LiveData Observer onChnaged在活动上被称为两次安卓

如何解决LiveData Observer onChnaged在活动上被称为两次安卓

我在活动中使用实时日期观察器。当我启动活动的首次观察者onChanged（）时，像往常一样仅调用一次。但是当我按回并关闭活动，然后再次启动活动时 观察者onChanged（）被调用了两次。之后，每次我重复这些步骤时，它就会触发两次。

这是活动代码：

  @Override
    protected void onCreate(Bundle savedInstanceState) {
       super.onCreate(savedInstanceState);
       mLocLangQualViewModel = new ViewModelProvider(this).get(LocLangQualViewModel.class);
       mActivityLocLangQualSetupBinding = 
       DataBindingUtil.setContentView(this,R.layout.activity_loc_lang_qual_setup);
       mActivityLocLangQualSetupBinding.rvLanguages.setAdapter(mSelectedLanguageAdapter);
       mActivityLocLangQualSetupBinding.rvLanguages.setLayoutManager(new 
       LinearLayoutManager(this,LinearLayoutManager.HORIZONTAL,false));

    mLocLangQualViewModel.getAllLangsofUser().observe(this,new Observer<ArrayList<LanguageModel>>() 
    {
            @Override
            public void onChanged(ArrayList<LanguageModel> languageModels) {
                if (languageModels!=null){
                    Log.d("Observer","Called");
                   mSelectedLanguageAdapter = new SelectedLanguageAdapter(languageModels);
                   mActivityLocLangQualSetupBinding.rvLanguages.setAdapter(mSelectedLanguageAdapter);
                }

            }
        });

我确保getAllLangsofUser（）函数被调用一次。.所以只有观察者的onchanged（）被调用两次。

ViewModelCode：

public class LocLangQualViewModel extends ViewModel {

private LocLangQualSetupRepo  mLocLangQualSetupRepo= LocLangQualSetupRepo.getInstance();
private MutableLiveData<ArrayList<LanguageModel>> langListLiveData;


public MutableLiveData<ArrayList<LanguageModel>> getAllLangsofUser(){
    Log.d("ViewModel","Method Called");
    if (langListLiveData==null){
        langListLiveData = mLocLangQualSetupRepo.getAllLangsOfUser();
    }
    return langListLiveData;
}