Android 视图未通过数据绑定进行更新

Question

我创建了一个简单的应用程序，它从 API 加载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。起初我创建了一个 ViewModel，它从 API

中获取数据

class RandomJokeViewModel: ViewModel() {

private val jokeService = RetrofitService()

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

在我的 Fragment 中，我调用了加载笑话和更新视图的方法

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}")
    })
}

我的数据调用如下所示：

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)

在我的片段布局中，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>

所以当我运行应用程序时，我的 TextView 是空的。在 Logcat 和我验证的调试器中，randomJoke 响应有数据。为什么获取数据后我的视图没有更新？我错过了什么？

Answer 1

不完全确定是这个原因但是：

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。

改为这样尝试：

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 return在：

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

但你需要 return:

return binding.root

Android 视图未通过数据绑定进行更新

Android View is not updating over data binding

android

data-binding

textview

android-databinding