Develop Reference

WPF DragMove() causes issues

I'm trying to figure out if there's an elegant solution to the problem I've been faced with.
So basically, I designed a borderless loading splash screen which is completely movable via dragging. I find that this happens if the splash screen gets hidden via Hide(), then displays a window via ShowDialog() with the owner set to the splash screen. Things get extremely buggy, but only if you're in mid-drag (with left mouse button down). You become unable to click or move anything, even Visual Studio becomes unresponsive unless you explicitly alt-tab out of the application.
Considering I know when I'm going to spawn the window, I was thinking maybe there'd be a way to cancel the DragMove operation, but I'm having no luck. What I've figured out is that DragMove is synchronous, so I'd guess it'd have to be cancelled from a different thread or in an event callback.
Edit:
public partial class Window_Movable : Window
{
public Window_Movable()
{
InitializeComponent();
}
public Boolean CanMove { get; set; } = true;
private void Window_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
if (CanMove == false)
return;
Task.Factory.StartNew(() => {
System.Threading.Thread.Sleep(1000);
Dispatcher.Invoke(() => {
Hide();
new Window_Movable() {
Title = "MOVABLE 2",
CanMove = false,
Owner = this
}.ShowDialog();
});
});
DragMove();
}
private void Button_Click(object sender, RoutedEventArgs e)
{
Console.WriteLine("DING");
}
}

I had the same problem and found out that DragMove() method is a problem.
https://groups.google.com/forum/#!topic/wpf-disciples/7OcuXrf2whc
To solve I decided to refuse from using it and implement moving logic.
I've combined some solutions from
https://www.codeproject.com/Questions/284995/DragMove-problem-help-pls
and
C# WPF Move the window
private bool _inDrag;
private Point _anchorPoint;
private bool _iscaptured;
private void AppWindowWindowOnMouseMove(object sender, MouseEventArgs e)
{
if (!_inDrag)
return;
if (!_iscaptured)
{
CaptureMouse();
_iscaptured = true;
}
var mousePosition = e.GetPosition(this);
var mousePositionAbs = new Point
{
X = Convert.ToInt16(_appWindowWindow.Left) + mousePosition.X,
Y = Convert.ToInt16(_appWindowWindow.Top) + mousePosition.Y
};
_appWindowWindow.Left = _appWindowWindow.Left + (mousePositionAbs.X - _anchorPoint.X);
_appWindowWindow.Top = _appWindowWindow.Top + (mousePositionAbs.Y - _anchorPoint.Y);
_anchorPoint = mousePositionAbs;
}
private void AppWindowWindowOnMouseLeftButtonUp(object sender, MouseButtonEventArgs e)
{
if (_inDrag)
{
_inDrag = false;
_iscaptured = false;
ReleaseMouseCapture();
}
}
private void AppWindowWindowOnMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
_anchorPoint = e.GetPosition(this);
_anchorPoint.Y = Convert.ToInt16(_appWindowWindow.Top) + _anchorPoint.Y;
_anchorPoint.X = Convert.ToInt16(_appWindowWindow.Left) + _anchorPoint.X;
_inDrag = true;
}
I've spend all yesterday evening and find a more hacky but more functional solution. Which support Maximized state and not require manual coordinate calculation.
private bool _mRestoreForDragMove;
private void OnAppWindowWindowOnMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
if (e.ClickCount == 2)
{
if (_appWindowWindow.ResizeMode != ResizeMode.CanResize &&
_appWindowWindow.ResizeMode != ResizeMode.CanResizeWithGrip)
{
return;
}
_appWindowWindow.WindowState = _appWindowWindow.WindowState == WindowState.Maximized
? WindowState.Normal
: WindowState.Maximized;
}
else
{
_mRestoreForDragMove = _appWindowWindow.WindowState == WindowState.Maximized;
SafeDragMoveCall(e);
}
}
private void SafeDragMoveCall(MouseEventArgs e)
{
Task.Delay(100).ContinueWith(_ =>
{
Dispatcher.BeginInvoke((Action)
delegate
{
if (Mouse.LeftButton == MouseButtonState.Pressed)
{
_appWindowWindow.DragMove();
RaiseEvent(new MouseButtonEventArgs(e.MouseDevice, e.Timestamp, MouseButton.Left)
{
RoutedEvent = MouseLeftButtonUpEvent
});
}
});
});
}
private void OnMouseMove(object sender, MouseEventArgs e)
{
if (_mRestoreForDragMove)
{
_mRestoreForDragMove = false;
var point = PointToScreen(e.MouseDevice.GetPosition(this));
_appWindowWindow.Left = point.X - (_appWindowWindow.RestoreBounds.Width * 0.5);
_appWindowWindow.Top = point.Y;
_appWindowWindow.WindowState = WindowState.Normal;
_appWindowWindow.DragMove();
SafeDragMoveCall(e);
}
}
private void OnMouseLeftButtonUp(object sender, MouseButtonEventArgs e)
{
_mRestoreForDragMove = false;
}
The thing is to send LeftMouseButtonUp event after a short delay to avoid blocking from DragMove()
Sources for last solve:
DragMove() and Maximize
C# WPF - DragMove and click

