WPF 按钮内容绑定
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WPF Button content binding
提问by GETah
I am sure the solution to this problem is obvious but I simply can't figure it out. I tried every answer I could find on SO with no hope.
我确信这个问题的解决方案是显而易见的，但我就是想不通。我毫无希望地尝试了所有可以在 SO 上找到的答案。
Problem
问题
I have a simple WPF form that holds a button. The button's text is defined by a view model that changes the text content on click. For the sake of completeness, below is my xaml and the view model laying behind.
我有一个包含按钮的简单 WPF 表单。按钮的文本由视图模型定义，该模型在单击时更改文本内容。为了完整起见，下面是我的 xaml 和后面的视图模型。
XAML:
XAML：
<Window x:Class="MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:vms="clr-namespace:MyVm"
Height="163.762" Width="201.758" WindowStyle="ToolWindow" ResizeMode="NoResize" Topmost="True" WindowStartupLocation="CenterScreen">
<Window.DataContext>
<vms:MyVm />
</Window.DataContext>
<Button Name="Action" Content="{Binding Path=NextAction, UpdateSourceTrigger=PropertyChanged, Mode=OneWay}" Margin="0" MinHeight="50" FontWeight="Bold" FontSize="16" Click="Action_Click"></Button>
</Window>
ViewModel:
视图模型：
public class MyVm: INotifyPropertyChanged
{
private String _nextAction = "START";
public String NextAction {
get { return _nextAction; }
set
{
_nextAction = value;
OnPropertyChanged("NextAction");
}
}
public void ExecuteAction()
{
if (_nextAction == "START")
NextAction = "STOP";
if (_nextAction == "STOP")
NextAction = "START";
}
public event PropertyChangedEventHandler PropertyChanged;
[NotifyPropertyChangedInvocator]
public void OnPropertyChanged(string propertyName)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null) handler(this, new PropertyChangedEventArgs(propertyName));
}
}
Question
题
When I click on the button, I want the text to change from "START" to "STOP" and vice versa.
当我单击按钮时，我希望文本从“开始”更改为“停止”，反之亦然。
- The logic in the view model seem to work fine.
- The
OnPropertyChangedis correctly called. - The
handlerinsideOnPropertyChangedis notnull
- 视图模型中的逻辑似乎工作正常。
- 在
OnPropertyChanged正确调用。 - 在
handler里面OnPropertyChanged是不是null
Clicking the button has no effect on the UI. What am I doing wrong?
单击该按钮对 UI 没有影响。我究竟做错了什么？
回答by BenjaminPaul
The following logic is incorrect...
以下逻辑不正确...
public void ExecuteAction()
{
if (_nextAction == "START")
NextAction = "STOP";
if (_nextAction == "STOP")
NextAction = "START";
}
It should be...
它应该是...
public void ExecuteAction()
{
if (_nextAction == "START") {
NextAction = "STOP";
} else {
NextAction = "START";
}
}
You are changing the next action to stop then the following lines of code are changing it back again immediately.
您正在将下一个操作更改为停止，然后以下代码行立即将其更改回来。
