一寨蹋、基本類型

image.png

定義變量：

 var a:Int=1

也可以

val a:Int=1

也可以簡寫擂涛，自動轉(zhuǎn)換

var a=1

var和val的區(qū)別是，var定義的變量可以變聊记，val定義的變量不可變撒妈，val，相當(dāng)于java的final,注意kotlin不需要以分號結(jié)尾排监。
類型間轉(zhuǎn)換

 toByte(): Byte
 toShort(): Short
 toInt(): Int
 toLong(): Long
 toFloat(): Float
 toDouble(): Double
 toChar(): Char

二狰右、控制語句

if語句

val a:Int=1
val b:Int=3
val max = if (a > b) a else b

When 表達(dá)式

  when (dataItem.type) {
        "Android" -> holder?.ivType?.setImageResource(R.mipmap.android_icon)
        "iOS" -> holder?.ivType?.setImageResource(R.mipmap.ios_icon)
        "前端" -> holder?.ivType?.setImageResource(R.mipmap.js_icon)
        "拓展資源" -> holder?.ivType?.setImageResource(R.mipmap.other_icon)
        else -> holder?.ivType?.setImageResource(R.mipmap.android_icon)
    }

For 循環(huán)
for 循環(huán)可以對任何提供迭代器（iterator）的對象進(jìn)行遍歷，語法如下:

     for (item in collection) print(item)

三社露、接口挟阻、屬性、類

類定義

 class Person(age: Int, name: String) {
   }

使用不需要new

  val person = Person(11, "張三")
 print(person.toString)

默認(rèn)下任何類都是繼承自Any( 類似 java中的Object峭弟，但是Any 不是 java.lang.Object ；尤其是脱拼，它除了 equals() 瞒瘸、 hashCode() 和 toString() 外沒有任何成員) ，但是我們可以繼承其它類熄浓。
所有的類默認(rèn)都是不可繼承的（final）情臭，所以我們只能繼承那些明確聲明open或者abstract的類：

  open class Animal(name: String)
  class Person(name: String, surname: String) : Animal(name)

Android適配器的ViewHolder類

 inner class GirlHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
    internal var ivGril: ImageView = itemView.findViewById(R.id.iv_girl)
 }

Android適配器的ViewHolder類（Kotlin代碼 不用縮寫 使用init初始化方法）

inner class HomeHolder(item: View) : RecyclerView.ViewHolder(item) {
    internal var ivType: ImageView
    internal var tvType: TextView
    internal var ivAuthor: ImageView
    internal var tvAuthor: TextView
    internal var tvTime: TextView
    internal var rlMessage: RelativeLayout
    internal var ivPart: ImageView
    internal var ivVedio: ImageView
    internal var tvItem: TextView

    init {
        ivType = itemView.findViewById<ImageView>(R.id.iv_type)
        tvType = itemView.findViewById<TextView>(R.id.tv_type)
        ivAuthor = itemView.findViewById<ImageView>(R.id.iv_author)
        tvAuthor = itemView.findViewById<TextView>(R.id.tv_author)
        tvTime = itemView.findViewById<TextView>(R.id.tv_time)
        rlMessage = itemView.findViewById<RelativeLayout>(R.id.rl_message)
        ivPart = itemView.findViewById<ImageView>(R.id.iv_part)
        ivVedio = itemView.findViewById<ImageView>(R.id.iv_vedio)
        tvItem = itemView.findViewById<TextView>(R.id.tv_item)
    }
}

函數(shù)（方法）可以使用fun關(guān)鍵字進(jìn)行定義：

 fun add(x: Int, y: Int) : Int {
   return x + y
 }

也可以

     fun add(x: Int,y: Int) : Int = x + y

接口：

     interface ItemClickListener {
          fun onItemClickListener(url:String)
    }

點(diǎn)擊回調(diào)

     girlAdapter?.setOnItemClickListener(object : GirlAdapter.ItemClickListener {
        override fun onItemClickListener(url: String) {
            val intent = Intent()
            val bun = Bundle()
            bun.putString("url", url)
            //獲取intent對象
            intent.setClass(activity, SeeBeautyActivity::class.java)
            // 獲取class是使用::反射
            intent.putExtra("extra", bun)
            startActivity(intent)
        }
    })

完整的適配器

class GirlAdapter(context: Context) : RecyclerView.Adapter<GirlHolder>() {
private var data = ArrayList<GankResults.Item>()
private var context: Context = context
private var onItemClickListener: ItemClickListener? = null
fun setOnItemClickListener(onItemClickListener: ItemClickListener) {
    this.onItemClickListener = onItemClickListener
}

fun setData(data: List<GankResults.Item>) {
    this.data.clear()
    this.data.addAll(data)
    notifyDataSetChanged()
}

fun addData(data: List<GankResults.Item>) {
    this.data.addAll(data)
    notifyDataSetChanged()
}

override fun onBindViewHolder(holder: GirlHolder?, position: Int) {
    Glide.with(context).load(data[position].url).into(holder?.ivGirl)
    holder?.itemView?.setOnClickListener {
        onItemClickListener?.onItemClickListener(data[position].url)
    }
}

override fun getItemCount(): Int = data.size

override fun onCreateViewHolder(parent: ViewGroup?, viewType: Int): GirlHolder {
    return GirlHolder(LayoutInflater.from(context).inflate(R.layout.adapter_gril, parent, false))
}

inner class GirlHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
    internal var ivGirl: ImageView = itemView.findViewById(R.id.iv_girl)
}

interface ItemClickListener {
    fun onItemClickListener(url:String)
}
}