在wpf中做一个计数器

本文介绍了在wpf中做一个计数器的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

嗨！ 我使用wpf开发了一个非常小的应用程序.我使用了一个名称/id为myCanvas的画布.然后，我在此画布上放置了一个按钮和文本框控件.我希望当我按下按钮时，我的文本框将显示从1到10的数字，持续时间为一秒.意思是，文本框显示1然后等待1秒，然后显示2，然后再次等待1秒，然后显示3，然后再次等待1秒，以此类推，直到10(..这是一个计数器.我的代码如下:

Hi! I have developed a very small application using wpf. I used a canvas with name/id myCanvas. Then i placed a button and textbox controls on this canvas. I wanted that when i clik on button then my textbox display numbers from 1 to 10 with one second duration. Means, textbox diplay 1 then wait for 1 second then display 2 and again wait for 1sec then 3 and again wait for 1second and so on till 10 (..it is a counter. My code for this is as:

namespace numberGenDelayThread { public partial class MainWindow : Window { int n = 1; public MainWindow() { InitializeComponent(); } private void btn_Start_Click(object sender, RoutedEventArgs e) { while (n < =10) { txt_Number.Text = n.ToString(); delay(1000); n++; } } void delay(double ms) { DateTime dt = DateTime.Now.AddMilliseconds(ms); while (DateTime.Now <= dt) { ; } } } }

问题:该程序等待近9秒钟，然后在文本框中仅显示10(在代码中名称为txt_Number). 它没有显示1秒持续时间从1到10的数字...换句话说，它没有像计数器那样扭曲.为什么会这样? 我该如何解决? 我应该使用帆布还是其他容器?

Problem: This program waits for almost 9 seconds and then display only 10 in textbox (with name txt_Number in code). It did not display numbers from 1 to 10 with 1second duration...in other words it did not wrok like counter. Why this so? how can i solve this? should i use canvas or some other container? how can i achieve this in wpf?

推荐答案

当然当然，它会等待所有迭代并仅显示最后一个值.您如何想象它还能以其他方式工作?您使UI线程处于休眠状态，因此它无法更新视图. 令人惊讶的是您提到线程"一词，而实际上没有使用线程.您正在UI线程中调用Thread.Sleep，但绝对不要这样做.您也不应在UI线程中进行任何阻塞调用或仅花费任何明显时间的调用.您需要在单独的线程中执行此操作.除了… 您无法从非UI线程调用与UI相关的任何操作.相反，您需要使用System.Windows.Threading.Dispatcher的Invoke或BeginInvoke方法(对于Forms或WPF)或System.Windows.Forms.Control(仅对于Forms). 在我过去的答案中，您将找到有关其工作原理的详细说明和代码示例: Control.Invoke()与Control.BeginInvoke() [ ^ ]， Treeview扫描仪和MD5的问题 [ ^ ]. 另请参阅有关线程的更多参考资料: 如何获取keydown事件在vb中的不同线程上操作 [ ^ ]， 启用禁用+多线程后控件事件不会触发 [ ^ ].

—SA

Of course it waits for all the iterations and displays only the last value. How did you imagine it could work in any other way? You keep the UI thread sleeping, so it cannot update the view. It''s amazing that you mention the term "thread" and don''t actually use threading. You are calling Thread.Sleep in a UI thread which you should never do. You also should not do any blocking calls or just calls taking any noticeable time in the UI thread. You need to do it in a separate thread. Besides… You cannot call anything related to UI from non-UI thread. Instead, you need to use the method Invoke or BeginInvoke of System.Windows.Threading.Dispatcher (for both Forms or WPF) or System.Windows.Forms.Control (Forms only). You will find detailed explanation of how it works and code samples in my past answers: Control.Invoke() vs. Control.BeginInvoke()[^], Problem with Treeview Scanner And MD5[^]. See also more references on threading: How to get a keydown event to operate on a different thread in vb[^], Control events not firing after enable disable + multithreading[^].

—SA