Java代码写了n多行，最近学习Kotlin语言，有点不太顺手，但最后你会发现是真的简洁。下面简单记录了一下Kotlin编写的关于RecyclerView控件的使用。
学习到什么
- Kotlin的Android语法
- Kotlin的接口回调
- RecyclerView的点击事件
- RecyclerView的分割线
Kotlin接口回调+点击事件
Adapter中的声明：
private lateinit var onItemClickListener: OnItemClickListener
fun setOnItemClickListener(listener: OnItemClickListener) {
this.onItemClickListener = listener
}
override fun onBindViewHolder(holder: ViewHolder, position: Int) {
holder.tv_item.text = data?.get(position)
holder.tv_item.setOnClickListener {
onItemClickListener?.onItemClick(holder.itemView, position)
}
holder.tv_item.setOnLongClickListener {
onItemClickListener?.onItemLongClick(holder.itemView, position)
true
}
}
interface OnItemClickListener{
fun onItemClick(view: View, position: Int)
fun onItemLongClick(view: View, position: Int)
}
Activity中的回调：
adapter?.setOnItemClickListener(object: MyAdapter.OnItemClickListener {
override fun onItemClick(view: View, position: Int) {
showToast("click " + position + " item")
}
override fun onItemLongClick(view: View, position: Int) {
showToast("long click " + position + " item")
}
})
recyclerview_click.jpg
完整代码：
MainActivity
class MainActivity: AppCompatActivity() {
private var myAdapter: MyAdapter? = null
private var myLayoutManager: LinearLayoutManager? = null
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
myLayoutManager = LinearLayoutManager(this)
myAdapter = MyAdapter(this, initData())
my_recycler_view.layoutManager = myLayoutManager
my_recycler_view.adapter = myAdapter
my_recycler_view.addItemDecoration(RecycleViewDivider(this, LinearLayoutManager.VERTICAL))
setOnClickListener()
myAdapter?.setOnItemClickListener(object: MyAdapter.OnItemClickListener {
override fun onItemClick(view: View, position: Int) {
showToast("click " + position + " item")
}
override fun onItemLongClick(view: View, position: Int) {
showToast("long click " + position + " item")
}
})
}
fun setOnClickListener(){
rv_add_item.setOnClickListener{
myAdapter?.addItem()
myLayoutManager?.scrollToPosition(0)
}
rv_delete_item.setOnClickListener{
myAdapter?.deleteItem()
}
}
private fun initData(): ArrayList<String> {
var list = ArrayList<String>()
var temp = " item"
for (i in 1..30){
list.add(i.toString() + temp)
}
return list
}
private fun showToast(message: String){
Toast.makeText(applicationContext,message, Toast.LENGTH_SHORT).show()
}
}
MyAdapter
class MyAdapter: RecyclerView.Adapter<MyAdapter.ViewHolder>{
private var context: Context
private var data: ArrayList<String>
private lateinit var onItemClickListener: OnItemClickListener
constructor(context: Context, data: ArrayList<String>) : super() {
this.context = context
this.data = data
}
fun setOnItemClickListener(listener: OnItemClickListener) {
this.onItemClickListener = listener
}
fun addItem(){
if(data == null)
data = ArrayList<String>()
data.add(0, "我是新添加的 item")
notifyDataSetChanged()
}
fun deleteItem(){
if(data == null || data.isEmpty())
return
data.removeAt(0)
notifyDataSetChanged()
}
override fun onCreateViewHolder(parent: ViewGroup?, viewType: Int): ViewHolder{
var v = LayoutInflater.from(parent?.context).inflate(R.layout.view_item, parent, false)
var viewHolder = ViewHolder(v)
return viewHolder
}
override fun getItemCount(): Int {
return data?.size
}
override fun onBindViewHolder(holder: ViewHolder, position: Int) {
holder.tv_item.text = data?.get(position)
holder.tv_item.setOnClickListener {
onItemClickListener?.onItemClick(holder.itemView, position)
}
holder.tv_item.setOnLongClickListener {
onItemClickListener?.onItemLongClick(holder.itemView, position)
true
}
}
class ViewHolder : RecyclerView.ViewHolder{
var tv_item : TextView
constructor(itemView: View) : super(itemView){
tv_item = itemView.findViewById(R.id.tv_item)
}
}
interface OnItemClickListener{
fun onItemClick(view: View, position: Int)
fun onItemLongClick(view: View, position: Int)
}
}
RecycleViewDivider
class RecycleViewDivider: RecyclerView.ItemDecoration {
private var mDivider: Drawable? = null
private var mOrientation: Int? = null
constructor(context: Context, mOrientation: Int) {
val a = context.obtainStyledAttributes(ATTRS)
mDivider = a.getDrawable(0)
a.recycle()
setOrientation(mOrientation)
}
private fun setOrientation(orientation: Int){
if(orientation != LinearLayoutManager.VERTICAL
&& orientation != LinearLayoutManager.HORIZONTAL)
throw IllegalAccessException(".....")
