Question

我正在尝试在android中创建侧边栏导航，但是我面临的一个问题。我在stackoverflow上经历了很多帖子，但并没有解决我的问题

我正在遵循完全提到的here

教程

但是当我运行我的应用程序时，我得到了错误

   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，让我知道我要去哪里了

Answer 1

您尚未设置ActionBar，请将此行放在

上方

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

在Android中创建侧栏导航时出现空指针异常

1 个答案: