Content Providers

package com.example.content_providers

import android.database.Cursor
import android.net.Uri
import android.os.Bundle
import android.provider.ContactsContract
import android.util.Log
import android.widget.SimpleCursorAdapter
import androidx.appcompat.app.AppCompatActivity
import kotlinx.android.synthetic.main.activity_main.*


class MainActivity : AppCompatActivity() {
    val TAG = "MainActivity"

    val uri = ContactsContract.CommonDataKinds.Phone.CONTENT_URI
    val SELECTED_COLUMNS = arrayOf(
        ContactsContract.CommonDataKinds.Phone._ID,       // needed by simplecursoradapter
        ContactsContract.CommonDataKinds.Phone.DISPLAY_NAME,
        ContactsContract.CommonDataKinds.Phone.NUMBER
    )


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

        doContentProvidersWithAdapter()
    }

    fun doContentProvidersWithAdapter() {

        val cursor: Cursor? = contentResolver.query(uri, SELECTED_COLUMNS, null, null, null)
        if (cursor != null) {

            // link the SELECTED_COLUMNS to some view IDs. S
            val toViews = intArrayOf(
                -1, // since we don't want to display Phone_ID, we are assigning -1 to it, which doesn't match to any real View in our layout
                R.id.name_textview,
                R.id.number_textview)

            val cursorAdapter = SimpleCursorAdapter(
                this,               // context
                R.layout.list_row,  // layout that defines the views for this list item
                cursor,             // the database cursor
                SELECTED_COLUMNS,   // "From" - column names of the data to bind to the UI
                toViews,            // TextViews that should display column in the "from" param
                0)                  // flags used to determine the behaviour of the adapter

            main_listview.setAdapter(cursorAdapter)


        }
    }

}