从另一个 Activity (Kotlin) 将项目添加到 RecyclerView

Question

I have the following:

• Main Activity with RecyclerView which is filled from Array List
• Adapter (of course)
• Another Activity where a new item should be created, added to RecyclerView on Main Activity and then be closed

The main question is, how can I add an item to RecyclerView from another Activity?

MainActivity Code

 override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        val items = arrayListOf<CustomData>()

        items.add(CustomData("Name", R.drawable.icon, 50, "Weekly", "Monday", 1, 50))

        button.setOnClickListener {
            val intent = Intent(this, NewItem::class.java)
            startActivity(intent)
        }
        itemsListView.apply {
            layoutManager = LinearLayoutManager(this@MainActivity)
            adapter = ItemsAdapter(items)
        }

    }

Adapter Code

class ItemsAdapter(private val items: ArrayList<CustomData>) :
    RecyclerView.Adapter<ItemsAdapter.ViewHolder>() {


    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
        val view = LayoutInflater.from(parent.context).inflate(R.layout.wish_row, parent, false)
        val holder = ViewHolder(view)
        view.setOnClickListener {
            val intent = Intent(parent.context, ItemView::class.java)
            intent.putExtra("Name", items[holder.adapterPosition].name)
            intent.putExtra("Price", items[holder.adapterPosition].price)
            intent.putExtra("Icon", items[holder.adapterPosition].image)
            parent.context.startActivity(intent)
        }

        return holder
    }

    override fun getItemCount() = items.size

    override fun onBindViewHolder(holder: ItemsAdapter.ViewHolder, position: Int) {
        holder.name.text = items[position].name
        holder.price.text = items[position].price.toString()
        holder.image.setImageDrawable(holder.image.context.getDrawable(items[position].image))
    }

    class ViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
        val image: ImageView = itemView.findViewById(R.id.imageView)
        val name: TextView = itemView.findViewById(R.id.textView)
        val price: TextView = itemView.findViewById(R.id.textView2)
    }
}

Another Activity from which I want to add item to Recyclerview

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

            val items = arrayListOf<CustomData>()

            items.add(CustomData("Name2", R.drawable.icon, 50, "Weekly", "Monday", 2, 50))

            newItemButton.setOnClickListener {

                itemsListView.layoutManager = LinearLayoutManager(this)
                itemsListView.adapter = itemsAdapter(items)
                finish()
            }
        }
    }

Answer 1

When adding new item from your NewItem activity, pass a bundle adding that item to your MainActivity .

Then in your MainActivity , get that bundle and set that new item to your RecyclerView.

Answer 2

Use startActivityForResult when starting your NewItem Intent

button.setOnClickListener {
            val intent = Intent(this, NewItem::class.java)
            startActivityForResult(1, intent)
        }

Then in your NewItem activity, call setResult with appropriate resultCode

// on success
val returnIntent = Intent()
returnIntent.putExtra("result",result) //result is data you want to add to recycler
setResult(Activity.RESULT_OK,returnIntent)
finish()

Now override onActivityResult in the main activity like below

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

    if (requestCode == 1 && resultCode == Activity.RESULT_OK && data != null) {

        val newItem = data.getSerializableExtra("result") as CustomData
        adapter.addNewItem(newItem)
    }
}

Then finally in your adapter add this method

fun addNewItem(newItem: CustomData){
    items.add(newItem)
    notifyItemInserted(items.size-1)
}

Make sure CustomData class implements Serializable thus class CustomData:Serializable{//your code}