Question

我试图在延迟一段时间后更改TextView的文本。我编写了一个在执行某些操作后调用的方法。

public void Update()
{
      Task.Delay(10000).ContinueWith(t =>
        {
            dotsLoaderView.Hide(); // This works fine
            imgOverlay.Visibility = ViewStates.Gone;  // This works fine
            ll_Info.Visibility = ViewStates.Visible;  // This doesn't work
            txt_Info.Text = "Some mesage !";  // This doesn't work
        });
}

其中ll_info是包含id txt_info的textview的线性布局的id。我查看了我的layout.xml文件，android：name标签中没有冲突，每个id都不同。当我从任何其他地方更改此textview的文本时，它可以正常工作，但当我尝试更改Task.Delay()内部时，它无法正常工作。为什么呢？

Answer 1

必须在UI线程上查看更新。尝试：

public void Update()
{
    Task.Delay(10000).ContinueWith(t =>
    {
        dotsLoaderView.Hide();
        RunOnUiThread(delegate
        {
            imgOverlay.Visibility = ViewStates.Gone;
            ll_Info.Visibility = ViewStates.Visible; 
            txt_Info.Text = "Some mesage !";
        });
    });
}

Answer 2

更新方法以使用async以便更容易继续。

public async Task UpdateAsync() {
    await Task.Delay(10000);//Non blocking delay on other thread
    //Back on the UI thread
    dotsLoaderView.Hide();
    imgOverlay.Visibility = ViewStates.Gone;
    ll_Info.Visibility = ViewStates.Visible;
    txt_Info.Text = "Some mesage !";
}

并在一个凸起事件的处理程序中调用它

public async void Action(object sender, EventArgs e) {
    await UpdateAsync();
}

或者在事件处理程序中完成所有事情

private event EventHandler Update = delegate { };

private async void OnUpdate(object sender, EventArgs e) {
    await Task.Delay(10000);//Non blocking delay on other thread
    //Back on the UI thread
    dotsLoaderView.Hide();
    imgOverlay.Visibility = ViewStates.Gone;
    ll_Info.Visibility = ViewStates.Visible;
    txt_Info.Text = "Some mesage !";
}

您使用事件

注册事件处理程序

Update += OnUpdate;

并且在执行操作后直接提升事件

Updated(this, EventArgs.Empty);

Xamarin.Android：在Task.Delay（）c＃之后TextView文本没有改变

2 个答案: