blocks|key|4173662|text|您可以通过ManualResetEvent或TaskCompletionSource创建一个Task-based对话框，因此您可以这样调用它：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|4173663|通过TaskCompletionSource使用示例：|4173664|try
{
++++var+result+=+await+DialogAsync.Show(this,+"StackOverflow",+"Does+it+rock?");
++++Log.Debug("SO",+$"Dialog+result:+{result}");
}
catch+(TaskCanceledException+ex)
{
++++Log.Debug("SO",+$"Dialog+cancelled;+backbutton,+click+outside+dialog,+system-initiated,+....+");
}|code-block|syntax|javascript|4173665|通过TaskCompletionSource的DialogAsync示例：|4173666|public+class+DialogAsync+:+Java.Lang.Object,+IDialogInterfaceOnClickListener,+IDialogInterfaceOnCancelListener
{
++++readonly+TaskCompletionSource<bool?>+taskCompletionSource+=+new+TaskCompletionSource<bool?>();

++++public+DialogAsync(IntPtr+handle,+Android.Runtime.JniHandleOwnership+transfer)+:+base(handle,+transfer)+{+}
++++public+DialogAsync()+{+}

++++public+void+OnClick(IDialogInterface+dialog,+int+which)
++++{
++++++++switch+(which)
++++++++{
++++++++++++case+-1:
++++++++++++++++SetResult(true);
++++++++++++++++break;
++++++++++++default:
++++++++++++++++SetResult(false);
++++++++++++++++break;
++++++++}
++++}

++++public+void+OnCancel(IDialogInterface+dialog)
++++{
++++++++taskCompletionSource.SetCanceled();
++++}

++++void+SetResult(bool?+selection)
++++{
++++++++taskCompletionSource.SetResult(selection);
++++}

++++public+async+static+Task<bool?>+Show(Activity+context,+string+title,+string+message)
++++{
++++++++using+(var+listener+=+new+DialogAsync())
++++++++using+(var+dialog+=+new+AlertDialog.Builder(context)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++.SetPositiveButton("Yes",+listener)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++.SetNegativeButton("No",+listener)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++.SetOnCancelListener(listener)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++.SetTitle(title)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++.SetMessage(message))
++++++++{
++++++++++++dialog.Show();
++++++++++++return+await+listener.taskCompletionSource.Task;
++++++++}
++++}
}|4173667|通过ManualResetEvent使用示例：|4173668|using+(var+cancellationTokenSource+=+new+CancellationTokenSource())
{
++++var+result+=+await+DialogAsync.Show(this,+"StackOverflow",+"Does+it+rock?",+cancellationTokenSource);
++++if+(!cancellationTokenSource.Token.IsCancellationRequested)
++++{
++++++++Log.Debug("SO",+$"Dialog+result:+{result}");
++++}
++++else
++++{
++++++++Log.Debug("SO",+$"Dialog+cancelled;+backbutton,+click+outside+dialog,+system-initiated,+....+");
++++}
}|4173669|通过ManualResetEvent的DialogAsync示例：|4173670|public+class+DialogAsync+:+Java.Lang.Object,+IDialogInterfaceOnClickListener,+IDialogInterfaceOnCancelListener
{
++++readonly+ManualResetEvent+resetEvent+=+new+ManualResetEvent(false);
++++CancellationTokenSource+cancellationTokenSource;
++++bool?+result;

++++public+DialogAsync(IntPtr+handle,+Android.Runtime.JniHandleOwnership+transfer)+:+base(handle,+transfer)+{+}
++++public+DialogAsync()+{+}

++++public+void+OnClick(IDialogInterface+dialog,+int+which)
++++{
++++++++switch+(which)
++++++++{
++++++++++++case+-1:
++++++++++++++++SetResult(true);
++++++++++++++++break;
++++++++++++default:
++++++++++++++++SetResult(false);
++++++++++++++++break;
++++++++}
++++}

++++public+void+OnCancel(IDialogInterface+dialog)
++++{
++++++++cancellationTokenSource.Cancel();
++++++++SetResult(null);
++++}

++++void+SetResult(bool?+selection)
++++{
++++++++result+=+selection;
++++++++resetEvent.Set();
++++}

++++public+async+static+Task<bool?>+Show(Activity+context,+string+title,+string+message,+CancellationTokenSource+source)
++++{
++++++++using+(var+listener+=+new+DialogAsync())
++++++++using+(var+dialog+=+new+AlertDialog.Builder(context)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++.SetPositiveButton("Yes",+listener)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++.SetNegativeButton("No",+listener)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++.SetOnCancelListener(listener)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++.SetTitle(title)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++.SetMessage(message))
++++++++{
++++++++++++listener.cancellationTokenSource+=+source;
++++++++++++context.RunOnUiThread(()+=>+{+dialog.Show();+});
++++++++++++await+Task.Run(()+=>+{+listener.resetEvent.WaitOne();+},+source.Token);
++++++++++++return+listener.result;
++++++++}
++++}
}|4173671|entityMap^0|5|G|M|K|1A|4|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|10|8|@$9|11|A|12|B|C]|$9|13|A|14|B|C]|$9|15|A|16|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|17|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|18|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|19|8|@]|D|@]|E|$]]|$1|O|3|P|5|J|7|1A|8|@]|D|@]|E|$K|L]]|$1|Q|3|R|5|6|7|1B|8|@]|D|@]|E|$]]|$1|S|3|T|5|J|7|1C|8|@]|D|@]|E|$K|L]]|$1|U|3|V|5|6|7|1D|8|@]|D|@]|E|$]]|$1|W|3|X|5|J|7|1E|8|@]|D|@]|E|$K|L]]|$1|Y|3|-4|5|6|7|1F|8|@]|D|@]|E|$]]]|Z|$]]

