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

以下是基于 Kotlin 和 RecyclerView 实现左滑显示删除按钮和删除 item 的完整代码实现：

首先，我们需要在 app 的 build.gradle 文件中添加 RecyclerView 和 Material Design 的依赖：

dependencies {
    implementation "com.google.android.material:material:1.4.0"
    implementation "androidx.recyclerview:recyclerview:1.2.1"
}

接着，在 activity 的布局文件中添加 RecyclerView：

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

然后，我们需要定义 RecyclerView 的 Adapter 和 ViewHolder：

class MyAdapter(private val items: List<String>, private val listener: (Int) -> Unit) :
    RecyclerView.Adapter<MyAdapter.ViewHolder>() {

    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], listener)
    }

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

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

        fun bind(item: String, listener: (Int) -> Unit) {
            textView.text = item
            deleteButton.setOnClickListener { listener(adapterPosition) }
        }
    }
}

其中，ViewHolder 中有一个 deleteButton，我们将在左滑时显示它。

接下来，我们需要在 activity 中设置 RecyclerView 的 Adapter 和 ItemTouchHelper，实现左滑显示删除按钮和删除 item 的功能：

class MainActivity : AppCompatActivity() {
    private lateinit var recyclerView: RecyclerView
    private lateinit var adapter: MyAdapter
    private lateinit var items: MutableList<String>

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

        items = mutableListOf("Item 1", "Item 2", "Item 3", "Item 4", "Item 5")
        adapter = MyAdapter(items) { position ->
            items.removeAt(position)
            adapter.notifyItemRemoved(position)
        }

        recyclerView = findViewById(R.id.recyclerView)
        recyclerView.adapter = adapter

        val itemTouchHelper = ItemTouchHelper(object : ItemTouchHelper.SimpleCallback(
            0,
            ItemTouchHelper.LEFT or ItemTouchHelper.RIGHT
        ) {
            override fun onMove(
                recyclerView: RecyclerView,
                viewHolder: RecyclerView.ViewHolder,
                target: RecyclerView.ViewHolder
            ): Boolean {
                return false
            }

            override fun onSwiped(viewHolder: RecyclerView.ViewHolder, direction: Int) {
                val position = viewHolder.adapterPosition
                if (direction == ItemTouchHelper.LEFT) {
                    items.removeAt(position)
                    adapter.notifyItemRemoved(position)
                } else {
                    // do something on right swipe
                }
            }

            override fun onChildDraw(
                c: Canvas,
                recyclerView: RecyclerView,
                viewHolder: RecyclerView.ViewHolder,
                dX: Float,
                dY: Float,
                actionState: Int,
                isCurrentlyActive: Boolean
            ) {
                if (actionState == ItemTouchHelper.ACTION_STATE_SWIPE) {
                    val itemView = viewHolder.itemView
                    val deleteIcon = ContextCompat.getDrawable(
                        this@MainActivity,
                        R.drawable.ic_delete
                    )

                    val iconMargin = resources.getDimension(R.dimen.icon_margin).toInt()
                    val iconTop = itemView.top + (itemView.height - deleteIcon!!.intrinsicHeight) / 2
                    val iconBottom = iconTop + deleteIcon.intrinsicHeight

                    if (dX > 0) {
                        val iconLeft = itemView.left + iconMargin
                        val iconRight = itemView.left + iconMargin + deleteIcon.intrinsicWidth
                        deleteIcon.setBounds(iconLeft, iconTop, iconRight, iconBottom)

                        c.clipRect(itemView.left, itemView.top, itemView.left + dX.toInt(), itemView.bottom)
                        deleteIcon.draw(c)
                    } else {
                        val iconLeft = itemView.right - iconMargin - deleteIcon.intrinsicWidth
                        val iconRight = itemView.right - iconMargin
                        deleteIcon.setBounds(iconLeft, iconTop, iconRight, iconBottom)

                        c.clipRect(itemView.right + dX.toInt(), itemView.top, itemView.right, itemView.bottom)
                        deleteIcon.draw(c)
                    }
                }
                super.onChildDraw(c, recyclerView, viewHolder, dX, dY, actionState, isCurrentlyActive)
            }
        })
        itemTouchHelper.attachToRecyclerView(recyclerView)
    }
}

在 ItemTouchHelper 的 onChildDraw 方法中，我们根据滑动的方向和距离画出了删除按钮的图标，并通过 clipRect 方法限制了按钮的显示范围。

最后，我们在 res/drawable 目录下创建了一个名为 ic_delete 的图标，用于显示删除按钮。

完整代码实现请参考以下 GitHub 仓库：https://github.com/linroid/RecyclerViewSwipeToDelete