在片段和活动中观察LiveData实例

Question

class MyViewModel(application: Application) : AndroidViewModel(application) {
    
   ...
    
    fun getUser(id: String): LiveData<User> {
        return repository.getUser(id)
    }
}

class MyFragment : Fragment() {

    private lateinit var myViewModel: MyViewModel

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        activity?.run {
            myViewModel = ViewModelProviders.of(this).get(MyViewModel::class.java)
        } ?: throw Exception("Invalid Activity")
    }

    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
        return inflater.inflate(R.layout.fragment, container, false)
    }

    override fun onActivityCreated(savedInstanceState: Bundle?) {
        super.onActivityCreated(savedInstanceState)
        button.setOnClickListener {
            showProgressBar()
            myViewModel.getUser(editText.text.toString()).observe(this, Observer { it ->
                //TODO
            })
        }
    }
}

class MainActivity : AppCompatActivity() {

    private lateinit var myViewModel: MyViewModel

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        myViewModel = ViewModelProviders.of(this).get(MyViewModel::class.java)
        //Here I would like to observe the user instance returned from the getUser() method
    }
}

因此，我遇到的问题是，我希望在MyViewModel中有一个LiveData 的实例，以便在活动和片段中观察它。我怎样才能做到这一点？

Answer 1

在类MyViewModel create中

    val userLiveData =MutableLiveData<User>()

和吸气剂

    fun getUserLiveData(id: String): MutableLiveData<User> {
            return userLiveData
    }

    fun getUser(id: String){
    val disposableUser = repository.getUser(id)
    .subscribe({
        userLivedata.postValue(it)
    })

}

   myViewModel.getUserLiveData.observe(this, Observer { it ->
      //TODO
    })
   myViewModel.getUser(...)