We Keep Coding

Device.StartTimer equivalent in Native Xamarin

I'm working on an application that simulates an old phone keypad like the ones in a Nokia 3310 where multiple button clicks changes the letter thats being written from 1 to A, B, etc.
I've originally built the application in Xamarin Forms but the assignment needs it to be in Native Xamarin so I need to pass it there. The original code I used in Xamarin forms was the following:
private void Button_Clicked(object sender, EventArgs e)
{
if (ButtonCount < 1)
{
TimeSpan tt = new TimeSpan(0, 0, 1);
Device.StartTimer(tt, NumberofClicks);
}
ButtonCount++;
}
With the NumberofClicks method being the following:
bool NumberofClicks()
{
if (ButtonCount > 1)
{
//Event for 2 button clicks
}
else
{
//Event for 1 button click
}
ButtonCount = 0;
return false;
Since Xamarin Native supports applying tags to buttons I want to try and make a method for all the buttons to be more efficient where it uses the tag it has, for this purpose I use the expression of var Btn = ((Android.Widget.Button)btnPresionado) so I can simply use Btn.Tag.ToString() when adding it to text. As for what I tried to use as a Device.StarTimer equivalent, I used a System.Threading.Timer as seen in the following code:
public void ButtonClick(object btnPresionado, EventArgs e)
{
if (ButtonCount < 1)
{
System.Threading.Timer timer = new Timer(NumberofClicks,btnPresionado, 2000, Infinite);
}
ButtonCount++;
}
public void NumberofClicks(object btnPresionado)
{
var Btn = ((Android.Widget.Button)btnPresionado);
if (ButtonCount > 1)
{
//Double click event
}
else
{
//Single click event
}
ButtonCount = 0;
}
Unfortunately when testing this, it does not work and makes the app crash in the emulator (I cant see what exactly goes wrong since this is a 3rd party emulator because Hyper-V simply refuses to install itself on my PC at the moment) so I want to ask what would be a good equivalent for Device.StartTimer() or what exactly am I doing wrong here?
Thank you

create and move a point on canvas at once

I got a Problem with creating and moving a point (an ellipse) in WPF MVVM.
Right now i have a RelayCommand which calls my create point handler in my vm which creates a command and executes it:
private void CreatePointHandler(MouseEventArgs e)
{
AddConnectionPointCommand addConnectionPointCommand = new AddConnectionPointCommand(this, e);
PetriNetViewModel.ExecuteCommand(addConnectionPointCommand);
}
Furthermore for an already existing point, I got a Move handler aswell (in another vm tho):
public void MovePointHandler(ConnectionPoint pointMoved, Point oldLocation, Point newLocation)
{
Vector move = new Vector(newLocation.X - oldLocation.X, newLocation.Y - oldLocation.Y);
PetriNetViewModel.ExecuteCommand(new MoveDragCanvasElementsCommand(new ConnectionPoint[] { pointMoved }, move));
}
Adding and moving a point afterwards is just working as expected.
Now i want to give the user the possibility to add and move a point in one step. In my CreatePointHandler i can figure out if the left mouse buttin it still pressed like this:
if (e.LeftButton == MouseButtonState.Pressed) {
}
but how would I move the point now? The MovePointHandler is called by an event in the codebehind (I know this shouldnt be done in mvvm, but my collegues and I think it's ok if you don't have too much code in it), which is also passing an ElementsMovedEventArgs which I dont have here.
thanks for your help in advance.

It's hard to say without seeing your codebehind that calls these handlers.
I would have thought you should have a concept of a SelectedPoint, at which you can always check if there is an intended drag happening when the mouse is moved.
i.e.
private ConnectionPoint SelectedPoint { get; set; }
private void OnMouseMove(object sender, MouseEventArgs e)
{
if (e.LeftButton == MouseButtonState.Pressed)
{
// dragging something.. check if there is a point selected
if (SelectedPoint != null)
{
_viewModel.MovePointHandler(SelectedPoint, _oldLocation, _newLocation);
}
}
}
Then, as part of your CreatePointHandler, you immediately set the newly created instance to the SelectedPoint, until a MouseUp is detected.
private void ExecuteAddConnectionPointCommand()
{
// standard logic...
ConnectionPoint addedPoint = ...
SelectedPoint = addedPoint;
}
The specifics of the implementation will likely change depending on your architecture, but hopefully you get the point.

