最近MVP火的不要不要的，我也来凑盘热闹，其实MVP的文章看了好多了，但是一直还停留在概念阶段，这几天对Google Android的todoapp的代码进行了解析，然后使用Kotlin翻译了一下，算了对MVP有了一个大概的认识，那么MVP究竟是什么，网上一搜一大堆，我就把名字复述一下，MVP的全称为Model-View-Presenter，即模型-视图-协调器(主持者)，最重要的功能还是解耦，代码也更容易扩展和维护，下面我们还是来看具体的例子：demo还是做一个干货的列表页：
先看目录结构，
Paste_Image.png
这里单独建了个MVP的包，base中定义了两个接口BaseView和BasePresenter
BaseView
package com.vslimit.kotlindemo.mvp.base
/**
* Created by vslimit on 17/1/6.
*/
interface BaseView<T> {
fun setPresenter(presenter: T)
}
BasePresenter
package com.vslimit.kotlindemo.mvp.base
/**
* Created by vslimit on 17/1/6.
*/
interface BasePresenter {
fun start()
}
实现Contract
GanksContract
package com.vslimit.kotlindemo.mvp.ganks
import com.vslimit.kotlindemo.model.Gank
import com.vslimit.kotlindemo.mvp.base.BasePresenter
import com.vslimit.kotlindemo.mvp.base.BaseView
/**
* Created by vslimit on 17/1/10.
*/
interface GanksContract {
interface View : BaseView<Presenter> {
fun showGanks(ganks: List<Gank>)
fun showTip(message:String)
fun showLoading()
fun hideLoading()
}
interface Presenter : BasePresenter {
fun loadGanks()
}
}
接口中定义了需要实现想要展示的View，而Presenter处理交互，下面我们来看具体的实现类：
GanksPresenter
package com.vslimit.kotlindemo.mvp.ganks
import com.vslimit.kotlindemo.model.Gank
import com.vslimit.kotlindemo.model.GankListResult
import com.vslimit.kotlindemo.service.RestfulService
import com.vslimit.kotlindemo.service.ServiceFactory
import rx.Subscriber
import rx.android.schedulers.AndroidSchedulers
import rx.schedulers.Schedulers
/**
* Created by vslimit on 17/1/11.
*/
class GanksPresenter : GanksContract.Presenter {
var mGanksView: GanksContract.View? = null
constructor(ganksView: GanksContract.View) {
mGanksView = checkNotNull(ganksView)
mGanksView!!.setPresenter(this)
}
override fun loadGanks() {
mGanksView!!.showLoading()
val service = ServiceFactory.createRetrofitService(RestfulService::class.java, RestfulService.GANK_SERVICE_ENDPOINT)
service.loadGanks().subscribeOn(Schedulers.newThread()).observeOn(AndroidSchedulers.mainThread()).subscribe(object : Subscriber<GankListResult>() {
override fun onCompleted() {
mGanksView!!.hideLoading()
}
override fun onError(e: Throwable) {
mGanksView!!.showTip(e.toString())
}
override fun onNext(result: GankListResult) {
processGanks(result.results)
}
})
}
override fun start() {
loadGanks()
}
fun processGanks(ganks: List<Gank>) {
mGanksView!!.showGanks(ganks)
}
}
这里只实现了一个交互，即从服务端获取ganks数据，获取数据的实现请参考之前的文章传送门，既然数据OK了，那我们就来看看View是如何展示的：
GanksFragment
package com.vslimit.kotlindemo.mvp.ganks
import android.os.Bundle
import android.support.v7.widget.LinearLayoutManager
import android.view.View
import com.vslimit.kotlindemo.R
import com.vslimit.kotlindemo.adapter.BaseAdapter
import com.vslimit.kotlindemo.extensions.loading
import com.vslimit.kotlindemo.fragment.BaseFragment
import com.vslimit.kotlindemo.model.Gank
import com.vslimit.kotlindemo.util.Const
import kotlinx.android.synthetic.main.fragment_ganks.*
import kotlinx.android.synthetic.main.item_list_gank.view.*
import org.jetbrains.anko.info
import org.jetbrains.anko.onClick
import org.jetbrains.anko.support.v4.act
import org.jetbrains.anko.support.v4.toast
/**
* Created by vslimit on 17/1/10.
