ItemTouchHelper实现RecyclerView拖拽重排序

引言

今天，就来实现一下RecyclerView的重排序，即拖拽每个ItemView能完成重新布局，当然少不了DataBinding做数据绑定，Kotlin再加上ItemBinding写起来代码量也能精简不少，，一起来看看吧。话不多说，先上效果。

效果

---

分步实现

• 第一步：添加依赖

//Databinding
kapt "com.android.databinding:compiler:3.1.4"
// recyclerView的Databinding套装-ItemBinding用到
implementation 'me.tatarka.bindingcollectionadapter2:bindingcollectionadapter:4.0.0'
implementation 'me.tatarka.bindingcollectionadapter2:bindingcollectionadapter-recyclerview:4.0.0'

• 第二步：两个布局文件

主布局文件

RecyclerView的ItemView布局：

• 第三步：Activity书写业务逻辑

class Kotlin06 : AppCompatActivity() {

    private lateinit var binding:ActivityKotlin06Binding
    private lateinit var viewModel:Kotlin06ViewModel

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        binding = DataBindingUtil.setContentView(this,R.layout.activity_kotlin06);
        viewModel = ViewModelProviders.of(this).get(Kotlin06ViewModel::class.java)
        binding.viewModel = viewModel
        binding.lifecycleOwner = this

                //主要的三句代码，借助ItemTouchHelper类
        val callback = ItemTouchHelperCallback()
        val helper = ItemTouchHelper(callback)
        helper.attachToRecyclerView(binding.mRecycler)
    }
}

• 第四步：ViewModel加载数据，通过itemBinding绑定数据到RecyclerView

app:items="@{viewModel.items}"

app:itemBinding="@{viewModel.itemBinding}"

/**
 * @data on 3/31/21 5:18 PM
 * @auther KC
 * @describe
 */
class Kotlin06ViewModel:ViewModel(){
    var adapter = GoodsSortAdapter()
    var items = ObservableArrayList()
    var itemBinding = ItemBinding.of(BR.item, R.layout.item_view_06)
            .bindExtra(BR.viewModel, this)
    init {
        initData()
    }

    fun initData(){
        items.add(Good("苹果"))
        items.add(Good("栗子"))
        items.add(Good("李"))
        items.add(Good("火龙果"))
        items.add(Good("芒果"))
        items.add(Good("香蕉"))
        items.add(Good("柿子"))
        items.add(Good("圣女果"))
        items.add(Good("荔枝"))
    }
}

• 第五步：实体类DataBean

/**
 * @data on 3/31/21 6:39 PM
 * @auther KC
 * @describe
 */
data class Goods(val goodsList: List)

data class Good(val name: String)

• 第六步：定义接口及Item移动方法

/**
 * @data on 3/31/21 7:00 PM
 * @auther KC
 * @describe
 */
interface OnItemMoveListener {
    /**
     * Item移动后 触发
     */
    fun onItemMove(fromPosition: Int, toPosition: Int)
}

• 第七步：写ItemTouchHelperCallback类，继承自ItemTouchHelper的Callback接口

/**
 * @data on 3/31/21 5:20 PM
 * @auther KC
 * @describe RecyclerView拖拽重排序
 */
class ItemTouchHelperCallback : ItemTouchHelper.Callback() {
    override fun getMovementFlags(
        recyclerView: RecyclerView,
        viewHolder: RecyclerView.ViewHolder
    ): Int {
        val manager = recyclerView.layoutManager
        val dragFlags = if (manager is GridLayoutManager || manager is StaggeredGridLayoutManager) {
            ItemTouchHelper.UP or ItemTouchHelper.DOWN or ItemTouchHelper.LEFT or ItemTouchHelper.RIGHT
        } else {
            ItemTouchHelper.UP or ItemTouchHelper.DOWN
        }
        val swipeFlags = 0
        return makeMovementFlags(dragFlags, swipeFlags)
    }

    override fun onMove(
        recyclerView: RecyclerView,
        viewHolder: RecyclerView.ViewHolder,
        target: RecyclerView.ViewHolder
    ): Boolean {
        if (recyclerView.adapter is OnItemMoveListener) {
            val listener = recyclerView.adapter as OnItemMoveListener?
            listener!!.onItemMove(viewHolder.adapterPosition, target.adapterPosition)
        }
        return true
    }

    override fun onSwiped(viewHolder: RecyclerView.ViewHolder, direction: Int) { }

    override fun onSelectedChanged(viewHolder: RecyclerView.ViewHolder?, actionState: Int) {
        if (actionState !== ItemTouchHelper.ACTION_STATE_IDLE) {
            val title = viewHolder!!.itemView.findViewById(R.id.tvTitle)
            title.setTextColor(Color.parseColor("#FF7028"))
            title.setBackgroundColor(Color.WHITE)
        }
        super.onSelectedChanged(viewHolder, actionState)
    }

    override fun clearView(recyclerView: RecyclerView, viewHolder: RecyclerView.ViewHolder) {
        super.clearView(recyclerView, viewHolder)
        val title = viewHolder.itemView.findViewById(R.id.tvTitle)
        title.setTextColor(Color.parseColor("#333333"))
        title.setBackgroundColor(Color.parseColor("#eeeeee"));
    }
}

• 第八步：书写Adapter实现重排序，同样绑定到RecyclerView上

adapter="@{viewModel.adapter}"

/**
 * @data on 3/31/21 6:38 PM
 * @auther KC
 * @describe
 */
class GoodsSortAdapter : BindingRecyclerViewAdapter() , OnItemMoveListener {
    var items = ArrayList()

    override fun onBindBinding(
        binding: ViewDataBinding,
        variableId: Int,
        layoutRes: Int,
        position: Int,
        item: Good
    ) {
        super.onBindBinding(binding, variableId, layoutRes, position, item)
        items.add(item)
        Log.d(
            "onBindBinding",
            "position:::--->" + position + "<---title:::" + item.name
        )
    }

    override fun onItemMove(fromPosition: Int, toPosition: Int) {
        val item:Good = items[fromPosition]
        items.removeAt(fromPosition)
        items.add(toPosition, item)
        notifyItemMoved(fromPosition, toPosition)
    }
}

代码链接：https://github.com/Kingcool759/MyKotlinDemo