Make text scroll a given amount of times

I'm only just getting into GUIs, so please forgive me if I've missed something obvious. Google hasn't helped much I'm afraid.
My base objective is to have Marquee style text scrolling across the screen a set number of times. I've achieved the scrolling aspect utilizing a timer which scrolls a label named "My text here" across the screen (taken from this tutorial: http://www.youtube.com/watch?v=-y-Z0i-DeAs Note: I don't speak the language he does), but I've been unable to get the thing to stop. I'm open to using a different way to achieve the scrolling, but this is the only example I've found so far that worked well with my current level of knowledge of GUIs (basically dragging and dropping).
private void timer_Tick(object sender, EventArgs e)
{
this.Refresh();
labelTesting.Left += 5;
if (labelTesting.Left >= this.Width)
{
labelTesting.Left = labelTesting.Width * -1;
}
}
My best guess is that the timer is simply starting the whole process over with each tick. I've tried countering this by having it return after running i times and telling the label what to display, but that's not working. Nor can I seem to find a way to tell the thing to stop.
http://www.dotnetperls.com/timer has an example where a timer is set to run for a given amount of time, but I do not know how to implement that when messing around with GUIs. What would be the best way to implement the feature I desire? Any insight or suggestions would be greatly appreciated.
EDIT: Based on suggestions in the answers and comments I have edited the code to run for what should be 30 seconds before setting itself to a given position. However the text no longer scrolls. I'm going to keep working at it, but more input would be appreciated.
private void timer_Tick(object sender, EventArgs e)
{
var time = DateTime.Now;
if(time < DateTime.Now.AddSeconds(-30)) // you decide when to stop scrolling
{
Timer timer = (Timer)sender;
timer.Stop();
labelTesting.Left = 0; // or wherever it should be at the end of the scrolling
}
this.Refresh();
labelTesting.Left += 5;
if (labelTesting.Left >= this.Width)
{
labelTesting.Left = labelTesting.Width * -1;
}
}

You need to stop the timer:
private void timer_Tick(object sender, EventArgs e)
{
if (someConditionToEndScroll) // you decide when to stop scrolling
{
Timer timer = (Timer) sender;
timer.Stop();
labelTesting.Left = 0; // or wherever it should be at the end of the scrolling
}
this.Refresh();
labelTesting.Left += 5;
if (labelTesting.Left >= this.Width)
{
labelTesting.Left = labelTesting.Width * -1;
}
}