And one more completely different solution. To make a window movable you can use CaptionHeight of WindowChrome.
i.e.
var windowChrome =
WindowChrome.GetWindowChrome(appWindow.Window);
windowChrome.CaptionHeight = MainWindowToolbar.Height;
WindowChrome.SetWindowChrome(appWindow.Window, windowChrome);
but you should also set attached property WindowChrome.IsHitTestVisibleInChrome="True" for all controls in the window.

C# KeyDown not working

I have a picturebox that I want to relocate when a key is pressed.
I'm making a game of pong. With the code below I want to make the paddle of player 1, which is a picturebox that should move up and down while a key is pressed. The following code doesn't seem to work:
public partial class Form1 : Form
{
bool upPressed, downPressed;
public Form1()
{
InitializeComponent();
}
private void PongTimer_Tick(object sender, EventArgs e)
{
if(upPressed){
paddlePlayer1.Location = new Point(paddlePlayer1.Location.X, paddlePlayer1.Location.Y + 5);
}
if (downPressed)
{
MessageBox.Show("Numlock");
}
}
private void Form1_KeyDown(object sender, KeyEventArgs e)
{
if(e.KeyCode == Keys.Up){
upPressed = true;
}
if (e.KeyCode == Keys.NumLock)
{
downPressed = true;
}
}
private void Form1_KeyUp(object sender, KeyEventArgs e)
{
if(e.KeyCode == Keys.Up){
upPressed = false;
}
}
}
I used the Numlock to see if the problem was in the picture, this isn't the case. I've put the KeyPreview propery to true but this didnt solve it either. The timer does work properly.
I hope somebody here can tell me what I'm doing wrong.

This is a code example to move a PictureBox:
Drag/drop a PictureBox on a form (in this case Form1).
Change the Background color of the PictureBox to e.g. red. (This way it is visible during runtime).
Implement the KeyDown event of Form1 (in this case Form1_KeyDown).
Run the application.
Start pressing an arrow key and the PictureBox will move.
private void Form1_KeyDown(object sender, KeyEventArgs e)
{
int x = pictureBox1.Location.X;
int y = pictureBox1.Location.Y;
if (e.KeyCode == Keys.Right) { x += 1; }
else if (e.KeyCode == Keys.Left) { x -= 1; }
else if (e.KeyCode == Keys.Up) { y -= 1; }
else if (e.KeyCode == Keys.Down) { y += 1; }
pictureBox1.Location = new Point(x, y);
}

Removing the delay after KeyDown event?

When I hold a key in my game to move my player:
public void MainForm_KeyDown(object sender, KeyEventArgs e)
{
if (e.KeyCode == Keys.Up)
{
Player.MoveUp();
}
}
The player instantly moves one step as soon as I press the down arrow, and then pauses for a short duration before starting to smoothly move again. Why's this? How can I prevent it?

