更改 Xamarin Forms Picker 按钮样式

Question

我正在尝试在我的 xamarin 表单应用程序中获得一些样式一致性（目前仅针对 android）。我试图让所有按钮看起来都一样。通常，这很容易通过在 App.xaml 文件中添加一个 Style 并将 TargetType 设置为 Button 来完成。问题是我使用的是 Picker（也是具有类似问题的 TimePicker）。单击此选择器时，会显示一个带有取消按钮的弹出窗口。我无法更改此取消按钮的样式（例如更改背景和边框）。这个虚拟项目的屏幕截图更多地解释了这个问题：

除了尝试App.xaml的解决方案，我还尝试通过调整styles.xml来设置android项目中的样式。这确实也对除选择器对话框中的按钮之外的所有按钮产生了影响。

有人知道如何解决它吗？

Answer 1

格特，为 Picker 的样式找到了一些东西。这是 Android .

更改取消的颜色或更改它的文本，没有尝试调整字体或其他东西

[assembly: ExportRenderer(typeof(Picker), typeof(MyPickerRenderer))]
namespace Pickerstyle.Droid
{
   
    public class MyPickerRenderer : Xamarin.Forms.Platform.Android.PickerRenderer
    {
        Typeface fontFace = null;
        private IElementController ElementController => Element as IElementController;
        private AlertDialog _dialog;
        public MyPickerRenderer(Context context) : base(context)
        {
            AutoPackage = false;
        }
        [Obsolete("This constructor is obsolete as of version 2.5. Please use PickerRenderer(Context) instead.")]
        public MyPickerRenderer()
        {
            AutoPackage = false;
        }
        protected override void OnElementChanged(ElementChangedEventArgs<Picker> e)
        {
            base.OnElementChanged(e);

            if (e.NewElement == null || e.OldElement != null || Control == null)
                return;

          //  fontFace = Typeface.CreateFromAsset(this.Context.Assets, "somefont.ttf");

            GradientDrawable gd = new GradientDrawable();
            gd.SetStroke(0, Android.Graphics.Color.Transparent);
            Control.SetBackground(gd);

            Control.TextSize = 18f;
            Control.SetTypeface(fontFace, TypefaceStyle.Normal);

            Control.Click += Control_Click;
        }
        protected override void Dispose(bool disposing)
        {
            Control.Click -= Control_Click;
            base.Dispose(disposing);
        }

        private void Control_Click(object sender, EventArgs e)
        {
            Picker model = Element;
            NumberPicker picker = new NumberPicker(Context);

            int count = picker.ChildCount;
            for (int i = 0; i < count; i++)
            {
                Android.Views.View v = picker.GetChildAt(i);
                if (v.GetType() == typeof(EditText))
                {
                    Java.Lang.Reflect.Field field = picker.Class.GetDeclaredField("mSelectorWheelPaint");
                    field.Accessible = true;
                    ((Paint)field.Get(picker)).SetTypeface(fontFace);
                    ((EditText)v).SetTypeface(fontFace, TypefaceStyle.Normal);
                    picker.Invalidate();
                }
            }

            if (model.Items != null && model.Items.Any())
            {
                picker.MaxValue = model.Items.Count - 1;
                picker.MinValue = 0;
                picker.SetDisplayedValues(model.Items.ToArray());
                picker.WrapSelectorWheel = false;
                picker.DescendantFocusability = DescendantFocusability.BlockDescendants;
                picker.Value = model.SelectedIndex;
                picker.Visibility = ViewStates.Visible;

            }


            var layout = new LinearLayout(Context) { Orientation = Orientation.Vertical };
            layout.Visibility = ViewStates.Visible;
            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);
                Control?.ClearFocus();
                _dialog = null;
            });

            builder.SetPositiveButton("Or this", (s, a) =>
            {
                ElementController.SetValueFromRenderer(Picker.SelectedIndexProperty, picker.Value);
                if (Element != null)
                {
                    if (model.Items.Count > 0 && Element.SelectedIndex >= 0)
                        Control.Text = model.Items[Element.SelectedIndex];
                    ElementController.SetValueFromRenderer(VisualElement.IsFocusedProperty, false);
                    Control?.ClearFocus();
                }
                _dialog = null;
            });

            _dialog = builder.Create();

            _dialog.DismissEvent += (ssender, args) =>
            {
                ElementController?.SetValueFromRenderer(VisualElement.IsFocusedProperty, false);
            };
            _dialog.Show();


            Android.Widget.Button nbutton = _dialog.GetButton((int)Android.Content.DialogButtonType.Positive);
            nbutton.SetTypeface(fontFace, TypefaceStyle.Normal);
            nbutton.SetTextColor(Android.Graphics.Color.ParseColor("#ff9500"));
            nbutton.TextSize = 16f;
            LinearLayout layOut = (LinearLayout)nbutton.Parent;
            layOut.SetGravity(GravityFlags.CenterHorizontal);
            Android.Views.View v1 = layOut.GetChildAt(1);
            v1.Visibility = ViewStates.Gone;


            int res = Resources.GetIdentifier("alertTitle", "id", "android");
            TextView textView = (TextView)_dialog.FindViewById(res);
            textView.SetTextColor(Android.Graphics.Color.Green);
            textView.SetTypeface(fontFace, TypefaceStyle.Normal);
            textView.Gravity = GravityFlags.Center;

        }
    }
}

Answer 2

找到了一种相当简单的方法来调整选择器弹出窗口上的按钮样式，只需调整 styles.xml。此解决方案仅适用于 android。在这里找到解决方案：

styles.xml 看起来像这样：

<style name="MainTheme" >
    <item name="buttonBarNegativeButtonStyle">@style/ButtonStyle</item>
    <item name="buttonBarPositiveButtonStyle">@style/ButtonStyle</item>
    <item name="android:buttonStyle">@style/ButtonStyle</item>
</style>

<style name="ButtonStyle" >
    <item name="android:textColor">#000000</item>
    <item name="android:background">#FF0000</item>
</style>

buttonBarNegativeButtonStyle，改变取消按钮样式。该解决方案还将调整例如 TimePicker 中的按钮。（这也有 buttonBarPositiveButtonStyle）

如果你想控制整个picker popup，那么Bas H的方案会更合适

更改 Xamarin Forms Picker 按钮样式

Changing Xamarin Forms Picker button style

android

xamarin.forms

styles