App ScreenShopt 当用户点击应用上的标签以实现长按手势时，我试图检测按下和释放事件。
我已经从另一个StackOverflow问题创建了LongPressbehavior类，但是标签没有附带新闻和发布事件。我可以使用按钮，但我仍然需要带有URL链接的带格式文本（FormattedString），用户可以单击该URL链接导航到网站。
C＃
public class LongPressBehavior : BehaviorBase<ExtendedLabel>
{
private readonly object _syncObject = new object();
private const int Duration = 1000;
//timer to track long press
private Timer _timer;
//the timeout value for long press
private readonly int _duration;
//whether the button was released after press
private volatile bool _isReleased;
/// <summary>
/// Occurs when the associated button is long pressed.
/// </summary>
public event EventHandler LongPressed;
public static readonly BindableProperty CommandProperty = BindableProperty.Create(nameof(Command),
typeof(ICommand), typeof(LongPressBehavior), default(ICommand));
public static readonly BindableProperty CommandParameterProperty =
BindableProperty.Create(nameof(CommandParameter), typeof(object), typeof(LongPressBehavior));
/// <summary>
/// Gets or sets the command parameter.
/// </summary>
public object CommandParameter
{
get => GetValue(CommandParameterProperty);
set => SetValue(CommandParameterProperty, value);
}
/// <summary>
/// Gets or sets the command.
/// </summary>
public ICommand Command
{
get => (ICommand)GetValue(CommandProperty);
set => SetValue(CommandProperty, value);
}
protected override void OnAttachedTo(ExtendedLabel button)
{
base.OnAttachedTo(button);
this.BindingContext = button.BindingContext;
button.Clicked += Button_Pressed;
//button.Released += Button_Released;
}
protected override void OnDetachingFrom(ExtendedLabel button)
{
base.OnDetachingFrom(button);
this.BindingContext = null;
button.Clicked -= Button_Pressed;
//button.Released -= Button_Released;
}
/// <summary>
/// DeInitializes and disposes the timer.
/// </summary>
private void DeInitializeTimer()
{
lock (_syncObject)
{
if (_timer == null)
{
return;
}
_timer.Change(Timeout.Infinite, Timeout.Infinite);
_timer.Dispose();
_timer = null;
Debug.WriteLine("Timer disposed...");
}
}
/// <summary>
/// Initializes the timer.
/// </summary>
private void InitializeTimer()
{
lock (_syncObject)
{
_timer = new Timer(Timer_Elapsed, null, _duration, Timeout.Infinite);
}
}
private void Button_Pressed(object sender, EventArgs e)
{
Debug.WriteLine("Pressed");
_isReleased = false;
InitializeTimer();
}
private void Button_Released(object sender, EventArgs e)
{
Debug.WriteLine("Released");
_isReleased = true;
DeInitializeTimer();
}
protected virtual void OnLongPressed()
{
var handler = LongPressed;
handler?.Invoke(this, EventArgs.Empty);
if (Command != null && Command.CanExecute(CommandParameter))
{
Command.Execute(CommandParameter);
}
}
public LongPressBehavior()
{
_isReleased = true;
_duration = Duration;
}
public LongPressBehavior(int duration) : this()
{
_duration = duration;
}
private void Timer_Elapsed(object state)
{
DeInitializeTimer();
if (_isReleased)
{
return;
}
Device.BeginInvokeOnMainThread(OnLongPressed);
}
}
public class ExtendedLabel : Label
{
private event EventHandler Pressed;
private event EventHandler Released;
public string Name
{
get; set;
}
public void DoClick()
{
Pressed.Invoke(this, null);
}
public event EventHandler Clicked
{
add
{
lock (this)
{
Pressed += value;
TapGestureRecognizer g = new TapGestureRecognizer();
g.Tapped += (s, e) => Pressed?.Invoke(s, e);
GestureRecognizers.Add(g);
}
}
remove
{
lock (this)
{
Pressed -= value;
GestureRecognizers.Clear();
}
}
}
public event EventHandler UnClicked
{
add
{
lock (this)
{
Released += value;
TapGestureRecognizer g = new TapGestureRecognizer();
g.Tapped += (s, e) => Released?.Invoke(s, e);
GestureRecognizers.Add(g);
}
}
remove
{
lock (this)
{
Released -= value;
GestureRecognizers.Clear();
}
}
}
}
XAML
<controls:ExtendedLabel HorizontalOptions="Fill" HorizontalTextAlignment="End" TextColor="White" FormattedText="{Binding OutFormattedBody}">
<controls:ExtendedLabel.Behaviors>
<behaviors:LongPressBehavior LongPressed="OnClick"/>
</controls:ExtendedLabel.Behaviors>
</controls:ExtendedLabel>
我希望能够在标签上点击并按住一秒钟左右以触发LongPress事件，但仍然能够在FormattedString中的链接上单击一下。
答案 0 :(得分：0)
您可以尝试在每个平台上实现它。首先，在您的Forms项目中定义效果类：
