Once a VariableSizedWrapGrid has rendered its content, is there a way to refresh its layout so that it re-renders and re-applies the sizes if they have changed?
For example, the first item is twice the size of the rest, then I change the column and row span values in the view model. Now I want to invoke the grid to re-render.
Here's a simple way:
public void Update(GridView gridView)
{
if (!(gridView.ItemsPanelRoot is VariableSizedWrapGrid))
throw new ArgumentException("ItemsPanel is not VariableSizedWrapGrid");
foreach (var container in gridView.ItemsPanelRoot.Children.Cast<GridViewItem>())
{
var data = container.Content as Common.ModelBase;
VariableSizedWrapGrid.SetRowSpan(container, data.RowSpan);
VariableSizedWrapGrid.SetColumnSpan(container, data.ColSpan);
}
gridView.ItemsPanelRoot.InvalidateMeasure();
}
Assuming Windows.UI.Xaml.Controls.GridView as ItemsControl
Assuming Windows.UI.Xaml.Controls.VariableSizedWrapGrid as ItemPanel
I integrated it into the custom grid like this: http://codepaste.net/aopvks
Best of luck!
Related
I am adding a 'sticky-header' class to my dynamically, but when its sticky i obviously also need to add padding to my so the content doesnt go behind the header.
The problem is that when adding the padding via class-binding(v-bind:class="{'fixed-header': stickyHeader}")on scroll, this reloads all the lazy-loaded images (that are lazy loaded using vue lazy)
This makes all images go from loading to loaded in a split second, but its very noticable.
stickyHeaderis a boolean that gets recalculated on scroll, if the window is scrolled past a certain element (with a eventlistener on scroll: checkHeader())
checkHeader() {
var elementTarget = document.getElementById("notice");
if(window.scrollY > (elementTarget.offsetTop + elementTarget.offsetHeight)){
this.stickyHeader = true;
}
else{
this.stickyHeader = false;
}
}
Anyone know what exactly triggers the images to go back to 'loading' for a split second?
To solve this instead of dynamically binding the class with v-bind i simply add it in the scroll listener method with basic javascript, now it doesnt rerender :) !
I run often into many problems which leads to refactoring my code...
That is why I want to ask for some recommendations.
The problems I'm running into are:
1) Providing data to XAML
Providing simple data to control value instead of using a value converter. For instance I have a color string like "#FF234243" which is stored in a class. The value for the string is provided by a web application so I can only specify it at runtime.
2) UI for every resolution
In the beginnings of my learning I got told that you can create a UI for every possible resolution, which is stupid.
So I've written a ValueConverter which I bind on an element and as ConverterParameter I give a value like '300' which gets calculated for every possible resolution... But this leads to code like this...
<TextBlock
Height={Binding Converter={StaticResource SizeValue}, ConverterParameter='300'}
/>
3) DependencyProperties vs. NotifyProperties(Properties which implement INotifyPropertyChanged) vs. Properties
I have written a control which takes a list of value and converts them into Buttons which are clickable in the UI. So I did it like this I created a variable which I set as DataContext for this specific Control and validate my data with DataContextChanged but my coworker mentioned that for this reason DependencyProperties where introduced. So I created a DependecyProperty which takes the list of items BUT when the property gets a value I have to render the buttons... So I would have to do something like
public List<string> Buttons
{
get { return (List<string>)GetValue(ButtonsProperty); }
set
{
SetValue(ButtonsProperty, value);
RenderButtons();
}
}
// Using a DependencyProperty as the backing store for Buttons. This enables animation, styling, binding, etc...
public static readonly DependencyProperty ButtonsProperty =
DependencyProperty.Register("Buttons", typeof(List<string>), typeof(MainPage), new PropertyMetadata(""));
private void RenderButtons()
{
ButtonBar.Children.Clear();
ButtonBar.ColumnDefinitions.Clear();
if(Buttons != null)
{
int added = 0;
foreach (var item in Buttons)
{
var cd = new ColumnDefinition() { Width = new GridLength(1, GridUnitType.Star) };
var btn = new Button() { Content = item };
ButtonBar.ColumnDefinitions.Add(cd);
ButtonBar.Children.Add(btn);
Grid.SetColumn(btn, added);
}
}
}
And have to use it like this:
<Controls:MyControl
x:Name="ButtonBar" Button="{Binding MyButtons}">
</Controls:MyControl>
Since these are a lot of topics I could seperate those but I think that this is a pretty common topic for beginners and I have not found a got explanation or anything else
1. Providing data to XAML
There are two options: prepare data in the ViewModel or to use converter.