Silverlight UI lag - Crosshair on Graph

I've got a telerik radchart that's displaying a beautiful and incredibly-useful-to-end-user line chart.
One of the requirements for this chart was to have a x-value crosshair on the graph (e.g. when a user hovers at any point over the graph, a horizontal line appears, and where this line intersects the actual graph line, a value is displayed in another area of the screen).
In a previous iteration, I used flotJS to do my graphing & crosshair'ing, worked great, and was blazing fast. In converting this to silverlight, I've seen a tremendous amount of lag, and I'd like to know if anyone has any ideas on improving performance.
I currently expose the chart's MouseEnter/MouseLeave events to hide/show the horizontal line. This is done via a System.Windows.Visibility property sitting in my viewmodel (which my crosshair's visibility property is bound to). I then use the MouseMove method to actually calculate the x position.
Here is the code that runs this (first in my chart view's code behind)
private void rad_MouseMove(object sender, System.Windows.Input.MouseEventArgs e)
{
var plotAreaPanel = this.rad.DefaultView.ChartArea.ChildrenOfType<ClipPanel>().FirstOrDefault();
var position = e.GetPosition(plotAreaPanel);
var x = rad.DefaultView.ChartArea.AxisX.ConvertPhysicalUnitsToData(position.X);
(this.DataContext as ViewModels.DateCountsViewModel).XVolume = x;
}
private void rad_MouseEnter(object sender, System.Windows.Input.MouseEventArgs e)
{
(this.DataContext as ViewModels.DateCountsViewModel).XVolumeVisibility = System.Windows.Visibility.Visible;
}
private void rad_MouseLeave(object sender, System.Windows.Input.MouseEventArgs e)
{
(this.DataContext as ViewModels.DateCountsViewModel).XVolumeVisibility = System.Windows.Visibility.Collapsed;
}
Then in my viewmodel, in the setter for XVolume (which is being Set in the MouseMove method above), this code:
public double XVolume
{
get { return xVolume; }
set
{
this.xVolume = value;
decimal currentX = (decimal)Math.Round(value, 0);
var vol = this.VolumeCollection.Where(x => x.XValue == currentX).FirstOrDefault() as Models.ChartModel;
this.Volume = (vol == null) ? 0 : (int)vol.YValue;
RaisePropertyChanged("XVolume");
}
}
With heavy usage, the line lags up to several inches behind my pointer. I tried throttling my mouse events outlined here, but it's still really laggy.
[Note regarding link above: It uses the CompositionTarget.Rendering event, which is fired just before a frame is rendered. Therefore, to throttle the effect of the mouse event, we set a flag to indicate that we are waiting for a change to be rendered, then reset this flag just before rendering occurs... not allowing simultaneous rendering]
What can I do to mitigate this lag?

C# loop while mousedown button pressed

I'd like to use loop while left mousebutton is pressed:
private void Loop_MouseDown(object sender, MouseEventArgs e)
{
while (e.Button==MouseButtons.Left)
{
//Loop
}
}
I can't use solution from this thread:
C# how to loop while mouse button is held down
because I'm sending via RS232 data and using timer with it's own interval doesn't work. Also any solution from this topic doesn't work for me.
It can't also work one like here:
if (e.Button == MouseButtons.Left)
{
//loop
}
This solution also doesn't work:
bool isLooping = false;
//on mouse down
private void myControl_MouseUp(object sender, System.Windows.Forms.MouseEventArgs e) {
isLooping = true;
runLoop();
}
//on mouse up event
private void myControl_MouseUp(object sender, System.Windows.Forms.MouseEventArgs e) {
isLooping = false;
}
//This is the main loop you care about. Put this in your application
//This should go in its own thread
void runLoop() {
while (isLooping) {
//do stuff
}
}
because calling runLoop would block the thread, and so the MouseUp event would never fire.
So how to make it work correctly?

Use a BackGroundWorker. Perfect for your problem.
Put the loop function in the worker and start / stop the worker on mouse events.

If using a timer won't work, you'll need to send the data on a different thread, and signal that thread from the MouseUp handler.

The correct way to do this would be to put the rs-232 send function into a separate thread so the UI will remain responsive, then you can start and stop it when the mouse events change.
This page might be useful:
http://www.yoda.arachsys.com/csharp/threads/winforms.shtml

These scenarios are very complicated to implement - see your handlers and boolean variables for storing the state.
I would suggest to use Reactive Extensions.
Edit:
It will probably be slightly over-engineered (I don't know if this is the only scenario Elfoc wants to implement). In Rx you can create observable sequence of events
var mouseDown = Observable.FromEvent<MouseButtonEventArgs>(source, "MouseDown");
var mouseUp = Observable.FromEvent<MouseButtonEventArgs>(image, "MouseUp");
var mouseMove = from evt in Observable.FromEvent<MouseEventArgs>(image, "MouseMove")
select evt.EventArgs.GetPosition(this);
use LINQ-to-Rx to query and filter the events
var leftMouseDown = from evt in mouseDown
where evt.LeftButton == MouseButtonState.Pressed
select evt;
and compose it using Rx operators - until any mouse up event is raised take all the positions while left mouse is down
var q = from position in leftMouseDown
from pos in mouseMove.Until(mouseUp)
select new { X = pos.X - imageOffset.X, Y = pos.Y - imageOffset.Y };
Finally, subscribe to the observable sequence of positions and do your stuff
q.Subsribe(value => { ... });
Slightly modified from the code here.