[英]Synthetic import in kotlin not working
在Fragment
中,所提供的布局Kotlins合成進口Anko
不工作。 我試圖設置視圖的可見性,但它說視圖為空。 我有以下代碼。
class HistoryFragment : Fragment(), HistoryContract.view, LoaderManager.LoaderCallbacks<List<SongEntity>>{
private lateinit var mPresenter : HistoryContract.Presenter
private lateinit var adapter: HistoryAdapte
private val loaderId : Int = 101
override fun onLoadFinished(loader: Loader<List<SongEntity>>?, data: List<SongEntity>?) {
hideLoadingIndicator()
if (data == null) {
showErrorView()
} else {
//update the adapter
adapter.updateDataset(data)
}
}
override fun onLoaderReset(loader: Loader<List<SongEntity>>?) {
}
override fun onCreateLoader(id: Int, args: Bundle?): Loader<List<SongEntity>> {
showLoadingIndicator()
return object : AsyncTaskLoader<List<SongEntity>>(activity!!.baseContext){
override fun loadInBackground(): List<SongEntity>? {
return mPresenter.fetchSongs()
}
}
}
override fun showLoadingIndicator() {
song_history_pv.visibility = View.VISIBLE
}
override fun hideLoadingIndicator() {
song_history_pv.visibility = View.INVISIBLE
}
override fun showErrorView() {
song_history_error_tv.visibility = View.VISIBLE
}
override fun hideErrorView() {
song_history_error_tv.visibility = View.INVISIBLE
}
override fun setPresenter(presenter: HistoryContract.Presenter) {
mPresenter = presenter
}
override fun showDiscoveredSongs(songs: List<SongEntity>) {
}
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View {
val rootView = inflater.inflate(R.layout.fragment_song_history, container, false)
loaderManager.initLoader(loaderId, null , this)
songHistoryRv.layoutManager = LinearLayoutManager(context)
songHistoryRv.adapter = HistoryAdapter {
Toast.makeText(activity!!.baseContext, "${it.name}", Toast.LENGTH_SHORT).show()
}
return rootView
}
}
現在,當我在showLoadingIndicator函數中設置進度視圖的可見性時,我收到視圖為空的錯誤。
下面是我用於片段的布局文件
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent">
<android.support.v7.widget.RecyclerView
android:id="@+id/songHistoryRv"
android:layout_width="0dp"
android:layout_height="0dp"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintTop_toTopOf="parent"/>
<ProgressBar
android:id="@+id/song_history_pv"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="32dp"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent"/>
<TextView
android:id="@+id/song_history_error_tv"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/song_history_error"
android:visibility="invisible"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintBottom_toBottomOf="parent"/>
</android.support.constraint.ConstraintLayout>
import kotlinx.android.synthetic.main.fragment_song_history。*是我正在使用的綜合導入。
請幫我解決這個問題。 我錯過了什么嗎? 我是kotlin的新手。
您的問題是您過早地嘗試訪問該視圖。 在#onCreateView
您正在給視圖充氣,但只要您不返回膨脹的視圖, Fragment#getView()
仍將返回null。 在內部,Kotlin Android Extensions使用getView().findViewById(int)
方法在您第一次嘗試訪問它時綁定視圖。
TL;博士
要解決您的問題,只需在#onCreateView
返回膨脹的視圖, #onCreateView
有關LoaderManager
的操作移至#onViewCreated
:
class HistoryFragment : Fragment(), HistoryContract.view, LoaderManager.LoaderCallbacks<List<SongEntity>>{
// ...
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View {
return inflater.inflate(R.layout.fragment_song_history, container, false)
}
override fun onViewCreated(view: View?, savedInstanceState: Bundle?) {
loaderManager.initLoader(loaderId, null , this)
songHistoryRv.layoutManager = LinearLayoutManager(context)
songHistoryRv.adapter = HistoryAdapter {
Toast.makeText(activity!!.baseContext, "${it.name}", Toast.LENGTH_SHORT).show()
}
}
}
請嘗試在onViewCreated
使用/ do代碼...像這樣
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
myRequestListRV.layoutManager = LinearLayoutManager(homeActivity)
}
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