ios – Xamarin.forms捏和缩放

2023年2月14日 266次阅读

有没有办法让一个控件允许我使用只有Xamarin.Forms控件捏和缩放.

我想在xamarin.forms(WebView或Image或任何其他)的任何控件中显示图像,并能够从应用程序中进行缩放.

最佳答案 截至本文发布时,无法使用纯内置Forms控件进行捏合/缩放.有一种方法可以实现这一点,但您必须为此实现本机渲染器.

我通过创建一个继承自Xamarin.Forms.ContentView – PanGestureContainer的类在我正在编写的应用程序中实现了这一点,该类具有诸如最小/最大触摸点数和要侦听的事件之类的属性.

在iOS项目中,我为我的视图创建了一个自定义渲染器,其中渲染器从视图中获取属性并挂钩触摸事件侦听器.

另外,我创建了一个可附加属性(也称为Behavior),可以应用于其他视图,当应用它时,它从其父视图中获取视图,将其包装在PanGestureRecognizer中,另一个附加属性以相同的方式充当事件侦听器包装器.

这是一个完整的黑客,但涵盖了缺少的功能,直到Xamarin干净地实现它

更新：现在使用示例代码,严重修剪,因为它会发布太多,它应该让您知道如何实现这一点,而不是复制/粘贴解决方案.如果它看起来似乎太多了,我肯定有更好的方法,但它会成功,直到这个功能被烘焙.

  public abstract class BaseInteractiveGestureRecognizer : BindableObject, IInteractiveGestureRecognizer
    {
        public static readonly BindableProperty CommandProperty = BindableProperty.Create<BaseInteractiveGestureRecognizer, ICommand> ((b) => b.Command, null, BindingMode.OneWay, null, null, null, null);

        public ICommand Command {
            get {
                return (ICommand)base.GetValue (BaseInteractiveGestureRecognizer.CommandProperty);
            }
            set {
                base.SetValue (BaseInteractiveGestureRecognizer.CommandProperty, value);
            }
        }

        public object CommandParameter {get;set;} // make bindable as above

        public GestureState State { get;set;} // make bindable as above

        public View SourceView{ get; set; } 

        public void Send ()
        { 
            if (Command != null && Command.CanExecute (this)) {
                Command.Execute (this);
            }
        }
    }

public class PanGesture : BaseInteractiveGestureRecognizer
{
    public uint MinTouches { get;set; } // make bindable
    public uint MaxTouches { get;set; } // make bindable
    // add whatever other properties you need here - starting point, end point, touch count, current touch points etc.
}

然后在iOS项目中：

public abstract class BaseInteractiveGestureRenderer : BindableObject,IGestureCreator<UIView>
    {
        public abstract object Create (IInteractiveGestureRecognizer gesture, Element formsView, UIView nativeView);

        public static GestureState FromUIGestureState (UIGestureRecognizerState state)
        {
            switch (state) {
            case UIGestureRecognizerState.Possible:
                return GestureState.Possible;
            case UIGestureRecognizerState.Began:
                return GestureState.Began;
            case UIGestureRecognizerState.Changed:
                return GestureState.Update;
            case UIGestureRecognizerState.Ended:
                return GestureState.Ended;
            case UIGestureRecognizerState.Cancelled:
                return GestureState.Cancelled;
            case UIGestureRecognizerState.Failed:
                return GestureState.Failed; 
            default:
                return GestureState.Failed;
            }    
        }
    }


using StatementsHere;
[assembly: ExportGesture (typeof(PanGesture), typeof(PanGestureRenderer))]
namespace YourNamespaceHere.iOS
{
public class PanGestureRenderer : BaseInteractiveGestureRenderer
{
    public PanGestureRenderer () : base ()
    {   
    }

    #region IGestureCreator implementation

    public override object Create (IInteractiveGestureRecognizer gesture, Element formsView, UIView nativeView)
    {   
        PanGesture panGesture = gesture as PanGesture; 
        nativeView.UserInteractionEnabled = true; 

        UIPanGestureRecognizer panGestureRecognizer = null;
        panGestureRecognizer = new UIPanGestureRecognizer (() => panGesture.Send());
    }
}
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