Android Kotlin RecyclerView Databinding

一个已经能进行简单的按按钮操作的RecyclerView项目

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apply plugin: 'kotlin-android'
apply plugin: 'kotlin-kapt'
apply plugin: 'kotlin-android-extensions'

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dataBinding {
    enabled = true
}

一个数据绑定辅助类

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  /**
    * 赋予ImageView和ImageButton以 app:img 的属性, 用于绑定图片
    * @author linx
    */
  class BindingUtil {
      companion object {
          @BindingAdapter("app:img")
          @JvmStatic
          fun imgData(iv: ImageView, data: Int) {
              iv.setImageResource(data)
          }

          @BindingAdapter("app:img")
          @JvmStatic
          fun imgData(iv: ImageButton, data: Int) {
              iv.setBackgroundResource(android.R.color.transparent)
              iv.setImageResource(data)
          }

          /**
           * ImageView绑定图片地址url
           * @param iv ImageView
           * @param data Any
           */
          @BindingAdapter("app:url")
          @JvmStatic
          fun ImageViewUrl(iv: ImageView, data: Any) {
              if (data is String) {
                  if (!data.isEmpty()) {
                      Glide.with(iv.context).load(Uri.parse(data)).into(iv)
                  } else {
                      iv.setImageResource(R.mipmap.touxiang2_default)
                  }

              } else if (data is Int) {
                  iv.setImageResource(data)
              }
          }

      }
  }

一个数据adapter

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  import android.view.LayoutInflater
  import android.view.View
  import android.view.ViewGroup
  import androidx.databinding.DataBindingUtil
  import androidx.databinding.ViewDataBinding
  import androidx.recyclerview.widget.RecyclerView.Adapter
  import androidx.recyclerview.widget.RecyclerView.ViewHolder
  import java.util.*

  /**
  * RecylerView 数据绑定适配器
  * @param T
  * @property mList List<T>?
  * @property layoutId Int?
  * @property brId Int?
  * @property itemClick ItemClick?
  * @constructor
  */
  open class QJBaseAdapter<T>(var mList: List<T>?, var layoutId: Int?, var brId: Int?) :
      Adapter<QJBaseAdapter.QJBaseViewHolder>() {


      var itemClick: ItemClick? = null

      /**
      * 更新数据
      * @param items ArrayList<T>?
      */
      fun updateData(items: ArrayList<T>?) {
          this.mList = items
          notifyDataSetChanged()
      }

      interface ItemClick {
          fun OnItemClick(v: View, position: Int)
      }

      fun setItemClickListener(itemClick: ItemClick) {
          this.itemClick = itemClick
      }


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

          val binding: ViewDataBinding = DataBindingUtil.inflate(
              LayoutInflater.from(parent.context), this.layoutId!!, parent, false
          )
          return QJBaseViewHolder(binding)
      }

      override fun getItemCount(): Int = mList!!.size

      override fun onBindViewHolder(holder: QJBaseViewHolder, position: Int) {
          var item = mList!![position] // 这里必须为var 因为需要修改列表的数据
          doBeforeShow(holder.binding.root, item)
          holder.binding.setVariable(this.brId!!, mList!![position])
          holder.binding.executePendingBindings()
          // item点击事件
          holder.binding.root.setOnClickListener {
              itemClick?.OnItemClick(holder.binding.root, position)
          }
          forInnerControl(holder.binding.root, item)
      }


      /**
      * 在绑定数据之前执行, 可以修改数据 item 的值
      * @param itemView View?
      * @param item T
      */
      open fun doBeforeShow(itemView: View?, item: T) {

      }

      /**
      * 用于给ItemView内部的组件绑定事件
      * @param itemView View?
      * @param item T
      */
      open fun forInnerControl(itemView: View?, item: T) {

      }

      class QJBaseViewHolder(var binding: ViewDataBinding) : ViewHolder(binding.root)
  }

声明数据类

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  data class SchoolNews(
      val title: String = "", //标题
      val contentShort: String = "", //内容简写
      val date: String = "", //日期
      val state: Int = 0, //0 unreaded 1 readed 2 pinned
      var img:Int =0
  )

RecyclerView 的itemview中声明, 注意顶层元素使用layout, 其他盲敲即可, IDE会补全

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  <layout xmlns:android="http://schemas.android.com/apk/res/android"
      xmlns:app="http://schemas.android.com/apk/res-auto">
  <data>
      <variable
          name="schoolNews"
          type="model.SchoolNews" />
  </data>

以 android:text="@{schoolNews.title}" 这样的方式绑定数据, ImageView和ImageButton则以 app:img="@{schoolNews.img}" img 是resId即资源id, 图片的值不能直接绑定, 需要用代码setImageResource来实现

创建一个特定的适配器, 重写两个方法

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  class SchoolNewsAdapter(mList: List<SchoolNews>?, layoutId: Int?, brId: Int?) :
      QJBaseAdapter<SchoolNews>(mList, layoutId, brId) {

      override fun forInnerControl(itemView: View?, item: SchoolNews) {
          // 这里可以为每个 itemView 的子控件添加事件

      }

      // 在这个方法中对item进行修改是可以应用到界面的, 不过肯定不能执行过于耗时的操作
      override fun doBeforeShow(itemView: View?, item: SchoolNews) {
          // 根据state字段的值来决定显示哪张图片
          when (item.state) {
              0-> item.img = R.mipmap.yuandian
              2-> item.img = R.mipmap.schoolnews_guding
              else->item.img = R.color.mainwhite
          }
      }


  }

顺便说下, 代码中访问内置颜色是这样的android.R.color.transparent

最后就是使用了

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  var mAdapter: SchoolNewsAdapter? = null

  private fun initView() {
      mAdapter = SchoolNewsAdapter(
          schoolNews, R.layout.recycler_view_item_school_news_info,
          BR.schoolNews
      )

      schoolNewsRv.adapter = mAdapter
  }

这里说明下 schoolNews为 ArrayList<SchoolNews>, R.layout.recycler_view_item_school_news_info为item的布局文件, BR.schoolNews这个就是前面 <layout>内的variable了, 如果最开始的插件没有配置好, 这个会报错. 原理其实就是编译器自动帮我们生成好了代码

更新数据则使用 mAdapter!!.updateData(schoolNews)即可