本文介绍一种点击空白处使控件暗藏的实现办法。
问题形容
思考如下场景,在白板类软件中,点击按钮弹出一个View,心愿在点击空白处间接暗藏掉View,同时能够间接书写,如下图:
实现该需要,能够通过View间通信解决,但这样会减少代码耦合且使逻辑显得简单。
本文通过派生UserControl,将解决逻辑封装在View外部,从而升高代码耦合度。
解决方案
通过剖析需要能够想到,点击空白处时,该View会失去焦点,因而能够通过监听LostFocus事件来解决。
首先,须要设置Focusable属性为true,其默认值为false。而后监听LostFocus事件,当View失去焦点时,Visibility属性置为Collapsed。
此处有个问题,如果点击View外部的子控件,View会先LostFocus,而后立马GotFocus,通过测试距离在20ms内。因而还要响应下GotFocus事件,获取到焦点时,Visibility属性置为Visible。
另外,当点击按钮显示View时,此View并未获取焦点,因而须要监听IsVisibleChanged事件,当NewValue为true时,通过调用Focus使View获取焦点。
还须要解决一个问题。如上文动图所示,需点击按钮显示,再次点击按钮暗藏。但再次点击按钮时,View曾经失去了焦点,此时已暗藏,所以再次点击会导致View暗藏后立马显示。通过测试统计,点击按钮执行命令,到View响应命令执行显示/暗藏,工夫在(50,200)ms范畴内。因而如果在该范畴内View先暗藏后显示,需将其Visibility置为Collapsed。
至此,逻辑根本解决完了,然而还有一个坑。如果应用bool值绑定Visibility(Mode需设置为TwoWay),点击按钮批改bool时,PropertyChanged事件会告诉监听者属性扭转,此时由上个步骤中的逻辑晓得,咱们须要批改Visibility的值,这实践上又会导致bool值的扭转,但bool值并未批改(属性未修改完再次批改),这就导致Visibility与bool值不统一,再次点击按钮不会显示View。咱们只须要异步执行上个步骤,就能够解决。
通过上述解决,点击空白处暗藏View的逻辑就封装到View外面了,外围代码如下所示,感兴趣的能够下载残缺demo试试。如果有其它好的办法,欢送交换(WPF或开源库或者有更好的解决方案)。
// 派生UserControlpublic class MyAutoHideControl : UserControl{ public MyAutoHideControl() : base() { Focusable = true; _lastTimeCollapsed = DateTime.Now.Ticks / 10000; IsVisibleChanged += AutoHideControl_IsVisibleChanged; GotFocus += AutoHideControl_GotFocus; LostFocus += AutoHideControl_LostFocus; } private void AutoHideControl_GotFocus(object sender, RoutedEventArgs e) { if (Visibility != Visibility.Visible) Visibility = Visibility.Visible; } private void AutoHideControl_LostFocus(object sender, RoutedEventArgs e) { if (Visibility == Visibility.Visible) Visibility = Visibility.Collapsed; } private void AutoHideControl_IsVisibleChanged(object sender, DependencyPropertyChangedEventArgs e) { if ((bool)e.NewValue == (bool)e.OldValue) return; if ((bool)e.NewValue) { long interval = DateTime.Now.Ticks / 10000 - _lastTimeCollapsed; if (interval > MinInterval && interval < MaxInterval) { if (Visibility == Visibility.Visible) { Dispatcher.BeginInvoke(new Action(() => { Visibility = Visibility.Collapsed; })); } } else Focus(); } else _lastTimeCollapsed = DateTime.Now.Ticks / 10000; } private long _lastTimeCollapsed; // 需解决再次点击按钮暗藏的状况 private const long MinInterval = 50; private const long MaxInterval = 200;}
// View<Window ... xmlns:c="clr-namespace:CalcBinding;assembly=CalcBinding" xmlns:local="clr-namespace:AutoHideControl" Title="AutoHideControl" Height="200" Width="350"> <Window.Resources> <BooleanToVisibilityConverter x:Key="BooleanToVisibility"/> </Window.Resources> <Grid> <InkCanvas Background="LightCyan"/> <DockPanel VerticalAlignment="Bottom" Margin="10" Height="Auto"> <local:MyAutoHideView DockPanel.Dock="Top" Width="150" Height="50" Margin="10" Visibility="{Binding ShowView,Converter={StaticResource BooleanToVisibility},Mode=TwoWay}"/> <Button Width="80" Height="30" Command="{Binding ButtonClickedCommand}" Content="{c:Binding ShowView ? \'Hide\' : \'Show\'}"/> </DockPanel> </Grid></Window>// ViewModelpublic class MainWindowViewModel : INotifyPropertyChanged{ public bool ShowView { get => _showView; set { _showView = value; OnPropertyChanged(); } } public DelegateCommand ButtonClickedCommand => _buttonClickedCommand ?? (_buttonClickedCommand = new DelegateCommand { ExecuteAction = (_)=> ShowView = !_showView }); public void OnPropertyChanged([CallerMemberName] string name = "")=> PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(name)); public event PropertyChangedEventHandler PropertyChanged; private bool _showView;