需求場(chǎng)景 ：
在viewmodel中需要改變一個(gè)自定義view的自定義屬性（比如 smartrefashlayout的下拉刷新去請(qǐng)求數(shù)據(jù)，以及加載完成或者刷新完成關(guān)閉加載動(dòng)畫）

思路：
1.mvvmlight 提供的command 方式（只適合自定義view中存在暴露給外部監(jiān)聽的方式，或者自
己通過(guò)bindadapter監(jiān)聽某個(gè)狀態(tài)達(dá)到目的的場(chǎng)景，后面會(huì)講具體實(shí)現(xiàn)）
command 的解決問(wèn)題的方式是利用了bindadapter 和 java8的函數(shù)式編程（當(dāng)然你用rxjava
也ok）。

2.通過(guò)bindadapter 和 InverseBindingAdapter （http://www.itdecent.cn/p/a05c9735f595）/（https://yq.aliyun.com/articles/615840）

方式1 實(shí)現(xiàn)步驟：

 a. 定義command   (jdk8的函數(shù)接口)
   @FunctionalInterface
  public interface ReplyCommand {
   void exectue();
 }

b.BindingAdapter

     public class BindingAdapters {
     @BindingAdapter({"onRefreshCommand"})
     public static void setonRefreshCommand(SmartRefreshLayout smartRefreshLayout, final ReplyCommand onRefreshCommand) {
         smartRefreshLayout.setOnRefreshListener(new OnRefreshListener() {
             @Override
             public void onRefresh(RefreshLayout refreshLayout) {
                 onRefreshCommand.exectue();
             }
         });
     }

     @BindingAdapter({"onloadmoreCommand"})
     public static void setonloadmoreCommand(SmartRefreshLayout smartRefreshLayout, final ReplyCommand onloadmoreCommand) {
         smartRefreshLayout.setOnLoadMoreListener(new OnLoadMoreListener() {
             @Override
             public void onLoadMore(RefreshLayout refreshLayout) {
                 onloadmoreCommand.exectue();
             }
         });
     }

     @BindingAdapter({"oncompleteCommand"})
     public static void setoncompleteCommand(SmartRefreshLayout smartRefreshLayout, final ReplyCommandParam oncompleteCommand) {
         oncompleteCommand.exectue(smartRefreshLayout);
     }
 }

c. xml 中引用

 <com.scwang.smartrefresh.layout.SmartRefreshLayout
     android:layout_width="match_parent"
     android:layout_height="match_parent"
     bind:onRefreshCommand="@{viewModel.onrefreshCommand}"
     bind:onloadmoreCommand="@{viewModel.onloadmoreCommand}">

     <android.support.v7.widget.RecyclerView
         android:id="@+id/recycle"
         android:layout_width="match_parent"
         android:layout_height="match_parent"
         bind:itemView="@{viewModel.KnowitemBinding}"
         bind:items="@{viewModel.knowItems}"
         bind:layoutManager="@{LayoutManager.linear()}" />

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

 d.viewmodel 中使用

 public final ReplyCommand onrefreshCommand = ()->{ getKnowledgeHierarchyData();};

 public final ReplyCommand onloadmoreCommand = ()->{ getKnowledgeHierarchyData();};

 結(jié)果： 發(fā)現(xiàn)下拉刷新絲滑了，數(shù)據(jù)驅(qū)動(dòng)，但是你會(huì)發(fā)現(xiàn)數(shù)據(jù)獲取成功后加載的動(dòng)畫并沒有關(guān)閉 so 方式二就需要出場(chǎng)救急了

方式二實(shí)現(xiàn)步驟

1. 下載smartrefashlayout 的源碼，使用導(dǎo)入module的方式引入項(xiàng)目（因?yàn)閷?duì)反向綁定的InverseBindingMethods使用的不多，接下來(lái)會(huì)研究，等第二篇）

2. 增加view的自定義屬性 <attr name="refreshcomplete" format="boolean"/> 3. initview的時(shí)候獲取屬性并提供setter getter，
   refreshcomplete =
   ta.getBoolean(R.styleable.SmartRefreshLayout_refreshcomplete,false);

      public boolean getRefreshcomplete() {
        return refreshcomplete;
       }
        public void setRefreshcomplete(boolean refreshcomplete) {
        this.refreshcomplete = refreshcomplete;
        }
   

   4. 自己領(lǐng)會(huì)下，等后邊步驟看完就知道為嘛要這樣了
      @BindingAdapter("refreshcompleteAttrChanged")
      public static void setRefreshcompleteAttrChanged(SmartRefreshLayout view, InverseBindingListener inverseBindingListener) {
      if (inverseBindingListener == null) {
      view.setListener(null);
      } else {
      view.setListener(inverseBindingListener::onChange);
      }
      }
      @BindingAdapter(value = "refreshcomplete")
      public static void setcomplete(SmartRefreshLayout view, boolean refreshcomplete) {
      view.setRefreshcomplete(refreshcomplete);
      if(refreshcomplete){
      view.finishRefresh();
      view.finishLoadMore();
      }
      }
      @InverseBindingAdapter(attribute = "refreshcomplete", event = "refreshcompleteAttrChanged")
      public static boolean getcomplete(SmartRefreshLayout view) {
      return view.getRefreshcomplete();
      }

   private OnValueChangedListener listener;

   public interface OnValueChangedListener {
   void onValueChanged();
   }

   public void setListener(OnValueChangedListener listener) {
   this.listener = listener;
   }

   5. 定義 實(shí)體類，xml中使用

   public class Testvo extends BaseObservable implements Serializable {

public boolean complete;
@Bindable
public boolean getComplete() {
    return complete;
}

public void setComplete(boolean complete) {
    this.complete = complete;
    notifyPropertyChanged(BR.complete);
}

}

注意規(guī)范，類的首字母必須大寫，書寫規(guī)范能避免很多大坑

  <variable
        name="data"
        type="com.docker.moduleplayer.vo.Testvo"/>

    <import type="com.docker.commonlibrary.bind.recycleviewbind.LayoutManager" />
</data>

<com.scwang.smartrefresh.layout.SmartRefreshLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"

    bind:refreshcomplete="@={data.complete}"

    bind:onRefreshCommand="@{viewModel.onrefreshCommand}"
    bind:onloadmoreCommand="@{viewModel.onloadmoreCommand}">

    <android.support.v7.widget.RecyclerView
        android:id="@+id/recycle"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        bind:itemView="@{viewModel.KnowitemBinding}"
        bind:items="@{viewModel.knowItems}"
        bind:layoutManager="@{LayoutManager.linear()}" />

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

6. viewmodel 中實(shí)例化
   public Testvo vo = new Testvo();
   activity 中setData

7.完成，再回頭看步驟4，有沒有明白呢？