak.myapplication.Naviagtion.onCreate(Naviagtion.java:29)
    at android.app.Activity.performCreate(Activity.java:6871)
    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1119)
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2674)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2782) 
    at android.app.ActivityThread.-wrap12(ActivityThread.java) 
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1521) 
    at android.os.Handler.dispatchMessage(Handler.java:102) 
    at android.os.Looper.loop(Looper.java:163) 
    at android.app.ActivityThread.main(ActivityThread.java:6228) 
    at java.lang.reflect.Method.invoke(Native Method) 
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:904) 
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:794)

我正在使用提到的样式

    <style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">

我也在扩展 AppCompatActivity

所以请帮助我，让我知道哪里出错了

Answer 1

你还没有设置ActionBar，把这行放在上面

 setSupportActionBar(toolbar);  // <--- put this 
 ActionBar.setDisplayHomeAsUpEnabled(true)

在 android 中创建侧边栏导航时出现空指针异常

Null Pointer Exception While Creating side bar navigation in android

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