我遇到了与TaskCompletionSource对象和警报的Dismiss函数相关的问题。此问题不会出现在应用程序的IOS版本中
当应用程序发送通知时，当用户激活应用程序时，将显示两个具有工作功能的警报：
但是，当我进入应用程序时，我只能看到身份验证（因为此警报首先在应用程序中被调用），第二个警报从未显示。我已经尝试覆盖Dismiss函数并将TaskCompletionSource对象结果设置为null，但这会导致相同的警报在应用程序崩溃之前出现X次。有没有办法重复TaskCompletionSource对象，以便我可以看到所有警报？或者我需要对Dismiss函数进行哪些修改，以便在显示所有警报后完成TaskCompletionSource？
Android Fragment示例代码：
public static readonly int AlertWidth = Device.Idiom == TargetIdiom.Phone ? 270 : 320;
class AlertDialogFragment : DialogFragment
{
public string Title;
public string Body;
public View Content;
public List<AlertButton> Buttons;
public TaskCompletionSource<object> tsc;
public Dialog AndroidCustomAlert(Activity activ)
{
Android.Views.LayoutInflater inflater = Android.Views.LayoutInflater.From(activ);
Android.Views.View view = inflater.Inflate(Resource.Layout.AlertDialogLayout, null);
AlertDialog.Builder builder = new AlertDialog.Builder(activ);
builder.SetView(view);
Android.Widget.TextView title = view.FindViewById<Android.Widget.TextView>(Resource.Id.Login);
title.Text = Title;
Android.Widget.TextView body = view.FindViewById<Android.Widget.TextView>(Resource.Id.pincodeText);
body.Text = Body;
body.MovementMethod = new Android.Text.Method.ScrollingMovementMethod();
Android.Widget.EditText pincode = view.FindViewById<Android.Widget.EditText>(Resource.Id.pincodeEditText);
Android.Widget.Button btnPositive = view.FindViewById<Android.Widget.Button>(Resource.Id.btnLoginLL);
Android.Widget.Button btnNegative = view.FindViewById<Android.Widget.Button>(Resource.Id.btnClearLL);
Android.Widget.Button btnNeutral = view.FindViewById<Android.Widget.Button>(Resource.Id.btnNeutral);
if (Title.Contains("Time"))
{
Android.Views.View secondView = inflater.Inflate(Resource.Layout.TimePickerLayout, null);
builder.SetView(secondView);
btnPositive = secondView.FindViewById<Android.Widget.Button>(Resource.Id.btnLoginLL);
btnNegative = secondView.FindViewById<Android.Widget.Button>(Resource.Id.btnClearLL);
var tp = secondView.FindViewById<Android.Widget.TimePicker>(Resource.Id.timePicker1);
tp.SetIs24HourView((Java.Lang.Boolean)true);
//Positive button feedback
btnPositive.Text = Buttons.Last().Text;
btnPositive.Click += delegate
{
var car = (Xamarin.Forms.TimePicker)Content;
var ts = new TimeSpan(tp.Hour, tp.Minute, 0);
car.Time = ts;
CommandsForButtons(Buttons.Last());
};
//Negative button feedback
btnNegative.Text = Buttons.First().Text;
btnNegative.Click += delegate
{
CommandsForButtons(Buttons.First());
};
}
else if (Title.Contains("How are you"))
{
btnPositive.Visibility = Android.Views.ViewStates.Gone;
btnNegative.Visibility = Android.Views.ViewStates.Gone;
btnNeutral.Visibility = Android.Views.ViewStates.Visible;
pincode.Visibility = Android.Views.ViewStates.Gone;
var happySlider = view.FindViewById<Android.Widget.SeekBar>(Resource.Id.happinessSlider);
happySlider.SetProgress(5, false);
happySlider.Visibility = Android.Views.ViewStates.Visible;
btnNeutral.Text = Buttons.First().Text;
btnNeutral.Click += delegate
{
var car = (StackLayout)Content;
var layoutView = (Xamarin.Forms.AbsoluteLayout)car.Children[1];
var slider = (Slider)layoutView.Children[1];
