如何在Android中重新选择选项卡时更改TabbedPage图标？
Sam*_*tar 8 c# xamarin xamarin.forms
我有一个应用程序使用Xamarin Forms TabbedPage它有一个功能,允许用户暂停和播放页面.请参阅下面的代码.
共享代码
public partial class MainPage : TabbedPage
{
public MainPage()
{
InitializeComponent();
var homePage = new NavigationPage(new HomePage())
{
Title = "Home",
Icon = "ionicons_2_0_1_home_outline_25.png"
};
var phrasesPage = new NavigationPage(new PhrasesPage())
{
Title = "Play",
Icon = "ionicons_2_0_1_play_outline_25.png"
};
Children.Add(homePage);
Children.Add(phrasesPage);
}
}
在iOS渲染器中:
public class TabbedPageRenderer : TabbedRenderer
{
private MainPage _page;
protected override void OnElementChanged(VisualElementChangedEventArgs e)
{
base.OnElementChanged(e);
var tabbarController = (UITabBarController)this.ViewController;
if (null != tabbarController)
{
tabbarController.ViewControllerSelected += OnTabBarReselected;
}
}
void OnTabBarReselected(object sender, UITabBarSelectionEventArgs e)
{
var tabs = Element as TabbedPage;
var playTab = tabs.Children[4];
if (TabBar.SelectedItem.Title == "Play") {
if (tabs != null)
{
playTab.Title = "Pause";
playTab.Icon = "ionicons_2_0_1_pause_outline_22.png";
}
App.pauseCard = false;
}
else {
if (tabs != null) {
playTab.Title = "Play";
playTab.Icon = "ionicons_2_0_1_play_outline_25.png";
}
App.pauseCard = true;
}
}
Android渲染器
public class MyTabbedPageRenderer: TabbedPageRenderer, TabLayout.IOnTabSelectedListener
{
if (e.PropertyName == "Renderer")
{
viewPager = (ViewPager)ViewGroup.GetChildAt(0);
tabLayout = (TabLayout)ViewGroup.GetChildAt(1);
setup = true;
ColorStateList colors = null;
if ((int)Build.VERSION.SdkInt >= 23)
{
colors = Resources.GetColorStateList(Resource.Color.icon_tab, Forms.Context.Theme);
}
else
{
colors = Resources.GetColorStateList(Resource.Color.icon_tab);
}
for (int i = 0; i < tabLayout.TabCount; i++)
{
var tab = tabLayout.GetTabAt(i);
var icon = tab.Icon;
if (icon != null)
{
icon = Android.Support.V4.Graphics.Drawable.DrawableCompat.Wrap(icon);
Android.Support.V4.Graphics.Drawable.DrawableCompat.SetTintList(icon, colors);
}
}
}
void TabLayout.IOnTabSelectedListener.OnTabReselected(TabLayout.Tab tab)
{
var tabs = Element as TabbedPage;
var playTab = tabs.Children[4];
var selectedPosition = tab.Position;
if(selectedPosition == 4)
{
if (playTab.Title == "Play")
{
if (tabs != null)
{
playTab.Title = "Pause";
playTab.Icon = "ionicons_2_0_1_pause_outline_22.png";
}
App.pauseCard = false;
}
else
{
if (tabs != null)
{
playTab.Title = "Play";
playTab.Icon = "ionicons_2_0_1_play_outline_25.png";
}
App.pauseCard = true;
}
}
}
}
这完全有效iOS.但不知何故Android只会Title改变而不是改变Icon.任何人都知道我错过了什么或应该怎么做？此外,这可以在共享代码中完成,而不是在每个平台的代码上重复几乎完全相同的行吗？
Custom Renderer不需要，您可以直接在共享代码中更改Title和Icon。
只是在实现CurrentPageChanged事件TabbedPage
完整的代码
public partial class TabbedPage1 : TabbedPage
{
NavigationPage homePage;
NavigationPage phrasesPage;
public TabbedPage1 ()
{
InitializeComponent();
var homePage = new NavigationPage(new Page1())
{
Title = "Home",
Icon = "1.png"
};
var phrasesPage = new NavigationPage (new Page2())
{
Title = "Play",
Icon = "1.png"
};
Children.Add(homePage);
Children.Add(phrasesPage);
this.CurrentPageChanged += (object sender, EventArgs e) => {
var i = this.Children.IndexOf(this.CurrentPage);
if (i == 0)
{
homePage.Title = "HomeChanged";
homePage.Icon = "2.png";
}
else {
phrasesPage.Title = "PlayChanged";
phrasesPage.Icon = "2.png";
}
};
}
}
结果
PS：使图像文件可从其他平台访问。
iOS- Resources
Android- Resources->drawable
OnTabReselected您可以通过使用在 .txt 文件中的参数中传递给您的选项卡来完成此操作TabRenderer。
您可以使用此对象移动整个逻辑。
这是我的整个渲染器文件（Android）：
[assembly: ExportRenderer(typeof(SWTabSelection.MainPage), typeof(SWTabSelection.Droid.MyTabbedPageRenderer))]
namespace SWTabSelection.Droid
{
public class MyTabbedPageRenderer : TabbedPageRenderer, TabLayout.IOnTabSelectedListener
{
private ViewPager viewPager;
private TabLayout tabLayout;
private bool setup;
public MyTabbedPageRenderer() { }
public MyTabbedPageRenderer(Context context) : base(context)
{
//Use this constructor for newest versions of XF saving the context parameter
// in a field so it can be used later replacing the Xamarin.Forms.Forms.Context which is deprecated.
}
protected override void OnElementPropertyChanged(object sender, PropertyChangedEventArgs e)
{
base.OnElementPropertyChanged(sender, e);
if (e.PropertyName == "Renderer")
{
viewPager = (ViewPager)ViewGroup.GetChildAt(0);
tabLayout = (TabLayout)ViewGroup.GetChildAt(1);
setup = true;
ColorStateList colors = GetTabColor();
for (int i = 0; i < tabLayout.TabCount; i++)
{
var tab = tabLayout.GetTabAt(i);
SetTintColor(tab, colors);
}
}
}
void TabLayout.IOnTabSelectedListener.OnTabReselected(TabLayout.Tab tab)
{
// To have the logic only on he tab on position 1
if(tab == null || tab.Position != 1)
{
return;
}
if(tab.Text == "Play")
{
tab.SetText("Pause");
tab.SetIcon(Resource.Drawable.ionicons_2_0_1_pause_outline_25);
App.pauseCard = false;
}
else
{
tab.SetText("Play");
tab.SetIcon(Resource.Drawable.ionicons_2_0_1_play_outline_25);
App.pauseCard = true;
}
SetTintColor(tab, GetTabColor());
}
void SetTintColor(TabLayout.Tab tab, ColorStateList colors)
{
var icon = tab?.Icon;
if(icon != null)
{
icon = Android.Support.V4.Graphics.Drawable.DrawableCompat.Wrap(icon);
Android.Support.V4.Graphics.Drawable.DrawableCompat.SetTintList(icon, colors);
}
}
ColorStateList GetTabColor()
{
return ((int)Build.VERSION.SdkInt >= 23)
? Resources.GetColorStateList(Resource.Color.icon_tab, Forms.Context.Theme)
: Resources.GetColorStateList(Resource.Color.icon_tab);
}
}
}
我在上面的代码中遇到的唯一问题是图标没有采用色调颜色，因此创建了一个具有与设置色调相同逻辑的函数，并且我在选项卡重新选择上使用它。如果您的应用程序中只有一个选项卡，您可以在 Android 主题/样式 xml 中设置全局色调。
希望这可以帮助。
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