Question

我有一个简单的场景，我会零碎地做一些事情，当我收到LiveData时，我想在Activity中做某事。

ViewModel：

class MyViewModel(application: Application) : AndroidViewModel(application) {

    ...

    fun getUser(id: String): LiveData<User> {
        return repository.getUser(id)
    }

}

片段：

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
        })
    }
}

}

活动：

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
}}

所以我遇到的问题是，我想在LiveData<User>中有一个MyViewModel的实例，以便可以在Activity和Fragment中观察它。我该如何实现？

Answer 1

在MyViewModel类创建中

    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)
    })

}

在活动或片段中被称为

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

现在在ViewModel中，您有了对象User（userLiveData.getValue（））

Answer 2

在活动doSomethingWithUser(user: User)中写方法

在您的实时数据中

myViewModel.getUser(editText.text.toString()).observe(this, Observer { it ->
            (requireActivity() as MainActivity).doSomethingWithUser(it)
        })

在片段和活动中观察LiveData实例

2 个答案: