Custom Renderer for Picker in Xamarin.Forms - xamarin

Question

I want to customize my picker. I created a custom renderer for my picker but I dont know how the customization settings. How can I change the font style and size of the item? and How can I remove the two lines?
public class CustomPickerRenderer : PickerRenderer
{
public CustomPickerRenderer(Context context) : base(context)
{
AutoPackage = false;
}
protected override void OnElementChanged(ElementChangedEventArgs<Picker> e)
{
base.OnElementChanged(e);
if (e.OldElement == null)
{
Control.Background = null;
var layoutParams = new MarginLayoutParams(Control.LayoutParameters);
layoutParams.SetMargins(0, 0, 0, 0);
Control.LayoutParameters = layoutParams;
Control.SetPadding(0, 0, 0, 0);
SetPadding(0, 0, 0, 0);
}
}
}

Answer 1

If you want to set the fontSize of the text , you first need to customize a subclass extends from NumberPicker and overwrite the method AddView.
public class TextColorNumberPicker: NumberPicker
{
public TextColorNumberPicker(Context context) : base(context)
{
}
public override void AddView(View child, int index, ViewGroup.LayoutParams #params)
{
base.AddView(child, index, #params);
UpdateView(child);
}
public void UpdateView(View view)
{
if ( view is EditText ) {
//set the font of text
((EditText)view).TextSize = 8;
}
}
}
If you want to remove the lines,you should rewrite the NumberPicker
in Android Custom Renderer
public class MyAndroidPicker:PickerRenderer
{
IElementController ElementController => Element as IElementController;
public MyAndroidPicker()
{
}
private AlertDialog _dialog;
protected override void OnElementChanged(ElementChangedEventArgs<Picker> e)
{
base.OnElementChanged(e);
if (e.NewElement == null || e.OldElement != null)
return;
Control.Click += Control_Click;
}
protected override void Dispose(bool disposing)
{
Control.Click -= Control_Click;
base.Dispose(disposing);
}
private void SetPickerDividerColor(TextColorNumberPicker picker)
{
Field[] fields = picker.Class.GetDeclaredFields();
foreach (Field pf in fields)
{
if(pf.Name.Equals("mSelectionDivider"))
{
pf.Accessible = true;
// set the color as transparent
pf.Set(picker, new ColorDrawable(this.Resources.GetColor(Android.Resource.Color.Transparent)));
}
}
}
private void Control_Click(object sender, EventArgs e)
{
Picker model = Element;
var picker = new TextColorNumberPicker(Context);
if (model.Items != null && model.Items.Any())
{
picker.MaxValue = model.Items.Count - 1;
picker.MinValue = 0;
picker.SetBackgroundColor(Android.Graphics.Color.Yellow);
picker.SetDisplayedValues(model.Items.ToArray());
//call the method after you setting DisplayedValues
SetPickerDividerColor(picker);
picker.WrapSelectorWheel = false;
picker.Value = model.SelectedIndex;
}
var layout = new LinearLayout(Context) { Orientation = Orientation.Vertical };
layout.AddView(picker);
ElementController.SetValueFromRenderer(VisualElement.IsFocusedProperty, true);
var builder = new AlertDialog.Builder(Context);
builder.SetView(layout);
builder.SetTitle(model.Title ?? "");
builder.SetNegativeButton("Cancel ", (s, a) =>
{
ElementController.SetValueFromRenderer(VisualElement.IsFocusedProperty, false);
// It is possible for the Content of the Page to be changed when Focus is changed.
// In this case, we'll lose our Control.
Control?.ClearFocus();
_dialog = null;
});
builder.SetPositiveButton("Ok ", (s, a) =>
{
ElementController.SetValueFromRenderer(Picker.SelectedIndexProperty, picker.Value);
// It is possible for the Content of the Page to be changed on SelectedIndexChanged.
// In this case, the Element & Control will no longer exist.
if (Element != null)
{
if (model.Items.Count > 0 && Element.SelectedIndex >= 0)
Control.Text = model.Items[Element.SelectedIndex];
ElementController.SetValueFromRenderer(VisualElement.IsFocusedProperty, false);
// It is also possible for the Content of the Page to be changed when Focus is changed.
// In this case, we'll lose our Control.
Control?.ClearFocus();
}
_dialog = null;
});
_dialog = builder.Create();
_dialog.DismissEvent += (ssender, args) =>
{
ElementController?.SetValueFromRenderer(VisualElement.IsFocusedProperty, false);
};
_dialog.Show();
}
}

Answer 2

I also used this CustomRenderer which was posted before only instead of overriding it you can change the properties like this.
private void Control_Click(object sender, EventArgs e)
{
Picker model = Element;
var picker = new MyNumberPicker(Context);
if (model.Items != null && model.Items.Any())
{
// set style here
picker.MaxValue = model.Items.Count - 1;
picker.MinValue = 0;
picker.SetBackgroundColor(Android.Graphics.Color.Transparent);
picker.SetDisplayedValues(model.Items.ToArray());
//call the method after you setting DisplayedValues
SetPickerDividerColor(picker);
picker.WrapSelectorWheel = false;
picker.Value = model.SelectedIndex;
// change Text Size and Divider
picker.TextSize = 30;
picker.SelectionDividerHeight = 1;
}