How do you change the font of the 'spinner' portion of the picker? I can change the display font doing the following
public class MyPickerRenderer : PickerRenderer
{
protected override void OnElementChanged(ElementChangedEventArgs<Picker> e)
{
base.OnElementChanged(e);
if (Control != null)
{
**Control.Font = UIFont.SystemFontOfSize(8);**
}
}
}
Unfortunately this is not possible at least it's not subclassing the PickerRenderer defined in Xamarin.Forms for iOS.
The UIPickerView control that is displayed is marked as private for the renderer implementation, hence it will not be accesible from the subclass.
You could anyway do your own implementation of the Renderer and for this you could follow the implementation made by Xamarin.Forms (here you can see it) and do the modifications you need.
You will also need to subclass the UIPickerView class and override the ViewFor and there set the font size you want for the items..
Hope this helps.-
Related
I'm building a layout like the main page of AppStore
This app has handled when the user scrolls ListView, SearchBar will gradually hide like the following GIF image:
How to calculate position value (height) when scrolling item on ListView (Xamarin Forms)?
Example: When I scroll an apart of an item on ListView, Layout contains Searchbar will hide an apart of it (layout contains SearchBar),
with height (an apart of item is scrolled on ListView) = height (an apart of SearchBar is hidden)
Please suggest me an idea and solution!
You have to use custom renderer to detect the value of height you scrolled, I wrote a simple example in iOS:
[assembly: ExportRenderer (typeof(myListView), typeof(MyListViewRenderer))]
namespace App556.iOS
{
public class MyListViewRenderer : ListViewRenderer
{
protected override void OnElementChanged(ElementChangedEventArgs<Xamarin.Forms.ListView> e)
{
base.OnElementChanged(e);
Control.Delegate = new myDeleagte();
}
}
public class myDeleagte : UITableViewDelegate {
public override void Scrolled(UIScrollView scrollView)
{
Console.WriteLine(scrollView.ContentOffset.X);
Console.WriteLine(scrollView.ContentOffset.Y);
}
}
}
Handle your event in the Scrolled method or use messaging-center to handle event in Xamarin.forms.Project.
ListView only has itemappearing method for you to do something when scrolling, you can have a look at it.
In my Xamarin app, I create a button (Xamarin.Forms.Button) programmatically. I need this button to show a different background image under normal vs hovered state. I have created a style resource similar to what is described at How to indicate currently selected control in Xamarin?. However, I cannot figure out how to apply this style to the button.
The Button class exposes a property called Image that is of FileImageSource type. The closest API I found to load my style resource is ImageSource.FromResource static method. However, this method seems to return StreamImageSource instance which is not what we need.
Class Button does not seem to provide any Style property.
Can you please suggest how I can programmatically associate a style to the button? Regards.
To achieve this request you need custom renderers.
To be able to apply your style f.e.: "myButtonStyle.xml" you have to create a custom renderer for your target platform:
Android:
[assembly: ExportRenderer (typeof (YourExtendedButtonClass), typeof (MyCustomButtonRenderer))]
namespace YourApp.Droid
{
public class MyCustomButtonRenderer : ButtonRenderer
{
protected override void OnElementChanged(ElementChangedEventArgs<Button> e)
{
base.OnElementChanged(e);
var myButton = this.Control as Android.Widget.Button;
myButton?.SetBackgroundResource(Resource.Drawable.myButtonStyle);
}
}
}
In XAMARIN FORMS ButtonRenderer only provide two methods which i can override: OnElementChanged and OnElementPropertyChanged. Which method do I want to override to handle button clicks?
You have a reference to the button in your Renderer (search for the proeprty Control). Just add the click-event/listener/command for this Control (but be carefull, it may be that the Control is NULL, depending on your renderer implementation).
Quick code sample for ios (depends on your renderer):
protected override void OnElementChanged(ElementChangedEventArgs<MyButtonRenderer> e)
{
var mybutton = Control as UIButton;
mybutton.TouchUpInside += (s, args) => { /* your logic */};
}
For android you can find a sample on this page.
Is it possible to truncate long texts with ellipsis in a picker control. I have already created a custom renderer to set a fontsize and no border in order to achieve the following result.
