FMX TListbox 中的项目选择不正确(Grid Metropolis UI) [英] Incorrect selection of items in an FMX TListbox (Grid Metropolis UI)

问题描述

我遇到了一个问题，即在我的应用程序中的 TListBox 中的项目选择不正确，表单中有一个 HorzScrollBox.表单上有两个(或更多)TListBox.它们彼此远离放置，因此它们的绝对左坐标差大于当前设备屏幕宽度的宽度.错误出现在以下用户操作序列中.

I have met an issue of unproper selection of items in TListBox in my application with a HorzScrollBox in the form. The form has two (or more) TListBox on it. They are placed away from each other so that their absolute left coordinates difference is more than the width of the current device screen width. The error appears in the following sequence of user actions.

1. 从左侧选择一个项目TListBox
2. HorzScrollBox 向右滚动，第二个 TListBox 对用户可见，而左边的 - 不可见.
3. HorzScrollBox 向左滚动.
4. 从左侧TListBox中选择了一个新项目.

1. An item is selected from the left TListBox
2. The HorzScrollBox is scrolled to the right and the second TListBox becomes visible to user and the left one - invisible.
3. The HorzScrollBox is scrolled back to the left.
4. An new item is selected from the left TListBox.

我们得到以下图片:新项目被选中，但即使我们上下滚动框，选择仍然绘制在先前选择的项目的位置上.

We get the following picture: The new item is selected but the selection stays painted over the position of the previously selected item even if we scroll the box up and down.

可以通过非常简单的方式重现该错误.

It is possible to reproduce the bug in a very simple way.

1. 创建一个新的 Grid MetropolisUI 应用程序.
2. 将左侧标准TListBox替换为新的(会更快).
3. 将表单的宽度设置为大于屏幕宽度
4. 将第二个新的 TListBox 放在 HorzScrollBox 内，这样左右 TListboxes 不会同时出现，并且选择只有在 HorzScrollBox 滚动后才能使用项目.
5. 从任何来源(例如两个 TPrototypeBindSource)填充它们并将创建的 LinkFieldControlToField 的 ListItemStyle 属性设置为 MetropolisUI.

1. Create a new Grid MetropolisUI Application.
2. Replace the left standard TListBox with a new one (it will be faster).
3. Set the width of the form larger then your screen width
4. Place the second new TListBox inside the HorzScrollBox in such a way so that left and right TListboxes will not be seen simultaneously and selection of items is possible only after scrolling of the HorzScrollBox.
5. Populate them from any sources (ex. two TPrototypeBindSource) and set the ListItemStyle properties of created LinkFieldControlToField to MetropolisUI.

完成.当您运行应用程序时，您会遇到问题.仅当您滚动 HorzScrollBox 时才会出现该错误，因此当您选择第一个中的项目时看不到第二个 ListBox.否则，项目会被正确选择(即使您滚动 HorzScrollBox).这是表单的资源(除了样式的二进制文件，它需要存在才能重现错误).

Done. When you run the application you get the issue. The bug appears only when you scroll the HorzScrollBox so that you do not see the second ListBox when you select an item in the first one. Otherwise the items are selected properly (even if you scroll the HorzScrollBox). Here is the resource of the form (except the binary of the style, it needs to be present to reproduce the bug).

