Question

我试图将我的应用程序从Java转换为Kotlin。

我使用了Android Studio内置转换器并修复了它生成的大部分错误。

对Kotlin来说，这个给我带来了非常艰难的时刻：

我得到了这个用Java编写并被转换的类，显然没有任何错误，这有助于我管理RecyclerView中的项目点击：

class ItemClickSupport private constructor(private val mRecyclerView: RecyclerView) {
    private var mOnItemClickListener: OnItemClickListener? = null
    private var mOnItemLongClickListener: OnItemLongClickListener? = null
    private val mOnClickListener = View.OnClickListener { v ->
        if (mOnItemClickListener != null) {
            val holder = mRecyclerView.getChildViewHolder(v)
            mOnItemClickListener!!.onItemClicked(mRecyclerView, holder.adapterPosition, v)
        }
    }

    private val mOnLongClickListener = View.OnLongClickListener { v ->
        if (mOnItemLongClickListener != null) {
            val holder = mRecyclerView.getChildViewHolder(v)
            return@OnLongClickListener mOnItemLongClickListener!!.onItemLongClicked(mRecyclerView, holder.adapterPosition, v)
        }
        false
    }

    private val mAttachListener = object : RecyclerView.OnChildAttachStateChangeListener {
        override fun onChildViewAttachedToWindow(view: View) {
            if (mOnItemClickListener != null) {
                view.setOnClickListener(mOnClickListener)
            }
            if (mOnItemLongClickListener != null) {
                view.setOnLongClickListener(mOnLongClickListener)
            }
        }

        override fun onChildViewDetachedFromWindow(view: View) {

        }
    }

    init {
        mRecyclerView.setTag(R.id.item_click_support, this)
        mRecyclerView.addOnChildAttachStateChangeListener(mAttachListener)
    }

    fun setOnItemClickListener(listener: OnItemClickListener): ItemClickSupport {
        mOnItemClickListener = listener
        return this
    }

    fun setOnItemLongClickListener(listener: OnItemLongClickListener): ItemClickSupport {
        mOnItemLongClickListener = listener
        return this
    }

    private fun detach(view: RecyclerView) {
        view.removeOnChildAttachStateChangeListener(mAttachListener)
        view.setTag(R.id.item_click_support, null)
    }

    interface OnItemClickListener {

        fun onItemClicked(recyclerView: RecyclerView, position: Int, v: View)
    }

    interface OnItemLongClickListener {

        fun onItemLongClicked(recyclerView: RecyclerView, position: Int, v: View): Boolean
    }

    companion object {

        fun addTo(view: RecyclerView): ItemClickSupport {
            var support: ItemClickSupport? = view.getTag(R.id.item_click_support) as ItemClickSupport
            if (support == null) {
                support = ItemClickSupport(view)
            }
            return support
        }

        fun removeFrom(view: RecyclerView): ItemClickSupport? {
            val support = view.getTag(R.id.item_click_support) as ItemClickSupport
            support?.detach(view)
            return support
        }
    }
}

在主要活动中，转换后它在onCreate函数中设置如下：

ItemClickSupport.addTo(recyclerView!!).setOnItemClickListener { recyclerView, position, v ->
            val itemIntent = Intent(this@AddSubscription, CreateSubscription::class.java)

            ...
        }

IDE给出了以下错误：

类型不匹配：

必需：ItemClickSupport.OnItemClickListener

找到：（???，???，???） - ＆gt;单元

现在，我知道Unit是Kotlin的void，但我无法弄清楚错误的位置。

按照建议检查this answer后，我编写了以下代码：

ItemClickSupport.addTo(recyclerView!!).setOnItemClickListener(
                object: ItemClickSupport.OnItemClickListener {
                    val itemIntent = Intent(this@AddSubscription, CreateSubscription::class.java)
                    val bundle = Bundle()
                    bundle.putParcelable("selected", filteredList!![position])
                    itemIntent.putExtras(bundle)
                    startActivity(itemIntent)
        })

现在我得到了

预期成员声明

如this other answer中所述，它与构造函数有关。

这是ItemClickSupport.OnItemClickListener构造函数吗？如果是这样，我应该改变什么？

我怀疑错误仍然是由于OnClickSupport类很难转换为kotlin，即使它没有任何sintax错误

Answer 1

由于您已将这两个文件都转换为Kotlin，而OnItemClickListener界面是用Kotlin编写的，因此您无法传递函数lambda。最好的方法是创建一个匿名的界面实例（你也可以使用lambda，但我为了理解而没有使用lambda发布）

ItemClickSupport.addTo(recyclerView!!)
    .setOnItemClickListener (object:OnItemClickListener{
        override fun onItemClicked(recyclerView: RecyclerView, position: Int, v: View ){ 
            val itemIntent = Intent(this@AddSubscription, CreateSubscription::class.java)
             ... 
        }
    })

或者，您可以在ItemClickSupport中使用HighOrder函数来仅接收lambda并避免接口。

科特林 - 期待会员申报

1 个答案: