Question

是否有任何理由说明Xamarin.Forms搜索栏无法在Android上显示（目前正在运行Android 7.0）。我读过，做一个HeightRequest可能是一个好主意但是在尝试之后，搜索栏仍然没有出现。这是我在xaml中初始化搜索栏的内容：

<SearchBar x:Name="searchBarList" Placeholder="Search" HeightRequest="42" Opacity="1"/>

知道如何前进吗？

更新：整个布局如下：

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
         xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
         x:Class="SalApp.views.MainList" BackgroundColor="LightGray" NavigationPage.HasNavigationBar="False">
<ContentPage.ToolbarItems>
    <ToolbarItem Icon="shopping_cart_icon.png" 
            Priority="0" Order="Primary" />
</ContentPage.ToolbarItems>
<SearchBar x:Name="searchBarList"
                    Placeholder="Search"
                    HeightRequest="42"
           Opacity="1"/>
<ListView x:Name="listView" Opacity="0" SeparatorColor="AntiqueWhite" RowHeight="80" ItemSelected="listView_ItemSelected" IsPullToRefreshEnabled="True"/>

但它目前只是为了查看搜索栏而设置如此，但它仍然不可见

Answer 1

您的问题是View的根目录中有多个ContentPage。

将您的View分组在父控件下，例如：

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
            xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
            x:Class="SalApp.views.MainList" BackgroundColor="LightGray" NavigationPage.HasNavigationBar="False">
<ContentPage.ToolbarItems>
    <ToolbarItem Icon="shopping_cart_icon.png" 
            Priority="0" Order="Primary" />
</ContentPage.ToolbarItems>
    <StackLayout>
        <SearchBar x:Name="searchBarList"
                            Placeholder="Search"
                            HeightRequest="42"
                    Opacity="1"/>
        <ListView x:Name="listView" Opacity="0" SeparatorColor="AntiqueWhite" RowHeight="80" ItemSelected="listView_ItemSelected" IsPullToRefreshEnabled="True"/>
    </StackLayout>
</ContentPage>

Answer 2

如果您想要更通用的方法来解决此问题，而不是手动添加HeightRequest，则可以实施SearchBarRenderer

using Android.OS;
using AppTTM_AVI.Droid;
using Xamarin.Forms;
using Xamarin.Forms.Platform.Android;

[assembly: ExportRenderer(typeof(SearchBar), typeof(CustomSearchBarRenderer))]
namespace App.Droid
{
    /// <summary>
    /// Workaround for searchBar not appearing on Android >= 7
    /// </summary>
    public class CustomSearchBarRenderer : SearchBarRenderer
    {
        public CustomSearchBarRenderer()
        {
        }

        protected override void OnElementChanged(ElementChangedEventArgs<SearchBar> e)
        {
            base.OnElementChanged(e);

            if (e.OldElement != null || Element == null)
            {
                return;
            }

            if (Build.VERSION.SdkInt >= BuildVersionCodes.N)
            {
                Element.HeightRequest = 42;
            }
        }
    }
}

来源：https://forums.xamarin.com/discussion/comment/296772/#Comment_296772

Answer 3

Android 7.0和7.1搜索栏在安装后第一次出现，一旦我退出或将方向更改为横向模式，它已经实现了。

permute

Xamarin搜索栏未显示

3 个答案: