[英]Android Kotlin: How can I delete the data from Firebase
我是 Android Kotlin 的新手。 當我單擊應用程序上的按鈕時,我嘗試從 Cloud Firebase 中刪除數據。 我在我的適配器上做了一些必要的代碼,但是我如何在我的 Activity 上調用數據庫集合? 我在下面分享了我的適配器和我的活動代碼。
class NoteAdapter(val titleText: ArrayList<String>, val rowImage: ArrayList<String>, val noteText: ArrayList<String>, val listener: onClick) : RecyclerView.Adapter<NoteAdapter.NoteHolder>() {
interface onClick {
fun onItemClickListener(v: View, pos: Int, data: Any)
}
class NoteHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
val itemImage : ImageView = itemView.findViewById(R.id.recyclerImage)
val itemDelete: ImageView = itemView.findViewById(R.id.delete)
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): NoteHolder {
val v = LayoutInflater.from(parent.context).inflate(R.layout.recycler_row, parent, false)
return NoteHolder(v)
}
override fun onBindViewHolder(holder: NoteHolder, position: Int) {
holder.itemView.recyclerTitleText.text = titleText[position]
Picasso.get().load(rowImage[position]).resize(150,150).into(holder.itemImage)
holder.itemView.setOnClickListener {
val intent = Intent(holder.itemView.context, PastNotesActivity:: class.java)
intent.putExtra("oldTitle", titleText[position])
intent.putExtra("oldNote", noteText[position])
intent.putExtra("oldImage", rowImage[position])
holder.itemView.context.startActivity(intent)
}
holder.itemDelete.setOnClickListener { v: View ->
titleText.removeAt(position)
noteText.removeAt(position)
rowImage.removeAt(position)
notifyItemRemoved(position)
listener.onItemClickListener(v, position, holder.itemView)
}
}
override fun getItemCount(): Int {
return titleText.size
}
override fun getItemId(position: Int):Long {
return position.toLong()
}
override fun getItemViewType(position: Int):Int {
return position
}
}
這是我的活動代碼,我在此活動中創建了 itemDelete 樂趣,但如何在此樂趣中定義我的適配器代碼? 我試圖在我的文檔中寫“{id.data}”但沒有用我應該寫什么?
class ListViewActivity : AppCompatActivity() {
var selectedPicture: Uri? = null
private lateinit var auth: FirebaseAuth
private lateinit var db : FirebaseFirestore
var titleTextFromFB : ArrayList<String> = ArrayList()
var noteTextFromFB : ArrayList<String> = ArrayList()
var imageFromFB : ArrayList<String> = ArrayList()
var adapter: NoteAdapter? = null
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_list_view)
auth = FirebaseAuth.getInstance()
db = FirebaseFirestore.getInstance()
getDataFromFirestore()
// recyclerview
var layoutManager = LinearLayoutManager(this)
recyclerView.layoutManager = layoutManager
// adapter = NoteAdapter(titleTextFromFB, imageFromFB, noteTextFromFB)
//recyclerView.adapter = adapter
adapter = NoteAdapter(titleTextFromFB, imageFromFB, noteTextFromFB, object: NoteAdapter.onClick{
override fun onItemClickListener(v: View, pos: Int, data: Any) {
when(v.id){
R.id.delete -> itemDelete(data)
}
}
})
recyclerView.adapter = adapter
}
override fun onCreateOptionsMenu(menu: Menu?): Boolean {
val menuInflater = menuInflater
menuInflater.inflate(R.menu.add_note, menu)
return super.onCreateOptionsMenu(menu)
}
override fun onOptionsItemSelected(item: MenuItem): Boolean {
if (item.itemId == R.id.add_note_click) {
// Take Notes Activity
val intent = Intent(applicationContext, TakeNotesActivity::class.java)
intent.putExtra("info","new")
startActivity(intent)
} else if (item.itemId == R.id.log_out) {
val alert = AlertDialog.Builder(this)
alert.setTitle("Log Out")
alert.setMessage("Are you sure to logout from the app ?")
alert.setPositiveButton("Yes") {dialog, which ->
auth.signOut()
val intent = Intent(applicationContext, MainActivity::class.java)
startActivity(intent)
finish()
}
alert.setNegativeButton("No") {dialog, which ->
}
alert.show()
}
return super.onOptionsItemSelected(item)
}
// get data from firestore
fun getDataFromFirestore() {
db.collection("Notes").orderBy("date", Query.Direction.DESCENDING).addSnapshotListener{ snapshot, exception ->
if (exception != null) {
// If there is a error ,
Toast.makeText(applicationContext, exception.localizedMessage.toString(), Toast.LENGTH_LONG).show()
} else {
if (snapshot != null) {
if (!snapshot.isEmpty) {
titleTextFromFB.clear()
noteTextFromFB.clear()
imageFromFB.clear()
val documents = snapshot.documents
for (document in documents) {
val userEmail = document.get("userEmail") as String
val noteTitle = document.get("noteTitle") as String
val yourNote = document.get("yourNote") as String
val downloadUrl = document.get("downloadUrl") as String
val timestamp = document.get("date") as Timestamp
val date = timestamp.toDate()
titleTextFromFB.add(noteTitle)
imageFromFB.add(downloadUrl)
noteTextFromFB.add(yourNote)
adapter!!.notifyDataSetChanged()
}
}
}
}
}
}
fun itemDelete(data: Any) {
db.collection("Notes").document().delete().addOnSuccessListener {
}
.addOnFailureListener { exception ->
Toast.makeText(applicationContext, exception.localizedMessage.toString(), Toast.LENGTH_LONG).show()
}
}
}
此代碼將不起作用:
db.collection("Notes").document().delete().addOnSuccessListener {
db.collection("Notes").document()
調用創建對新文檔的引用,然后您將其刪除。 所以什么都不會發生。
您需要做的是確定用戶單擊的文檔的 ID,並將其傳遞到document(...)
調用中。 這為您提供了對正確文檔的DocumentReference
,以便delete()
調用將刪除該文檔。
確定用戶單擊的文檔 ID 的關鍵在於以下代碼:
adapter = NoteAdapter(titleTextFromFB, imageFromFB, noteTextFromFB, object: NoteAdapter.onClick{
override fun onItemClickListener(v: View, pos: Int, data: Any) {
when(v.id){
R.id.delete -> itemDelete(data)
}
}
})
您需要根據以下參數之一確定 ID: v
、 post
或data
。 我通常通過在我的適配器或活動中保留文檔 ID 或DocumentSnapshot
對象的列表來完成此操作,然后按其位置/索引查找單擊的項目。
因此,在您的getDataFromFirestore
函數中,將快照添加到您在活動類中定義為字段的列表中:
// in your activity, declare a list;
var mDocuments: List<DocumentSnapshot>? = null
// Then in getDataFromFirestore store that list
...
mDocuments = snapshot.documents;
val documents = snapshot.documents
for (document in documents) {
...
}
...
// And use it when calling itemDelete:
adapter = NoteAdapter(titleTextFromFB, imageFromFB, noteTextFromFB, object: NoteAdapter.onClick{
override fun onItemClickListener(v: View, pos: Int, data: Any) {
when(v.id){
R.id.delete -> itemDelete(mDocuments[pos])
}
}
})
// To then finally delete the document by its ID
fun itemDelete(doc: DocumentSnapshot) {
db.collection("Notes").document(doc.Id).delete()
}
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