Can one use system icons on tabs in Xamarin Forms? - xamarin

Question

Is there a way to specify a "system" icon to be displayed on a tab when using Xamarin Forms? I would like to use icons such as Favourites, Bookmark, History etc but I do not want to supply all my own images for the various platforms.
Using Xamarin.iOS one can use this syntax:
tab1.TabBarItem = new UITabBarItem (UITabBarSystemItem.Favorites, 0);
I can however not find how to do this in the cross-platform Xamarin.Forms project.
This is my current code:
var profilePage = new ContentPage {
Title = "Profile",
//This requires my own images to be added to the project whereas
//I wish to use built-in images which are platform specific for
//Favourites, Bookmark, More, etc...
//Icon = "Profile.png",
Content = new StackLayout {
Spacing = 20, Padding = 50,
VerticalOptions = LayoutOptions.Center,
Children = {
new Entry { Placeholder = "Username" },
new Entry { Placeholder = "Password", IsPassword = true },
new Button {
Text = "Login",
TextColor = Color.White,
BackgroundColor = Color.FromHex("77D065") }}}};
var settingsPage = new ContentPage {
Title = "Settings",
Content = new StackLayout {
Spacing = 20, Padding = 50,
VerticalOptions = LayoutOptions.Center,
Children = {
new Entry { Placeholder = "Username" },
new Entry { Placeholder = "Password", IsPassword = true }}}
};
MainPage = new TabbedPage { Children = {profilePage, settingsPage} };

Answer 1

For iOS
you need a custom renderer for your page. In my example, it is CustomTabsPage class. You cannot just use system icons to create a UIImage. We need to use UITabBarItem. The problem is that UITabBarItem doesn't allow changes to either title or image/icon. But, we can copy an image from it.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using UIKit;
using ButtonRendererDemo;
using ButtonRendererDemo.iOS;
using Xamarin.Forms;
using Xamarin.Forms.Platform.iOS;
[assembly: ExportRenderer(typeof(CustomTabsPage), typeof(CustomTabsPageRenderer))]
namespace ButtonRendererDemo.iOS
{
public class CustomTabsPageRenderer : TabbedRenderer
{
#region Sytem Image with custom title
public override void ViewWillAppear(bool animated)
{
base.ViewWillAppear(animated);
foreach (var item in TabBar.Items)
{
item.Image = GetTabIcon(item.Title);
}
}
private UIImage GetTabIcon(string title)
{
UITabBarItem item = null;
switch (title)
{
case "Profile":
item = new UITabBarItem(UITabBarSystemItem.Search, 0);
break;
case "Settings":
item = new UITabBarItem(UITabBarSystemItem.Bookmarks, 0);
break;
}
var img = (item != null) ? UIImage.FromImage(item.SelectedImage.CGImage, item.SelectedImage.CurrentScale, item.SelectedImage.Orientation) : new UIImage();
return img;
}
#endregion
}
}
For Android
things are easier
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using ButtonRendererDemo;
using ButtonRendererDemo.Droid;
using Xamarin.Forms;
using Xamarin.Forms.Platform.Android;
using Xamarin.Forms.Platform.Android.AppCompat;
using Android.Support.Design.Widget;
[assembly: ExportRenderer(typeof(CustomTabsPage), typeof(CustomTabsPageRenderer))]
namespace ButtonRendererDemo.Droid
{
public class CustomTabsPageRenderer : TabbedPageRenderer
{
protected override void OnElementChanged(ElementChangedEventArgs<TabbedPage> e)
{
base.OnElementChanged(e);
//var layout = (TabLayout)ViewGroup.GetChildAt(1); //should be enough but just for robustness we use loop below
TabLayout layout = null;
for (int i = 0; i < ChildCount; i++)
{
layout = GetChildAt(i) as TabLayout;
if (layout != null)
break;
}
if (layout != null)
{
for (int tabIndex = 0; tabIndex < layout.TabCount; tabIndex++)
SetTabIcon(layout, tabIndex);
}
}
private void SetTabIcon(TabLayout layout, int tabIndex)
{
var tab = layout.GetTabAt(tabIndex);
switch (tabIndex)
{
case 0:
tab.SetIcon(Resource.Drawable.icon2);//from local resource
break;
case 1:
tab.SetIcon(Resource.Drawable.ic_media_play_dark);//from Android system, depends on version !
break;
}
}
}
}

Answer 2

In order to use icons, you need a platform-specific structure. In Xamarin.Forms, for this to work:
Icon = "youricon.png";
You need:
iOS: put the image in /Resources/youricon.png
Android: put the image in /Resources/drawable/youricon.png
Win Phone: put the image in the Windows Phone application project root.

Answer 3

You should write custom TabbedPage renderer for iOS project:
public class YourTabbedRenderer : TabbedRenderer {
public override void ViewWillAppear(bool animated)
{
base.ViewWillAppear(animated);
var items = TabBar.Items;
for (var i = 0; i < items.Length; i++) {
// set your icons here, you could do some string comparison (check tab title or tab icon resource name)
// items[i].Image =
// items[i].SelectedImage =
}
}
}
http://developer.xamarin.com/guides/cross-platform/xamarin-forms/custom-renderer/