activity kotlin RecyclerView 左滑显示删除按钮删除item 完整代码实现

下面是一个基于 Kotlin 和 RecyclerView 实现左滑显示删除按钮删除 item 的示例代码：

1. 在 build.gradle 文件中添加 RecyclerView 依赖：

implementation 'androidx.recyclerview:recyclerview:1.2.0'

2. 在布局文件中添加 RecyclerView：

<androidx.recyclerview.widget.RecyclerView
    android:id="@+id/recyclerView"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />

3. 创建 RecyclerView 的 adapter：

class MyAdapter(private val items: MutableList<String>) :
    RecyclerView.Adapter<MyAdapter.ViewHolder>(), ItemTouchHelperAdapter {

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
        val view = LayoutInflater.from(parent.context)
            .inflate(R.layout.item_layout, parent, false)
        return ViewHolder(view)
    }

    override fun onBindViewHolder(holder: ViewHolder, position: Int) {
        holder.bind(items[position])
    }

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

    override fun onItemMove(fromPosition: Int, toPosition: Int) {
        Collections.swap(items, fromPosition, toPosition)
        notifyItemMoved(fromPosition, toPosition)
    }

    override fun onItemDismiss(position: Int) {
        items.removeAt(position)
        notifyItemRemoved(position)
    }

    class ViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
        private val textView: TextView = itemView.findViewById(R.id.textView)
        private val deleteButton: Button = itemView.findViewById(R.id.deleteButton)
        private val itemLayout: LinearLayout = itemView.findViewById(R.id.itemLayout)

        fun bind(item: String) {
            textView.text = item
            deleteButton.setOnClickListener {
                // 删除当前项
                adapterPosition.takeIf { it != RecyclerView.NO_POSITION }?.also { position ->
                    (itemView.context as MainActivity).deleteItem(position)
                }
            }
            itemLayout.translationX = 0f
            itemLayout.setOnTouchListener(object : View.OnTouchListener {
                private var initialX = 0f
                private var lastX = 0f
                private val slop = ViewConfiguration.get(itemView.context).scaledTouchSlop
                override fun onTouch(v: View, event: MotionEvent): Boolean {
                    when (event.action) {
                        MotionEvent.ACTION_DOWN -> {
                            initialX = event.x
                            lastX = event.x
                        }
                        MotionEvent.ACTION_MOVE -> {
                            val dx = event.x - initialX
                            if (Math.abs(dx) > slop) {
                                itemLayout.translationX = dx
                            }
                            lastX = event.x
                        }
                        MotionEvent.ACTION_UP -> {
                            val dx = lastX - initialX
                            val threshold = itemLayout.width * 0.5f
                            if (Math.abs(dx) > threshold) {
                                (itemView.context as MainActivity).deleteItem(adapterPosition)
                            } else {
                                itemLayout.animate().translationX(0f).duration = 100
                            }
                        }
                    }
                    return true
                }
            })
        }
    }
}

4. 在 MainActivity 中使用 RecyclerView：

class MainActivity : AppCompatActivity() {
    private lateinit var recyclerView: RecyclerView
    private lateinit var adapter: MyAdapter
    private lateinit var touchHelper: ItemTouchHelper
    private val items = mutableListOf<String>()

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

        // 初始化 RecyclerView
        recyclerView = findViewById(R.id.recyclerView)
        recyclerView.layoutManager = LinearLayoutManager(this)
        adapter = MyAdapter(items)
        recyclerView.adapter = adapter

        // 添加测试数据
        for (i in 1..20) {
            items.add("Item $i")
        }
        adapter.notifyDataSetChanged()

        // 添加左滑删除功能
        touchHelper = ItemTouchHelper(MyItemTouchHelperCallback(adapter))
        touchHelper.attachToRecyclerView(recyclerView)
    }

    fun deleteItem(position: Int) {
        adapter.onItemDismiss(position)
    }
}

5. 创建 ItemTouchHelperAdapter 接口和 MyItemTouchHelperCallback 类：

interface ItemTouchHelperAdapter {  
    fun onItemMove(fromPosition: Int, toPosition: Int)
    fun onItemDismiss(position: Int)
}

class MyItemTouchHelperCallback(private val adapter: ItemTouchHelperAdapter) :
    ItemTouchHelper.Callback() {

    override fun isLongPressDragEnabled(): Boolean {
        return true
    }

    override fun isItemViewSwipeEnabled(): Boolean {
        return true
    }

    override fun getMovementFlags(
        recyclerView: RecyclerView,
        viewHolder: RecyclerView.ViewHolder
    ): Int {
        val dragFlags = ItemTouchHelper.UP or ItemTouchHelper.DOWN
        val swipeFlags = ItemTouchHelper.START or ItemTouchHelper.END
        return makeMovementFlags(dragFlags, swipeFlags)
    }

    override fun onMove(
        recyclerView: RecyclerView,
        viewHolder: RecyclerView.ViewHolder,
        target: RecyclerView.ViewHolder
    ): Boolean {
        adapter.onItemMove(viewHolder.adapterPosition, target.adapterPosition)
        return true
    }

    override fun onSwiped(viewHolder: RecyclerView.ViewHolder, direction: Int) {
        adapter.onItemDismiss(viewHolder.adapterPosition)
    }
}

完成以上步骤后，就可以左滑删除 RecyclerView 中的 item 了。