如何使用在函数内部声明的 onBindViewHolder 外部变量？

Question

我正在 kotlin 中创建一个基本的 ToDo 列表应用程序，并将其数据存储在 SQLiteDatabase 中。我正在尝试添加滑动以删除功能。该功能有效，但我无法将任务的 ID 传递给删除功能。我可以在上面的 onCreate 类中使用 DisplayAdapter 中的 list[p1].id 吗？

显示适配器：

class DashboardAdapter(private val activity: dashboard, var list: MutableList<ToDo>) :
        RecyclerView.Adapter<DashboardAdapter.ViewHolder>(){


        override fun onCreateViewHolder(p0: ViewGroup, p1: Int): ViewHolder {
            return ViewHolder(LayoutInflater.from(activity).inflate(R.layout.rv_child_layout,p0,false))

        }
        override fun onBindViewHolder(holder: ViewHolder, p1: Int) {
            holder.toDoName.text = list[p1].name
            holder.toDoName.setOnClickListener{
                val id_long = list[p1].id
                val intent = Intent(activity,subtask_list::class.java)
                intent.putExtra(INTENT_TODO_ID,id_long)
                intent.putExtra(INTENT_TODO_NAME,list[p1].name)
                activity.startActivity(intent)
            }

        }

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


        fun removeItem(todoId: Long) {
            val db = DBHandler(null).db
            db.delete(TABLE_TODO_ITEM,"$COL_TODO_ID=?", arrayOf(todoId.toString()))
            db.delete(TABLE_TODO,"$COL_ID=?", arrayOf(todoId.toString()))
        }

        class ViewHolder(v : View) : RecyclerView.ViewHolder(v){
            val toDoName : TextView = v.findViewById(R.id.tv_todo_name)
        }

    }

removeItem 是需要 list.id 的删除功能

调用 removeItem 函数：

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

            override fun onSwiped(viewHolder: RecyclerView.ViewHolder, position: Int) {
                DashboardAdapter(dashboard(),dataset).removeItem(list[p1].id)
            }

        }
        val itemTouchHelper = ItemTouchHelper(itemTouchHelperCallback)
        itemTouchHelper.attachToRecyclerView(rv_dashboard)

我尝试过声明但不明白如何初始化以下内容：

private var dataset= mutableListOf<ToDo>()

    lateinit var list: MutableList<ToDo>

我在 displayAdapter 之外还有一个 refreshList 函数，用于在更新后刷新 ToDo 列表：

private fun refreshList(){
        rv_dashboard.adapter  = DashboardAdapter(this,dbHandler.getToDo())
    }

如何初始化列表变量或从显示适配器获取列表[p1].id？

Answer 1

有很多方法可以解决这个问题。我建议您不要在您的适配器中执行您的数据库和导航逻辑，而是为项目单击实现一个侦听器并在片段/活动中编写您的数据库逻辑（最好在您的 ViewModel 中有逻辑）。我已经重构了你的代码。

适配器：

class DashboardAdapter(
    private var list: MutableList<ToDo>,
    private val itemClickListener: (Long) -> Unit,
) : RecyclerView.Adapter<DashboardAdapter.ViewHolder>() {

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
        return ViewHolder.create(parent, itemClickListener)
    }

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

    override fun getItemCount() = list.size

    fun refreshList(list: List<Todo>) {
        this.list = list
        notifyDataSetChanged()
    }

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

    class ViewHolder private constructor(
        v: View,
        private val itemClickListener: (Long) -> Unit,
    ) : RecyclerView.ViewHolder(v) {
        private val toDoName: TextView = v.findViewById(R.id.tv_todo_name)

        fun bind(todo: ToDo) {
            toDoName.text = todo.name
            toDoName.setOnClickListener {
                itemClickListener.invoke(todo.id)
            }
        }

        companion object {
            fun create(parent: ViewGroup, itemClickListener: (Long) -> Unit): ViewHolder {
                val view = LayoutInflater.from(parent.context).inflate(R.layout.rv_child_layout, parent, false)
                return ViewHolder(view, itemClickListener)
            }
        }
    }
}

片段/活动：

private lateinit var listAdapter: DashboardAdapter

fun setupRecyclerView() {
    ...

    listAdapter = DashboardAdapter(list) { id: Long ->
        // Navigate to sub list task activity
    }

    rv_dashboard.adapter = listAdapter

    val swipeCallback = object : ItemTouchHelper.SimpleCallback(0, ItemTouchHelper.LEFT) {
        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

            //Get id from list and delete from database

            listAdapter.removeItemAt(position)
        }
    }

    val itemTouchHelper = ItemTouchHelper(swipeCallback)
    itemTouchHelper.attachToRecyclerView(rv_dashboard)
}

要刷新您的列表，请调用适配器中的 refreshList 函数：

listAdapter.refreshList(list)