在 Kotlin 中为 RecyclerView 创建一个删除按钮

Question

这是我在 Kotlin 中的第一个应用程序，但我认为我不太理解其中的逻辑。 我正在尝试为带有 Recycler 视图的列表中的每个元素制作一个删除按钮：

我的 MusicianRecyclerAdapter：

package com.example.genremusicians

import android.content.Context
import android.content.Intent
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.TextView
import androidx.recyclerview.widget.RecyclerView
import com.example.genremusicians.Models.MusicianInfo
import kotlinx.android.synthetic.main.item_musician_list.view.*

class MusicianRecyclerAdapter (private val context: Context, private val musicians:List<MusicianInfo>) : RecyclerView.Adapter<MusicianRecyclerAdapter.ViewHolder>() {

    private val  layoutInflater = LayoutInflater.from(context)
    inner class ViewHolder(itemView: View): RecyclerView.ViewHolder(itemView){
        val deleteButton = itemView.deleteButton
        val textGenre = itemView.findViewById<TextView>(R.id.textViewTitle)
        val textMusician = itemView.findViewById<TextView>(R.id.textViewText)
        var musicianPosition = 0
        init {
            itemView.setOnClickListener{
                val intent = Intent(context,MainActivity::class.java)
                intent.putExtra(EXTRA_MUSICIAN_POSITION,musicianPosition)
                context.startActivity(intent)
            }
        }
        init {
            deleteButton.setOnClickListener{
                val intent = Intent(context,MainActivity::class.java)
                intent.removeExtra(EXTRA_MUSICIAN_POSITION)
                context.startActivity(intent)
            }
        }
    }

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

    override fun getItemCount(): Int {
        return musicians.size
    }

    override fun onBindViewHolder(holder: ViewHolder, position: Int) {
        var musician = musicians[position]
        holder.textGenre.text = musician.genre?.title
        holder.textMusician.text = musician.name
        holder.musicianPosition = position
    }
}

这是我的 MainActivity

package com.example.genremusicians

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.view.Menu
import android.view.MenuItem
import android.widget.ArrayAdapter
import com.example.genregenres.Models.DataManager
import com.example.genremusicians.Models.GenreInfo
import com.example.genremusicians.Models.MusicianInfo
import kotlinx.android.synthetic.main.activity_main.*

class MainActivity : AppCompatActivity() {
    private var musicianPosition = POSITION_NOT_SET
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        var adapterGenres = ArrayAdapter<GenreInfo>(
            this,
            android.R.layout.simple_spinner_item,
            DataManager.genres.values.toList()
        )

        adapterGenres.setDropDownViewResource(android.R.layout.simple_dropdown_item_1line)
        spinnerGenre.adapter = adapterGenres

        musicianPosition = savedInstanceState?.getInt(EXTRA_MUSICIAN_POSITION, POSITION_NOT_SET)
            ?: intent.getIntExtra(EXTRA_MUSICIAN_POSITION, POSITION_NOT_SET)


        if (musicianPosition != POSITION_NOT_SET) {
            displayMusician()
        } else {
            createMusician()
        }

    }

    private fun createMusician() {
        DataManager.musicians.add(MusicianInfo())
        musicianPosition = DataManager.musicians.lastIndex
    }

    override fun onRestart() {
        super.onRestart()
    }

    override fun onPause() {
        super.onPause()
        saveMusician()
    }

    private fun saveMusician() {
        val musician = DataManager.musicians[musicianPosition]
        musician.name = editTextName.text.toString()
        musician.album = editTextAlbum.text.toString()
        musician.genre = spinnerGenre.selectedItem as GenreInfo
    }

    override fun onStop() {
        super.onStop()
    }

    override fun onSaveInstanceState(outState: Bundle) {
        super.onSaveInstanceState(outState)
        outState.putInt(EXTRA_MUSICIAN_POSITION, musicianPosition)
    }

    private fun displayMusician() {
        val musician = DataManager.musicians[musicianPosition]
        editTextName.setText(musician.name)
        editTextAlbum.setText(musician.album)
        val genrePosition = DataManager.genres.values.indexOf(musician.genre)
        spinnerGenre.setSelection(genrePosition)
    }

    override fun onCreateOptionsMenu(menu: Menu?): Boolean {
        menuInflater.inflate(R.menu.menu_main, menu)
        return super.onCreateOptionsMenu(menu)
    }

    override fun onOptionsItemSelected(item: MenuItem): Boolean {
        when (item.itemId) {
            R.id.action_settings -> true
            R.id.action_next -> {
                MoveNext()
            }
            else -> super.onOptionsItemSelected(item)
        }
        return super.onOptionsItemSelected(item)
    }

    override fun onPrepareOptionsMenu(menu: Menu?): Boolean {
        if (musicianPosition >= DataManager.musicians.lastIndex) {
            var item = menu?.findItem(R.id.action_next)
            if (item != null) {
                item.icon = getDrawable(R.drawable.ic_baseline_block_24)
                item.isEnabled = false
            }
        }
        return super.onPrepareOptionsMenu(menu)
    }

    override fun invalidateOptionsMenu() {
        super.invalidateOptionsMenu()
    }

    private fun MoveNext() {
        musicianPosition++
        displayMusician()
        invalidateOptionsMenu()
    }
}

我从我创建的文件中获取数据以开始学习，但我不明白我在创建删除按钮时做错了什么，以及我应该如何做。 谢谢你们

Answer 1

要设置要删除的点击事件，您必须使用下面和您的适配器中的代码：

private var onClickListener : OnClickListener? = null

fun setOnClickListener(onClickListener: OnClickListener){
    this.onClickListener = onClickListener
}

interface OnClickListener {
    fun onClick(position: Int){
    }
}

然后，您可以创建一个函数来删除 recyclerview 中的项目，这将删除列表中指定位置的项目，并通知 recylerview 一个项目已被删除，以便它会更新：

private fun removeItem(position: Int){
    list.removeAt(position)
    notifyItemRemoved(position)
}

这将允许您在创建接口实例时调用 onClick 函数。 您必须在项目视图的 xml 文件中有一个删除按钮，然后您可以为 onBindViewHolder 中的按钮设置一个 onClickListener ，如下所示：

holder.itemView.btn_delete.setOnClickListener {
                if(onClickListener != null){
                    onClickListener!!.onClick(position)
                    removeItem(position)
                }
            }