Kotlin Recyclerview ItemClick to new Intent

Question

I have a problem. I can print a toast message when I click on any item in Recyclerview. But I want to switch to a different activity when clicked. Could you please help me in a very specific way? It is a very important project for me. The code blocks I wrote are as follows. Thanks in advance.

CustomersAdapter

class CustomersAdapter(private val companynameArray:ArrayList,private val companyoffArray:ArrayList, private val companyPhoneArray:ArrayList): RecyclerView.Adapter<CustomersAdapter.CustomerHolder>() {

class CustomerHolder(view: View) : RecyclerView.ViewHolder(view) {

    var recycleCompanyName: TextView?=null
    var recycleOffName: TextView?=null
    var recycleOffPhone: TextView?=null


    init {
        recycleCompanyName=view.findViewById(R.id.recycleCompanyName)
        recycleOffName=view.findViewById(R.id.recycleOffName)
        recycleOffPhone=view.findViewById(R.id.recycleOffPhone)

        itemView.setOnClickListener {


        }


    }



}

override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): CustomerHolder {
    val inflater= LayoutInflater.from(parent.context)
    val view= inflater.inflate(R.layout.recycler_view_customer_row,parent,false)
    return CustomersAdapter.CustomerHolder(view)
}

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

override fun onBindViewHolder(holder: CustomerHolder, position: Int) {
    holder.recycleCompanyName?.text="Şirket Adı:"+companynameArray[position]
    holder.recycleOffName?.text="Şirket Yetkilisi :"+companyoffArray[position]
    holder.recycleOffPhone?.text="İrtibat No : "+companyPhoneArray[position]
    }
}

I did not specify the activity I want to go to. I would appreciate it if you could help as a method.

If it helps, I write the codes of the client class here.

class Customers: AppCompatActivity()

{

private lateinit var auth: FirebaseAuth
private lateinit var db: FirebaseFirestore

var companynameFB:ArrayList<String> = ArrayList()
var companyoffFB:ArrayList<String> = ArrayList()
var companyphoneFB:ArrayList<String> = ArrayList()
var adapter :CustomersAdapter?=null


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

    auth= FirebaseAuth.getInstance()
    db= FirebaseFirestore.getInstance()
     getDataFromFirestore()

    var layoutManager= LinearLayoutManager(this)
    recyclerView.layoutManager=layoutManager

    adapter= CustomersAdapter(companynameFB,companyoffFB,companyphoneFB)
    recyclerView.adapter=adapter

}

fun getDataFromFirestore(){

    db.collection("Customers")
        .addSnapshotListener { snapshot, exception ->

        if(exception!=null){

            Toast.makeText(applicationContext,exception.localizedMessage.toString(),Toast.LENGTH_LONG).show()

        }else{

            if(snapshot!=null){

                if (!snapshot.isEmpty){

                    companynameFB.clear()
                    companyoffFB.clear()
                    companyphoneFB.clear()


                    val documents=snapshot.documents
                    for (document in documents){


                        val compname=document.get("compname") as String
                        val compoff=document.get("compoff") as String
                        val compphone=document.get("compphone") as String
                        val user=document.get("user") as String
                        val timeStamp=document.get("date") as Timestamp
                        val date=timeStamp.toDate()

                        companynameFB.add(compname)
                        companyoffFB.add(compoff)
                        companyphoneFB.add(compphone)

                        adapter!!.notifyDataSetChanged()



                    }
                }
            }

        }


    }



}


override fun onCreateOptionsMenu(menu: Menu?): Boolean {

val menuInflater=getMenuInflater() menuInflater.inflate(R.menu.add_customer,menu)

    return super.onCreateOptionsMenu(menu)
}

override fun onOptionsItemSelected(item: MenuItem): Boolean {

    if(item.itemId==R.id.add){


        val intent= Intent(this,AddCustomers::class.java)

intent.putExtra("info","new") startActivity(intent)

    }


    return super.onOptionsItemSelected(item)
}

Answer 1

put your click listener inside onBindViewHolder method

override fun onBindViewHolder(holder: CustomerHolder, position: Int) {
    holder.recycleCompanyName?.text="Şirket Adı:"+companynameArray[position]
    holder.recycleOffName?.text="Şirket Yetkilisi :"+companyoffArray[position]
    holder.recycleOffPhone?.text="İrtibat No : "+companyPhoneArray[position]

 holder.itemView.setOnClickListener {
            // do what ever you want here
            holder.itemView.context.startActivity( /*your intent here*/)
        }
    }
}

Answer 2

Step 1: pass context here

class CustomersAdapter(val context:Context,private val 
companynameArray:ArrayList,private val 
companyoffArray:ArrayList, private val companyPhoneArray:ArrayList): 
RecyclerView.Adapter<CustomersAdapter.CustomerHolder>() {

step 2:

  itemView.setOnClickListener {
       val intent=Intent(context,yourActivity::java.class)
       startActivity(intent)
    }

Answer 3

you need a context for intent so you can get it form the activity or fragment that are associated with this adapter and pass it to your intent or you can get it from any view in your inflated layout like this

 val context=holder.title.context
    val intent = Intent( context, EventDetail::class.java)
    context.startActivity(intent)

Answer 4

For starting a new Activity you need at least a context instance. And as is written in some other answers here, you could start the activity directly inside ViewHolder with View's context. But for better separations of responsibilities, I suggest you move your navigation to your Fragment/Activity , where all other navigations happen. That way you know at the look of Activity/Fragment , which navigations could be done from that screen, and you don't need to search for some hidden navigations that happen inside Adapter or ViewHolder . Also, if you need to perform startActivityForResult , then an instance of Context is not enough to do that. You need an Activity or Fragment instance for that and we have another reason to put all navigations there.

So you can do this like that:

ADD LAMBDA TO ADAPTER CONSTRUCTOR:

class CustomersAdapter(private val companynameArray: ArrayList,
private val companyoffArray: ArrayList, 
private val companyPhoneArray: ArrayList, 
private val onItemClick: () -> Unit) : RecyclerView.Adapter<CustomersAdapter.CustomerHolder>() {

NOTE : put lambda as the last constructor parameter.

ADD LAMBDA TO VIEWHOLDER CONSTRUCTOR:

class CustomerHolder(view: View, 
    private val onItemClick: () -> Unit) : RecyclerView.ViewHolder(view) {

MODIFY VIEWHOLDER CONSTRUCTOR CALL:

override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): CustomerHolder {
    val inflater = LayoutInflater.from(parent.context)
    val view = inflater.inflate(R.layout.recycler_view_customer_row,parent,false)
    return CustomersAdapter.CustomerHolder(view, onItemClick) //Add onItemClick lambda instance from adapter here
}

INVOKE LAMBDA ON CLICK:

itemView.setOnClickListener {
    onItemClick()
}

FIX ADAPTER CONSTRUCTOR CALL:

val adapter = CustomersAdapter(companynameArray, companyoffArray, companyPhoneArray) {
    startActivity() // do your navigation here
}

Why did we place lambda as the last parameter of a constructor in our adapter? If the last parameter of a function is a function, then a lambda expression passed as the corresponding argument can be placed outside the parentheses( SOURCE ). And we did exactly that with the last junk of code above where we handle our navigation.