Attempt to invoke virtual method 'void android.widget.Spinner.setSelection(int)' on a null object reference

Question

Hello There I'm a beginner to Android development. I'm facing null pointer exception in my MainActivity. (I know there are many questions asked on this topic but nothing helps me specifically)

> 07-05 05:23:00.407 3229-3229/package.name E/AndroidRuntime: FATAL EXCEPTION: main
    Process: my.package.name, PID: 3229
    java.lang.RuntimeException: Unable to start activity ComponentInfo{my.package.name/my.package.name.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Spinner.setSelection(int)' on a null object reference
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2817)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2892)
        at android.app.ActivityThread.-wrap11(Unknown Source:0)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1593)
        at android.os.Handler.dispatchMessage(Handler.java:105)
        at android.os.Looper.loop(Looper.java:164)
        at android.app.ActivityThread.main(ActivityThread.java:6541)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Spinner.setSelection(int)' on a null object reference
        at graphicstool.battlegrounnd.gfx.MainActivity.revertConfig(MainActivity.java:235)
        at graphicstool.battlegrounnd.gfx.MainActivity.onCreate(MainActivity.java:377)
        at android.app.Activity.performCreate(Activity.java:6975)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1213)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2770)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2892) 
        at android.app.ActivityThread.-wrap11(Unknown Source:0) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1593) 
        at android.os.Handler.dispatchMessage(Handler.java:105) 
        at android.os.Looper.loop(Looper.java:164) 
        at android.app.ActivityThread.main(ActivityThread.java:6541) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767) 

See above error. Here is my code for specific error

private void revertConfig() {
        SharedPreferences sharedPreferences = getSharedPreferences(getPackageName(), 0);
        this.sprGraphicsQuality.setSelection(sharedPreferences.getInt("sprGraphicsQuality", 0));

    }
protected void onCreate(Bundle bundle) {
        super.onCreate(bundle);
        setContentView(R.layout.activity_main);
        verifyStoragePermissions(this);
        Spinner sprGraphicsQuality =(Spinner) findViewById(R.id.sprGraphicsQuality);

            ArrayAdapter adapter = createFromResource(this, R.array.qualitysetting, R.layout.activity_main);

            adapter.setDropDownViewResource(R.layout.activity_main);

            sprGraphicsQuality.setAdapter(adapter);
            revertConfig();

Please help me in this matter. Let me know if you need more details.