simplenotesdroid/MainActivity.cs

using System.Net.Http.Json;
using System.Text.Json.Serialization;
using Android.Content;
using Android.Runtime;
using Android.Views;
using AndroidX.AppCompat.App;
using AndroidX.RecyclerView.Widget;
using AndroidX.SwipeRefreshLayout.Widget;
using Google.Android.Material.Color;
using Google.Android.Material.FloatingActionButton;
using Google.Android.Material.Snackbar;
using Google.Android.Material.TextField;

namespace SimpleNotes;

[Activity(Label = "@string/app_name", MainLauncher = true,Theme ="@style/Theme.SimpleNotes")]
public class MainActivity : AppCompatActivity
{
    public static (string Endpoint,string Username,string Password) GetPrefs(Context ctx)
    {
        var config=ctx.GetSharedPreferences("config",Android.Content.FileCreationMode.Private);
       if(config != null)
        {
            var endpoint = config.GetString("endpoint","") ?? "";
            var username = config.GetString("username","") ?? "";
            var password = config.GetString("password","") ?? "";
            
            return (endpoint.TrimEnd('/'),username,password);
        }
        return ("","","");
    }
    public static readonly HttpClient Client =new HttpClient();
    public override bool OnCreateOptionsMenu(IMenu? menu)
    {
        MenuInflater.Inflate(Resource.Menu.menu_main,menu);
        return true;
    }
    public override bool OnOptionsItemSelected(IMenuItem item)
    {
        int id=item.ItemId;
        if(id == Resource.Id.action_settings)
        {
            var intent = new Intent(this,typeof(SettingActivity));
            StartActivityForResult(intent,0);
        }
        return base.OnOptionsItemSelected(item);
    }
    Func<Task>? fItems;
    protected override void OnCreate(Bundle? savedInstanceState)
    {
        base.OnCreate(savedInstanceState);
        DynamicColors.ApplyToActivityIfAvailable(this);
        // Set our view from the "main" layout resource
        SetContentView(Resource.Layout.activity_main);
        SetSupportActionBar(FindViewById<AndroidX.AppCompat.Widget.Toolbar>(Resource.Id.toolbar));
        FloatingActionButton? fab = FindViewById<FloatingActionButton>(Resource.Id.fab);
        SwipeRefreshLayout? swipeRefreshLayout = FindViewById<SwipeRefreshLayout>(Resource.Id.swiperefresh);
        RecyclerView? recyclerView = FindViewById<RecyclerView>(Resource.Id.recyclerView);        
        if(fab == null || swipeRefreshLayout == null || recyclerView == null) return;
        recyclerView.SetLayoutManager(new LinearLayoutManager(this));
        recyclerView.SetAdapter(new NoteAdapter(new List<Note>()));
        fab.Click += (sender,e)=>{
            var intent = new Intent(this,typeof(NoteActivity));
            StartActivityForResult(intent,0);
        };
        SemaphoreSlim slim=new SemaphoreSlim(1,1);
        fItems = FetchItems;
        async Task FetchItems()
        {
            await slim.WaitAsync();
            Console.WriteLine("ready to fetch");
            var (endpoint,username,password) = GetPrefs(this);
             if(!string.IsNullOrWhiteSpace(endpoint) && !string.IsNullOrWhiteSpace(username) && !string.IsNullOrWhiteSpace(password))
            {            
                var request = new HttpRequestMessage(HttpMethod.Get,$"{endpoint}/api/note");
                request.Headers.Add("Authorization",$"Basic {Convert.ToBase64String(System.Text.Encoding.UTF8.GetBytes($"{username}:{password}"))}");
                var response=await MainActivity.Client.SendAsync(request);
                if(response.IsSuccessStatusCode)
                {
                    Console.WriteLine("Success status code");
                    var notes = await response.Content.ReadFromJsonAsync<_NotesResponse>();
                    Console.WriteLine($"{notes == null} {notes?.Success ?? false}");
                    if(notes != null && notes.Success)
                    {
                        this.RunOnUiThread(()=>{
                        var adapter = new NoteAdapter(notes.Notes);
                        adapter.LaunchNote += LaunchNote;
                        adapter.DeleteNote += DeleteNote;
                        recyclerView.SetAdapter(adapter);
                        });
                        void LaunchNote(object? sender,long e)
                        {
                            Intent intent=new Intent(this,typeof(NoteActivity));
                            intent.PutExtra("note_id",e);
                            StartActivityForResult(intent,0);
                        }
                        
