我有 getActionBar() 的问题，当我收到此错误时会发生此问题：

java.lang.RuntimeException: Unable to start activity ComponentInfo{h.ui01/h.ui01.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.ActionBar.setNavigationMode(int)' on a null object reference
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3119)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3218)
            at android.app.ActivityThread.access$1000(ActivityThread.java:198)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1676)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:145)
            at android.app.ActivityThread.main(ActivityThread.java:6837)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1404)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1199)
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.ActionBar.setNavigationMode(int)' on a null object reference
            at h.ui01.MainActivity.onCreate(MainActivity.java:28)
            at android.app.Activity.performCreate(Activity.java:6500)
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1120)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3072)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3218)
            at android.app.ActivityThread.access$1000(ActivityThread.java:198)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1676)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:145)
            at android.app.ActivityThread.main(ActivityThread.java:6837)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1404)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1199)

我的代码在这里：

public class MainActivity extends Activity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        final ActionBar actionBar = getSupportActionBar();
        actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_STANDARD);
        LayoutInflater inflater = (LayoutInflater) this.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        View view = inflater.inflate(R.layout.action_bar, null);
        actionBar.setCustomView(view, new ActionBar.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT));
        actionBar.setDisplayOptions(ActionBar.DISPLAY_SHOW_CUSTOM);
    }
}

即使我试图隐藏操作栏或更改操作栏的颜色，我也看到了类似的错误 .

android