I'm having a problem with combobox popup (not sure if it's a problem of combobox). First when i click it, dropdown popup opens correct - upwards(there are about 50 items in it, and combobox is located in the bottom of the page, if it goes downwards, there would be only 5 items visible). But then if i select any item, and them open it again - it will open downwards and put items in a scroll. So how can I fix this and force popup open in the desired direction?
Are you setting the "MaxDropDownHeight" at some point? By default it is infinity but maybe setting to hard # greater than # in combo box might help.
Also I just tested this in SL4/Firefox and the combo box pops up each time (with or without a selected item). What version of SL are you using?
Well, what I've done - I subscribed to SizeChanged event of the Border element which is a child of Popup.Child canvas. In that method, I'm calculating space below and above the combo box and then setting Top offset using Canvas.SetTop method to that border and it's MaxHeight. Maybe I will post some code later.
I was having this exact same issue (actually with Silverlight 5, but the same behavior nonetheless). I tried various things with MaxDropDownHeight but that did not correct the problem.
#Walker the approach you mentioned in your answer sounded promising but I was not able to tell from your description how you actually implemented that.
In any case, I found a rather unlikely solution. I discovered that if I populated my ComboBox with ComboBoxItems instead of a collection of custom objects, then the dropdown/selection/direction issue does not occur. I've posted an answer here that goes into a little more detail.
Related
I'm making a custom dropdown button (since the one included in wpf requires too much hacking to style right). Now that i got the button bit out of the way i need to add the drop down part.
My first thought was to add a stackpanel and use that to contain the items but it gets cut off if it leaves the borders of the grid that the button is in. Next up was the popup primitive, it gets on top of everything nicely enough but position wise it just free floats and i haven't figured out how to make it follow the button it was spawned by. I also tried using contextmenu but that seems to have no positioning controls at all and just sits where the mouse made it..
Anyways wpf is a big package and I'm just getting into it, anybody know which direction i might find what I'm looking for?
Preferred approach normally is to use a Popup. You got two very important properties with a Popup
PlacementTarget and Placement
Setup a binding for PlacementTarget on the Popup to your custom Button and then use Placement to position the Popup accordingly w.r.t to the PlacementTarget(Button)
Placement accepts an enum of type PlacementMode which gives you quite a few options to position the Popup.
I am building a WP7 application using Silverlight. This application includes a Page that makes use of the ListPicker. This ListPicker has data that is bound to it via my Page's view-model. The ListPicker displays the options correctly. However, the display looks odd.
When the options initially load, the first option appears selected. This selected item looks to be several pixels off from the top and the left. If I open-and-close the ListPicker, it looks as intended.
Has anyone else experienced this? Does any have any ideas how to overcome this? I attempted setting a binding on the SelectedIndex and SelectedValue properties, but this did not work.
Thank you!
I believe the SL ListPicker works under the assumption that there is always an active selection as long as it is bound to a non-empty dataset. Not sure if you can override this behavior; but seems like your problem is that the selected item looks awkward. Anyway you can adjust the template? Also, please see this post to make sure you are not caught off-guard with the SelectionChanged event.
Hope this helps!
I need to have a ComboBox with multiple columns and column headers. I found Marco Zhou's GridComboBox demo which I like because it's a pretty bare bones approach to doing so and it supports declarative column binding. I've found a couple minor "bugs" or lacking styles with it, but the one that has me stumped is when I bind the combobox to a DataView with a few thousand rows, the first time I open the drop down, the popup displays in the top left hand corner for a few seconds, then jumps down under the toggle button where it should be. I notice while its displaying in the top left, if I hover my mouse over the items its response lags. After it pops back into the correct position it responds quickly. So it seems like it is still loading/processing while it is in the top left and then updates its position once it's done. Almost like virtualization is not working. How can this be fixed?
http://www.cnblogs.com/Files/sheva/GridComboBoxDemo.zip
ComboBox is not virtualizing by default. It must be switched on manually and this is not done in the code you provided. Read about: VirtualizingStackPanel for ComboBoxes.
I have a ListBox that contains a number of User items that are DataTemplated to appear as UserControls in the ListBox. Each UserControl can be expanded in size. To start with, the ListBox is big enough to display them all in their unexpanded state. The problem that I have is that when a number of these UserControls are expanded together, they extend out of the ListBox's visible area. The ListBox does not recognise this fact and no ScrollBars appear, even when they are set to Visible.
I am using DoubleAnimations to alter the UserControl heights when the user clicks on a button in each one. Is there something that I have to do, or some setting on the ListBox that must be set to get it to register the size changes of the UserControls that represent its items and display ScrollBars when needed?
Edit>>>
I have tracked down the problem to a custom WrapPanel that I am using in the ListBox.ItemsPanel. When I remove it, or replace it with a standard WrapPanel, ScrollBars appear when required. I got the code for the Panel from a good article about creating custom WPF panels. Can anyone see what's missing from the code given in the article and why it might stop the ScrollBars from displaying?
I wonder whether ListBoxes normally do what you are expecting? You might try calling InvalidateMeasure/Layout on the ListBox if you know when the item sizes change, just to see?
I decided to write the custom WrapPanel code again completely and this time it worked correctly! When comparing the new version with the previous version, I could see that a + was missing from a += in a measuring calculation and so the Panel thought that the items were much smaller than they really were... hence no ScrollBars.
So, if you have this problem, check your measuring code carefully.
How can I define different ContextMenus for each column in the DataGrid (Microsoft's grid)? I found out that the grid provides a ContextMenu attribute, but i want different context menu items for the columns, not the same ContextMenu for the whole grid.
Edit: Thanks for your answer! I tried to listen to the ContextMenuOpeningEvent as you suggested which was a first success: the ContextMenu can be modified in the EventHandler. But it raises another (hopefully small) problem - I now have to identify the column the mouse cursor was over when the ContextMenuOpeningEvent was triggered. I'm going to research how to do (or work around) that later.
I haven't played with it at all, so this might be wrong, but you may be able to override the ContextMenuOpening event and create the appropriate menu on the fly.
add menu item to default context menu might give you a starting point.
Good luck.