Kotlin多方法回调简化（Lambda表达式，recyclerView回调）

2024-02-19 10:55:28

kotlin（RecyclerView）多方法回调，单方法回调利用Lambda表达式进行简化

用喜欢的RecyclerView作为例子，来记录一下kotlin中多回调和单回调的简化，kotlin确实是一个比较有趣的语言。

当然，也可以利用java风格去写，不过代码会略显臃肿，也体现不出kotlin的独特之处。下面就记录一下这个时刻。

一、单方法回调

不需要定义接口，只定义一个函数变量
```
lateinit var mListener: (String) -> Unit
```
这是一个入参为一个String类型参数，无返回值的函数变量
adapter设置回调监听
```
 fun setListener(listener: (String) -> Unit) {
        this.mListener = listener
 }
```
参数就是上面所定义的一个参数，无返回值的函数变量

二、多方法回调

需要先定义一个接口

    /**
     * 定义一个回调接口
     */
    interface SimpleCallback {
        fun onSuccess(response: String)
        fun onFailed(errorCode: Int, msg: String)
    }

两个方法，成功返回response，失败返回errorCode和msg

按照惯例，定义一个builder


    /**
     * 定义个Builder,简化回调接口
     */
    class Builder : SimpleCallback {

        // 定义一个函数变量
        private lateinit var onSuccessVal: (response: String) -> Unit

        // 给函数变量赋值
        fun onSuccessFun(listener: (response: String) -> Unit) {
            this.onSuccessVal = listener
        }

        // 回调方法
        override fun onSuccess(response: String) {
            onSuccessVal.invoke(response)
        }

        //  定义一个函数变量
        private lateinit var onFailedVal: (errorCode: Int, msg: String) -> Unit

        // 给函数变量赋值
        fun onFailedFun(listener: (errorCode: Int, msg: String) -> Unit) {
            this.onFailedVal = listener
        }

        // 回调方法
        override fun onFailed(errorCode: Int, msg: String) {
            onFailedVal.invoke(errorCode, msg)
        }
    }

定义回调接口的函数变量

    private lateinit var listener: SimpleCallback

设置回调监听

    fun setSimpleListener(listener: Builder.() -> Unit) {
        val builder = Builder()
        builder.listener()
        this.listener = builder
    }

在adapter中定义点击方法，进行回调

    override fun onBindViewHolder(holder: ViewHolder, position: Int) {
        holder.content.text = list[position]
        // 这是单一回调函数的点击监听方法
        holder.content.setOnClickListener { this.mListener(holder.content.text as String) }
        // 这是多回调方法的点击监听方法
        holder.content.setOnClickListener {
            this.listener.onSuccess(holder.content.text as String)
            this.listener.onFailed(1, holder.content.text as String)
        }
    }

最后贴出Adapter和Activity的代码

Adapter代码

class MyRecyclerViewAdapter : RecyclerView.Adapter<MyRecyclerViewAdapter.ViewHolder>() {

    private var list: List<String> = listOf()

    override fun onCreateViewHolder(viewGroup: ViewGroup, viewType: Int): ViewHolder {

        val view: View = View.inflate(viewGroup.context, R.layout.item_recyclerview, null)
        return ViewHolder(view)
    }

    override fun getItemCount(): Int {
        return list.size
    }

    override fun onBindViewHolder(holder: ViewHolder, position: Int) {
        holder.content.text = list[position]
        // 这是单一回调函数的点击监听方法
        holder.content.setOnClickListener { this.mListener(holder.content.text as String) }
        holder.content.setOnClickListener {
            this.listener.onSuccess(holder.content.text as String)
            this.listener.onFailed(1, holder.content.text as String)
        }
    }

    class ViewHolder(view: View) : RecyclerView.ViewHolder(view) {
        val content: TextView = view.findViewById(R.id.tv_con)
    }


    fun setData(list: List<String>) {
        this.list = list
        notifyDataSetChanged()
    }



