如何将项目添加到回收视图中 Kotlin

Question

package com.example.mytodolist

import android.content.Intent
import android.os.Bundle
import android.util.Log
import android.view.View
import android.widget.Button
import android.widget.EditText
import androidx.appcompat.app.AppCompatActivity
import androidx.fragment.app.FragmentActivity
import androidx.recyclerview.widget.LinearLayoutManager
import androidx.recyclerview.widget.RecyclerView
import com.google.android.gms.tasks.OnCompleteListener
import com.google.firebase.firestore.FirebaseFirestore
import com.google.firebase.firestore.QuerySnapshot


class MainActivity : AppCompatActivity() {

    lateinit var storeTextView: EditText
    lateinit var itemTextView: EditText
    lateinit var buttonSave: Button

    lateinit var recyclerView: RecyclerView

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        val db = FirebaseFirestore.getInstance()

        val shoppingItems = mutableListOf<Item>()

        db.collection("items")
            .addSnapshotListener { snapshot, e ->
                if (snapshot != null) {
                    shoppingItems.clear()
                    for (document in snapshot.documents) {
                        val newItem = document.toObject(Item::class.java)
                        if (newItem != null) {
                            newItem.id = document.id
                            shoppingItems.add(newItem)
                        }
                    }
                    recyclerView.adapter?.notifyDataSetChanged()
                } else {
                    Log.w(
                        "hej",
                        "Error getting documents."
                    )
                }
            }



        recyclerView = findViewById<RecyclerView>(R.id.studentList)
        recyclerView.layoutManager = LinearLayoutManager(this)
        recyclerView.adapter = ItemRecyclerAdapter(this, shoppingItems)

        val fab = findViewById<View>(R.id.floatingActionButton)
        fab.setOnClickListener { view ->
            val intent = Intent(this, ChooseItem::class.java)
            startActivity(intent)

        }

    }

    override fun onResume() {
        super.onResume()
        recyclerView.adapter?.notifyDataSetChanged()
    }


}

适配器

package com.example.mytodolist

import android.content.Context
import android.content.Intent
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.ImageButton
import android.widget.TextView
import androidx.recyclerview.widget.RecyclerView
import com.google.android.material.snackbar.Snackbar
import com.google.firebase.firestore.FirebaseFirestore

class ItemRecyclerAdapter(private val context: Context, private val items: List<Item>) :
    RecyclerView.Adapter<ItemRecyclerAdapter.ViewHolder>() {
    private val layoutInflator = LayoutInflater.from(context)


    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
        val itemView = layoutInflator.inflate(R.layout.student_list_view, parent, false)
        return ViewHolder(itemView)
    }

    override fun getItemCount() = items.size

    override fun onBindViewHolder(holder: ViewHolder, position: Int) {
        val getItem = items[position]
        holder.itemName.text = getItem.store
        holder.textstoreName.text = getItem.item
        holder.itemPosition = position

    }

    fun removeItem(position: Int) {

        val db = FirebaseFirestore.getInstance()

        val item = items[position]
        val docId = item.id
        if(docId != null){
            db.collection("items").document(docId).delete()
        }
    }

    inner class ViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
        val itemName = itemView.findViewById<TextView>(R.id.item_name)
        val textstoreName = itemView.findViewById<TextView>(R.id.text_storeName)
        val delete = itemView.findViewById<ImageButton>(R.id.delete)
        var itemPosition = 0

        init {

            // Denna gör så att om du klickar på på en recyclerview field kommer du till en annan.

            itemView.setOnClickListener {
                val intent = Intent(context, ChooseItem::class.java)
                context.startActivity(intent)

            }
            delete.setOnClickListener { view ->
                removeItem(itemPosition)
                Snackbar.make(view, "Item Removed", Snackbar.LENGTH_SHORT).show()
            }

        }
    }
}

数据结构

package com.example.mytodolist

data class Item(var store : String? = null,
                var item : String? = null,
                var id : String? = null
)

选择项目

package com.example.mytodolist

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.widget.Button
import android.widget.EditText
import com.google.firebase.firestore.FirebaseFirestore
import kotlinx.android.synthetic.main.activity_choose_item.*

class ChooseItem : AppCompatActivity() {

    lateinit var  storeTextView : EditText
    lateinit var itemTextView : EditText



    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_choose_item)

        storeTextView = findViewById(R.id.edit_store)
        itemTextView = findViewById(R.id.edit_item)

        val saveButton = findViewById<Button>(R.id.save_to_list)

        save_to_list.setOnClickListener { view ->
            addNewItem()
        }

    }
    private fun addNewItem() {

        val db = FirebaseFirestore.getInstance()


        val getStore = storeTextView.text.toString()
        val insertItem = itemTextView.text.toString()

        val item = Item(getStore, insertItem)
        db.collection("items").add(item)
        DataManager.items.add(item)
        finish()
    }

}

xml文件

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="wrap_content">

    <TextView
        android:id="@+id/item_name"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="20dp"
        android:layout_marginTop="16dp"
        android:layout_marginBottom="16dp"
        android:text="TextView"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.0" />

    <TextView
        android:id="@+id/text_storeName"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginTop="16dp"
        android:layout_marginEnd="59dp"
        android:text="TextView"
        app:layout_constraintEnd_toStartOf="@+id/delete"
        app:layout_constraintTop_toTopOf="parent" />

    <ImageButton
        android:id="@+id/delete"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="4dp"
        android:layout_marginEnd="20dp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:srcCompat="@drawable/ic_delete" />
</androidx.constraintlayout.widget.ConstraintLayout>

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* 我已经用Kotlin创建了一个recyclerview，你可以添加一个项目，然后按ADD按钮，这些项目就会被添加到recyclerview:n中。但我曾试过在同一回收视图中使用clicklistener来添加更多的项目，但我没有找到任何好的解决方案欧互联网？

怎么可能让它工作呢？*

Answer 1

在你的适配器类中写一个方法。

   public fun updateItems(var newItems: List<Item>){
      this.items.clear()
      this.item.addAll(newItems)
   }

在你的适配器类中写一个方法：然后在你的 MainActivity onResume 方法，从数据库中获取最新的项目，然后调用你的适配器类方法来更新RecyclerView中的项目，就像这样。

recyclerView.adapter?.updateItems(newItems) / 传递从数据库中获取的新项目。

override fun onResume() {
        super.onResume()
        // Fetch newItems from database
        recyclerView.adapter?.updateItems(newItems)
        recyclerView.adapter?.notifyDataSetChanged()
    }