问NullPointerException reference SharedPrefence java.lang.String，整型

EN

Fatal Exception: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.SharedPreferences android.content.Context.getSharedPreferences(java.lang.String, int)' on a null object reference
       at com.myproject.utils.PreferencesUtils.setAdmobEnable(PreferencesUtils.java:3)
       at com.myproject.ui.MainActivity$9.onDataChange(MainActivity.java:220)

protected Context mContext;

public static boolean getAdMobEnable(final Context context) {
    SharedPreferences preferences = context.getSharedPreferences(
        Constants.SHARED_PREFERENCE, 0
    );
    return preferences.getBoolean(Constants.ADMOB_ENABLE, true);
}
    
public static void setAdmobEnable(final Context context, boolean value) {
    SharedPreferences preferences = context.getSharedPreferences(
        Constants.SHARED_PREFERENCE, 0
    );
    SharedPreferences.Editor editor = preferences.edit();
    editor.putBoolean(Constants.ADMOB_ENABLE, value);
    editor.apply();
}

PreferencesUtils.setAdmobEnable(mContext, true);

if (user.membership == null || user.membership != 1) {
    //user.membership is an Integer data and this data is downloaded with Firebase realtime database.
    PreferencesUtils.setAdmobEnable(mContext, true);
} else {
    PreferencesUtils.setAdmobEnable(mContext, false);
}