wpf中的DispatcherTimer基本用法，本文不在叙述。主要写一些不同的，来提醒自己不要再犯同样错误。
前几天写代码时发现。当在非UI线程创建DispatcherTimer实例时，程序无法进入Tick事件
private static System.Windows.Threading.DispatcherTimer timer;
private void Button_Click(object sender, RoutedEventArgs e)
{
new System.Threading.Thread(CreateTimer).Start();
}
private void CreateTimer()
{
timer = new System.Windows.Threading.DispatcherTimer();
timer.Interval = TimeSpan.FromSeconds(1);
timer.Tick += DispatcherTimer_Click;
timer.Start();
}
private void DispatcherTimer_Click(object sender, EventArgs e)
{
Console.WriteLine("DispatcherTimer_Click");
}
在DispatcherTimer_Click函数入口设断点，发现程序无法进入。
如果这样创建对象
private static System.Windows.Threading.DispatcherTimer timer;
private void Button_Click(object sender, RoutedEventArgs e)
{
new System.Threading.Thread(CreateTimer).Start();
}
private void CreateTimer()
{
timer = new System.Windows.Threading.DispatcherTimer(System.Windows.Threading.DispatcherPriority.SystemIdle, this.Dispatcher);
timer.Interval = TimeSpan.FromSeconds(1);
timer.Tick += DispatcherTimer_Click;
timer.Start();
}
private void DispatcherTimer_Click(object sender, EventArgs e)
{
Console.WriteLine("DispatcherTimer_Click");
}
程序可以进入Tick事件。
或者这样创建对象
private static System.Windows.Threading.DispatcherTimer timer;
private void Button_Click(object sender, RoutedEventArgs e)
{
new System.Threading.Thread(CreateTimer).Start();
}
private void CreateTimer()
{
this.Dispatcher.Invoke(() =>
{
timer = new System.Windows.Threading.DispatcherTimer();
});
timer.Interval = TimeSpan.FromSeconds(1);
timer.Tick += DispatcherTimer_Click;
timer.Start();
}
private void DispatcherTimer_Click(object sender, EventArgs e)
{
Console.WriteLine("DispatcherTimer_Click");
}
原因如下
DispatcherTimer.Tick 集成到按指定时间间隔和指定优先级处理的 Dispatcher 队列中的计时器。
在线程中创建DispatcherTimer对象时，DispatcherTimer的Dispatcher是线程的Dispatcher。
而此时如果线程如果没有操作UI对象，则其Dispatcher==null，详情见博客 https://www.cnblogs.com/DoNetCoder/p/4369903.html