    //这是单一函数回调

    lateinit var mListener: (String) -> Unit

    fun setListener(listener: (String) -> Unit) {
        this.mListener = listener
    }


    private lateinit var listener: SimpleCallback

    fun setSimpleListener(listener: Builder.() -> Unit) {
        val builder = Builder()
        builder.listener()
        this.listener = builder
    }


    /**
     * 定义一个回调接口
     */
    interface SimpleCallback {
        fun onSuccess(response: String)
        fun onFailed(errorCode: Int, msg: String)
    }


    /**
     * 定义个Builder,简化回调接口
     */
    class Builder : SimpleCallback {

        // 定义一个函数变量
        private lateinit var onSuccessVal: (response: String) -> Unit

        // 给函数变量赋值
        fun onSuccessFun(listener: (response: String) -> Unit) {
            this.onSuccessVal = listener
        }

        // 回调方法
        override fun onSuccess(response: String) {
            onSuccessVal.invoke(response)
        }

        //  定义一个函数变量
        private lateinit var onFailedVal: (errorCode: Int, msg: String) -> Unit

        // 给函数变量赋值
        fun onFailedFun(listener: (errorCode: Int, msg: String) -> Unit) {
            this.onFailedVal = listener
        }

        // 回调方法
        override fun onFailed(errorCode: Int, msg: String) {
            onFailedVal.invoke(errorCode, msg)
        }
    }


}

Activity代码

package com.schema.kotlin_study

import android.content.Context
import android.support.v7.app.AppCompatActivity
import android.os.Bundle
import android.support.v7.widget.LinearLayoutManager
import android.support.v7.widget.RecyclerView
import android.util.Log
import android.view.View
import android.widget.Toast
import java.util.concurrent.Executors

class MainActivity : AppCompatActivity(), View.OnClickListener {

    var rvTest: RecyclerView? = null
    var myRecyclerViewAdapter: MyRecyclerViewAdapter? = null
    var list: MutableList<String> = ArrayList()

    override fun onClick(v: View?) {
        when (v?.id) {
            R.id.btn_add -> addData()
            R.id.btn_remove -> removeData()
        }
    }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        rvTest = findViewById(R.id.rv_test)

        initView()
        initData()

    }

    private fun initView() {

        myRecyclerViewAdapter = MyRecyclerViewAdapter()
        rvTest?.adapter = myRecyclerViewAdapter
        rvTest?.layoutManager = LinearLayoutManager(this)

        for (i in 0..10) {
            list.add(i.toString())
        }
        // 单函数回调设置
        //myRecyclerViewAdapter?.setListener { Toast.makeText(this, it, Toast.LENGTH_SHORT).show() }
        // 多函数回调设置， 在这个地方，可以实现一个方法，也可以都实现
        myRecyclerViewAdapter?.setSimpleListener {
            onSuccessFun {
                it.toast(this@MainActivity)
                it.loge()
              }

            onFailedFun { errorCode, msg ->
                (errorCode.toString(10) + msg).toast(this@MainActivity)
                (errorCode.toString(10) + msg).loge()
            }
        }

        /**  这里就是只实现一个方法
        myRecyclerViewAdapter?.setSimpleListener {
            onSuccessFun {
                it.toast(this@MainActivity)
                it.loge()
              }
        }*/
    }

    private fun initData() {
        myRecyclerViewAdapter?.setData(list)
    }


    private fun Any.toast(context: Context, duration: Int = Toast.LENGTH_SHORT): Toast {
        return Toast.makeText(context, this.toString(), duration).apply { show() }
    }

    private fun Any.loge(TAG: String = this@MainActivity.localClassName) {
        Log.e(TAG, this.toString())
    }

}

最后贴出两个工具类，也是扩展函数，打印log和显示toast。各位可以作为一个顶层函数去使用，把private去掉。

    private fun Any.toast(context: Context, duration: Int = Toast.LENGTH_SHORT): Toast {
        return Toast.makeText(context, this.toString(), duration).apply { show() }
    }

    private fun Any.loge(TAG: String = this@MainActivity.localClassName) {
        Log.e(TAG, this.toString())
    }

码农公寓

kotlin（RecyclerView）多方法回调，单方法回调利用Lambda表达式进行简化

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