var totalHappyValue = happySlider.Progress / 10;
slider.Value = totalHappyValue;
CommandsForButtons(Buttons.First());
};
}
else
{
//Checks if there are no buttons, and if there aren't any, creates a neutral one
if (Buttons == null || Buttons.Count == 0)
{
btnPositive.Visibility = Android.Views.ViewStates.Gone;
btnNegative.Visibility = Android.Views.ViewStates.Gone;
btnNeutral.Visibility = Android.Views.ViewStates.Visible;
pincode.Visibility = Android.Views.ViewStates.Gone;
Buttons = new List<AlertButton> {
new AlertButton {
Text = "Oké",
IsPreferred = true,
Action = () => false
}
};
btnNeutral.Text = Buttons.First().Text;
btnNeutral.Click += delegate
{
CommandsForButtons(Buttons.First());
};
}
if (Content == null)
{
pincode.Visibility = Android.Views.ViewStates.Gone;
}
//Positive button feedback
btnPositive.Text = Buttons.Last().Text;
btnPositive.Click += delegate
{
var test = (StackLayout)Content;
if (test != null)
{
var car = (Entry)test.Children[0];
car.Text = pincode.Text;
}
CommandsForButtons(Buttons.Last());
};
//Negative button feedback
btnNegative.Text = Buttons.First().Text;
btnNegative.Click += delegate
{
CommandsForButtons(Buttons.First());
};
}
return builder.Create();
}
public void CommandsForButtons(AlertButton button)
{
Func<Task> dismiss = null;
var command = new Command(async () =>
{
var ab = button;
var cont = true;
if (ab.Action != null)
cont = ab.Action();
if (ab.ActionAsync != null)
{
cont = cont && await ab.ActionAsync();
}
if (!cont)
{
await dismiss();
}
});
dismiss = async () =>
{
dismiss = async () => { };
await Task.Run(() =>
{
Dismiss();
tsc.SetResult(null);
});
Log.Debug("TSC", tsc.Task.Status.ToString());
};
command.Execute(this);
}
public override Dialog OnCreateDialog(Bundle savedInstanceState)
{
var test = AndroidCustomAlert(Activity);
test.SetCanceledOnTouchOutside(false);
return test;
}
public override void Dismiss()
{
base.Dismiss();
}
}
public async Task Show(string title, string body, View content, List<AlertButton> buttons)
{
var tcs = new TaskCompletionSource<object>();
var adf = new AlertDialogFragment
{
Title = title,
Body = body,
Content = content,
Buttons = buttons,
tsc = tcs
};
var FragmentManager = ((Activity)Forms.Context).FragmentManager;
FragmentTransaction ft = FragmentManager.BeginTransaction();
//Remove fragment else it will crash as it is already added to backstack
Fragment prev = FragmentManager.FindFragmentByTag("alert");
if (prev != null)
{
ft.Remove(prev);
}
ft.AddToBackStack(null);
adf.Show(ft, "alert");
await tcs.Task;
}
方法：
await Authentication();
await UserCheck();
和IOS代码：
public static readonly int AlertWidth = Device.Idiom == TargetIdiom.Phone ? 270 : 320;
public async Task Show(string title, string body, View content, List<AlertButton> buttons)
{
if (buttons == null || buttons.Count == 0)
{
buttons = new List<AlertButton> {
new AlertButton {
Text = "Oké",
IsPreferred = true,
Action = () => false
}
};
}
Func<Task> dismiss = null;
var captionSize = (double)StyleKit.PhoneDarkLabelStyles.Caption.Setters.First(s => s.Property == Label.FontSizeProperty).Value;
var titleSize = (double)StyleKit.PhoneDarkLabelStyles.Title.Setters.First(s => s.Property == Label.FontSizeProperty).Value;
