F# Xamarin 中的 SizeforItematIndexPath

Posted 2023-03-14

【中文标题】F# Xamarin 中的 SizeforItematIndexPath

【英文标题】：SizeforItematIndexPath in F# Xamarin

【发布时间】：2018-01-18 11:58:07

【问题描述】：

我正在尝试覆盖UICollectionViewFlowLayout 的以下方法，以指定我的UICollectionViewCell 的大小：

    [MonoTouch.Foundation.Export("collectionView:layout:sizeForItemAtIndexPath:")]
public virtual SizeF GetSizeForItem (UICollectionView collectionView, UICollectionViewLayout layout, NSIndexPath indexPath)

为此，我执行以下操作：

type CollectionViewFlowDelegate (handle:IntPtr) as this = 
inherit UICollectionViewFlowLayout (handle)

override this.GetSizeForItem(collectionView : UICollectionView, layout : UICollectionViewLayout, indexPath : NSIndexPath) =
    CGSize(100.0, 300.0)

但是，这会引发错误，说明没有这样的方法。我已经打开了UICollectionViewFlowLayout 的F# 实现，但是我在那里找不到这个方法：

using CoreGraphics;
using Foundation;
using ObjCRuntime;
using System;
using System.ComponentModel;
using System.Runtime.CompilerServices;

namespace UIKit

    [Register ("UICollectionViewFlowLayout", true), Introduced (PlatformName.ios, 6, 0, PlatformArchitecture.None, null)]
    public class UICollectionViewFlowLayout : UICollectionViewLayout
    
        //
        // Static Properties
        //
        [Field ("UICollectionViewFlowLayoutAutomaticSize", "UIKit"), Introduced (PlatformName.iOS, 10, 0, PlatformArchitecture.None, null), Introduced (PlatformName.TvOS, 10, 0, PlatformArchitecture.None, null)]
        public static CGSize AutomaticSize 
            [Introduced (PlatformName.iOS, 10, 0, PlatformArchitecture.None, null), Introduced (PlatformName.TvOS, 10, 0, PlatformArchitecture.None, null)]
            get;
        

        //
        // Properties
        //
        public override IntPtr ClassHandle 
            get;
        

        [Introduced (PlatformName.iOS, 8, 0, PlatformArchitecture.None, null), CompilerGenerated]
        public virtual CGSize EstimatedItemSize 
            [Export ("estimatedItemSize"), Introduced (PlatformName.iOS, 8, 0, PlatformArchitecture.None, null)]
            get;
            [Export ("setEstimatedItemSize:"), Introduced (PlatformName.iOS, 8, 0, PlatformArchitecture.None, null)]
            set;
        

        [CompilerGenerated]
        public virtual CGSize FooterReferenceSize 
            [Export ("footerReferenceSize")]
            get;
            [Export ("setFooterReferenceSize:")]
            set;
        

        [CompilerGenerated]
        public virtual CGSize HeaderReferenceSize 
            [Export ("headerReferenceSize")]
            get;
            [Export ("setHeaderReferenceSize:")]
            set;
        

        [CompilerGenerated]
        public virtual CGSize ItemSize 
            [Export ("itemSize")]
            get;
            [Export ("setItemSize:")]
            set;
        

        [CompilerGenerated]
        public virtual nfloat MinimumInteritemSpacing 
            [Export ("minimumInteritemSpacing")]
            get;
            [Export ("setMinimumInteritemSpacing:")]
            set;
        

        [CompilerGenerated]
        public virtual nfloat MinimumLineSpacing 
            [Export ("minimumLineSpacing")]
            get;
            [Export ("setMinimumLineSpacing:")]
            set;
        

        [CompilerGenerated]
        public virtual UICollectionViewScrollDirection ScrollDirection 
            [Export ("scrollDirection")]
            get;
            [Export ("setScrollDirection:")]
            set;
        

        [Introduced (PlatformName.iOS, 9, 0, PlatformArchitecture.None, null), CompilerGenerated]
        public virtual bool SectionFootersPinToVisibleBounds 
            [Export ("sectionFootersPinToVisibleBounds"), Introduced (PlatformName.iOS, 9, 0, PlatformArchitecture.None, null)]
            get;
            [Export ("setSectionFootersPinToVisibleBounds:"), Introduced (PlatformName.iOS, 9, 0, PlatformArchitecture.None, null)]
            set;
        

        [Introduced (PlatformName.iOS, 9, 0, PlatformArchitecture.None, null), CompilerGenerated]
        public virtual bool SectionHeadersPinToVisibleBounds 
            [Export ("sectionHeadersPinToVisibleBounds"), Introduced (PlatformName.iOS, 9, 0, PlatformArchitecture.None, null)]
            get;
            [Export ("setSectionHeadersPinToVisibleBounds:"), Introduced (PlatformName.iOS, 9, 0, PlatformArchitecture.None, null)]
            set;
        

        [CompilerGenerated]
        public virtual UIEdgeInsets SectionInset 
            [Export ("sectionInset")]
            get;
            [Export ("setSectionInset:")]
            set;
        

        [Introduced (PlatformName.iOS, 11, 0, PlatformArchitecture.None, null), Introduced (PlatformName.TvOS, 11, 0, PlatformArchitecture.None, null), Unavailable (PlatformName.WatchOS, PlatformArchitecture.All, null), CompilerGenerated]
        public virtual UICollectionViewFlowLayoutSectionInsetReference SectionInsetReference 
            [Export ("sectionInsetReference", ArgumentSemantic.Assign), Introduced (PlatformName.iOS, 11, 0, PlatformArchitecture.None, null), Introduced (PlatformName.TvOS, 11, 0, PlatformArchitecture.None, null), Unavailable (PlatformName.WatchOS, PlatformArchitecture.All, null)]
            get;
            [Export ("setSectionInsetReference:", ArgumentSemantic.Assign), Introduced (PlatformName.iOS, 11, 0, PlatformArchitecture.None, null), Introduced (PlatformName.TvOS, 11, 0, PlatformArchitecture.None, null), Unavailable (PlatformName.WatchOS, PlatformArchitecture.All, null)]
            set;
        

        //
        // Constructors
        //
        [Export ("init"), EditorBrowsable (EditorBrowsableState.Advanced), CompilerGenerated]
        public UICollectionViewFlowLayout ();

        [Export ("initWithCoder:"), DesignatedInitializer, EditorBrowsable (EditorBrowsableState.Advanced), CompilerGenerated]
        public UICollectionViewFlowLayout (NSCoder coder);

        [EditorBrowsable (EditorBrowsableState.Advanced), CompilerGenerated]
        protected UICollectionViewFlowLayout (NSObjectFlag t);
    

我不确定我做错了什么。

【参考方案1】：

GetSizeForItem 定义在UICollectionViewDelegateFlowLayout

您必须创建从UICollectionViewDelegateFlowLayout 派生的子类，并将其分配给CollectionView.Delegate。