To my mind using converter is better since you can have crossplatform viewModel with color like you mentioned in your example and converter will create platform dependent color. We had similar problem with image. On android it should be converted to Bitmap class, while on UWP it's converted to BitmapImage class. In the viewModel we have byte[].
2. UI for every resolution
You don't need to use converter, since Height is specified in effective pixels which will suit all the required resolutions automatically for you. More info can be found at the following link:
https://learn.microsoft.com/en-us/windows/uwp/design/layout/layouts-with-xaml
There are two options how to deal with textblock sizes:
a) Use predefined textblock styles and don't invent the wheel (which is the recommended option):
https://learn.microsoft.com/en-us/windows/uwp/design/style/typography#type-ramp
Or
b) Specify font size in pixels. They are not pixels, but effective pixels. They will be automatically scaled on different devices:
https://learn.microsoft.com/en-us/windows/uwp/design/style/typography#size-and-scaling
Furthermore, use adaptive layout to have different Layout for different screen sizes.
3) DependencyProperties vs. NotifyProperties(Properties which implement INotifyPropertyChanged) vs. Properties
As per your code you can try to use ListView or ItemsControl and define custom item template.
DependencyProperties are created in DependencyObject and are accessible in xaml. All controls are inherited from DependencyObjects. Usually you create them when you want to set them in xaml. They are not stored directly in the objects, but in the global dictionary and resolved at runtime.
DependencyProperties were created long time ago and you can find lots of links which explain them in details:
http://www.wpftutorial.net/dependencyproperties.html
https://techpunch.wordpress.com/2008/09/25/wpf-wf-what-is-a-dependency-property/
When should I use dependency properties in WPF?
What is a dependency property? What is its use?
What is a dependency property?
INotifyPropertyChanged INPC are the central part of MVVM. You bind your view to viewModel which implements INPC and when you change value of the property control is notified and rereads the new value.
Download the following video in high resolution which explains MVVM in details (by Laurent Bugnion):
https://channel9.msdn.com/Events/MIX/MIX11/OPN03
MVVM: Tutorial from start to finish?
Normal properties are used in model classes or when there is no need to notify UI regarding changes.
I am new to C#/XAML development and I have just started creating very basic windows phone 8 application. I want to get all the elements (Controls) added in the stackpanel as child to the stackpanel using stackpanel.Children.Add(name_of_the_control).
Now I want to get all the elements or controls added in the stackpanel but do not know how to do it. I have searched on the net but could not get helpful link.
Please help me with the process of how to achieve it.
You can access all controls added to StackPanel from it's Children property, for example :
foreach(var control in stackpanel.Children)
{
//here you can get each element of stackpanel in control variable
//further example :
if(control is RadioButton)
{
var radio = (RadioButton)control;
//do something with RadioButton
}
else if(control is TextBlock)
{
var textblok = (TextBlock)control;
//do something with TextBlock
}
//add other possible type of control you want to manipulate
}
I Build a scrollViewer and its elements in my ViewModel, and it's built into a property FrameworkElement PageElement I rebuild the pageElement every time some event happens, I want to bind the PageElement to a real scrollViewer in the View so that whenever I change pageElement, it draws itself in it's view.
Let me give you a little armchair advice. I don't know the details of your project but the details in your question make me draw a few conclusions.
First, to have your view model create UI elements is not wrong. But it is really unusual. It sounds like you might be missing the concept of data template or data template selector.
Using a data template allows you to have a rich presentation of data that is built as the individual record is generated and rendered in a repeater or in a single content control.
