I have dynamic list with 20~ cells.
I have 3 types of cells so i can't use Listview.
I am using ScrollView that contains StackLayout with the cell elements.
each cell element is also a StackLayout that contains some labels and buttons
the scrolling is smooth.
I have option in each cell to add image by a pressing a button inside the cell.
After the image is added, the scroll is getting very slow when arriving to the cell with the image.
when scrolling beyond the image, the scroll become smooth again
I have also tried TableView but the scrolling is not smooth when presenting the Cells (without adding the image)
How can i improve the rendering of the image ?
I have 3 types of cells so i can't use Listview.
Actually you can use a ListView, by using a DataTemplateSelector. As long as you have a collection containing all of the objects to be displayed, and each object in the collection indicates the cell type (usually because of it model's type), ListView with DataTemplateSelector will work great.
Whether you stick with ScrollView or move to ListView, look into FFImageLoading for displaying images if possible. While it doesn't solve all image display problems, it often does help with responsiveness and image size issues.
Related
I have been having issues with using the ScrollToAsync function of a ScrollView when running on Android, not tested on iOS yet.
I'm using Xamarin.Forms version 2.5.1.444934 using .Net Standard
Testing on the Android Emulator (8.0, API26) and a Google Pixel (8.1 API27), both have the same issue.
I use NavigationPage and Navigation.PushAsync to move between pages (therefore have navigation bars on every page).
I want to create an auto populate field control, the user types in the first few letters and I look up the results in a database / static list of string and display the results below for the user to click/tap.
I have this working using a composite control (the contents of the frame marked interesting below).
The problem I have is scrolling the view to show the results.
My page has this layout hierarchy:-
ContentPage
StackLayout
ScrollView
StackLayout
Frame (some label and entry fields inside a stack layout)
Frame (some label and entry fields inside a stack layout)
Frame (some label and entry fields inside a stack layout)
Frame (the interesting one that deals with scrolling)
StackLayout
Heading Label
StackLayout
Label x:Name="ScrollToLabel"
Entry x:Name="ScrollToEntry"
Grid x:Name="ScrollToGrid"
Entry x:Name="Hidden" Text="I should stay visible as you type"
/StackLayout
/StackLayout
/Frame
Frame (some label and entry fields inside a stack layout)
Frame (some label and entry fields inside a stack layout)
/StackLayout
/ScrollView
StackLayout
Button Text = Done
/StackLayout
/StackLayout
/ContentPage
When the user clicks/taps in to ScrollToEntry, the keyboard opens and pans the control to above the keyboard (ok so far).
When the user starts typing in ScrollToEntry, the code populates ScrollToGrid with up to 5 results.
At this point I want to make sure that the grid results are visible for the user to tap on.
I have tried 2 different options, ScrollToAsync(ScrollToLabel, Start) and ScrollToAsync(Hidden, MakeVisible).
Neither work as I would like 100% of the time.
ScrollToAsync(ScrollToLabel, Start)
If the ScrollToEntry is at the bottom of the screen, the navigation bar is hidden and the view pans up too far.
The ScrollToLabel is now off the top of the screen.
When the second letter is clicked/tapped, the Navigation bar is restored and the scroll scrolls correctly, ScrollToLabel at the top of the screen.
If the ScrollToEntry is near the top of the screen, the navigation bar is not hidden and it scrolls correctly.
ScrollToAsync(Hidden, MakeVisible)
This is my preferred option because it would only scroll as far as needed to display all the results (not all the way to the top).
This works even worse than the first one.
In most cases, it does not scroll at all, I assume it thinks it already visible but is actually behind the keyboard?
If it does scroll, the label Hidden is still not displayed (I tested with both a HeightRequest="0" version and a visible version, both the same result).
I tried using the below code to change the adjust to resize.
Application.Current.On<Xamarin.Forms.PlatformConfiguration.Android>().UseWindowSoftInputModeAdjust(WindowSoftInputModeAdjust.Resize);
2 issues,
1. Because it resizes, the Done button now is above the keyboard, taking up space.
2. When clicking the hardware back button (not the done or navigation back button) the previous view now has a white space where the keyboard was.
If using the done or navigation back, the screen initially appears with the white space but then refreshes to full screen.
I have created a sample app that highlights the issues (by default using pan, not resize).
It's the most simple version of the layout I'm using...
Am I doing something wrong or is this just how it works? If its how it works, this must be a bug? If I'm doing it wrong, can someone tell me what or suggest a different way of doing it?
I am trying to create a grid layout of images kind of like how google images does it.
I want to add fixed sized images left to right, top to bottom but I am having trouble is figuring out when adding another image to a row would make it not fit and then decide that that images should be placed in a new row.
Also when the window resizes it should move images into/from rows based on how many it can fit in.
Ive got a scroll area with a grid layout in it which is fine if I know what can fit, but I can't figure out how to make it move items if say the window width is shrunk, and say an item needs to be moved down 1 row which moves other etc.
Assuming you are using QWidgets I'd suggest you to use QListView which does the layouting for free, if you want more control on how items are displayed use a QItemDelegate. For QListView the view mode should be set to QListView::IconMode so that you have a grid of items and not a list.
But if you are using QtQuick things are much easier, a GridView with Image delegates would do what you want really quickly and using GPU power to build you UI.
Hi i'm trying to get a photoshop-like behaviour for my QGraphicsScene
The grid in the background should not resize with the call of scale. And I must be able to save the picture with QPixmap::grabWidget(view) but without the background grid. I can probably do it with removing the background layer just before saving the picture, but i'm not sure if its cleanest way to do it.
Any ideas ?
thx.
Question 1
The grid in the background should not resize with the call of scale.
Use the QGraphicsItem::ItemIgnoresTransformations flag.
The item ignores inherited transformations (i.e., its position is
still anchored to its parent, but the parent or view rotation, zoom or
shear transformations are ignored). This flag is useful for keeping
text label items horizontal and unscaled, so they will still be
readable if the view is transformed. When set, the item's view
geometry and scene geometry will be maintained separately.
In order to set this flag use the setFlag function when creating the grid item.
Question 2
I must be able to save the picture with QPixmap::grabWidget(view) but without the
background grid.
Call the hide function on the grid item before calling the grabWidget. After you have grabbed it you show it again by calling the show function.
I am not able to figure out how to zoom the image displayed with the help of an item renderer.If i apply the Zoom effect on rollover ,the particular cell zooms the image with the scroll bars.Is their any other way of doing this without showing the scrollbars.
You'll need to duplicate the image and place it outside of the datagrid component. If it's inside the datagrid, it'll be forced into one of the rows. It might be helpful for you to look at the code for the DataGridDragProxy - it does does something sorta similar.
I am using a horizontal tilelist in flex to display an image gallery with only one item in horiz. tilelist being shown at a time. I have next and previous buttons on both sides.
The problem is I want to display a particular item/image in that list when user clicks on a thumb image from another thumbimages tilelist at bottom.
I used someTilelist.selectedIndex property but it just selects that particular index in list, it does not show that particular item/image. I want the list to show that particular image, not just select it. Please take note that the horiz. tilelist shows only one image at time.
tilelist.scrollToIndex(index);