The answer in the proposed duplicate is incorrect, unfortunately. It doesn't ignore repeated KeyDown events, and so will gradually increase the "delta" value in the direction being handled by each key case. It also doesn't respond to the keypress immediately (i.e. no action happens until the first timer tick).
This answer to Holding Arrow Keys Down For Character Movement C# .Net ISSUES explains how to ignore the subsequent KeyDown events, but doesn't explain how then your character would move.
In other words, I couldn't find a duplicate question that actually correctly answers your question. So…
The basic technique you want to do is:
Don't move on the actual key input. Instead, generate your own timing logic that will move the object.
Instead of using the KeyDown event to actually move the object, use it to set a movement direction, which is then processed by your timing logic.
There are a variety of ways to accomplish this. One version would look like this:
private bool _moveUp;
private bool _moveDown;
private bool _moveLeft;
private bool _moveRight;
// You can add the Timer in the Winforms Designer instead if you like;
// The Interval property can be configured there at the same time, along
// with the Tick event handler, simplifying the non-Designer code here.
private System.Windows.Forms.Timer _movementTimer = new Timer { Interval = 100 };
public MainForm()
{
InitializeComponent();
_movementTimer.Tick += movementTimer_Tick;
}
private void movementTimer_Tick(object sender, EventArgs e)
{
_DoMovement();
}
private void _DoMovement()
{
if (_moveLeft) Player.MoveLeft();
if (_moveRight) Player.MoveRight();
if (_moveUp) Player.MoveUp();
if (_moveDown) Player.MoveDown();
}
// You could of course override the OnKeyDown() method instead,
// assuming the handler is in the Form subclass generating the
// the event.
public void MainForm_KeyDown(object sender, KeyEventArgs e)
{
if (e.IsRepeat)
{
// Ignore key repeats...let the timer handle that
return;
}
switch (e.KeyCode)
{
case Keys.Up:
_moveUp = true;
break;
case Keys.Down:
_moveDown = true;
break;
case Keys.Left:
_moveLeft = true;
break;
case Keys.Right:
_moveRight = true;
break;
}
_DoMovement();
_movementTimer.Start();
}
public void MainForm_KeyUp(object sender, KeyEventArgs e)
{
switch (e.KeyCode)
{
case Keys.Up:
_moveUp = false;
break;
case Keys.Down:
_moveDown = false;
break;
case Keys.Left:
_moveLeft = false;
break;
case Keys.Right:
_moveRight = false;
break;
}
if (!(_moveUp || _moveDown || _moveLeft || _moveRight))
{
_movementTimer.Stop();
}
}
Do note that the timer objects in .NET have limited resolution. I show an interval of 100 ms (10 times per second) above (same as in the other question's answer), and this is about as frequent an update as you're going to reliably get. Even then, the timer's Tick event may not (and probably won't) be raised on exactly 100 ms intervals. There will be some variation back and forth. But it will be close enough for a basic game.
If you need more precision than that, you will have to implement your own state-polling-and-animation loop somewhere. That's a whole other ball o' wax. :)

A subjectivly elegent approach:
public partial class Form1 : Form
{
private static Timer timer;
private static bool[] keys_down;
private static Keys[] key_props;
private void Form1_Load(object sender, EventArgs e)
{
keys_down = new bool[4];
key_props = new []{Keys.A, Keys.D, Keys.W, Keys.S};
timer = new Timer();
timer.Interval = 15; // Roughly 67 FPS
timer.Tick += tick;
timer.Start();
KeyDown += key_down_event;
KeyUp += key_up_event;
... // More things to do when the form loads.
}
private void tick(Object source, EventArgs e)
{
... // Do this every timing interval.
byte n = 0;
foreach (var v in keys_down)
{
if (n == 3 && v)
... // If the "s" key is being held down, no key delay issues. :)
n++;
}
...
}
private void key_down_event(object sender, KeyEventArgs e)
{
byte n = 0;
foreach (var v in keys_down)
{
if (e.KeyCode == key_props[n])
keys_down[n] = true;
n++;
}
}
private void key_up_event(object sender, KeyEventArgs e)
{
byte n = 0;
foreach (var v in keys_down)
{
if (e.KeyCode == key_props[n])
keys_down[n] = false;
n++;
}
}
public Form1()
{
InitializeComponent();
}
}

