Android 使用kotlin+注解+反射+泛型实现MVP架构

一，MVP模式的定义

①Model：用于存储数据。它负责处理领域逻辑以及与数据库或网络层的通信。

②View：UI层，提供数据可视化界面，并跟踪用户的操作，以便通知presenter。

③Presenter：从Model层获取数据，并且应用UI逻辑来决定显示什么。它管理View的状态，并且根据来自于View的用户的输入执行动作。

实现mvp模式的核心点就是将view层和presenter绑定，将view层和model层解耦

二，代码实现

首先，我们先三个基本的接口：

/**
*View层接口
*/
interface IView {fun getContext(): Context?fun getRootViews(): View?fun <T : View?> getView(id: Int): Tfun getActivity(): Activity?fun getFragment(): Fragment?
}

/*** module层接口* */
interface IModule {
}

/*** Presenter层接口* */
interface IPresenter {fun onCreate(savedInstanceState: Bundle?, mContext: Context?)fun onResume()fun onStart()fun onRestart()fun onPause()fun onStop()fun onDestroy()fun onSaveInstanceState(outState: Bundle)fun onRestoreInstanceState(savedInstanceState :Bundle)fun onActivityResult( requestCode :Int, resultCode :Int, data : Intent)}

View层主要是获取Activity，布局文件等操作

Presenter层主要是控制Activity生命周期等

Module层就是用户根据自己的业务逻辑具体的自己去定义

接下来我们就利用反射+注解，在系统启动activity的时候，自动的生成相应的presenter实例，这样就不用手动去绑定view和presenter了

创建一个注解：

@Retention(AnnotationRetention.RUNTIME)
annotation class Request(val value:KClass<*>)

在运行时生效，传入kotlin的Class实例KClass

采用工厂模式来生产presenter

先创建一个工厂模式的接口：

interface IPresenterFactory<P> {/*** 创建presenter* */fun createPresenter():P
}

因为我的Presenter需要等到运行的时候才会知道是哪个，所以使用泛型P代表

创建具体的Presenter工厂类，在静态方法findClass中，通过传入的Activity获得Activity的注解，并通过注解获得相应的presenter的Class

在createPresenter方法中，通过presenter的Class反射生成presenter对象

class PresenterFactory<P>() :IPresenterFactory<P>{private var presenterKClass :KClass<*> ?=nullconstructor(presenterKClass :KClass<*>): this(){this.presenterKClass =presenterKClass}companion object{fun <P> findClass(viewClass:Class<*>) : PresenterFactory<P>{val annotation = viewClass.getAnnotation(Request::class.java)val value:KClass<*> =annotation.valuereturn PresenterFactory(value)}}override fun createPresenter(): P {return presenterKClass?.java!!.newInstance() as P}}

创建一个BasePresenter，实现IPresenter接口，将具体的View层的实例传过来。因为不知道具体的View是哪一个，所以使用泛型T表示

abstract class BasePresenter<T> :IPresenter{protected var mView: @UnsafeVariance T? = nullfun attachViewCompont(view: T) {mView = view}fun detechViewCompont() {mView = null}abstract fun setListeners()
}

为了实现设计模式的单一性原则，我们增加一个工厂类的代理类，来控制presenter的创建，已及view的绑定等操作：

class PresenterDelegate<P,V>() where P:BasePresenter<V>,V:IView {private var presenterFactory :IPresenterFactory<P>?=nullprivate var presenter :P ?=nullconstructor(presenterFactory :IPresenterFactory<P>):this(){this.presenterFactory =presenterFactory}open fun getPresenter():P{if(presenter!=null){return presenter!!}if (presenterFactory != null) {if (presenter == null) {presenter = presenterFactory?.createPresenter()}}return presenter!!}open fun setPresenter(presenter: P) {this.presenter = presenter}open fun bindViewCompont(view: IView) {if (presenter == null) {getPresenter()}if (presenter != null) {presenter!!.attachViewCompont(view as V)}}open fun unbindViewCompont() {if (presenter != null) {presenter!!.detechViewCompont()}}}