public class PressedEffect : RoutingEffect
{
public PressedEffect() : base("MyApp.PressedEffect")
{
}
public static readonly BindableProperty LongPressedCommandProperty = BindableProperty.CreateAttached("LongPressedCommand", typeof(ICommand), typeof(PressedEffect), (object)null);
public static ICommand GetLongPressedCommand(BindableObject view)
{
return (ICommand)view.GetValue(LongPressedCommandProperty);
}
public static void SetLongPressedCommand(BindableObject view, ICommand value)
{
view.SetValue(LongPressedCommandProperty, value);
}
public static readonly BindableProperty LongParameterProperty = BindableProperty.CreateAttached("LongParameter", typeof(object), typeof(PressedEffect), (object)null);
public static object GetLongParameter(BindableObject view)
{
return view.GetValue(LongParameterProperty);
}
public static void SetLongParameter(BindableObject view, object value)
{
view.SetValue(LongParameterProperty, value);
}
public static readonly BindableProperty LongRelesedCommandProperty = BindableProperty.CreateAttached("LongRelesedCommand", typeof(ICommand), typeof(PressedEffect), (object)null);
public static ICommand GetLongRelesedCommand(BindableObject view)
{
return (ICommand)view.GetValue(LongRelesedCommandProperty);
}
public static void SetLongRelesedCommand(BindableObject view, ICommand value)
{
view.SetValue(LongRelesedCommandProperty, value);
}
}
Android实现：
[assembly: ResolutionGroupName("MyApp")]
[assembly: ExportEffect(typeof(AndroidPressedEffect), "PressedEffect")]
namespace LongPressedDemo.Droid
{
public class AndroidPressedEffect : PlatformEffect
{
private bool _attached;
public AndroidPressedEffect()
{
}
protected override void OnAttached()
{
if (!_attached)
{
if (Control != null)
{
Control.LongClickable = true;
Control.Touch += Control_Touch;
}
else
{
Container.LongClickable = true;
Container.Touch += Control_Touch;
}
_attached = true;
}
}
private void Control_Touch(object sender, Android.Views.View.TouchEventArgs e)
{
if (e.Event.Action == MotionEventActions.Down)
{
var command = PressedEffect.GetLongPressedCommand(Element);
command?.Execute(PressedEffect.GetLongParameter(Element));
}
else if (e.Event.Action == MotionEventActions.Up)
{
var command = PressedEffect.GetLongRelesedCommand(Element);
command?.Execute(PressedEffect.GetLongParameter(Element));
}
}
protected override void OnDetached()
{
if (_attached)
{
if (Control != null)
{
Control.LongClickable = true;
Control.Touch -= Control_Touch;
}
else
{
Container.LongClickable = true;
Container.Touch -= Control_Touch;
}
_attached = false;
}
}
}
}
iOS实现：
[assembly: ResolutionGroupName("MyApp")]
[assembly: ExportEffect(typeof(iOSPressedEffect), "PressedEffect")]
namespace LongPressedDemo.iOS
{
public class iOSPressedEffect : PlatformEffect
{
private bool _attached;
private readonly UILongPressGestureRecognizer _longPressRecognizer;
public iOSPressedEffect()
{
_longPressRecognizer = new UILongPressGestureRecognizer(HandleLongClick);
}
protected override void OnAttached()
{
if (!_attached)
{
if (Control != null)
{
Control.AddGestureRecognizer(_longPressRecognizer);
Control.UserInteractionEnabled = true;
}
else
{
Container.AddGestureRecognizer(_longPressRecognizer);
}
_attached = true;
}
}
private void HandleLongClick(UILongPressGestureRecognizer recognizer)
{
if (recognizer.State == UIGestureRecognizerState.Began)
{
var command = PressedEffect.GetLongPressedCommand(Element);
command?.Execute(PressedEffect.GetLongParameter(Element));
}
else if (recognizer.State == UIGestureRecognizerState.Ended)
{
var command = PressedEffect.GetLongRelesedCommand(Element);
command?.Execute(PressedEffect.GetLongParameter(Element));
}
}
protected override void OnDetached()
{
if (_attached)
{
if (Control != null)
{
Control.RemoveGestureRecognizer(_longPressRecognizer);
}
else
{
Container.RemoveGestureRecognizer(_longPressRecognizer);
}
_attached = false;
}
}
}
}
最后，消耗了如下效果：
<Label Text="Welcome to Xamarin.Forms!"
local:PressedEffect.LongPressedCommand="{Binding PressedCommand}"
local:PressedEffect.LongRelesedCommand="{Binding ReleasedCommand}">
<Label.Effects>
<local:PressedEffect/>
</Label.Effects>
</Label>