*/
class GanksFragment : BaseFragment(), GanksContract.View {
override val layoutResourceId: Int = R.layout.fragment_ganks
var mPresenter: GanksContract.Presenter? = null
var adapter: BaseAdapter<Gank>? = null
companion object {
fun getInstance(): GanksFragment {
return GanksFragment()
}
}
override fun onViewCreated(view: View?, savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
val layoutManager: LinearLayoutManager = LinearLayoutManager(act)
gankListRv.layoutManager = layoutManager
adapter = BaseAdapter(R.layout.item_list_gank, arrayListOf()) { view: View, item: Gank ->
view.item_gank_title.text = item.desc
view.item_gank_who.text = item.who
view.item_gank_date.text = item.publishedAt
view.onClick {
showTip("onclick")
}
}
gankListRv.adapter = adapter
}
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
}
override fun hideLoading() {
loading(Const.HIDE)
}
override fun showLoading() {
loading(Const.SHOW)
}
override fun showTip(message: String) {
toast(message)
}
override fun setPresenter(presenter: GanksContract.Presenter) {
mPresenter = checkNotNull(presenter)
info("demo")
}
override fun onResume() {
super.onResume()
mPresenter?.start()
}
override fun showGanks(ganks: List<Gank>) {
adapter!!.items = ganks
adapter!!.notifyDataSetChanged()
}
}
在这个fragment同样使用了之前文章封装的通用RecycleView.Adapter，有兴趣的朋友可以回头看看之前的文章传送门，最后我们来看看Activity都实现了什么：
GanksActivity
package com.vslimit.kotlindemo.mvp.ganks
import android.os.Bundle
import android.support.design.widget.NavigationView
import android.support.v4.view.GravityCompat
import android.support.v4.widget.DrawerLayout
import android.view.MenuItem
import com.vslimit.kotlindemo.R
import com.vslimit.kotlindemo.activity.BaseActivity
import com.vslimit.kotlindemo.ui.DrawerLayoutManager
import org.jetbrains.anko.find
/**
* Created by vslimit on 17/1/10.
*/
class GanksActivity(override val layoutResourceId: Int = R.layout.activity_tasks) :BaseActivity(),DrawerLayoutManager{
override val drawerLayout by lazy { find<DrawerLayout>(R.id.drawer_layout) }
val navigationView by lazy { find<NavigationView>(R.id.nav_view) }
var mGanksPresenter: GanksPresenter? = null
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setupDrawerContent(navigationView, R.id.drawLayoutTask)
val ganksFragment = GanksFragment.getInstance()
if (savedInstanceState == null) {
initFragment(ganksFragment)
}
mGanksPresenter = GanksPresenter(ganksFragment)
}
override fun onOptionsItemSelected(item: MenuItem): Boolean {
when (item.itemId) {
android.R.id.home -> {
drawerLayout.openDrawer(GravityCompat.START)
return true
}
}
return super.onOptionsItemSelected(item)
}
}
至此，基于Kotlin的MVP已经实现，从代码中不难看出，model与view实现了解耦，那么问题来了，是不是MVP适用于所有场景，就我个人的感觉，如果页面UI设计复杂，交互多，那应该使用MVP，这样，能达到解耦的目的和效果，并且便于以后的维护和扩展，但是，如果只是单一的交互，比如登录或者像本文的只是个列表展示或详情，那就直接用Activity和Fragment即可，毕竟杀鸡用牛刀确实有点小题大做的感觉；至于说项目中究竟用MVC还是MVP要看具体场景以及个人喜好。
哦，对了，效果图（懒得截图，就使用之前的了，不过点击按钮在侧滑菜单中，列表效果是一样的）：
Screenshot_2017-01-01-00-07-36.png
本文中的所有代码已经提交到git上了，大家如果喜欢就去git下star下吧。
下期预告：其实我也不晓得下期是继续深入MVP还是说去研究研究最近流行的第三方库，抑或是写个实际的项目呢，懵逼中...
