Question

我创建了一个简单的应用程序，该应用程序从API加载了一个随机笑话，并将其显示在TextView中。出于学习原因，我已经使用数据绑定实现了该应用程序。最初，我创建了一个ViewModel，可以从API获取数据

class RandomJokeViewModel: ViewModel() {

private val jokeService = RetrofitService()

fun getRandomJoke(): MutableLiveData<RandomJoke> ? {
    Log.e("getRandomJokeData", "yes")
    return jokeService.loadRandomJoke()
}

在我的片段中，我调用该方法来加载笑话并更新视图

class RandomJokeFragment : Fragment() {

private lateinit var binding: FragmentRandomJokeBinding

override fun onCreateView(
    inflater: LayoutInflater, container: ViewGroup?,
    savedInstanceState: Bundle?
): View? {
    binding = DataBindingUtil.inflate(layoutInflater, R.layout.fragment_random_joke, container, false)
    binding.lifecycleOwner = this
    // Inflate the layout for this fragment
    return inflater.inflate(R.layout.fragment_random_joke, container, false)
}

override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
    super.onViewCreated(view, savedInstanceState)
    loadRandomJoke()
}

private fun loadRandomJoke() {
    Log.e("getAndroidVersion", "yes")
    val randomJokeViewModel =
        ViewModelProviders.of(requireActivity()).get(RandomJokeViewModel::class.java)
    randomJokeViewModel.getRandomJoke()?.observe(this, Observer<RandomJoke> { randomJoke ->
        binding.randomJoke = randomJoke
        Log.e("RandomJokeFragment", "This is your Joke: ${randomJoke.value}")
    })
}

我的数据通话如下：

data class RandomJoke (
@SerializedName("categories") val categories: ArrayList<String>,
@SerializedName("created_at") val createdAt: String,
@SerializedName("icon_url") val iconUrl: String,
@SerializedName("id") val id: String,
@SerializedName("updated_at:") val updatedAt: String,
@SerializedName("url") val url: String,
@SerializedName("value") val value: String)

在“片段布局”中，我定义了这样的数据绑定资源

<data>
    <variable
        name="randomJoke" type="com.example.jokegenerator.data.remote.response.RandomJoke"
        />
</data>

<androidx.constraintlayout.widget.ConstraintLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@color/colorPrimaryDark"
    >

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginLeft="1dp"
        android:layout_marginStart="1dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        android:text="@{randomJoke.value}"
        android:textColor="#ffff"
        tools:text="Hello World"/>

</androidx.constraintlayout.widget.ConstraintLayout>

因此，当我运行该应用程序时，我的TextView为空。在Logcat和Debugger中，我验证了randomJoke响应中是否包含数据。为什么获取数据后视图没有更新？我想念什么？

Answer 1

不能完全确定这是原因，但是：

override fun onCreateView(
    inflater: LayoutInflater, container: ViewGroup?,
    savedInstanceState: Bundle?
): View? {
    binding = DataBindingUtil.inflate(layoutInflater, R.layout.fragment_random_joke, container, false)
    binding.lifecycleOwner = this
    // Inflate the layout for this fragment
    return inflater.inflate(R.layout.fragment_random_joke, container, false)
}

在这里您将布局膨胀2次。

请尝试这样：

override fun onCreateView(
    inflater: LayoutInflater, container: ViewGroup?,
    savedInstanceState: Bundle?
): View? {
    // This will inflate your layout. You just have to return the root view.
    binding = DataBindingUtil.inflate(layoutInflater, R.layout.fragment_random_joke, container, false)
    binding.lifecycleOwner = this
    return binding.root // Returning your root view
}

数据绑定可能是两种布局的混合。

Answer 2

在您的onCreateView（）中，您将返回：

return inflater.inflate(R.layout.fragment_random_joke, container, false)

但您需要返回：

return binding.root

Android View不会通过数据绑定进行更新

2 个答案: