Android：将新项目添加到列表并使用 Kotlin 通过 RecyclerView 适配器显示

Question

我有一个带有 RecyclerView 的片段。 当用户单击片段中的按钮（添加新项目）时，应用程序会将用户（通过意图）带到一个表单以填写一些数据。

当我单击 (ADD ITEM) 时，它应该将数据添加到数组列表并完成该屏幕。 回到片段之后，应该使用适配器将这些数据添加到 RecyclerView 中。

这是我的代码：

这是片段：

private val REQUEST_CODE = 2

internal lateinit var adapter: ShipmentItemAdapter

override fun onCreateView(inflater: LayoutInflater?, container: ViewGroup?, savedInstanceState: Bundle?): View? {

    return inflater!!.inflate(R.layout.fragment_step_three_shipment, container, false)
}

override fun onViewCreated(view: View?, savedInstanceState: Bundle?) {
    super.onViewCreated(view, savedInstanceState)

    btnAddNewShipmentStep3.setOnClickListener {
        val intent = Intent(context, AddItemActivity::class.java)
        startActivityForResult(intent, REQUEST_CODE)
    }
}

override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
    super.onActivityResult(requestCode, resultCode, data);

    val items = ArrayList<ItemsItem>()

    if (requestCode == REQUEST_CODE) {

        adapter = ShipmentItemAdapter(context, items)

        if (resultCode == Activity.RESULT_OK) {
            itemsShipments.visibility = View.VISIBLE
            itemsShipments.layoutManager = LinearLayoutManager(context)
            itemsShipments.setHasFixedSize(true)
            itemsShipments.adapter = adapter

        } else if (resultCode == Activity.RESULT_CANCELED) {
            itemsShipments.visibility = View.GONE
        }
    }
}

这是活动：

class AddItemActivity : AppCompatActivity() {
  override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_add_item_form)

    linPackageAddShipment.setOnClickListener {
        edtPackageAddShipment.requestFocus()
    }

    linPiecesAddShipment.setOnClickListener {
        edtPiecesAddShipment.requestFocus()
    }

    linWeightAddShipment.setOnClickListener {
        edtWeightAddShipment.requestFocus()
    }

    linDescriptionAddShipment.setOnClickListener {
        edtDescriptionAddShipment.requestFocus()
    }


    btnAddItemAddShipment.setOnClickListener {
        val errors = collectData()

        collectData()

        if (errors.isEmpty()) {

            val intent = Intent()
            setResult(Activity.RESULT_OK, intent)
            finish()

        } else {
            val errorBody = errors.map { getString(it) }.joinToString("\n") { it }
            MaterialDialog.Builder(this)
                    .title("Oops")
                    .content(errorBody)
                    .positiveText(R.string.ok)
                    .positiveColor(ContextCompat.getColor(this, R.color.colorPrimary))
                    .onAny({ dialog, _ -> dialog.dismiss() })
                    .show()
        }
    }
  }

  private fun collectData(): ArrayList<Int> {
    val errors = ArrayList<Int>()
    val item = ItemsItem()

    if (edtPackageAddShipment.text.toString().isEmpty()) {
        errors.add(R.string.packages_must_not_be_empty)

    } else {
        item.numberOfPackages = edtPackageAddShipment.text.toString().toInt()
    }

    if (edtPiecesAddShipment.text.toString().isEmpty()) {
        errors.add(R.string.pieces_must_not_be_empty)

    } else {
        item.numberOfPieces = edtPiecesAddShipment.text.toString()
    }

    if (edtWeightAddShipment.text.toString().isEmpty()) {
        errors.add(R.string.weight_must_not_be_empty)

    } else {
        item.weightUnit = edtWeightAddShipment.text.toString().toInt()
    }

    if (edtHeightAddShipment.text.toString().isEmpty()) {
        errors.add(R.string.height_must_not_be_empty)

    } else {
        item.height = edtHeightAddShipment.text.toString()
    }

    if (edtWidthAddShipment.text.toString().isEmpty()) {
        errors.add(R.string.width_must_not_be_empty)

    } else {
        item.width = edtWidthAddShipment.text.toString()
    }
    if (edtLengthAddShipment.text.toString().isEmpty()) {
        errors.add(R.string.length_must_not_be_empty)

