optimized and add diagnostic feature

Billing.Shared/Views/CategorySelectPage.xaml.cs

@@ -1,6 +1,5 @@
 using Billing.Languages;
 using Billing.Models;
-using Billing.Themes;
 using Billing.UI;
 using System;
 using System.Collections.Generic;
@@ -31,12 +30,10 @@ namespace Billing.Views
         public event EventHandler<UICategory> CategoryTapped;
 
         private readonly int categoryId;
-        private readonly Color defaultColor;
 
         public CategorySelectPage(int id)
         {
             categoryId = id;
-            defaultColor = BaseTheme.CurrentPrimaryColor;
             TapTopCategory = new Command(OnTopCategoryTapped);
             TapSubCategory = new Command(OnSubCategoryTapped);
 
@@ -45,6 +42,22 @@ namespace Billing.Views
                 new(Resource.Spending, App.Categories.Where(c => c.Type == CategoryType.Spending && c.ParentId == null).Select(c => WrapCategory(c))),
                 new(Resource.Income, App.Categories.Where(c => c.Type == CategoryType.Income && c.ParentId == null).Select(c => WrapCategory(c)))
             };
+            UICategory last;
+            if (App.Categories.Any(c => c.LastUsed != null))
+            {
+                last = new UICategory(null)
+                {
+                    IsChecked = true,
+                    Icon = "rank",
+                    Name = Resource.LastSelected,
+                    TintColor = Definition.TransparentColor
+                };
+                TopCategories.Insert(0, new(Resource.Recent) { last });
+            }
+            else
+            {
+                last = null;
+            }
 
             UICategory cat;
             var category = App.Categories.FirstOrDefault(c => c.Id == categoryId);
@@ -58,7 +71,7 @@ namespace Billing.Views
             }
             else
             {
-                cat = TopCategories.SelectMany(g => g).FirstOrDefault(c => c.Category.Id == category.ParentId);
+                cat = TopCategories.SelectMany(g => g).FirstOrDefault(c => c.Category?.Id == category.ParentId) ?? last;
             }
             DoRefreshSubCategories(cat);
 
@@ -72,7 +85,7 @@ namespace Billing.Views
                 IsChecked = c.Id == categoryId,
                 Icon = c.Icon,
                 Name = c.Name,
-                TintColor = c.TintColor.IsTransparent() ? defaultColor : c.TintColor.ToColor()
+                TintColor = c.TintColor
             };
         }
 
@@ -83,7 +96,18 @@ namespace Billing.Views
             {
                 m.IsChecked = m == category;
             }
-            SubCategories = App.Categories.Where(c => c.ParentId == category.Category.Id).Select(c => WrapCategory(c)).ToList();
+            if (category == null)
+            {
+                return;
+            }
+            if (category.Category == null)
+            {
+                SubCategories = App.Categories.Where(c => c.ParentId != null && c.LastUsed != null).OrderByDescending(c => c.LastUsed).Take(10).Select(c => WrapCategory(c)).ToList();
+            }
+            else
+            {
+                SubCategories = App.Categories.Where(c => c.ParentId == category.Category.Id).Select(c => WrapCategory(c)).ToList();
+            }
         }
 
         private async void OnTopCategoryTapped(object o)
@@ -97,7 +121,7 @@ namespace Billing.Views
                 if (o is UICategory category)
                 {
                     DoRefreshSubCategories(category);
-                    if (SubCategories.Count == 0)
+                    if (SubCategories?.Count == 0)
                     {
                         CategoryTapped?.Invoke(this, category);
                         await Navigation.PopAsync();