Kotlin编写RecyclerView的Adapter

kotlin在现在的Android开发中已经较为常见，空闲之余学习一下还是非常必要的，没准儿哪天就可以利用它进行些骚操作呢（梦想还是要有的）。

利用Kotlin编写一个简单的Adapter

class SimpleAdapter(private val context: Context, private val data: List<String>) : RecyclerView.Adapter<SimpleAdapter.SimpleViewHolder>() {    override fun onBindViewHolder(holder: SimpleViewHolder?, position: Int) {        holder?.textView?.text = data[position]    }    override fun getItemCount(): Int = data.size    override fun onCreateViewHolder(parent: ViewGroup?, viewType: Int): SimpleViewHolder            = SimpleViewHolder(LayoutInflater.from(context)            .inflate(R.layout.item_recycler, parent, false))    inner class SimpleViewHolder(view: View) : RecyclerView.ViewHolder(view) {        var textView: TextView = view.findViewById(R.id.item_tv)    }}

上面adapter完成了一个List集合数据的简单绑定，是不是发现相对于用Java实现同样功能代码更为精简。

在onBindViewHolder方法里面调用如下代码

holder?.textView?.setOnClickListener {            Toast.makeText(context, "click", Toast.LENGTH_SHORT).show()        }

为item中的控件设置监听器，至此一个简单的adapter编写完成。

Adapter中包含不同item类型

废话不多说直接上代码

class RecyclerAdapter(private val context: Context, private val data: List<String>)    : RecyclerView.Adapter<RecyclerView.ViewHolder>() {    private val HEADER = 0    private val NORMAL = 1    private val FOOTER = 2    override fun getItemCount(): Int = data.size    override fun onCreateViewHolder(parent: ViewGroup?, viewType: Int): RecyclerView.ViewHolder? = when (viewType) {        HEADER -> {            HeaderViewHolder(LayoutInflater.from(context).                    inflate(R.layout.item_header, parent, false))        }        FOOTER -> {            FooterViewHolder(LayoutInflater.from(context)                    .inflate(R.layout.item_footer, parent, false))        }        else -> {            RecyclerViewHolder(LayoutInflater.from(context)                    .inflate(R.layout.item_recycler, parent, false))        }    }    /**     * 利用kotlin中的when代替Java中的if/else     * 返回不同的item类型     */    override fun getItemViewType(position: Int): Int = when (position) {        0 -> {            HEADER        }        itemCount - 1 -> {            FOOTER        }        else -> {            NORMAL        }    }    /**     * 根据不同的item类型绑定不同的数据     */    override fun onBindViewHolder(holder: RecyclerView.ViewHolder?, position: Int) {        when (getItemViewType(position)) {            HEADER -> {                if (holder is HeaderViewHolder) {                    holder.tv.text = "I am Header"                    holder.tv.setOnClickListener {                        Toast.makeText(context, "I am Header", Toast.LENGTH_SHORT).show()                    }                }            }            FOOTER -> {                if (holder is FooterViewHolder) {                    holder.tv.text = "I am Footer"                }            }            else -> {                if (holder is RecyclerViewHolder) {                    holder?.textView?.text = data[position]                    holder.textView.setOnClickListener {                        Toast.makeText(context, "click", Toast.LENGTH_SHORT).show()                    }                }            }        }    }    inner class RecyclerViewHolder(view: View) : RecyclerView.ViewHolder(view) {        var textView: TextView = view.findViewById(R.id.item_tv)    }    class HeaderViewHolder(view: View) : RecyclerView.ViewHolder(view) {        var tv: TextView = view.findViewById(R.id.tv_header)    }    inner class FooterViewHolder(view: View) : RecyclerView.ViewHolder(view) {        var tv: TextView = view.findViewById(R.id.tv_footer)    }}

全文字随便来张效果图吧

如果某个item中控件的监听器我不想写在或者不能写在（更新view某些原因导致的）onBindViewHolder方法中，ViewHolder该怎么写?

inner class FooterViewHolderTwo : RecyclerView.ViewHolder {        constructor(view: View) : super(view) {            tv = view.findViewById(R.id.tv_footer)            tv.setOnClickListener {                Toast.makeText(context, "I am Footer", Toast.LENGTH_SHORT).show()            }        }        var tv: TextView    }

注意：类FooterViewHolderTwo需要访问类RecyclerAdapter的成员context，需要用 inner 声明，不然是访问不到的哟！

接口的声明与调用

interface MyInterface {        fun test(position: Int)    }var myInterface: MyInterface? = nullfun setListener(myInterface: MyInterface?) {        this.myInterface = myInterface    }

很常规的操作

至此，关于Kotlin编写RecyclerView的Adapter就已介绍完毕！