[英]Firestore error retrieving data using Kotlin
I am trying to retrieve data from the Firebase Firestore using the MVVM pattern .我正在尝试使用 MVVM 模式从 Firebase Firestore 检索数据。 The build gets successfull everytime but the app fails to open up.
每次构建都成功,但应用程序无法打开。 I am not able to find faults in the code.The application is able to add data but retrieving data is the issue.
我找不到代码中的错误。应用程序能够添加数据,但检索数据是问题所在。 Please help.Thank-You
请帮忙。谢谢
ViewModel视图模型
import android.util.Log
import androidx.lifecycle.LiveData
import androidx.lifecycle.MutableLiveData
import androidx.lifecycle.ViewModel
import com.google.firebase.firestore.FirebaseFirestore
import com.karuneshpalekar.firestorepagination.models.Note
import java.lang.Exception
class DataViewModel : ViewModel() {
companion object{
private const val TAG =" VIEWMODEL"
}
private val db = FirebaseFirestore.getInstance()
private val noteref = db.collection("record")
private val _results = MutableLiveData<Exception>()
val results: LiveData<Exception>
get() = _results
private val _notes = MutableLiveData<List<Note>>()
val notes: LiveData<List<Note>>
get() = _notes
fun addData(note: Note) {
noteref.add(note).addOnCompleteListener {
if (it.isSuccessful) {
Log.w("TAG", "success")
_results.value = null
} else {
_results.value = it.exception
}
}
}
fun fetchData() {
noteref.addSnapshotListener{ snapshot,e->
if (e!=null){
Log.w(TAG,"Listen failed",e)
return@addSnapshotListener
}
if (snapshot != null) {
val items = mutableListOf<Note>()
for (docs in snapshot){
val notes = docs.toObject(Note::class.java)
notes.let {
items.add(it)
}
_notes.value = items
}
}
}
}
}
Adapter适配器
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.recyclerview.widget.RecyclerView
import com.karuneshpalekar.firestorepagination.R
import com.karuneshpalekar.firestorepagination.models.Note
import kotlinx.android.synthetic.main.list_item.view.*
class DataAdapter : RecyclerView.Adapter<RecyclerView.ViewHolder>() {
private var items= mutableListOf<Note>()
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RecyclerView.ViewHolder {
return DataViewHolder(
LayoutInflater.from(parent.context).inflate(R.layout.list_item, parent, false)
)
}
override fun getItemCount(): Int {
return items.size
}
override fun onBindViewHolder(holder: RecyclerView.ViewHolder, position: Int) {
when (holder) {
is DataViewHolder -> {
holder.bind(items[position])
}
}
}
fun setNote(items:List<Note>){
this.items = items as MutableList<Note>
notifyDataSetChanged()
}
class DataViewHolder constructor(itemView: View) : RecyclerView.ViewHolder(itemView) {
private val textName = itemView.text_view_name
fun bind(note: Note) {
textName.text = note.name
}
}
}
Fragment分段
import android.os.Bundle
import androidx.fragment.app.Fragment
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.lifecycle.Observer
import androidx.lifecycle.ViewModelProviders
import com.karuneshpalekar.firestorepagination.R
import kotlinx.android.synthetic.main.fragment_recyclerview.*
class RecyclerView : Fragment() {
private lateinit var viewModel: DataViewModel
private lateinit var dataadapter : DataAdapter
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
// Inflate the layout for this fragment
viewModel = ViewModelProviders.of(this).get(DataViewModel::class.java)
return inflater.inflate(R.layout.fragment_recyclerview, container, false)
}
override fun onActivityCreated(savedInstanceState: Bundle?) {
super.onActivityCreated(savedInstanceState)
recycler_view.apply {
dataadapter = DataAdapter()
adapter = dataadapter
}
viewModel.fetchData()
viewModel.notes.observe(viewLifecycleOwner, Observer {
dataadapter.setNote(it)
})
floating_btn_add.setOnClickListener {
DialogFragment().show(childFragmentManager, "")
}
}
}
DialogFragment - To add Data DialogFragment - 添加数据
class DialogFragment :DialogFragment(){
private lateinit var viewmodel:DataViewModel
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
viewmodel = ViewModelProviders.of(this).get(DataViewModel::class.java)
return inflater.inflate(R.layout.fragment_dialog, container, false)
}
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setStyle(STYLE_NO_TITLE, android.R.style.Theme_DeviceDefault_Light_Dialog_MinWidth)
}
override fun onActivityCreated(savedInstanceState: Bundle?) {
super.onActivityCreated(savedInstanceState)
viewmodel.results.observe(viewLifecycleOwner, Observer {
val message = if (it == null) {
getString(R.string.name_added)
} else {
getString(R.string.name_error)
}
Toast.makeText(requireContext(), message, Toast.LENGTH_SHORT).show()
dismiss()
})
button_add.setOnClickListener {
val names = edit_text_name.text.toString().trim()
val note= Note("",names)
viewmodel.addData(note)
}
}
}
RecyclerView XML RecyclerView XML
<androidx.coordinatorlayout.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
xmlns:app="http://schemas.android.com/apk/res-auto"
tools:context=".ui.RecyclerView">
<androidx.recyclerview.widget.RecyclerView
android:id="@+id/recycler_view"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:padding="@dimen/margin"
app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager"
tools:listitem="@layout/list_item"
/>
<com.google.android.material.floatingactionbutton.FloatingActionButton
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/floating_btn_add"
app:fabSize="normal"
android:layout_gravity="bottom|end"
android:layout_margin="@dimen/margin"
/>
</androidx.coordinatorlayout.widget.CoordinatorLayout>
The above is the code of my Project以上是我项目的代码
提供错误的代码中唯一缺少的是没有在 Model 类(即 Note Class)中进行空检查。
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