Kotlin学习笔记——RecyclerView

#define 小毛驴 xml

布局管理器

LinearLayoutManager

类似于线性布局

构造
(Context context)
(Context context,int orientation,boolean reverseLayout)
(Context context, AttributeSet attrs, int defStyleAttr,int defStyleRes)

参数	解释
Context context	上下文，初始化时，构造方法内部加载资源用
int orientation	方向，垂直和水平，默认为垂直
boolean reverseLayout	是否倒序，设置为True，从最后一个item开始，倒序加载。此时，RecyclerView第一个item是添加进Adapter中的最后一个，最后一个item是第一个加进Adapter的数据,RecyclerView会自动滑到末尾

参考英勇青铜5

GridLayoutManager

类似GridView

构造	解释
(Context context, int spanCount)	spanCount为列数
(Context context, int spanCount, int orientation,boolean reverseLayout)	orientation在GridLayoutManager中有静态常量

StaggeredGridLayoutManager

瀑布流

构造	解释
(int spanCount, int orientation)	显然法

使用方法

1. 写一个基础适配器

//abstract抽象类作为基类
abstract class RecyclerBaseAdapter<VH: RecyclerView.ViewHolder>(val context:Context)
    : RecyclerView.Adapter<RecyclerView.ViewHolder>(), AdapterView.OnItemClickListener, AdapterView.OnItemLongClickListener {
    //与小毛驴文件绑定
    val inflater:LayoutInflater = LayoutInflater.from(context)

    override abstract fun getItemCount(): Int

    override abstract fun onCreateViewHolder(p0: ViewGroup, p1: Int): RecyclerView.ViewHolder

    override fun getItemViewType(position: Int): Int = 0

    override fun getItemId(position: Int): Long = position.toLong()

    var itemClickListener:AdapterView.OnItemClickListener? = null
    fun setOnItemClickListener(listener:AdapterView.OnItemClickListener) {
        this.itemClickListener = listener
    }

    var itemLongClickListener: AdapterView.OnItemLongClickListener? = null
    fun setOnItemLongClickLostenner(listener: AdapterView.OnItemLongClickListener) {
        this.itemLongClickListener = listener
    }

    override fun onItemClick(parent: AdapterView<*>?, view: View?, position: Int, id: Long) {

    }

    override fun onItemLongClick(parent: AdapterView<*>?, view: View?, position: Int, id: Long): Boolean {
        return true
    }
}

2. 设计好item的小毛驴文件，写好传送数据的类
3. 完成业务逻辑的适配器

class RecyclerGridAdapter(context:Context, private val infos:MutableList<RecyclerInfo>) :
        RecyclerBaseAdapter<RecyclerView.ViewHolder>(context) {
        //继承刚才的基础类
    override fun getItemCount(): Int = infos.size

    override fun onCreateViewHolder(p0: ViewGroup, p1: Int): RecyclerView.ViewHolder {
        val view: View = inflater.inflate(R.layout.layout ,p0, false)
        return ItemHoder(view)
    }

    override fun onBindViewHolder(p0: RecyclerView.ViewHolder, p1: Int) {
        val vh = p0 as ItemHoder
        vh.pic.setImageResource(infos[p1].pic)
        vh.text.text = infos[p1].text
    }

    inner class ItemHoder(view:View): RecyclerView.ViewHolder(view) {
        val ll = view.findViewById<ConstraintLayout>(R.id.ll)
        var pic = view.findViewById<ImageView>(R.id.pic)
        var text = view.findViewById<TextView>(R.id.text)
    }

}

4. 为RecyclerView添加布局管理器和适配器

class MainActivity : AppCompatActivity() {
    var l:RecyclerView? = null
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        var data:MutableList<RecyclerInfo> = mutableListOf()
        //省略为data赋值的代码
        l  = findViewById(R.id.l)
        l?.layoutManager = LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false)
        val adapter = RecyclerGridAdapter(this, data)
        adapter.setOnItemClickListener(adapter)
        adapter.setOnItemLongClickLostenner(adapter)

        l?.adapter = adapter
        l?.itemAnimator = DefaultItemAnimator()
        l?.addItemDecoration(SpacesItemDecoration(30))
    }

    override fun onCreateOptionsMenu(menu: Menu?): Boolean {
        menu?.add("LinearLayoutManager(线性)")
        menu?.add("GridLayoutManager(网格)")
        menu?.add("StaggeredGridLayoutManager(瀑布流)")
        return super.onCreateOptionsMenu(menu)
    }

    override fun onOptionsItemSelected(item: MenuItem?): Boolean {
        if (item != null) {//菜单中选择各种布局
            when(item.title) {
                "LinearLayoutManager(线性)" -> l?.layoutManager = LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false)
                "GridLayoutManager(网格)" -> l?.layoutManager = GridLayoutManager(this, 2)
                "StaggeredGridLayoutManager(瀑布流)" -> l?.layoutManager = StaggeredGridLayoutManager(2, StaggeredGridLayoutManager.VERTICAL)
                else -> toast("error")
            }
        }
        return super.onOptionsItemSelected(item)
    }
}