i would like to enable/disable buttons according to the current active userlevel. i have a property in the MV for the current userlevel:
public int CurrentUserLevel
{
get { return _CurrentUserLevel; }
set
{
if (_CurrentUserLevel == value)
return;
_CurrentUserLevel = value;
RaisePropertyChanged("CurrentUserLevel");
}
}
how can i enable/disable the button if this value is >=x?
You'll need to create a property in your ViewModel, for which the Button's IsEnabled property can bind to. Make sure that the new property's PropertyChanged event is raised whenever the CurrentUserLevel is changed.
public int CurrentUserLevel
{
get { /*...*/ }
set
{
/*...*/
RaisePropertyChanged("CurrentUserLevel");
RaisePropertyChanged("IsAllowedToDoSomething"); //dependant property
}
}
public bool IsAllowedToDoSomething
{
get { return CurrentUserLevel > 1; }
}
And in your XAML:
<Button IsEnabled="{Binding IsAllowedToDoSomething}" Content="Click me!" />
Related
I'm creating an Xamarin.Forms MVVM App (only using Android) which needs certain buttons to be outlined red, whenever their text property holds a specific value. (Purpose: alert the user to press the button and select a value, which will change the Button Text Property and therefore remove the red outline)
To achieve this I've create the following documents:
A custom button CButton that extents the default Button:
public class CButton : Button
{
// this Hides the Default .Text-Property
public string Text
{
get => base.Text;
set
{
base.Text = value;
TextChangedEvent(this, new EventArgs());
}
}
// The Raised Event
protected virtual void TextChangedEvent(object sender, EventArgs e)
{
EventHandler<EventArgs> handler = TextChanged;
handler(sender, e);
}
public event EventHandler<EventArgs> TextChanged;
}
A custom behavior makes use of the raised TextChangedEvent
public class ButtonValBehavior : Behavior<CButton>
{
protected override void OnAttachedTo(CButton bindable)
{
bindable.TextChanged += HandleTextChanged;
base.OnAttachedTo(bindable);
}
void HandleTextChanged(object sender, EventArgs e)
{
string forbidden = "hh:mm|dd.mm.yyyy";
if (forbidden.Contains((sender as CButton).Text.ToLower()))
{
//Do when Button Text = "hh:mm" || "dd.mm.yyyy"
(sender as CButton).BorderColor = Color.Gray;
}
else
{
//Do whenever Button.Text is any other value
(sender as CButton).BorderColor = Color.FromHex("#d10f32");
}
}
protected override void OnDetachingFrom(CButton bindable)
{
bindable.TextChanged -= HandleTextChanged;
base.OnDetachingFrom(bindable);
}
}
The relevant parts of the ViewModel look the following:
public class VM_DIVI : VM_Base
{
public VM_DIVI(O_BasisProtokoll base)
{
Base = base;
}
private O_BasisProtokoll _base = null;
public O_BasisProtokoll Base
{
get => _base;
set
{
_base = value;
OnPropertyChanged();
}
}
Command _datePopCommand;
public Command DatePopCommand
{
get
{
return _datePopCommand ?? (_datePopCommand = new Command(param => ExecuteDatePopCommand(param)));
}
}
void ExecuteDatePopCommand(object param)
{
//launch popup
var p = new PP_DatePicker(param);
PopupNavigation.Instance.PushAsync(p);
}
}
The .xmal looks the following (b is the xmlns of the Namespace):
<b:CButton x:Name="BTN_ED_Datum"
Text="{Binding Base.ED_datum, Mode=TwoWay}"
Grid.Column="1"
Command="{Binding DatePopCommand}"
CommandParameter="{x:Reference BTN_ED_Datum}">
<b:CButton.Behaviors>
<b:ButtonValBehavior/>
</b:CButton.Behaviors>
</b:CButton>
This solution works fine whenever the input is caused by user interaction. However, when a Value is assigned during the initialization of the Page no red outline is created, in fact the TextChangedEvent isn't raised. By using breakpoints I noticed that during initialization the Text Property of CButton is never set, eventhough it actually will be in the view.
Despite fiddling around with my solution I cannot make this work on initialization. I tried to work around this issue by outlining every button by default in their constructor, however this will outline every button red, even when their text value doesn't require them to be.
How can I achieve my initial goal?
Many thanks in advance!
It's been a while but if I recall correctly what I ended up doing was:
Changing the new Text-Property of my custom Button to CText and
Making sure that I have Mode=TwoWay activated for any Element, that doesn't have it enabled by default. (Look up Binding modes on msdn for more)
making CText a bindable property of CButton
My custom button now looks the following:
using System;
using System.Collections.Generic;
using System.Text;
using Xamarin.Forms;
namespace EORG_Anton.Model
{
public class CButton : Button
{
public static readonly BindableProperty CTextProperty =
BindableProperty.Create(nameof(CText),
typeof(string),
typeof(CButton),
default(string),
BindingMode.TwoWay,
propertyChanged: OnTextChanged);
private static void OnTextChanged(BindableObject bindable, object oldValue, object newValue)
{
var control = (CButton)bindable;
var value = (string)newValue;
control.CText = value;
}
public string CText
{
get => base.Text;
set
{
base.Text = value;
TextChangedEvent(this, new EventArgs());
}
}
protected virtual void TextChangedEvent(object sender, EventArgs e)
{
EventHandler<EventArgs> handler = TextChanged;
handler(sender, e);
}
public event EventHandler<EventArgs> TextChanged;
}
}
I am trying to clear a form that has few textboxes and also a picker control.
