3 ms·

> one list view which updated it's contents to filter results out of an SQLite database as you type into a text field In racket/gui this could be maybe 100 cle

• ohgodplsno 6y ago
  Probably, yes. Hower, does Racket handle configuration changes (orientation, language, etc.), recycling list items to lower memory usage, arbitrary layouts for lists (and not just a single line of text) with diffs calculated between renders, and more ? Android is complex, yes. Sometimes for no reason (hello God Activities). But sometimes, it has good reasons to do so. I actually wrote one, with the bare minimum. HNActivity.kt is 81 lines and handles updating the list, querying import android.database.sqlite.SQLiteDatabase import android.os.Bundle import android.view.LayoutInflater import android.view.View import android.view.ViewGroup import android.widget.EditText import android.widget.TextView import androidx.appcompat.app.AppCompatActivity import androidx.core.widget.addTextChangedListener import androidx.recyclerview.widget.DiffUtil import androidx.recyclerview.widget.LinearLayoutManager import androidx.recyclerview.widget.RecyclerView import kotlin.concurrent.thread class ListItemVH(val view: TextView) : RecyclerView.ViewHolder(view) class HNActivity : AppCompatActivity() { private lateinit var recycler: RecyclerView private val adapter = object: RecyclerView.Adapter<ListItemVH>() { private var _items = listOf<String>() fun setItems(newItems: List<String>) { DiffUtil.calculateDiff(object: DiffUtil.Callback() { override fun getOldListSize(): Int = _items.size override fun getNewListSize(): Int = newItems.size override fun areItemsTheSame(oldItemPosition: Int, newItemPosition: Int) = _items[oldItemPosition] == newItems[newItemPosition] override fun areContentsTheSame(oldItemPosition: Int, newItemPosition: Int) = _items[oldItemPosition] == newItems[newItemPosition] }, true) _items = newItems } override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ListItemVH { val v = TextView(parent.context) return ListItemVH(v) } override fun getItemCount(): Int = _items.size override fun onBindViewHolder(holder: ListItemVH, position: Int) { holder.view.text = _items[position] } } private var search: String? = null override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContentView(R.layout.activity_scrolling) recycler = findViewById<RecyclerView>(R.id.fab) recycler.adapter = adapter recycler.layoutManager = LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false) findViewById<EditText>(R.id.toolbar).addTextChangedListener { search = it?.toString()?.takeIf { str -> str != null } } } private fun performSearch() { thread { val db = SQLiteDatabase.openOrCreateDatabase("items.sqlite", null) val query = when (search) { null -> "SELECT text FROM table" else -> "SELECT text FROM table WHERE text = ?%" } val args = listOfNotNull(search).toTypedArray() val res = db.rawQuery(query, args) val text = mutableListOf<String>() while (!res.isAfterLast) { text += res.getString(0) } adapter.setItems(text) res.close() db.close() } } override fun onResume() { super.onResume() performSearch() } } Add in another 30 lines for the Activity layout, and you've got your thing. You've also got every single developer you'll work with hating you, and you'll hate maintaining this code. Just in those few lines, so much can go wrong (thread gets started and activity gets backgrounded? Oops, you crashed.)
  • catalogia 6y ago
    It would be difficult at best to do these things in racket/gui (to the extent that cocoa/win32/gtk aren't doing them themselves, e.g. diffs between renders I guess?), it certainly does have many shortcomings. racket/gui seems primarily designed to accommodate the needs of Dr Racket, and starts to come up short the further you stray from anything Dr Racket does. I think a big part of this comes down to a lack of manpower, which certainly isn't true of Android. However I think it should be possible to design interfaces that make simple things simple while still giving you the flexibility to do complicated things. I think neither Android nor racket/gui has accomplished this, but at least racket/gui is fun rather than tedious. I agree with the article that there's a lack of user-centered design in the Android scene.
  • Koshkin 6y ago
    Now I want to take a shower and use Haskell for the rest of my life.