Also tried to set Control.Ellipsize = TextUtils.TruncateAt.End; but nothing happens
[assembly: ExportRenderer(typeof(NoBorderPicker), typeof(CustomPicker))]
namespace Prj.Droid.Renderers
{
public class CustomPicker : PickerRenderer
{
protected override void OnElementChanged(ElementChangedEventArgs<Picker> e)
{
base.OnElementChanged(e);
if (Control != null)
{
var customBG = new GradientDrawable();
customBG.SetColor(Android.Graphics.Color.Transparent);
customBG.SetCornerRadius(3);
Control.SetBackground(customBG);
Control.Ellipsize = TextUtils.TruncateAt.End;
var custdatepicker = (NoBorderPicker) this.Element;
this.Control.TextSize = (float)custdatepicker.FontSize;
}
}
}
}
Now, I could be sure that Control.SetSingleLine(true); will work.
if you are using a custom renderer can be the incorret inheritance.
Use Xamarin.Forms.Platform.Android.AppCompat.PickerRenderer not Xamarin.Forms.Platform.Android.PickerRenderer
Tks to https://www.damirscorner.com/blog/posts/20201204-CustomPickerRendererOnAndroid.html
Oddly enough, for me in the latest Xamarin Forms, on Android the Picker automatically truncates text, but on iOS the Picker becomes arbitrarily wide, covering up other UI elements.
The fix is to set the MinimumWidthRequest = 1, which for some reason re-enables text truncation. I have no idea why. Welcome to Xamarin.
Wanting to achieve a consistent look for my Xamarin Forms app, I need to know how to change the font for the tabbed page tab bar icons. Using UITabBarItem.Appearance as the iOS API would suggest does not appear to have any effect. What's necessary to do this?
U need to write a custom renderer like this one , take a clue from below code ! it has what u r seeking
[assembly: ExportRenderer(typeof(ExtendedTabbedPage), typeof(TabbedPageCustom))]
namespace App.iOS
{
public class TabbedPageCustom : TabbedRenderer
{
public TabbedPageCustom ()
{
TabBar.TintColor = UIKit.UIColor.White;
TabBar.BarTintColor = UIKit.UIColor.White;
TabBar.BackgroundColor = UIKit.UIColor.Red;
}
protected override void OnElementChanged (VisualElementChangedEventArgs e)
{
base.OnElementChanged (e);
// Set Text Font for unselected tab states
UITextAttributes normalTextAttributes = new UITextAttributes();
normalTextAttributes.Font = UIFont.FromName("ChalkboardSE-Light", 20.0F); // unselected
normalTextAttributes.TextColor = UIKit.UIColor.Blue;
UITabBarItem.Appearance.SetTitleTextAttributes(normalTextAttributes, UIControlState.Normal);
}
public override UIViewController SelectedViewController {
get {
UITextAttributes selectedTextAttributes = new UITextAttributes();
selectedTextAttributes.Font = UIFont.FromName("ChalkboardSE-Bold", 20.0F); // SELECTED
if (base.SelectedViewController != null)
{
base.SelectedViewController.TabBarItem.SetTitleTextAttributes(selectedTextAttributes, UIControlState.Normal);
}
return base.SelectedViewController;
}
set {
base.SelectedViewController = value;
foreach (UIViewController viewController in base.ViewControllers)
{
UITextAttributes normalTextAttributes = new UITextAttributes();
normalTextAttributes.Font = UIFont.FromName("ChalkboardSE-Light", 20.0F); // unselected
normalTextAttributes.TextColor = UIKit.UIColor.Blue;
viewController.TabBarItem.SetTitleTextAttributes(normalTextAttributes, UIControlState.Normal);
}
}
}
}
}
This was a particularly interesting problem. I tried:
UITabBarItem.Appearance
Using the UITabBarItem.Appearance.SetTitleTextAttributes method to update the UITextAttribute to my font (size 9.0f) for UIControlState.Normal. This didn't appear to make any difference.
UINavigationBar.Appearance
I found out that setting UINavigationBar.Appearance.SetTitleTextAttributes would update both the UINavigationBar text appearance as well as the UITabBarItem text appearance.
Which was a problem because the tabbed page item font size was far too large.
Customizing the TabbedRenderer
Inspired by a sample I saw somewhere, I subclassed TabbedRenderer in the iOS project.
I tried overriding the settor for TabbedRenderer.SelectedViewController property and loop through the ViewControllers property to set their items. The icons would display with the standard font, but once the user changed the tab they would all update to the desired font. Almost there!
I then tried overriding AddChildViewController and updating that controller's TabBarItem after it was added which ended up having no effect. The TabBarItem for the added page was being updated at some point after the controller was added.
Eventually I found out that overriding ViewWillAppear and setting the appearance for all the tab bar items at that time seemed to do the job I desired.
I've included a sample in this gist.