databinding+liveData+viewmodel r

在app build.gradle开启databinding 和 bindingAdapter

// DataBinding开启 启用中
    buildFeatures {
        dataBinding = true
    }

//  支持 bindingAdapter
apply plugin: "kotlin-kapt"

    kapt {
        generateStubs = true
    }

创建UserRepository ，用来请求网络拿数据，或者从数据库中拿数据

class Repository private constructor(){

    companion object{
        val mUserRepository = UserRepositoryHolder.holder
    }

    private object UserRepositoryHolder {
        val holder = Repository()
    }


    fun getArticles(listenner:onLoadArticleListenner){
        HttpClient.instance.instanceRetrofit(WanAndroidApi::class.java)
            .getArticles(1)
            .subscribeOn(Schedulers.io())
            .observeOn(AndroidSchedulers.mainThread())
            .subscribe(object : ResponseObserve<ArticleResponse>() {
                override fun success(data: ArticleResponse?) {
                    data?.let { listenner.loadSuccess(it) }
                }

                override fun failure(errorMsg: String?) {
                    errorMsg?.let { listenner.loadError(it) }
                }

            })
    }



    interface  onLoadArticleListenner{
        fun loadSuccess(data:ArticleResponse);
        fun loadError(msg:String)
    }


}

创建viewmodel 支持屏幕旋转数据能维持，和同个activity 里面的fragment 能够数据共享

class ArticleListViewModel : ViewModel() {
    var articles: MutableLiveData<List<Article>>? = null

    var loaddingLiveData: MutableLiveData<Boolean>? = null

    init {
        articles = MutableLiveData()
        loaddingLiveData = MutableLiveData()
    }

    fun getArticles() {
        loaddingLiveData?.value = true
        UserRepository.mUserRepository.getArticles(object : UserRepository.onLoadArticleListenner {
            override fun loadSuccess(data: ArticleResponse) {
                loaddingLiveData?.value = false
                articles?.setValue(data.datas);
            }

            override fun loadError(msg: String) {
                loaddingLiveData?.value = false
                articles?.setValue(null);
            }

        })
    }
    
}

activity布局 并引入前面创建的viewmodel

<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:bind="http://schemas.android.com/apk/res-auto">

    <data>
        <variable
            name="mv"
            type="com.amn.jetpackmvvm.test.ArticleListViewModel" />
    </data>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">

        <com.scwang.smartrefresh.layout.SmartRefreshLayout
            android:id="@+id/homeRefreshLayout"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
           >

            <androidx.recyclerview.widget.RecyclerView
                android:id="@+id/collectRecycleView"
                android:layout_width="match_parent"
                android:layout_height="match_parent" />

        </com.scwang.smartrefresh.layout.SmartRefreshLayout>
    </LinearLayout>
</layout>

在activity 绑定布局，和获取viewmodel并且设置viewmodel (在布局引入viewmodel 后 databinding才会有设置viewmodel 方法)

   override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        //databinding 绑定布局
        articlelistBinding =
            DataBindingUtil.setContentView<ActivityArticleListBinding>(this, activity_article_list)
        articlelistBinding?.lifecycleOwner = this

        //获取viewmodel
        artcleViewModel = ViewModelProvider(this).get(ArticleListViewModel::class.java);

        //databinding 和viewmodel 绑定
        articlelistBinding?.mv = artcleViewModel
}

目前这个和activity 绑定的viewmodel 暂没用到，后面可用来跟新刷新状态，或者可用bindingAdapter 绑定刷新和加载更多事件

接下来 recycleview 的设置，因在viewmodel 采用livedata 可用来数据双向绑定，这里只是单项，在activity中 监听 数据变化,设置对应的adapter 数据

  private fun observeLivaData() {
        artcleViewModel?.loaddingLiveData?.observe(this, Observer {
            if (!it) {
                articlelistBinding?.homeRefreshLayout?.finishRefresh()
            }
        })
        artcleViewModel?.articles?.observe(this, Observer {
            articleAdapter?.setData(it)
        })
    }

在adapter中

class ArticleAdapter(context: Context) : Adapter<ArticleAdapter.ArticleViewHolder>() {

    var datas: ArrayList<Article>? = ArrayList()
    val context: Context = context

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ArticleViewHolder {

        val inflate = DataBindingUtil.inflate<ItemArticleBinding>(
            LayoutInflater.from(context),
            R.layout.item_article,
            parent,
            false
        )
        return ArticleViewHolder(inflate.root)
    }

    override fun getItemCount(): Int {
        return (if (datas == null) 0 else datas?.size)!!
    }

    override fun onBindViewHolder(holder: ArticleViewHolder, position: Int) {
        val article = datas?.get(position)
        val binding = DataBindingUtil.getBinding<ItemArticleBinding>(holder.itemView);
        binding?.itemArticle = article
        binding?.executePendingBindings()

    }

    fun setData(articles: List<Article>) {

        datas?.clear()
        datas?.addAll(articles)
        notifyDataSetChanged()
    }

    class ArticleViewHolder(itemView: View) : ViewHolder(itemView) {

    }
}

databinding ,livedata,viewmodel 基础使用就到这里了，有空后面还会加room 以及他们更多用法