Kotlin中ListView与RecyclerView的应用讲解

写下来自己以后看：
先是item的布局文件：
里边放了一个图片和一个文本框

ListView：
布局文件：

适配器：

class FruitAdapter(private val context: Context, private val list : List) : BaseAdapter() {

    override fun getCount(): Int = list.size

    override fun getItem(position: Int): Any = list[position]

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

    override fun getView(position: Int, convertView: View?, parent: ViewGroup?): View? {
        var convertView = convertView
        var holder : ViewHolder? = null
        if (convertView == null){
            holder = ViewHolder()
            convertView = View.inflate(context,R.layout.item_list_view,null)
            holder.textView = convertView.findViewById(R.id.textView) as TextView
            holder.imageView = convertView.findViewById(R.id.imageView) as ImageView
            holder.linearLayout = convertView.findViewById(R.id.linearLayout) as LinearLayout
            convertView.tag = holder
        }else{
            holder = convertView.tag as ViewHolder
        }
        holder.textView!!.text = list[position].name
        holder.imageView!!.setImageResource(list[position].image)
        holder.linearLayout!!.setOnClickListener {
            Toast.makeText(context,list[position].name,Toast.LENGTH_SHORT).show()
        }
        return convertView
    }

    internal class ViewHolder{
        var textView : TextView? = null
        var imageView : ImageView? = null
        var linearLayout : LinearLayout? = null
    }
}

剩下的就是逻辑处理：

class ListViewActivity : AppCompatActivity() {

    private val bean = ArrayList()

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_list_view)
        for (i in 1..100){
            bean.add(Fruit(i.toString(),R.drawable.ic_launcher_foreground))
        }
        val adapter = FruitAdapter(this,bean)
        listView.adapter = adapter
    }
}

RecyclerView：
布局文件：

适配器：

class FruitRecyclerViewAdapter(private val context: Context,private val list: List) : RecyclerView.Adapter() {

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
        val view : View = LayoutInflater.from(context).inflate(R.layout.item_list_view,null)
        return ViewHolder(view)
    }

    override fun onBindViewHolder(holder: ViewHolder, position: Int) {
        holder.itemView.textView.text = list[position].name
        holder.itemView.imageView.setImageResource(list[position].image)
        holder.itemView.linearLayout.setOnClickListener {
            Toast.makeText(context,list[position].name,Toast.LENGTH_SHORT).show()
        }
    }

    override fun getItemCount(): Int = list.size

    class ViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
        private val textView : TextView = itemView.findViewById(R.id.textView)
        private val imageView : ImageView = itemView.findViewById(R.id.imageView)
        private val linearLayout : LinearLayout = itemView.findViewById(R.id.linearLayout)
    }
}

逻辑代码：

class RecyclerViewActivity : AppCompatActivity() {

    private val bean = ArrayList()

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_recycler_view)
        repeat(3){
            for (i in 1..15){
                bean.add(Fruit(i.toString(),R.drawable.ic_launcher_foreground))
            }
        }
        val layoutManger = LinearLayoutManager(this)
        //layoutManger.orientation = LinearLayoutManager.HORIZONTAL
        recyclerView.layoutManager = layoutManger
        val adapter = FruitRecyclerViewAdapter(this,bean)
        recyclerView.adapter = adapter
    }
}

这里的repeat函数是重复三次，意思就是会有三个1到15，也就是此recyclerView会有45个item.
现在的是纵向滑动的，如果要改成横向的，就把我代码中的注释掉的
//layoutManger.orientation = LinearLayoutManager.HORIZONTAL
取消注释就可以实现横向滑动了，如果不嫌弃难看，布局文件就不用改。
最后是实体类：

class Fruit(val name : String,val image : Int) {
}

定义了一个name用来显示名字，定义了一个image，用来显示图片。

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