How suppress multiple button clicks?

Question

I would like to know the best way to handle an http Request on Xamarin.Forms.

For now I was handling the request this way:

First I have a button on my forms like this:

btn_1.Clicked += (sender, e) => {
    Confirm(name, password);
};

My Confirm() function checks the entrees and throws the event of the request. Also it do the logic after the request event is completed. For example:

private async void Confirm(string name, string password) {
    UserController user_controller = new UserController();
    if (name != null && password != null) {
        User user = new User(name, password);
        bool ok = user_controller.Login(user);
        if(ok){
            Navigation.InsertPageBefore(new NextPage(), this);
            await Navigation.PopAsync();
        } else {
            //Show error code...
        }
    }
}

My UserController has two functions for each http request. The first one does the request. The second one calls the first one and handles the answer.

1º:

private async Task<HttpResponseMessage> user_login(User user){
    try {
        Uri uri = new Uri("http://localhost/user/login");
        string user_json = JsonConvert.SerializeObject(user);
        StringContent content = new StringContent(user_json, Encoding.UTF8, "application/json");
        return await Utilities.client.PostAsync(uri, content).ConfigureAwait(false);
    } catch {
        return null;
    }
}

2º:

public bool Login(User user) {
    http_response = user_login(user).GetAwaiter().GetResult();
    //If it doesn't reach the server...
    if (http_response != null) {
        //Depending of the status of the response
        switch (http_response.StatusCode) {
            case (System.Net.HttpStatusCode)200:
                 try {
                    string content = http_response.Content.ReadAsStringAsync().GetAwaiter().GetResult();
                    Response response = JsonConvert.DeserializeObject<Response>(content);
                    return (bool) response.aux;
                  } catch {

                  }
                  break;
            case (System.Net.HttpStatusCode)401:
                 ...
                 break;
            default:
                 ...
                 break;
        }
    } else {
        App.Current.MainPage.DisplayAlert("Error", "No server connection", "OK");
    }
    return false;
}

This completes my protocol for each request. My problem is:

1. I'm not sure if this is the correct way to do it

2. When I click several times the btn_1 it throws many times the request

How could I do to avoid this? I try to put a lock on my button but it doesn't work. I'm having many troubles with the asynchronous requests. I don't know which is the best way to handle the request to throw only one request at the time.

EDIT:

I have created this button extension:

public partial class LockableButton: Button {
    public event EventHandler ThrowEvent;
    public bool ShowLoading { get; set; }

    public LockableSimpleButton() {
        ShowLoading=false;

        InitializeComponent();

        this.Clicked += async (object sender,EventArgs e) => {
            if (!Utilities.Unlocked) { return; }
            Utilities.Unlocked=false;
            try {
                if (ShowLoading) {
                    await Navigation.PushModalAsync(new LoadingPopUp());
                    ThrowEvent(sender,e);
                    await Navigation.PopModalAsync();
                } else {
                    ThrowEvent(sender,e);
                }
            } finally {
                await Task.Delay(1000); 
                Utilities.Unlocked=true;
            }
        };
    }
}

And now my buttons are like this:

   btn_1.ThrowEvent += async (sender, e) => {
        Navigation.InsertPageBefore(new Page(),this);
        await Navigation.PopAsync(false);
   };

How it is even posible that the error still persisting?

When I click several times the button it throws an error because it is trying to PopAsyc to many time the same page... It is the delay to short?

Answer 1

2. When I click several times the btn_1 it throws many times the request

This problem has nothing to do with handling an Async HTTP Request.

Here are two classic coding techniques for discarding extra button presses.

They are variations on having a flag set, and discarding any clicks that happen while that flag is set.

Common pseudo-code:

static bool _busy;

...click handler... {
    if (_busy) return;

    _busy = true;
    // Special code as needed.

    ... handle the click ...

    // This code must always be executed.
    // If it isn't, the button action will never occur again.
    _busy = false;
}

1. When you finish processing the first click, start a one-time timer. Until that timer fires, discard any additional clicks.

Pseudo-code:

...click handler... {
    if (_busy) return;

    _busy = true;
    try {
        ... handle the click ...
    } finally {
        var timer = new Timer(TimerTick, 250 milliseconds, one-time);
        timer.Start();
    }
}

void TimerTick() {
    // This code must always be executed.
    // If it isn't, the button action will never occur again.
    _busy = false;
    //maybe timer.Stop();
}

2. When you start processing the first click, set a flag. Clear that flag when you are done processing. Discard any clicks that happen while that flag is set.

Pseudo-code:

// Must be `async` method, so events continue while processing.
// Otherwise, the second button press might simply be on hold,
// until after this finishes, so doesn't get suppressed.
...click handler... {
    if (_busy) return;

    _busy = true;
    try {
        ... handle the click ...
    } finally {
        // This code must always be executed.
        // If it isn't, the button action will never occur again.
        _busy = false;
    }
}