mOrientation = orientation
}
override fun onDraw(c: Canvas, parent: RecyclerView, state: RecyclerView.State?) {
super.onDraw(c, parent, state)
if (mOrientation == LinearLayoutManager.VERTICAL) {
drawVertical(c, parent)
} else {
drawHorizontal(c, parent)
}
}
// 获取分割线尺寸
override fun getItemOffsets(outRect: Rect, view: View, parent: RecyclerView, state: RecyclerView.State?) {
super.getItemOffsets(outRect, view, parent, state)
if(mOrientation == LinearLayoutManager.VERTICAL)
outRect.set(0,0,0,mDivider!!.intrinsicHeight)
else
outRect.set(0,0,mDivider!!.intrinsicWidth,0)
}
fun drawVertical(c: Canvas, parent: RecyclerView){
val left = parent.paddingLeft
val right = parent.width - parent.paddingRight
val childCount = parent.childCount
for (i in 0 until childCount) {
val child = parent.getChildAt(i)
val params = child
.layoutParams as RecyclerView.LayoutParams
val top = child.bottom + params.bottomMargin +
Math.round(ViewCompat.getTranslationY(child))
val bottom = top + mDivider!!.intrinsicHeight
mDivider!!.setBounds(left, top, right, bottom)
mDivider!!.draw(c)
}
}
fun drawHorizontal(c: Canvas, parent: RecyclerView){
val top = parent.paddingTop
val bottom = parent.height - parent.paddingBottom
val childCount = parent.childCount
for (i in 0 until childCount) {
val child = parent.getChildAt(i)
val params = child
.layoutParams as RecyclerView.LayoutParams
val left = child.right + params.rightMargin +
Math.round(ViewCompat.getTranslationX(child))
val right = left + mDivider!!.intrinsicHeight
mDivider!!.setBounds(left, top, right, bottom)
mDivider!!.draw(c)
}
}
companion object {
private val ATTRS = intArrayOf(android.R.attr.listDivider)
}
}
main_activity.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context="com.cmh.recyclerdmeo.MainActivity">
<TextView
android:id="@+id/rv_add_item"
android:layout_width="match_parent"
android:layout_height="80dp"
android:gravity="center"
android:clickable="true"
android:text="添加条目"
android:textSize="18dp"
android:background="#6a167fe9"/>
<TextView
android:id="@+id/rv_delete_item"
android:layout_width="match_parent"
android:layout_height="80dp"
android:gravity="center"
android:clickable="true"
android:text="删除条目"
android:textSize="18dp"
android:background="#f092f9"/>
<android.support.v7.widget.RecyclerView
android:id="@+id/my_recycler_view"
android:scrollbars="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent">
</android.support.v7.widget.RecyclerView>
</LinearLayout>
view_item.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="100dp">
<TextView
android:id="@+id/tv_item"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:gravity="center"
android:text="item"
android:textSize="20dp"/>
</LinearLayout>
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