win8.1 关于ComboBox弹出问题 如何点击后列表始终向上弹出？而不是根据选项

Question

ComboBox的弹出总是根据选项来决定的，如何固定这个弹出位置 始终向上弹出呢 ？

Answer 1

你好 lxdhuainan，

建议自己重写一个UserControl，这样比较容易指定位置，也可以通过Flyout.Placement来强制设定弹出的位置。个人认为这个是比较容易的办法（其实因为是下面这个办法我没有实现）。

如果单纯的想通过ComboBox中PopupBoder来重新定义位置的话，我没有实现这个改动。

我尝试过对PopupBoder的Visual State做修改，但是没有效果，如果你有兴趣的话可以继续研究一下。我发现每次ComboBox下拉的时候，OffsetFromCenter的值都会变化，我尝试给他设定固定值，但是发现没有用，我个人觉得关键就在这里：

  <SplitOpenThemeAnimation ClosedTargetName="ContentPresenter" 
         ContentTranslationOffset="0" 
         ContentTargetName="ScrollViewer" 
         ClosedLength="{Binding TemplateSettings.DropDownClosedHeight, RelativeSource={RelativeSource Mode=TemplatedParent}}" 
         OffsetFromCenter="{Binding TemplateSettings.DropDownOffset, Converter={StaticResource Converter1}, RelativeSource={RelativeSource Mode=TemplatedParent}}" 
         OpenedTargetName="PopupBorder" 
         OpenedLength="{Binding TemplateSettings.DropDownOpenedHeight, RelativeSource={RelativeSource Mode=TemplatedParent}}"
  />

--James

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Answer 2

谢谢James的回答，我按照你的方法再研究研究！！！

Answer 3

我这两天也在看这个，感觉似乎是写死的，貌似还是得自己使用一个ListBox和TextBox来重写吧。之前我有写过类似这样的代码，你可以参考一下：https://onedrive.live.com/?cid=d22c3bcb62964267&id=D22C3BCB62964267%21209

--James

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Answer 4

你好，做了个Sample上传了一下：http://code.msdn.microsoft.com/Traditional-Style-ComboBox-ed03ea63

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