Using a data template selector allows you to have various different presentations of data that using code-behind logic will switch between based on data or other criteria.
Ref on templates: http://blog.jerrynixon.com/2012/08/windows-8-beauty-tip-using.html
Second, to have your UI be re-generated as the result of an event being raised sounds like a short path to performance problems.
Every time you manually create elements and add them to the visual tree, you put your app at risk of binding lag while the layout is re-rendered. Run your app on an ARM and I bet you may already see it. Then again, a simplistic UI may not suffer from this general rule of thumb.
Because I do not know the event, I cannot presume it is frequently occurring. However, if it is frequently occurring, then even a simplistic UI will suffer from this.
Now to answer your question
Sherif, there is no write-enabled property on a scrollviewer that will set the horizontal or vertical offset. The only way to set the offset of a scrollviewer is to call changeview().
var s = new ScrollViewer();
s.ChangeView(0, 100, 0);
You cannot bind to a method, so binding to something like this is a non-starter without some code-behind to read the desired offset and calling the method directly.
Something like this:
public sealed partial class MainPage : Page
{
MyViewModel _Vm = new MyViewModel();
ScrollViewer _S = new ScrollViewer();
public MainPage()
{
this.InitializeComponent();
this._Vm.PropertyChanged += (s, e) =>
{
if (e.PropertyName.Equals("Offset"))
_S.ChangeView(0, _Vm.Offset, 0);
};
}
}
public class MyViewModel : INotifyPropertyChanged
{
private int _Offset;
public int Offset
{
get { return _Offset; }
set
{
_Offset = value;
PropertyChanged(this, new PropertyChangedEventArgs("Offset"));
}
}
public event PropertyChangedEventHandler PropertyChanged;
}
But let me caution you. The offset will need to be based on something. And those variables may change based on the window size, the font size, scaling from transforms, and lots of other factors. The code above will work most of the time, but it will possible fail frequently on other devices.
So, what to do? My recommendation is that you code this in your code-behind, monitoring for whatever scenario you feel would require a scroll, and simply programmatically scroll it from bode-behind. Beware, though, programmatically scrolling a scrollviewer could make your UI confusing to the user.
You know your app. You will have to choose.
Best of luck!
I need to develop a control which is similar to the Nested Grid in the Smart GWT.
User will be having a column for expansion images, when user clicking on the image in a particular row, a sub grid has to be opened there itself. Here all remaining rows needs to move down.
How can i achieve that functionality? Can anybody give me some clues so that i can proceed.
I have already a grid which is a celltable with custom header(with search functionality implemented).
Thanks,
Saritha.
Create your nested widget (myNestedWidget) that you want to show. It should have a CSS style "position: absolute", unless your grid is added to the LayoutPanel (or similar), in which case you can position your widget directly. Let's call the parent widget of your grid gridParentWidget.
In your CellTable add the following handler:
myTable.addCellPreviewHandler(new Handler<myObject>() {
#Override
public void onCellPreview(CellPreviewEvent<myObject> event) {
if ("click".equals(event.getNativeEvent().getType())) {
if (event.getColumn() == 0) {
int top = myTable.getRowElement(event.getIndex()).getAbsoluteBottom();
int left = myTable.getRowElement(event.getIndex()).getAbsoluteLeft();
myNestedWidget.getElement().getStyle().setTop(top, Unit.PX);
myNestedWidget.getElement().getStyle().setLeft(left, Unit.PX);
gridParentWidget.add(myNestedWidget);
Scheduler.get().scheduleDeferred(new ScheduledCommand() {
#Override
public void execute() {
int height = myNestedWidget.getOffsetHeight();
myTable.getRowElement(event.getIndex()).getStyle().setHeight(height + "px");
]
});
}
}
});
}
This is obviously an outline of the solution. The details of the implementation may vary slightly depending on which widgets you use for your parent widget and your nested widget. If you change z-indexes somewhere, you have to take it into account too. You also need to make sure that your nested widget fits into the width of your grid, or you'll need to wrap it in a ScrollPanel and set a width to it explicitly.