前言

之前写过一篇文章说的是如何用java实现mvp模式
Android MVP模式 简单入门实践
现在不是用的Kotlin比较多嘛，所以来做下用kotlin实现MVP模式的笔记
而且之前的也只是简单应用，实际开发它是存在着设计问题的，如重复代码、内存泄漏

正文

这次的mvp实现和之前用java实现的一模一样
所以一些解释就不在这里重复了
View+Contract+Presenter

MVPContract

interface MVPContract {

    interface View{
        fun onDataLoad(str: String)
    }

    interface Presenter{
        fun dataLoad()
    }
}

MVPPresenter

class MVPPresenter constructor(var mView: MVPContract.View) : MVPContract.Presenter{

    override fun dataLoad() {
        val str = "假装自己是从服务器获取到的数据"
        Thread(Runnable {
            try {
                Thread.sleep(2000)
            } catch (e: InterruptedException) {
                e.printStackTrace()
            }
        }).start()
        mView.onDataLoad(str)
    }

}

MVPActivity

class MVPActivity : AppCompatActivity(), MVPContract.View {

    private var mPresenter: MVPPresenter? = null

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_mvp)
        mPresenter = MVPPresenter(this)
        textView.setOnClickListener{ mPresenter!!.dataLoad()}
    }

    override fun onDataLoad(str: String) {
        textView.text = str
    }
}

存在问题

我们不难发现这样实现的MVP需要重复声明mPresenter、mView
而且mPresenter是一直持有对mView的引用的（在oncreat里面绑定却没有解绑）

解决方案

所以我们需要写一个baseActivity、basePresenter来避免重复声明mPresenter和mView
为了避免mPresenter导致的内存泄漏
还需要attachView()来获取view的实例在onCreat()里
和detachView()来释放view对象的引用让GC回收内存

BaseContract

attachView()和detachView()是重复的业务逻辑，所以将其放到这里

interface BaseContract {

    interface BaseView{

    }

    interface BasePresenter<in T>{
        fun attachView(view: T)
        fun detachView()
    }

}

BasePresenter

在kotlin里需要用open关键字声明该类是可继承的

open class BasePresenter<T : BaseContract.BaseView> : BaseContract.BasePresenter<T> {

    protected var mView: T? = null

    override fun attachView(view: T) {
        this.mView = view
    }

    override fun detachView() {
        this.mView = null
    }
}

BaseActivity

getLayoutId() 视图绑定
initPresenter() 初始presenter
configView() 相关view的事件

abstract class BaseActivity <in V: BaseContract.BaseView,P :BaseContract.BasePresenter<V>> : AppCompatActivity(){

    protected var mPresenter: P? = null

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        mPresenter = initPresenter()
        mPresenter!!.attachView(this as V)
        setContentView(getLayoutId())
        configView()
    }

    override fun onDestroy() {
        super.onDestroy()
        mPresenter!!.detachView()
    }

    protected abstract fun getLayoutId(): Int
    protected abstract fun initPresenter(): P
    protected abstract fun configView()
}

MainContract

需要注意的是Presenter绑定的view为该契约类生声明的view

interface MainContract {

    interface View: BaseContract.BaseView{
        fun onLoadData(str: String)
    }

    interface Presenter : BaseContract.BasePresenter<View>{
        fun loadData()
    }
}

MainPresenter

class MainPresenter : BasePresenter<MainContract.View>(),MainContract.Presenter{

    override fun loadData() {
        val str = "假装自己是从服务器获取到的数据"
        Thread(Runnable {
            try {
                Thread.sleep(2000)
            } catch (e: InterruptedException) {
                e.printStackTrace()
            }
        }).start()
        mView!!.onLoadData(str)
    }

}

MainActivity

class MainActivity : BaseActivity<MainContract.View,MainContract.Presenter>(),MainContract.View {


    override fun getLayoutId(): Int = R.layout.activity_main

    override fun initPresenter(): MainContract.Presenter = MainPresenter()

    override fun configView() {
        text.setOnClickListener{ mPresenter!!.loadData() }
    }

    override fun onLoadData(str: String) {
        text.text = str
    }
}

结语

以上就是用kotlin实现的mvp模式及基类的简单封装，谢谢观看