xamarin - How can we perform an action when as switch is changed in a TableView List? -

our application displays list of category groups:

list<categorygroupwordcountvm> categorygroups; 

on screen looks this:

sports 23 [switch on]

hobbies 5 [switch on]

countries 55 [switch on]

occupations 0 [switch off]

the rows objects this:

public class categorygroupwordcountvm : observableproperty {    public int id { get; set; }    public string name { get; set; }    public bool istoggled { get; set; } } 

page xaml:

<contentpage xmlns="http://xamarin.com/schemas/2014/forms" xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" xmlns:local="clr-namespace:japanese;assembly=japanese"        x:class="japanese.categorygrouppage" x:name="categorygrouppage">    <contentpage.content>       <tableview x:name="tableview" intent="settings">       </tableview>    </contentpage.content> </contentpage> 

row xaml:

<viewcell     xmlns="http://xamarin.com/schemas/2014/forms"     xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"     x:class="japanese.myviewcell">    <grid>       <label text = "{binding name}" />       <label text = "{binding totalwordcount}" />       <switch istoggled = "{binding istoggled}" />    </grid> </viewcell> 

backing c#

protected void refreshpage() {    categorygroups = app.db.getcategorygroupwithwordcount();    var section = new tablesection("available categories");    foreach (var category in categorygroups) {       var cell = new myviewcell { bindingcontext = category };   section.add(cell);    }    tableview.root.add(section); }  protected override void onappearing() {    base.onappearing();    refreshpage(); } 

what have when user switches toggle method following called , value of totalwordcount row switch changed updated.

void selectcategorygroup(object sender, selecteditemchangedeventargs e) {    if (e.selecteditem == null) {       return;    }    var categorygroup = (categorygroupwordcountvm)e.selecteditem;    app.db.updatecategorygroupistoggled(categorygroup.istoggled, categorygroup.id);    // row follows needs update value     // screen shows new value on left side of     // switch. when switch off    // 0. when on list of words in category    totalwordcount = getwordcountforcategory(categorygroup.id); } 

this implemented adding code `

<listview itemselected="selectcategorygroup" > 

but using tableview don’t have this.

so appreciate if give advice on how trigger method selectcategorygroup when switches changed.

note typically there 20-30 different entries in categorygroups list. if make easier happy if myviewcell coded in c#.

updated 08/21: restructured answer bit , added cleanup code; added solution based on property changed event

option 1 - use custom event

in order handle switch's toggled event @ parent tableview level; need propagate event parent viewcell. 1 of ways expose event in custom myviewcell.

steps:

1. declare event in custom viewcell (code-behind).

   public event eventhandler<selecteditemchangedeventargs> selectedortoggled; 

2. assign toggled event-handler switch defined in viewcell's xaml

   <viewcell      xmlns="http://xamarin.com/schemas/2014/forms"      xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"      x:class="japanese.myviewcell">     <grid>         <label text = "{binding name}" />         <label text = "{binding totalwordcount}" />         <switch istoggled = "{binding istoggled}" toggled="handle_toggled" />     </grid>    

3. and invoke custom event in (in control's code-behind)

   void handle_toggled(object sender, xamarin.forms.toggledeventargs e) {     var view = sender bindableobject;     selectedortoggled?.invoke(this, new      selecteditemchangedeventargs(view.bindingcontext)); } 

4. usage: can subscribe custom event in parent-page use/instantiate custom viewcell.

   //xaml usage //<local:myviewcell selectedortoggled="selectcategorygroup" />  protected void refreshpage() {     categorygroups = app.db.getcategorygroupwithwordcount();     var section = new tablesection("available categories");     foreach (var category in categorygroups)     {         var cell = new myviewcell { bindingcontext = category };         // assign method event-handler         cell.selectedortoggled += selectcategorygroup;         section.add(cell);     }     tableview.root.add(section); } 

5. cleanup: avoid memory leaks, recommend unsubscribe during unload.

   protected override void ondisappearing() {     base.ondisappearing();      foreach (var section in tableview.root)     {         foreach(var cell in section)         {             cell.tapped -= opencategoriespage;         }     } } 

selection behavior: can further customize handling tapped event in viewcell , raise selectedortoggled event (similar handle_toggled) in order mimic listview selection behavior.

option 2 - use propertychanged event in view-model

you can listen istoggled property change in categorygroupwordcountvm , react accordingly.

steps:

1. usage: can subscribe propertychanged event in viewmodel.

   protected void refreshpage() {     categorygroups = app.db.getcategorygroupwithwordcount();     var section = new tablesection("available categories");     foreach (var category in categorygroups)     {         var cell = new myviewcell { bindingcontext = category };         // assign method event-handler         cat.propertychanged += categoryvm_propertychanged;         section.add(cell);     }     tableview.root.add(section); }  async void categoryvm_propertychanged(object sender, propertychangedeventargs e) {     if(e.propertyname == nameof(categorygroupwordcountvm.istoggled))     {         var categorygroup = (categorygroupwordcountvm)sender;         ...//call update code here         ...     } } 

2. cleanup: avoid memory leaks, recommend unsubscribe during unload.

   protected override void ondisappearing() {     base.ondisappearing();      foreach (var section in tableview.root)     {         foreach(var cell in section)         {             (cell observableproperty)?.propertychanged -= categoryvm_propertychanged;         }     } }