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>
    
  • 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