                        void DeleteNote(object? sender,long e){
                            var alert=new AndroidX.AppCompat.App.AlertDialog.Builder(this);
                            alert.SetTitle("Delete Note?");
                            alert.SetPositiveButton("Yes",async(sender2,e2)=>{

                                var request = new HttpRequestMessage(HttpMethod.Delete,$"{endpoint}/api/note?id={e}");
                                request.Headers.Add("Authorization",$"Basic {Convert.ToBase64String(System.Text.Encoding.UTF8.GetBytes($"{username}:{password}"))}");
                                var response=await MainActivity.Client.SendAsync(request);
                                if(response.IsSuccessStatusCode)
                                {
                                    var data = await response.Content.ReadFromJsonAsync<_SuccessResp>();
                                    if(data == null || !data.Success) return;
                                    Note? sen = sender as Note;
                                    if(sen != null)
                                    notes.Notes.Remove(sen);
                                    this.RunOnUiThread(()=>{
                                        var adapter2 = new NoteAdapter(notes.Notes);
                                        adapter2.DeleteNote += DeleteNote;
                                        adapter2.LaunchNote += LaunchNote;
                                        recyclerView.SetAdapter(adapter2);
                                    });
                                }
                            });
                            alert.SetNegativeButton("No",(sender2,e2)=>{});
                            alert.Create().Show();
                        }

                    }
                }
            }               
            slim.Release();
        }
        swipeRefreshLayout.Refresh += async(sender,e)=>{
            await FetchItems();
            this.RunOnUiThread(()=>{
                swipeRefreshLayout.Refreshing=false;
            });
        }; 
        Task.Run(FetchItems).Wait(0);
    }
    protected override void OnActivityResult(int requestCode, [GeneratedEnum] Result resultCode, Intent? data)
    {
        base.OnActivityResult(requestCode, resultCode, data);
        if(fItems != null)
        Task.Run(fItems).Wait(0);
    }
}

internal class NoteAdapter : RecyclerView.Adapter
{
    private Note[] notes;

   
    public event EventHandler<long>? LaunchNote;

    public event EventHandler<long>? DeleteNote; 

    public NoteAdapter(List<Note> notes)
    {
        this.notes = notes.ToArray();
    }

    public void InvokeDeleteNote(Note n,long note)
    {
        DeleteNote?.Invoke(n,note);
    }
    public void InvokeLaunchNode(Note n,long note)
    {
        LaunchNote?.Invoke(n,note);
    }


    public override int ItemCount => notes.Length;
    public class NoteViewHolder : RecyclerView.ViewHolder
    {
    
        public Note Item {set {
                item = value;
                 if(tv != null)
            {
                tv.Text = item.Title;
            }
        }}
        ImageButton? imageButton;
        TextView? tv;
         Note item=new Note();
        public NoteViewHolder(View itemView,NoteAdapter adapter) : base(itemView)
        {
            tv=itemView.FindViewById<TextView>(Resource.Id.rvtextView);
            imageButton = itemView.FindViewById<ImageButton>(Resource.Id.rvimagebutton);
            if(imageButton != null)
            {
                imageButton.Click += (sender,e)=>{
                    adapter.InvokeDeleteNote(this.item,this.item.Id);
                };
            }
           
            itemView.Click += (sender,e)=>{
                adapter.InvokeLaunchNode(this.item,this.item.Id);
            };
        }
    }
    
    public override void OnBindViewHolder(RecyclerView.ViewHolder holder, int position)
    {
        var noteHolder=holder as NoteViewHolder;
        if(noteHolder != null)
        {
            noteHolder.Item = notes[position];
        }
    }

    public override RecyclerView.ViewHolder OnCreateViewHolder(ViewGroup parent, int viewType)
    {
       View? itemView = LayoutInflater.From(parent.Context)?.Inflate(Resource.Layout.note_view, parent, false);
        if(itemView == null) throw new Exception();
        return new NoteViewHolder(itemView,this);
    }
}
public class _SuccessResp
{
    [JsonPropertyName("success")]
    public bool Success {get;set;}
}
public class _NotesResponse
{
    [JsonPropertyName("success")]
    public bool Success {get;set;}
    [JsonPropertyName("notes")]
    public List<Note> Notes {get;set;}=new List<Note>();
}