完成WaterfallContentPanel，未测试

PixivFSUWP/Controls/WaterfallContentPanel.cs

@@ -0,0 +1,82 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using Windows.Foundation;
+using Windows.UI.Xaml;
+using Windows.UI.Xaml.Controls;
+
+namespace PixivFSUWP.Controls
+{
+    public class WaterfallContentPanel : Panel
+    {
+        //此属性决定瀑布流列数
+        public static readonly DependencyProperty ColumsProperty =
+            DependencyProperty.Register("Colums", typeof(int),
+                typeof(WaterfallContentPanel), new PropertyMetadata(2,
+                    (DepObj, e) =>
+                    {
+                        (DepObj as WaterfallContentPanel).InvalidateMeasure();
+                        (DepObj as WaterfallContentPanel).InvalidateArrange();
+                    }));
+
+        public int Colums
+        {
+            get => (int)GetValue(ColumsProperty);
+            set => SetValue(ColumsProperty, value);
+        }
+
+        //此属性决定项目间隔
+        public static readonly DependencyProperty ItemMarginProperty =
+            DependencyProperty.Register("ItemMargin", typeof(double),
+                typeof(WaterfallContentPanel), new PropertyMetadata(0,
+                    (DepObj, e) =>
+                    {
+                        (DepObj as WaterfallContentPanel).InvalidateMeasure();
+                        (DepObj as WaterfallContentPanel).InvalidateArrange();
+                    }));
+
+        public double ItemMargin
+        {
+            get => (double)GetValue(ItemMarginProperty);
+            set => SetValue(ItemMarginProperty, value);
+        }
+
+        //测量panel需要的空间
+        //宽度填满，高度进行计算
+        protected override Size MeasureOverride(Size availableSize)
+        {
+            Size toret = new Size();
+            List<double> heights = new List<double>(Colums);
+            toret.Width = availableSize.Width;
+            double itemwidth = (availableSize.Width - ItemMargin * (Colums - 1)) / Colums;
+            foreach (var i in Children)
+            {
+                i.Measure(new Size(itemwidth, double.PositiveInfinity));
+                heights[heights.IndexOf(heights.Min())] += ItemMargin + i.DesiredSize.Height;
+            }
+            toret.Height = heights.Max();
+            return toret;
+        }
+
+        //排版，不改变大小
+        protected override Size ArrangeOverride(Size finalSize)
+        {
+            List<double> Xs = new List<double>();
+            List<double> Ys = new List<double>();
+            for (int i = 0; i < Colums; i++)
+            {
+                Xs.Add(i * (DesiredSize.Width + ItemMargin) / Colums);
+                Ys.Add(0);
+            }
+            foreach (var i in Children)
+            {
+                var minC = Xs.IndexOf(Xs.Min());
+                i.Arrange(new Rect(Xs[minC], Ys[minC], i.DesiredSize.Width, i.DesiredSize.Height));
+                Ys[minC] += i.DesiredSize.Height + ItemMargin;
+            }
+            return finalSize;
+        }
+    }
+}

PixivFSUWP/MainPage.xaml

@@ -3,11 +3,18 @@
     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
     xmlns:local="using:PixivFSUWP"
+    xmlns:viewmodels="using:PixivFSUWP.ViewModels"
     xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
     xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
     mc:Ignorable="d"
     Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
-
+
+    <Page.Transitions>
+        <TransitionCollection>
+            <NavigationThemeTransition />
+        </TransitionCollection>
+    </Page.Transitions>
+
     <Grid>
 
     </Grid>

PixivFSUWP/PixivFSUWP.csproj

@@ -119,6 +119,7 @@
     <Compile Include="App.xaml.cs">
       <DependentUpon>App.xaml</DependentUpon>
     </Compile>
+    <Compile Include="Controls\WaterfallContentPanel.cs" />
     <Compile Include="Data\OverAll.cs" />
     <Compile Include="Data\WaterfallItem.cs" />
     <Compile Include="LoginPage.xaml.cs">