java - 如何删除类的arraylist中的重复项

Question

我正在尝试将来 self 服务器的数据放入我的应用程序中，使用 RecyclerView 和 volley，现在因为我正在使用一个适配器，这是我的适配器类

class TypeAdapter(var con: Context, var list: ArrayList<TypeItems>) : RecyclerView.Adapter<RecyclerView.ViewHolder>() {
override fun onBindViewHolder(p0: RecyclerView.ViewHolder, p1: Int) {

    (p0 as ItemView).bind(list[p1].cartype, list[p1].typetype, list[p1].modeltype, list[p1].photype)

}
override fun onCreateViewHolder(p0: ViewGroup, p1: Int): RecyclerView.ViewHolder {
    val v= LayoutInflater.from(con).inflate(R.layout.car_model_item, p0, false)

    return ItemView(v)
}

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

class ItemView(itemVeiw: View) : RecyclerView.ViewHolder(itemVeiw) {

    fun bind(car_type: String, type: String, modele: String, ph: String) {

        Picasso.with(itemView.context).load(ph).into(itemView.type)

        itemView.name.text= "$car_type $type"
        itemView.model.text= modele


    }
}
}

这是我的 TypeItems 类

class TypeItems(car_typetype: String, typetype: String, modeletype: String, phtype: String) {
var cartype:String = car_typetype
var typetype:String = typetype
var modeltype:String = modeletype
var photype:String = phtype

}

这是我的主课

class CarModelActivity : AppCompatActivity() {

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_car_model)

    val list= ArrayList<TypeItems>()

    val rq= Volley.newRequestQueue(this)

    val  url= ("http://test123456789.cf/sell_items/reportall.php?car_type=${car_item.cartype}").replace(" ", "%20")

    val srr= StringRequest(Request.Method.GET, url ,
        Response.Listener { response ->

            //converting the string to json array object
            val array = JSONArray(response)

            list.clear()

            //traversing through all the object
            for (i in 0 until array.length()) {

                //getting item object from json array
                val product = array.getJSONObject(i)


                //ex Image
                var url2= "https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcRj3LA1ERJCx8lM-qHsgaW_5IgzeW21w-Ona7iI05E9aoXrImtl"

                //adding the product to item list
                list.add(
                    TypeItems(
                        product.getString("car_type"),
                        product.getString("type"),
                        product.getString("model"),
                        url2
                    )
                )

            }

            //creating adapter object and setting it to recyclerview
            val adapter = TypeAdapter(this.applicationContext, list)
            rv.layoutManager= GridLayoutManager(this, 2)
            rv.adapter = adapter

        }, Response.ErrorListener { error ->
            Toast.makeText(this, error.message, Toast.LENGTH_LONG).show()
        })

    rq.add(srr)

}
}

this is image of the result

现在我想从我的列表中删除重复的项目，我想按 car_type 和 type 和 model 排序，如果该项目重复，我想删除它

Answer 1

您应该使用数据类。它将在内部包含重写的 equals() 方法:

data class TypeItems(
    val car_typetype: String,
    val typetype: String,
    val modeletype: String,
    val phtype: String
)

深入研究这个问题后，我发现，您不能在 Set 集合上调用方法 get()。所以，这段代码将不起作用:(p0 作为 ItemView).bind(list[p1].cartype, list[p1].typetype, list[p1].modeltype, list[p1].photype)
总结一下，Set 帮不了你。要解决您的问题，您只需要调用防御检查:

val typeItems = TypeItems(
                product.getString("car_type"),
                product.getString("type"),
                product.getString("model"),
                url2
        )
        if(!list.contains(typeItems)) {
            list.add(typeItems)
        }

因此，还有另一种方法可以解决这个问题:代替
val adapter = TypeAdapter(this.applicationContext, list)
调用
val adapter = TypeAdapter(this.applicationContext, list.distinct())
方法 distinct() 以相同的顺序返回列表的唯一值。不要忘记让它成为数据类。