I have this button that when the user presses it ,it should clear the form.
Whatever I do I seem to get an error
I have done the following
xaml: I have bound the picker to a selectedIndex property
ViewModel:Added a property and a method as follows
private int selectedIndex;
public int SelectedIndex
{
get { return selectedIndex; }
set { SetProperty(ref selectedIndex, value); }
}
private void ResetForm()
{
SelectedIndex = -1;
}
When I execute the code it crashes.
What is the way to reset the picker in the viewModel?
many thanks
I have a custom control for to show the "cancel" button inside the iOS SearchBars:
[assembly: ExportRenderer(typeof(SearchBar), typeof(AppSearchBarRenderer))]
namespace Elfo.VisionMobile.iOS.Renderers
{
public class AppSearchBarRenderer : SearchBarRenderer
{
protected override void OnElementChanged(ElementChangedEventArgs<SearchBar> e)
{
base.OnElementChanged(e);
Control.ShowsCancelButton = true;
}
}
}
And this is my XAML:
<SearchBar Text="{Binding SearchKey, Mode=TwoWay}" SearchCommand="{Binding SearchCommand}"/>
And the search execute method of the command (C#):
private void SearchExecute()
{
// whatever...
SearchKey = null;
}
And when I set the SearchKey to null or string.Empty , the "cancel" button disapears.
Guys, do you know something?
Ok I just fixed it.
I had to use the method OnElementPropertyChanged instead of OnElementChanged.
How could I detect tab was touched in xamarin forms TabbedPage?
(which is different from page changed detection which I figured how to detect)
Here is why:
I'm trying to work around a rather ugly tabbed page overflow UI
(the ugly scroller that shows up on the right over the tabbar
whenever there are >5 tabs)
So the 5th tab press shows a custom menu, second press hides that menu, etc.
Thanks!
If you are trying to find which page is selected in TabbedPage you could do it in this way.
With Index value you can perform whatever action you want..
Event for detecting page no:
this.CurrentPageChanged += (object sender, EventArgs e) => {
var i = this.Children.IndexOf(this.CurrentPage);
System.Diagnostics.Debug.WriteLine("Page No:"+i);
};
It has been a while since this was asked but just in case here is an answer.
Perform an action when a tab is tapped is the same as when:
The tab has changed
The tab is "reselected"
So for the first one you can use #femil-shajin 's answer or as I do here which is more direct and for the second one you need to make some custom renderers for the TabbedPage:
public class MyTabbedPage : TabbedPage
{
...
protected override void OnCurrentPageChanged()
{
// do whatever
}
public void OnTabReselected()
{
// do whatever
}
...
}
Then on Android:
[assembly: ExportRenderer(typeof(TabbedPage), typeof(CustomTabbedRenderer))]
namespace MyNamespace.Droid.Renderers
{
public class CustomTabbedRenderer : TabbedPageRenderer, NavigationBarView.IOnItemReselectedListener
{
...
protected override void OnElementChanged(ElementChangedEventArgs<TabbedPage> e)
{
base.OnElementChanged(e);
if (e.NewElement != null)
{
GetBottomNavigationView()?.SetOnItemReselectedListener(this);
}
}
private BottomNavigationView GetBottomNavigationView()
{
// this may need to change on some cases
for (var i = 0; i < ViewGroup.ChildCount; i++)
{
var childView = ViewGroup.GetChildAt(i);
if (childView is ViewGroup viewGroup)
{
for (var j = 0; j < viewGroup.ChildCount; j++)
{
var childRelativeLayoutView = viewGroup.GetChildAt(j);
if (childRelativeLayoutView is BottomNavigationView bottomNavigationView)
{
return bottomNavigationView;
}
}
}
}
return null;
}
public void OnNavigationItemReselected(IMenuItem item)
{
if (Element is MyTabbedPage tabbedPage)
{
tabbedPage.OnTabReselected();
}
}
...
}
}
And on iOS:
[assembly: ExportRenderer(typeof(TabbedPage), typeof(CustomTabbedRenderer))]
namespace MyNamespace.iOS.Renderers
{
public class CustomTabbedRenderer : TabbedRenderer
{
private UITabBarItem _previousSelectedItem;
...
public override void ViewDidAppear(bool animated)
{
base.ViewDidAppear(animated);
if (SelectedIndex < TabBar.Items.Length)
{
_previousSelectedItem = TabBar.Items[SelectedIndex];
}
}
public override void ItemSelected(UITabBar tabbar, UITabBarItem item)
{
if (_previousSelectedItem == item && Element is MyTabbedPage tabbedPage)
{
tabbedPage.OnTabReselected();
}
_previousSelectedItem = item;
}
...
}
}
Source: Part of this was based on this page
I want to create a custom control for a button. However wow can i override the visibility of the button?
For example if the access level of the user is false then it will hide the button.
Here is my coding
public override void Visible()
{//Get access right from session
blcAccessLevel accessLevel = (blcAccessLevel)HttpContext.Current.Session[gbcAccessLevel.sessionAcl];
if (accessLevel.Read_Access == true)
{
base.Visible = true;//error occu
}
else
{
base.Visible = false;
}
}
It return me the error.Error 'blcCustomControl.cusAclReadButton.Visible()': cannot override because 'System.Web.UI.Control.Visible' is not a function By the way, should I implement the get set method?
public class MyButton : Button
{
public new bool Visible
{
get
{
return (blcAccessLevel)HttpContext.Current.Session[gbcAccessLevel.sessionAcl].ReadAccess;
}
}
}