我们可以在 Xamarin.iOS 和 Xamarin.Android 中创建一个自定义渲染器来完成它。
这是一个示例应用程序供参考：
https://github.com/brminnick/GitTrends
这是一篇博文，展示了如何为 Xamarin.iOS 和 Xamarin.Android 的 Xamarin.Forms 应用添加搜索栏：https://www.codetraveler.io/2019/08/10/adding-a-search-bar-to-xamarin-forms-navigationpage/
App.cs
使用 Xamarin.Forms Platform-Specific 在 Xamarin.iOS 应用上使用 LargeTitles。
using Xamarin.Forms.PlatformConfiguration;
using Xamarin.Forms.PlatformConfiguration.iOSSpecific;
public class App : Xamarin.Forms.Application
{
public App()
{
var navigationPage = new Xamarin.Forms.NavigationPage(new MyContentPage());
navigationPage.On<iOS>().SetPrefersLargeTitles(true);
MainPage = navigationPage;
}
}
ISearchPage 接口
创建可跨 Xamarin.Forms、Xamarin.Android 和 Xamarin.iOS 项目使用的接口。
public interface ISearchPage
{
void OnSearchBarTextChanged(in string text);
event EventHandler<string> SearchBarTextChanged;
}
Xamarin.Forms 页面
public class MyContentPage : ContentPage, ISearchPage
{
public MyContentPage()
{
SearchBarTextChanged += HandleSearchBarTextChanged
}
public event EventHandler<string> SearchBarTextChanged;
public void OnSearchBarTextChanged(in string text) => SearchBarTextChanged?.Invoke(this, text);
void HandleSearchBarTextChanged(object sender, string searchBarText)
{
//Logic to handle updated search bar text
}
}
iOS 自定义渲染器
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using UIKit;
using MyNamespace;
using MyNamespace.iOS;
using Xamarin.Forms;
using Xamarin.Forms.Platform.iOS;
[assembly: ExportRenderer(typeof(MyContentPage), typeof(SearchPageRenderer))]
namespace MyNamespace.iOS
{
public class SearchPageRenderer : PageRenderer, IUISearchResultsUpdating
{
bool _isFirstAppearing = true;
public override void WillMoveToParentViewController(UIViewController parent)
{
base.WillMoveToParentViewController(parent);
var searchController = new UISearchController(searchResultsController: null)
{
SearchResultsUpdater = this,
DimsBackgroundDuringPresentation = false,
HidesNavigationBarDuringPresentation = false,
HidesBottomBarWhenPushed = true
};
searchController.SearchBar.Placeholder = string.Empty;
parent.NavigationItem.SearchController = searchController;
DefinesPresentationContext = true;
}
public override void ViewDidAppear(bool animated)
{
base.ViewDidAppear(animated);
//Work-around to ensure the SearchController appears when the page first appears https://stackoverflow.com/a/46313164/5953643
if (_isFirstAppearing)
{
ParentViewController.NavigationItem.SearchController.Active = true;
ParentViewController.NavigationItem.SearchController.Active = false;
_isFirstAppearing = false;
}
}
public void UpdateSearchResultsForSearchController(UISearchController searchController)
{
if (Element is ISearchPage searchPage)
searchPage.OnSearchBarTextChanged(searchController.SearchBar.Text);
}
}
}
Xamarin.Android 菜单 XML
-
在 Xamarin.Android 项目的 Resources 文件夹中，创建一个名为 menu 的新文件夹（如果尚不存在）。
在Resources > menu 文件夹中，创建一个名为MainMenu.xml 的新文件。
打开Resources > menu > MainMenu.xml
在MainMenu.xml添加如下代码：
<?xml version="1.0" encoding="utf-8" ?>
<menu xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto">
<item android:id="@+id/ActionSearch"
android:title="Filter"
android:icon="@android:drawable/ic_menu_search"
app:showAsAction="always|collapseActionView"
app:actionViewClass="android.support.v7.widget.SearchView"/>
</menu>
Xamarin.Android 自定义渲染器
使用Plugin.CurrentActivity NuGet Package。
using Android.Content;
using Android.Runtime;
using Android.Support.V7.Widget;
using Android.Text;
using Android.Views.InputMethods;
using Plugin.CurrentActivity;
using MyNamespace;
using MyNamespace.Droid;
using Xamarin.Forms;
using Xamarin.Forms.Platform.Android;
[assembly: ExportRenderer(typeof(MyContentPage), typeof(SearchPageRenderer))]
namespace MyNamespace.Droid
{
public class SearchPageRenderer : PageRenderer
{
public SearchPageRenderer(Context context) : base(context)
{
}
protected override void OnAttachedToWindow()
{
base.OnAttachedToWindow();
if (Application.Current.MainPage is NavigationPage navigationPage)
navigationPage.Popped += HandleNavigationPagePopped;
if (Element is ISearchPage && Element is Page page && page.Parent is NavigationPage navigationPage && navigationPage.CurrentPage is ISearchPage)
AddSearchToToolbar(page);
}
protected override void Dispose(bool disposing)
{
if (GetToolbar() is Toolbar toolBar)
toolBar.Menu?.RemoveItem(Resource.Menu.MainMenu);
base.Dispose(disposing);
}
void AddSearchToToolbar(in Page page)
{
if (GetToolbar() is Toolbar toolBar
&& toolBar.Menu?.FindItem(Resource.Id.ActionSearch)?.ActionView?.JavaCast<SearchView>().GetType() != typeof(SearchView))
{
toolBar.Title = page.Title;
toolBar.InflateMenu(Resource.Menu.MainMenu);
if (toolBar.Menu?.FindItem(Resource.Id.ActionSearch)?.ActionView?.JavaCast<SearchView>() is SearchView searchView)
{
searchView.QueryTextChange += HandleQueryTextChange;
searchView.ImeOptions = (int)ImeAction.Search;
searchView.InputType = (int)InputTypes.TextVariationFilter;
searchView.MaxWidth = int.MaxValue; //Set to full width - http://stackoverflow.com/questions/31456102/searchview-doesnt-expand-full-width
}
}
}
void HandleQueryTextChange(object sender, SearchView.QueryTextChangeEventArgs e)
{
if (Element is ISearchPage searchPage)
searchPage.OnSearchBarTextChanged(e.NewText);
}
void HandleNavigationPagePopped(object sender, NavigationEventArgs e)
{
if (sender is NavigationPage navigationPage
&& navigationPage.CurrentPage is ISearchPage)
{
AddSearchToToolbar(navigationPage.CurrentPage);
}
}
Toolbar GetToolbar() => CrossCurrentActivity.Current.Activity.FindViewById<Toolbar>(Resource.Id.toolbar);
}
}
示例应用
这是一个示例应用供参考：
https://github.com/brminnick/GitTrends
还有一篇博文展示了如何为 Xamarin.iOS 和 Xamarin.Android 添加搜索栏：https://www.codetraveler.io/2019/08/10/adding-a-search-bar-to-xamarin-forms-navigationpage/