    } else {
        item.length = edtLengthAddShipment.text.toString()
    }

    if (edtDescriptionAddShipment.text.toString().isEmpty()) {
        errors.add(R.string.description_must_not_be_empty)

    } else {
        item.description = edtDescriptionAddShipment.text.toString()
    }

    CreateNewShipmentActivity.mainShipment.shipmentObj.items?.add(item)

    return errors
  }

  override fun onBackPressed() {
    setResult(Activity.RESULT_CANCELED)
    super.onBackPressed()
  }
}

这是适配器：

class ShipmentItemAdapter internal constructor(private val context: Context, private val items: List<ItemsItem>) : RecyclerView.Adapter<ShipmentItemAdapter.MyViewHolder>() {

  private val inflater: LayoutInflater = LayoutInflater.from(context)


  override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): MyViewHolder {
    val view = inflater.inflate(R.layout.item_shipment_package, parent, false)

    return MyViewHolder(view).listen { pos, type ->
        val item = items[pos]
        val intent = Intent(context, AddItemActivity::class.java)
        startActivity(context, intent, null)
    }
  }


  override fun onBindViewHolder(holder: MyViewHolder, position: Int) {
    holder.namePackageShipmentPackage.text = items[position].description
    holder.quantityPackageShipmentPackage.text = items[position].description
    holder.dimensionPackageHeightShipmentPackage.text = items[position].description
    holder.dimensionPackageWidthShipmentPackage.text = items[position].description
    holder.dimensionPackageLengthShipmentPackage.text = items[position].description

  }

  override fun getItemCount(): Int {
    return items.size
  }

  inner class MyViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {

    var namePackageShipmentPackage: AppCompatTextView = itemView.findViewById(R.id.namePackageShipmentPackage)
    var quantityPackageShipmentPackage: AppCompatTextView = itemView.findViewById(R.id.quantityPackageShipmentPackage)
    var dimensionPackageHeightShipmentPackage: AppCompatTextView = itemView.findViewById(R.id.dimensionPackageHeightShipmentPackage)
    var dimensionPackageWidthShipmentPackage: AppCompatTextView = itemView.findViewById(R.id.dimensionPackageWidthShipmentPackage)
    var dimensionPackageLengthShipmentPackage: AppCompatTextView = itemView.findViewById(R.id.dimensionPackageLengthShipmentPackage)


  }

  private fun <T : RecyclerView.ViewHolder> T.listen(event: (position: Int, type: Int) -> Unit): T {
    itemView.setOnClickListener {
        event.invoke(adapterPosition, itemViewType)
    }
    return this
  }

这些是对象模型：

class ShipmentObj {
    var items: ArrayList<ItemsItem?>? = null
}


data class ItemsItem(
    var numberOfPieces: String? = null,
    var length: String? = null,
    var description: String? = null,
    var numberOfPackages: Int? = null,
    var number: Int? = null,
    var width: String? = null,
    var height: String? = null,
    var weightUnit: Int? = null
)

当我尝试添加新项目时，片段中没有显示任何内容！ 我现在不知道错在哪里？

谢谢。

Answer 1

您需要首先在您的适配器中添加一个用于向 Array 添加新项目的函数，在您的情况下是“项目：列表”：

第一步：

• 在您的适配器 ShipmentItemAdapter 中添加下一个乐趣

 fun addNewItem(itemsNew: List<ItemsItem>){ items.clear() // ->> optional if you need have clear of object items.addAll(itemsNew) notifyDataSetChanged() }

然后，在 onActivityResult 的片段中，当您收到 Activity.RESULT_OK 时，您可能会添加新项目

 adapter.addNewItem(itemsNew)

Answer 2

在 onActivityResult 你可以看到你的代码中的错误你做这样的事情

val items = ArrayList<ItemsItem>()
adapter = ShipmentItemAdapter(context, items)

您为适配器分配了一个空的项目列表。 如果我没猜错，您也不会传递您要发送的项目。

 if (errors.isEmpty()) {
        val intent = Intent()
        setResult(Activity.RESULT_OK, intent)
        finish()
 }

结果您完成了活动而没有传递任何项目。 之前的活动没有收到任何东西。 我无法执行您的代码，因为我没有执行它的所有元素。