<p>You can create a <code>Task</code>-based dialog via a <code>ManualResetEvent</code> or a <code>TaskCompletionSource</code> so you can call it like this:</p>

<h3>Usage via TaskCompletionSource Example:</h3>

<pre><code>try
{
    var result = await DialogAsync.Show(this, "StackOverflow", "Does it rock?");
    Log.Debug("SO", $"Dialog result: {result}");
}
catch (TaskCanceledException ex)
{
    Log.Debug("SO", $"Dialog cancelled; backbutton, click outside dialog, system-initiated, .... ");
}
</code></pre>

<h3>DialogAsync via TaskCompletionSource Example:</h3>

<pre><code>public class DialogAsync : Java.Lang.Object, IDialogInterfaceOnClickListener, IDialogInterfaceOnCancelListener
{
    readonly TaskCompletionSource&lt;bool?&gt; taskCompletionSource = new TaskCompletionSource&lt;bool?&gt;();

    public DialogAsync(IntPtr handle, Android.Runtime.JniHandleOwnership transfer) : base(handle, transfer) { }
    public DialogAsync() { }

    public void OnClick(IDialogInterface dialog, int which)
    {
        switch (which)
        {
            case -1:
                SetResult(true);
                break;
            default:
                SetResult(false);
                break;
        }
    }

    public void OnCancel(IDialogInterface dialog)
    {
        taskCompletionSource.SetCanceled();
    }

    void SetResult(bool? selection)
    {
        taskCompletionSource.SetResult(selection);
    }

    public async static Task&lt;bool?&gt; Show(Activity context, string title, string message)
    {
        using (var listener = new DialogAsync())
        using (var dialog = new AlertDialog.Builder(context)
                                                            .SetPositiveButton("Yes", listener)
                                                            .SetNegativeButton("No", listener)
                                                            .SetOnCancelListener(listener)
                                                            .SetTitle(title)
                                                            .SetMessage(message))
        {
            dialog.Show();
            return await listener.taskCompletionSource.Task;
        }
    }
}
</code></pre>

<h3>Usage Via ManualResetEvent Example:</h3>

<pre><code>using (var cancellationTokenSource = new CancellationTokenSource())
{
    var result = await DialogAsync.Show(this, "StackOverflow", "Does it rock?", cancellationTokenSource);
    if (!cancellationTokenSource.Token.IsCancellationRequested)
    {
        Log.Debug("SO", $"Dialog result: {result}");
    }
    else
    {
        Log.Debug("SO", $"Dialog cancelled; backbutton, click outside dialog, system-initiated, .... ");
    }
}
</code></pre>

<h3>DialogAsync via ManualResetEvent Example:</h3>

<pre><code>public class DialogAsync : Java.Lang.Object, IDialogInterfaceOnClickListener, IDialogInterfaceOnCancelListener
{
    readonly ManualResetEvent resetEvent = new ManualResetEvent(false);
    CancellationTokenSource cancellationTokenSource;
    bool? result;

    public DialogAsync(IntPtr handle, Android.Runtime.JniHandleOwnership transfer) : base(handle, transfer) { }
    public DialogAsync() { }

    public void OnClick(IDialogInterface dialog, int which)
    {
        switch (which)
        {
            case -1:
                SetResult(true);
                break;
            default:
                SetResult(false);
                break;
        }
    }

    public void OnCancel(IDialogInterface dialog)
    {
        cancellationTokenSource.Cancel();
        SetResult(null);
    }

    void SetResult(bool? selection)
    {
        result = selection;
        resetEvent.Set();
    }

    public async static Task&lt;bool?&gt; Show(Activity context, string title, string message, CancellationTokenSource source)
    {
        using (var listener = new DialogAsync())
        using (var dialog = new AlertDialog.Builder(context)
                                                            .SetPositiveButton("Yes", listener)
                                                            .SetNegativeButton("No", listener)
                                                            .SetOnCancelListener(listener)
                                                            .SetTitle(title)
                                                            .SetMessage(message))
        {
            listener.cancellationTokenSource = source;
            context.RunOnUiThread(() =&gt; { dialog.Show(); });
            await Task.Run(() =&gt; { listener.resetEvent.WaitOne(); }, source.Token);
            return listener.result;
        }
    }
}
</code></pre>


<p>I am trying to return a bool true if the user selects yes from AlertDialog and visa versa.</p>

<p>at the moment it always returns false. it seems like the bool "result" is never being set.</p>

<pre><code>public bool AskForConfirmation(string messege, Context context)
{
    bool result;

    Android.Support.V7.App.AlertDialog.Builder dialog = new Android.Support.V7.App.AlertDialog.Builder(context);

    dialog.SetPositiveButton("Yes", (sender, args) =&gt;
    {
        result = true;
    });

    dialog.SetNegativeButton("No", (sender, args) =&gt;
    {
        result = false;
    }).SetMessage(messege).SetTitle("System Message");


    dialog.Show();

    return result;
}
</code></pre>

<p>And I call the method</p>

<pre><code>this.RunOnUiThread(() =&gt;
{

    bool response = ioManager.AskForConfirmation("Message", this);

    Console.WriteLine("Response is " + response);

});
</code></pre>


c# Xamarin Android return response bool from AlertDialog

如果用户从AlertDialog中选择yes，我会尝试返回一个布尔值true，反之亦然。目前，它总是返回false。看起来布尔值“结果”永远不会被设定。public bool AskForConfirmation(string messege, Context context){    bool result;    ...

问来自AlertDialog的c# Xamarin安卓返回响应bool
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