在 iOS 上的 Xamarin.Forms 中,我如何扩展 TabbedPage
,以便除了使用底部的选项卡更改页面外,用户还可以向左或向右滑动以更改页面?理想情况下,滑动时页面转换应该是动画的。
所有页面本身都不使用向左或向右手势,因此向左或向右滑动可明确表示希望更改当前页面。
最佳答案
以下代码响应用户滑动手势,使用带有交叉溶解的选项卡更改动画。它为 TabbedPage
创建一个自定义渲染器,为每个方向添加一个 iOS UISwipeGestureRecognizer
。
手势识别器与页面上的其他手势同时工作(否则,滚动等页面手势将阻止滑动手势工作,除非手势是完全水平的),但它本身不起作用(否则,一次滑动将跨多个页面移动).
[assembly: ExportRenderer(typeof(TabbedPage), typeof(SwipeTabbedRenderer))]
class SwipeTabbedRenderer : TabbedRenderer
{
public override void ViewWillAppear(bool animated)
{
base.ViewWillAppear(animated);
NativeView.AddGestureRecognizer(new UISwipeGestureRecognizer(() => SelectNextTab(1)) { Direction = UISwipeGestureRecognizerDirection.Left, ShouldRecognizeSimultaneously = ShouldRecognizeSimultaneously });
NativeView.AddGestureRecognizer(new UISwipeGestureRecognizer(() => SelectNextTab(-1)) { Direction = UISwipeGestureRecognizerDirection.Right, ShouldRecognizeSimultaneously = ShouldRecognizeSimultaneously });
}
void SelectNextTab(int direction)
{
int nextIndex = TabbedPage.GetIndex(Tabbed.CurrentPage) + direction;
if (nextIndex < 0 || nextIndex >= Tabbed.Children.Count) return;
var nextPage = Tabbed.Children[nextIndex];
UIView.Transition(Platform.GetRenderer(Tabbed.CurrentPage).NativeView, Platform.GetRenderer(nextPage).NativeView, 0.15, UIViewAnimationOptions.TransitionCrossDissolve, null);
Tabbed.CurrentPage = nextPage;
}
static bool ShouldRecognizeSimultaneously(UIGestureRecognizer gestureRecognizer, UIGestureRecognizer otherGestureRecognizer) => gestureRecognizer != otherGestureRecognizer;
}
改进的机会:滑动手势比交叉溶解更好,但是当我尝试使用 CATransition 时要创建一个,动画的初始状态是空白页,而不是起始选项卡的页面。这导致动画感觉有点不和谐。
关于ios - iOS 上 Xamarin.Forms 中动画 TabbedPage 转换的滑动手势,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/47586897/