创建一个BaseActivity，继承AppCompatActivity实现IView接口，在BaseActivity中，通过创建工厂类的装饰类，创建具体的P层，并将P层和View层绑定

abstract class BaseActivity<P,V> :AppCompatActivity(),IView where P:BasePresenter<V>,V:IView{private var presenterDelegate = PresenterDelegate<P,V>(PresenterFactory.findClass(javaClass))protected val mViews = SparseArray<View>()protected var rootView: View? = nullprotected var mDecorView: View? = nullopen fun <T : View?> bindView(id: Int): T? {var view: T? = mViews[id] as Tif (view == null) {view = rootView?.findViewById(id)mViews.put(id, view)}return view}override fun getContext(): Context? {return this}override fun getRootViews(): View? {return rootView}override fun <T : View?> getView(id: Int): T {return bindView<View>(id) as T}override fun onCreate(savedInstanceState: Bundle?) {super.onCreate(savedInstanceState)presenterDelegate.bindViewCompont(this)rootView = layoutInflater.inflate(getLayoutId(), null, false)setContentView(rootView)initFields()bindEventListener()getPresenter().onCreate(savedInstanceState,this)getPresenter().setListeners()mDecorView = window.decorView}override fun onStart() {super.onStart()getPresenter().onStart()}override fun onRestart() {super.onRestart()getPresenter().onRestart()}override fun onResume() {super.onResume()getPresenter().onResume()}override fun onPause() {super.onPause()getPresenter().onPause()}override fun onStop() {super.onStop()getPresenter().onStop()}override fun onDestroy() {getPresenter().onDestroy()presenterDelegate.unbindViewCompont()super.onDestroy()}protected open fun onSaveInstanceState(outState: Bundle?) {super.onSaveInstanceState(outState!!)getPresenter().onSaveInstanceState(outState!!)}protected open fun onRestoreInstanceState(savedInstanceState: Bundle?) {super.onRestoreInstanceState(savedInstanceState!!)getPresenter().onRestoreInstanceState(savedInstanceState!!)}override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {super.onActivityResult(requestCode, resultCode, data)getPresenter().onActivityResult(requestCode, resultCode, data!!)}/*** 返回layout 布局文件的id** @return*/abstract fun getLayoutId(): Int/*** 初始化其他属性*/abstract fun initFields()/*** 设置监听*/abstract fun bindEventListener()open fun getPresenter(): P {return presenterDelegate.getPresenter()}open fun setPresenter(presenter: P) {presenterDelegate.setPresenter(presenter)}}

这样一个mvp架构就搭建完毕了，下面看看使用：

interface ITestView :IView {fun setContent(string: String)}

Module层：

class TestModule :IModule{fun doNetWork(){println("网络请求")}
}

Presenter层：

class TestPresenter: BasePresenter<ITestView>() {var module:TestModule? =nulloverride fun setListeners() {}override fun onCreate(savedInstanceState: Bundle?, mContext: Context?) {module =TestModule()}override fun onResume() {module?.doNetWork()mView?.setContent("222222222")}override fun onStart() {}override fun onRestart() {}override fun onPause() {}override fun onStop() {}override fun onDestroy() {}override fun onSaveInstanceState(outState: Bundle) {}override fun onRestoreInstanceState(savedInstanceState: Bundle) {}override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent) {}}

View层：

@Request(TestPresenter::class)
class TestActivity :BaseActivity<TestPresenter,ITestView>(),ITestView {var textView:TextView?=nulloverride fun getLayoutId(): Int {return R.layout.activity_main}override fun initFields() {textView =findViewById<TextView>(R.id.txt)}override fun bindEventListener() {}override fun setContent(string: String) {textView?.text =string}override fun getActivity(): Activity? {return this}override fun getFragment(): Fragment? {return null}
}