WPF Popup踩坑记录

Popup

看名字就知道，它是一个弹出控件，顾名思义，我们可以用它来实现类似Combobox那种，点击后弹出下面选项列表的操作。

System.Object
System.Windows.Threading.DispatcherObject
System.Windows.DependencyObject
System.Windows.Media.Visual
System.Windows.UIElement
System.Windows.FrameworkElement
System.Windows.Controls.Primitives.Popup

以上是MSDN对Popup的继承关系介绍。

需求：有一个文本框 ，鼠标点击后，弹出一个Popup。

我编写了以下xaml

<Grid>
            <TextBox PreviewMouseDown="text_PreviewMouseDown" x:Name="text" Text="666" BorderBrush="Red" BorderThickness="1" HorizontalAlignment="Left" VerticalAlignment="Top"
                 Width="100" FontSize="30" HorizontalContentAlignment="Center" VerticalContentAlignment="Center"/>
            <Popup Placement="Bottom" PlacementTarget="{Binding ElementName=text}"
                   IsOpen="{Binding IsOpen1}"
               AllowsTransparency="True" StaysOpen="False" Width="200" Height="200">
                <Border Margin="10" Background="Green">
                    <TextBox Text="弹出内容1" FontSize="30" HorizontalAlignment="Center" VerticalAlignment="Center"/>
                </Border>
            </Popup>
        </Grid>

这时，奇怪的现象出现了，我鼠标点击textbox后，一松开，popup就消失了。。。

经过一番研究，发现。

问题出在textbox的点击事件上，在PreviewMouseDown事件执行完毕之后，焦点会移到textbox上，这里popup就失去焦点了。。

编写以下MainWindow.xaml:

<Window x:Class="wpfcore.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:wpfcore"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800">
    <Grid>
        <Grid.ColumnDefinitions>
            <ColumnDefinition/>
            <ColumnDefinition/>
        </Grid.ColumnDefinitions>
        <Grid>
            <TextBox PreviewMouseUp="text_PreviewMouseDown" x:Name="text" Text="666" BorderBrush="Red" BorderThickness="1" HorizontalAlignment="Left" VerticalAlignment="Top"
                 Width="100" FontSize="30" HorizontalContentAlignment="Center" VerticalContentAlignment="Center"/>
            <Popup Placement="Bottom" PlacementTarget="{Binding ElementName=text}"
                   IsOpen="{Binding IsOpen1}"
               AllowsTransparency="True" StaysOpen="False" Width="200" Height="200">
                <Border Margin="10" Background="Green">
                    <TextBox Text="弹出内容1" FontSize="30" HorizontalAlignment="Center" VerticalAlignment="Center"/>
                </Border>
            </Popup>
        </Grid>
        <Grid Grid.Column="1">
            <TextBlock MouseUp="textBlock_PreviewMouseDown" x:Name="textblock" Text="666" Background="LightBlue" HorizontalAlignment="Left" VerticalAlignment="Top"
                 Width="100" FontSize="30" TextAlignment="Center"/>
            <Popup Placement="Bottom" PlacementTarget="{Binding ElementName=textblock}"
                   IsOpen="{Binding IsOpen2}"
               AllowsTransparency="True" StaysOpen="False" Width="200" Height="200">
                <Border Margin="10" Background="Green">
                    <TextBox Text="弹出内容2" FontSize="30" HorizontalAlignment="Center" VerticalAlignment="Center"/>
                </Border>
            </Popup>
        </Grid>
    </Grid>
</Window>

MainWindow.cs代码如下：

using System.Windows;
using System.Windows.Input;

namespace wpfcore
{
    public partial class MainWindow : Window
    {
        public bool IsOpen1
        {
            get { return (bool)GetValue(IsOpen1Property); }
            set { SetValue(IsOpen1Property, value); }
        }
        public static readonly DependencyProperty IsOpen1Property =
            DependencyProperty.Register("IsOpen1", typeof(bool), typeof(MainWindow), new PropertyMetadata(false));
        public bool IsOpen2
        {
            get { return (bool)GetValue(IsOpen2Property); }
            set { SetValue(IsOpen2Property, value); }
        }
        public static readonly DependencyProperty IsOpen2Property =
            DependencyProperty.Register("IsOpen2", typeof(bool), typeof(MainWindow), new PropertyMetadata(false));
        public MainWindow()
        {
            InitializeComponent();
            DataContext = this;
        }
        private void text_PreviewMouseDown(object sender, MouseButtonEventArgs e)
        {
            IsOpen1 = true;
        }

        private void textBlock_PreviewMouseDown(object sender, MouseButtonEventArgs e)
        {
            IsOpen2 = true;
        }
    }
}

通过对比可以发现，使用一个TextBlock的效果比textbox好多了。。

记录下来，备查。