将数据从 firebase 数据库提取到 android 应用程序时使用进度条

Question

I want to show progress bar on the screen untill all the required data is fetched from firebase database.

How can I use the below code in the fetchMenu() [in MenuFragment.kt]

.addOnSuccessListener(OnSuccessListener<Void?> { // Write was successful!
            // ...
            progressBar.visibility = View.GONE
        })
        .addOnFailureListener(OnFailureListener { // Write failed
            // ...
            progressBar.visibility = View.GONE
        })

MenuFragment.kt

class MenuFragment : Fragment() {

private var dishList: MutableList<DishModel> = mutableListOf()
private lateinit var myRef: DatabaseReference
lateinit var list: RecyclerView
lateinit var proceedToCartLayout: RelativeLayout
lateinit var addToCartBtn: Button
private var selectedCategory = ""
lateinit var progressLayout: RelativeLayout
lateinit var progressBar: ProgressBar

companion object {
    fun newInstance(): Fragment {
        return MenuFragment()
    }
}

override fun onCreateView(
    inflater: LayoutInflater, container: ViewGroup?,
    savedInstanceState: Bundle?
): View? {
    val view = inflater.inflate(R.layout.fragment_menu, container, false)
    //retrieve id
    val bundle = this.arguments
    selectedCategory = bundle!!.getString("CATEGORY_ID")!!
    list = view.findViewById(R.id.recyclerMenu)
    myRef = FirebaseDatabase.getInstance().getReference("Category")
    proceedToCartLayout = view.findViewById(R.id.ProceedToCart)
    addToCartBtn = view.findViewById(R.id.btn_cart)
    progressLayout = view.findViewById(R.id.progressLayout)
    progressBar = view.findViewById(R.id.progressBar)


    return view
}


override fun onResume() {

    if (ConnectionManager().checkConnectivity(activity as Context)) {
        fetchMenu()

    } else {

        val alterDialog = androidx.appcompat.app.AlertDialog.Builder(activity as 
Context)
        alterDialog.setTitle("No Internet")
        alterDialog.setMessage("Connect to internet to continue")
        alterDialog.setIcon(R.drawable.nointernet)
        alterDialog.setPositiveButton("Open Settings") { _, _ ->
            val settingsIntent = Intent(Settings.ACTION_SETTINGS)//open wifi settings
            startActivity(settingsIntent)
        }

        alterDialog.setNegativeButton("Exit") { _, _ ->
            ActivityCompat.finishAffinity(activity as Activity)
        }
        alterDialog.setCancelable(false)

        alterDialog.create()
        alterDialog.show()

    }

    super.onResume()
}

private fun fetchMenu() {


    progressLayout.visibility = View.VISIBLE

    myRef.child(selectedCategory)
        .addValueEventListener(object : ValueEventListener {
            override fun onCancelled(p0: DatabaseError) {
                progressLayout.visibility = View.GONE
                Toast.makeText(context, "$p0", Toast.LENGTH_SHORT).show()
            }


            override fun onDataChange(p0: DataSnapshot) {
                progressLayout.visibility = View.GONE
                if (p0.exists()) {
                    dishList.clear()
                    for (i in p0.children) {
                        val plan = i.getValue(DishModel::class.java)
                        dishList.add(plan!!)
                    }

                    val adapter = MenuAdapter(
                        context!!,
                        R.layout.menu_list_item,
                        dishList,
                        proceedToCartLayout,
                        addToCartBtn, selectedCategory
                    )
                    list.adapter = adapter

                }
            }


        })
}


}

I got the result after using progress bar but didn't get the required result as I want to display the progress bar untill all the rows of the RecyclerView get filled with the data fetched from the firebase database and all the views correctly placed.

I'm getting this while using progress bar

see the video

Answer 1

According to your shared image, you aren't displaying the "ProgressBar" at all. To solve this, please uncomment the following line of code:

progressLayout.visibility = View.VISIBLE

And add the following line:

progressLayout.visibility = View.GONE

Inside the "onDataChange()" method as well. In this way you are starting to display the ProgressBar when the "fetchMenu()" method is called and once you get a response, either the data or an Exception you can hide it.