问在自定义渲染器中基于IsFocused属性隐藏搜索栏图标
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Stack Overflow用户

提问于 2019-10-16 03:50:15

回答 2查看 716关注 0票数 3

我想使用基于SearchBarRenderer属性的自定义IsFocused来隐藏IOS中的搜索栏图标。我怎样才能做到这一点？

protected override void OnElementPropertyChanged(object sender, System.ComponentModel.PropertyChangedEventArgs e)
        {
            base.OnElementPropertyChanged(sender, e);

            if (Element == null || Control == null)
                return;

            var element = Element as CustomSearchBar;

            if (element.IsFocused)
            {

            }
            else
            {

            }
        }

xamarin

xamarin.forms

xamarin.ios

回答 2

Stack Overflow用户

回答已采纳

发布于 2019-10-16 19:00:23

如果您正在使用自定义渲染器来实现它，请编写如下代码。

[assembly: ExportRenderer(typeof(CustomSearchBar), typeof(CustomSearchBarRenderer))]
namespace App15.iOS
{
    public class CustomSearchBarRenderer : SearchBarRenderer
    {
        UIImage searchImg;
        protected override void OnElementChanged(ElementChangedEventArgs<SearchBar> e)
        {
            base.OnElementChanged(e);
            searchImg = Control.GetImageForSearchBarIcon(UISearchBarIcon.Search, UIControlState.Normal);
            if (e.OldElement != null)
            {
                Control.OnEditingStarted -= Control_OnEditingStarted;
                Control.OnEditingStopped -= Control_OnEditingStopped;
            }

            if (e.NewElement != null)
            {
                if (null != Control)
                {
                    Control.OnEditingStarted += Control_OnEditingStarted;
                    Control.OnEditingStopped += Control_OnEditingStopped;
                }
            }
        }

        private void Control_OnEditingStopped(object sender, EventArgs e)
        {
            var searchBar = sender as UISearchBar;
            searchBar.SetImageforSearchBarIcon(searchImg, UISearchBarIcon.Search, UIControlState.Normal);
        }

        private void Control_OnEditingStarted(object sender, EventArgs e)
        {
            var searchBar = sender as UISearchBar;
            searchBar.SetImageforSearchBarIcon(new UIImage(), UISearchBarIcon.Search, UIControlState.Normal);
        }
    }
}

注意: App15是本地项目中的命名空间。

正如document 效果导论 of Effect所说的那样，您也可以参考这个文档产生效果来实现它，因为它不需要使用自定义渲染器来实现它。

效果样本如下：

创建SearchBarEffects：

public class SearchBarEffects : RoutingEffect
{
    public SearchBarEffects() : base($"MyCompany.{nameof(SearchBarEffects)}")
    {

    }
}

在Xaml中使用：

// here is custom renderer
<local:CustomSearchBar Placeholder="renderer input"/> 
// here is custom effect
<SearchBar Placeholder="effect input">
    <SearchBar.Effects>
        <local:SearchBarEffects />
    </SearchBar.Effects>
</SearchBar>

在SearchBarEffect解决方案中创建iOS：

[assembly: ResolutionGroupName("MyCompany")]
[assembly: ExportEffect(typeof(App15.iOS.SearchBarEffect), "SearchBarEffects")]
namespace App15.iOS
{
    public class SearchBarEffect : PlatformEffect
    {
        UIImage searchImg;
        protected override void OnAttached()
        {
            searchImg = ((UISearchBar)Control).GetImageForSearchBarIcon(UISearchBarIcon.Search, UIControlState.Normal);
            ((UISearchBar)Control).OnEditingStarted += SearchBar_OnEditingStarted;
            ((UISearchBar)Control).OnEditingStopped += SearchBar_OnEditingStopped;
        }

        private void SearchBar_OnEditingStopped(object sender, EventArgs e)
        {
            var searchBar = sender as UISearchBar;
            searchBar.SetImageforSearchBarIcon(searchImg, UISearchBarIcon.Search, UIControlState.Normal);
        }

        private void SearchBar_OnEditingStarted(object sender, EventArgs e)
        {
            var searchBar = sender as UISearchBar;
            searchBar.SetImageforSearchBarIcon(new UIImage(), UISearchBarIcon.Search, UIControlState.Normal);
        }

        protected override void OnDetached()
        {
            ((UISearchBar)Control).OnEditingStarted -= SearchBar_OnEditingStarted;
            ((UISearchBar)Control).OnEditingStopped -= SearchBar_OnEditingStopped;
        }
    }
}

最后，以两种方式展示效果。上是效果的，下是伦德尔的。

票数 1

Stack Overflow用户

发布于 2019-10-16 03:59:44

个人注意-没有必要使用自定义渲染器，一个效果是远远超过-我测试的效果，而不是自定义渲染器。关于如何创建效果，请参见这里

如果只将此效果添加到<SearchBar> 元素.中，则this.Control将成为UISearchBar 。

因此您可以这样做(基于iOS和Xamarin.iOS文档)：

效果的iOS实现：

public class NoSearchIconEffect : PlatformEffect
{
    UIImage defaultIcon = null;

    protected override void OnAttached()
    {
        var searchBar = this.Control as UISearchBar;
        defaultIcon = defaultIcon ?? searchBar.GetImageForSearchBarIcon(UISearchBarIcon.Search, UIControlState.Normal); //This will save the default icon

        searchBar.OnEditingStarted += delegate
        {
            searchBar.SetImageforSearchBarIcon(new UIImage(), UISearchBarIcon.Search, UIControlState.Normal);
        };

        searchBar.OnEditingStopped += delegate
        {
            searchBar.SetImageforSearchBarIcon(defaultIcon, UISearchBarIcon.Search, UIControlState.Normal);
        };
    }

    protected override void OnDetached()
    {

    }
}