How to update tabbar badge-icon in Xamarin.Forms.iOS? - xamarin

Question

I can successfully work with the badge on my tabbar if i use it straight in my ViewWillAppear function but if i create a function where i try to control it then the badge does not appear.
This is the tabbedpaged renderer where I have to the function that changes the badge.
public override void ViewWillAppear(bool animated)
{
if (TabBar == null) return;
if (TabBar.Items == null) return;
var tabs = Element as TabbedPage;
if (tabs != null)
{
for (int i = 0; i < TabBar.Items.Length; i++)
{
UpdateItem(TabBar.Items[i], tabs.Children[i].Icon);
}
}
base.ViewWillAppear(animated);
}
private void UpdateItem(UITabBarItem item, string icon)
{
TabBar.UnselectedItemTintColor = UIColor.White;
}
public void UpdateBadge ()
{
var tabs = Element as TabbedPage;
if (tabs != null)
{
Device.BeginInvokeOnMainThread(() =>
{
var tab = TabBar.Items[3];
tab.BadgeValue = "New";
tab.BadgeColor = UIColor.Red;
});
}
}
Then I have another file where I handle a pushnotification and this is where I call the UpdateBadgefunction to both push a notification and also update the badge in the app.
void IPush.SendPush()
{
var notification = new UILocalNotification();
notification.SoundName = UILocalNotification.DefaultSoundName;
UIApplication.SharedApplication.PresentLocalNotificationNow(notification);
TabbedPage_Renderer tpr = new TabbedPage_Renderer();
tpr.UpdateBadge();
}
But as stated above this does not add the badge.
If I however add...
var tab = TabBar.Items[3];
tab.BadgeValue = "New";
tab.BadgeColor = UIColor.Red;
...inside the ViewWillAppear straight away it successfully shows an iconbadge when i start the app up but the idea is to control it so i can update the badge whenever i want.

Answer 1

We should not use the instance of the Renderer directly.
If you want to change the UI in the platform's renderer, we can try to define a BindableProperty in the forms. Then tell the renderer do some configuration when this property changed.
Firstly, define a BindableProperty in the page which you want to change its Badge like:
public static readonly BindableProperty BadgeTextProperty = BindableProperty.Create(nameof(BadgeText), typeof(string), typeof(MainPage), "0");
public string BadgeText {
set
{
SetValue(BadgeTextProperty, value);
}
get
{
return (string)GetValue(BadgeTextProperty);
}
}
Secondly, in the renderer, we can set the badge text when this property changed like:
for (int i = 0; i < TabBar.Items.Length; i++)
{
UpdateItem(TabBar.Items[i], tabs.Children[i].Icon);
//register the property changed event
tabs.Children[i].PropertyChanged += TabbarPageRenderer_PropertyChanged;
}
private void TabbarPageRenderer_PropertyChanged(object sender, System.ComponentModel.PropertyChangedEventArgs e)
{
var page = sender as Page;
if (page == null)
return;
if (e.PropertyName == "BadgeText")
{
if (CheckValidTabIndex(page, out int tabIndex))
{
switch(tabIndex)
{
case 0:
UpdateBadge(TabBar.Items[tabIndex], (page as MainPage).BadgeText);
break;
case 1:
//Second Page, you can expand this switch depending on your tabs children
UpdateBadge(TabBar.Items[tabIndex], (page as SecondPage).BadgeText);
break;
default:
break;
}
}
return;
}
}
public bool CheckValidTabIndex(Page page, out int tabIndex)
{
tabIndex = Tabbed.Children.IndexOf(page);
return tabIndex < TabBar.Items.Length;
}
private void UpdateItem(UITabBarItem item, string icon)
{
TabBar.UnselectedItemTintColor = UIColor.White;
...//set the tabItem
}
private void UpdateBadge(UITabBarItem item, string badgeText)
{
item.BadgeValue = text;
item.BadgeColor = UIColor.Red;
}
At last, set the BadgeText in the forms when you want to update the badge.