object GridViewForm: TGridViewForm
  Left = 0
  Top = 0
  Caption = 'Grid Form'
  ClientHeight = 946
  ClientWidth = 2600
  StyleBook = StyleBook2
  FormFactor.Width = 1280
  FormFactor.Height = 1024
  FormFactor.Devices = [dkDesktop]
  FormFamily = 'Main'
  FullScreen = True
  OnMouseUp = FormMouseUp
  Touch.InteractiveGestures = [igPan]
  OnGesture = FormGesture
  DesignerMobile = False
  DesignerWidth = 0
  DesignerHeight = 0
  DesignerDeviceName = ''
  DesignerOrientation = 0
  DesignerOSVersion = ''
  object MainLayout: TLayout
    Align = alContents
    Height = 921.000000000000000000
    Margins.Top = 25.000000000000000000
    Width = 2600.000000000000000000
    object HorzScrollBox1: THorzScrollBox
      Align = alClient
      Height = 921.000000000000000000
      TabOrder = 0
      Width = 2600.000000000000000000
      object GroupLayout1: TLayout
        Align = alLeft
        Anchors = [akLeft, akTop]
        Height = 905.000000000000000000
        Margins.Left = 110.000000000000000000
        Position.X = 110.000000000000000000
        Width = 540.000000000000000000
        object ListBox4: TListBox
          Align = alClient
          Height = 905.000000000000000000
          StyleLookup = 'collectionlistbox'
          TabOrder = 0
          Width = 540.000000000000000000
          DefaultItemStyles.ItemStyle = ''
          DefaultItemStyles.GroupHeaderStyle = ''
          DefaultItemStyles.GroupFooterStyle = ''
        end
      end
      object GroupLayout2: TLayout
        Align = alLeft
        Anchors = [akLeft, akTop]
        Height = 905.000000000000000000
        Margins.Left = 40.000000000000000000
        Position.X = 690.000000000000000000
        Width = 1225.000000000000000000
      end
      object Layout1: TLayout
        Align = alLeft
        Anchors = [akLeft, akTop]
        Height = 905.000000000000000000
        Margins.Left = 40.000000000000000000
        Margins.Right = 100.000000000000000000
        Position.X = 1955.000000000000000000
        Width = 660.000000000000000000
        object Label1: TLabel
          Align = alTop
          AutoSize = True
          Height = 40.000000000000000000
          Margins.Left = 10.000000000000000000
          Margins.Bottom = 5.000000000000000000
          Position.X = 10.000000000000000000
          StyleLookup = 'pagesubheaderlabel'
          Text = 'Group Title: 4'
          Width = 165.000000000000000000
          WordWrap = False
        end
        object ListBox1: TListBox
          Align = alClient
          Height = 855.000000000000000000
          StyleLookup = 'collectionlistbox'
          TabOrder = 1
          Width = 660.000000000000000000
          DefaultItemStyles.ItemStyle = ''
          DefaultItemStyles.GroupHeaderStyle = ''
          DefaultItemStyles.GroupFooterStyle = ''
        end
      end
    end
  end
  object StyleBook2: TStyleBook
    Left = 632
    Top = 544
    ResourcesBin = {...}
  end
  object PrototypeBindSource1: TPrototypeBindSource
    AutoActivate = True
    AutoPost = False
    FieldDefs = <
      item
        Name = 'ContactBitmapL1'
        FieldType = ftBitmap
        Generator = 'ContactBitmapsL'
        ReadOnly = False
      end
      item
        Name = 'ContactName1'
        Generator = 'ContactNames'
        ReadOnly = False
      end
      item
        Name = 'IntField1'
        FieldType = ftInteger
        Generator = 'Integers'
        ReadOnly = False
      end>
    ScopeMappings = <>
    Left = 1288
    Top = 456
  end
  object BindingsList1: TBindingsList
    Methods = <>
    OutputConverters = <>
    Left = 20
    Top = 5
    object LinkFillControlToField1: TLinkFillControlToField
      Category = 'Quick Bindings'
      Control = ListBox4
      Track = True
      FillDataSource = PrototypeBindSource1
      FillDisplayFieldName = 'ContactName1'
      AutoFill = True
      BufferCount = -1
      AutoBufferCount = False
      ListItemStyle = 'MetropolisUI'
      FillExpressions = <
        item
          SourceMemberName = 'ContactBitmapL1'
          ControlMemberName = 'Icon'
        end
        item
          SourceMemberName = 'IntField1'
          ControlMemberName = 'SubTitle'
        end>
      FillHeaderExpressions = <>
      FillBreakGroups = <>
    end
    object LinkFillControlToField2: TLinkFillControlToField
      Category = 'Quick Bindings'
      Control = ListBox1
      Track = True
      FillDataSource = PrototypeBindSource2
      FillDisplayFieldName = 'ContactName1'
      AutoFill = True
      BufferCount = -1
      AutoBufferCount = False
      ListItemStyle = 'MetropolisUI'
      FillExpressions = <
        item
          SourceMemberName = 'FloatField1'
          ControlMemberName = 'SubTitle'
        end
        item
          SourceMemberName = 'ContactBitmap1'
          ControlMemberName = 'Icon'
        end>
      FillHeaderExpressions = <>
      FillBreakGroups = <>
    end
  end
  object PrototypeBindSource2: TPrototypeBindSource
    AutoActivate = True
    AutoPost = False
    FieldDefs = <
      item
        Name = 'ContactBitmap1'
        FieldType = ftBitmap
        Generator = 'ContactBitmaps'
        ReadOnly = False
      end
      item
        Name = 'ContactName1'
        Generator = 'ContactNames'
        ReadOnly = False
      end
      item
        Name = 'FloatField1'
        FieldType = ftSingle
        Generator = 'Floats'
        ReadOnly = False
      end>
    ScopeMappings = <>
    Left = 1232
    Top = 448
  end
end

有人对如何应对有任何建议吗?

Does anyone have any suggestions how to cope with it?

推荐答案

我通过设置 ListBox1.CanFocus := false; 找到了答案.在某些情况下(实际上)错误会再次出现.

I found an answer by setting ListBox1.CanFocus := false;. In certain cases (rearly) the bug reoccurs.

这篇关于FMX TListbox 中的项目选择不正确(Grid Metropolis UI)的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！