var top = new StackLayout {
Padding = new Thickness(15, 20, 15, 20),
Spacing = 3,
Children = {
new Label {
Text = title,
Style = StyleKit.PhoneDarkLabelStyles.Title,
FontSize = Math.Max(16, titleSize),
HorizontalTextAlignment = TextAlignment.Center
},
new Label {
Text = body,
Style = StyleKit.PhoneDarkLabelStyles.Body,
//FontSize = ,
FontSize = Math.Max(14, captionSize),
HorizontalTextAlignment = TextAlignment.Center
} ,
new ContentView {
Padding = new Thickness(0,5,0,-10),
VerticalOptions = LayoutOptions.EndAndExpand,
Content = content
}
}
};
var buttonViews = buttons.Select(ab => new Button {
FontSize = Math.Max(16, titleSize),
Text = ab.Text,
FontAttributes = ab.IsPreferred ? FontAttributes.Bold : FontAttributes.None,
TextColor = ab.IsDestructive ? Color.Red : Color.Default,
Command = new Command(async () => {
var cont = true;
if (ab.Action != null)
cont = ab.Action();
if (ab.ActionAsync != null)
cont = cont && await ab.ActionAsync();
if (!cont)
await dismiss();
})
}).ToList();
var grid = new Grid {
RowDefinitions = {
new RowDefinition { Height = GridLength.Auto },
new RowDefinition { Height = GridLength.Auto }
},
ColumnSpacing = 0,
RowSpacing = 0
};
buttons.ForEach(button => {
grid.ColumnDefinitions.Add(
new ColumnDefinition {
Width = AlertWidth / buttonViews.Count
}
);
});
for (int i = 0; i < buttonViews.Count; i++)
{
grid.Children.Add(new BorderView {
BorderColor = Color.FromRgba(0,0,0,0.2),
Thickness = new Thickness(0, 1, (i + 1 < buttonViews.Count) ? 1 : 0, 0)
}, i, 1);
grid.Children.Add(buttonViews[i], i, 1);
}
grid.Children.Add(top, 0, buttons.Count, 0, 1);
var box = new Frame {
WidthRequest = AlertWidth,
BackgroundColor = Color.FromRgba(1,1,1,0.96),
Padding = 0,
Content = grid
};
var outer = new AbsoluteLayout {
BackgroundColor = Color.FromRgba(0,0,0,0.65),
Opacity = 0,
Children = { box }
};
AbsoluteLayout.SetLayoutFlags(box, AbsoluteLayoutFlags.PositionProportional);
AbsoluteLayout.SetLayoutBounds(box,
new Rectangle(0.5, 0.5, AbsoluteLayout.AutoSize, AbsoluteLayout.AutoSize));
var page = new ContentPage {
Content = /* new ScrollView { Content = */ outer // }
};
var tcs = new TaskCompletionSource<object>();
var topVC = UIApplication.SharedApplication.KeyWindow.RootViewController;
while (topVC.PresentedViewController != null) {
topVC = topVC.PresentedViewController;
}
var vc = page.CreateViewController();
topVC.Add(vc.View);
var innerView = vc.View.Subviews[0].Subviews[0];
vc.View.RemoveFromSuperview();
dismiss = async () => {
dismiss = async () => {};
await outer.FadeTo(0, 50);
innerView.RemoveFromSuperview();
tcs.SetResult(null);
};
topVC.Add(innerView);
var kbh = new KeyboardHelper();
kbh.KeyboardChanged += async (sender, e) => {
await box.TranslateTo(0, e.Visible ? (-e.Height / 2f) : 0, 100, Easing.CubicInOut);
};
await outer.FadeTo(1, 100);
await tcs.Task;
}
答案 0 :(得分：1)
这看起来像是线程之间的问题和/或问题，或者根本就没有设置任务完成。
在IOS版本中你有
dismiss = async () => {
dismiss = async () => {};
await outer.FadeTo(0, 50);
innerView.RemoveFromSuperview();
tcs.SetResult(null);
};
Android版本中没有匹配的tcs.SetResult(null);语句。
同样值得注意的是异步调用，因为等待调用SetResult会在没有它的情况下阻塞主线程。