MVP 契约模式（Kotlin）

1.创建View、Presenter和Model的基类

interface BaseModel
interface BasePresenter
interface BaseView

2.创建契约类Contract管理View、Presenter和Model的接口

interface TestContract {

    interface View : BaseView {
        fun setLoadUser(s: String)
    }

    interface Presenter : BasePresenter {
        fun loadUser()
        fun onDestroy()//必须
    }

    interface Model : BaseModel {
        fun loadUser(): String
    }

}

3.创建Model实现接口

class TestModel : TestContract.Model {

    override fun loadUser(): String {
        return "View --> Presenter --> Model --> Presenter --> View"
    }
}

4.创建Presenter控制器

class TestPresenter(private var mView: TestContract.View?, private val mModel: TestContract.Model) : TestContract.Presenter {

    override fun loadUser() {
        //2.Presenter --> Model
        val msg = mModel.loadUser()
        //3.Model返回值 --> Presenter --> View
        mView?.setLoadUser(msg)
    }

    override fun onDestroy() {
        mView = null
    }

}

注意，需要在Activity的onDestroy取消对view的持有防止内存泄漏

override fun onDestroy() {
    testPresenter.onDestroy()
    super.onDestroy()
}

5.创建View

class TestActivity : AppCompatActivity(), TestContract.View {

    private lateinit var testPresenter: TestPresenter

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_test)
        init()
    }

    private fun init() {
        testPresenter = TestPresenter(this, TestModel())

        button.setOnClickListener {
            //1.View --> Presenter
            testPresenter.loadUser()
        }
    }

    override fun setLoadUser(s: String) {
        //4.Presenter --> view
        textView.text = s
    }

    override fun onDestroy() {
        testPresenter.onDestroy()
        super.onDestroy()
    }
}