I was looking for solutions to create a small copy of Flappy Bird. Perhaps my decision will help someone.
I used the addition of a player position with a variable in timer to simulate gravity. When I press W, I turned off the further reception of the command using bool and simply inverted gravity
private void time_Tick(object sender, EventArgs e)
{
if (bird.Location.Y >= 540)
{
bird.Location = new Point(bird.Location.X, 540);
}
else
{
bird.Location = new Point(bird.Location.X, bird.Location.Y+grav);
}
}
private void Form1_KeyPress(object sender, KeyEventArgs e)
{
if (e.KeyData == Keys.W && press == false)
{
press = true;
grav = -10;
}
return;
}
private void Form1_KeyUp(object sender, KeyEventArgs e)
{
if (e.KeyData == Keys.W && press == true)
{
press = false;
grav = 5;
}
return;
}

Can't use KeyDown and KeyUp events properly? (Visual C# Windows Form)

I am having problems in breaking a loop (apparently) with the KeyUp event; Character moves, but then I can't make it stop after releasing the key. Looks like I am doing something wrong.
What could I change in this code for it to work? Thanks for the help!
private void Character_KeyDown(object sender, KeyEventArgs e)
{
if (e.KeyCode == Keys.A)
{
XSpeed = 1;
}
for (; e.KeyCode == Keys.A;)
{
Thread.Sleep(50);
Character.Left -= XSpeed;
if (XSpeed == 0)
{
break;
}
}
}
private void Character_KeyUp(object sender, KeyEventArgs e)
{
if (e.KeyCode == Keys.Left)
{
XSpeed = 0;
}
}

The problem here is that you are never going out from the Character_KeyDown handler does not terminate. Because of that, your bit of code in the Character_KeyUp is never executed.
The root issue that you may not realize is that you only have a single UI thread (at least in all UI frameworks that I know such has been the case), and you are monopolizing it with your for loop.
In order to do the right thing, something like WPF's Dispatcher.BeginInvoke, or DispatcherTimer can be used. (If you use WPF). If you can tell us which UI framework you are using, we might be able to come up with a satisfactory code sample.
Here is how you might do it with a DispatcherTimer in WPF:
// Add that field to your class.
private readonly DispatcherTimer moveLeftTimer;
// In the constructor, add the lines inside:
YourClassName() // This line is a stub - I do not know your class name.
{
moveLeftTimer = new DispatcherTimer()
{
Interval = TimeSpan.FromMilliseconds(50)
};
moveLeftTimer.Tick += MoveLeft;
}
private void MoveLeft(object source, EventArgs e)
{
Character.Left -= XSpeed;
}
private void Character_KeyDown(object sender, KeyEventArgs e)
{
if (e.KeyCode == Keys.A)
{
moveLeftTimer.IsEnabled = true;
}
}
private void Character_KeyUp(object sender, KeyEventArgs e)
{
if (e.KeyCode == Keys.A)
{
moveLeftTimer.IsEnabled = false;
}
}
In order to adapt for Windows Forms, use the Timer class instead of DispatcherTimer, and the property is named Enabled instead of IsEnabled.

That's because you are doing everything on one thread, in your case it happens to be the Main UI thread. All actions are done sequentially. It does't matter that you have a handler to change XSpeed = 0, it's not going to process until the Character_KeyDown is done. Put break points in both and you will see the point.
What you need to do is to put your processing on the background thread and release your UI handlers.
Task.Factory.StartNew creates a background thread and executes an action you give it.
now if you need to update something that belongs to the UI thread, you gotta do it on the UI thread...
private void Character_KeyDown(object sender, KeyEventArgs e)
{
Task.Factory.StartNew(() =>
{
if (e.KeyCode == Keys.A)
{
OnUI(() => XSpeed = 1);
}
for (; e.KeyCode == Keys.A;)
{
Thread.Sleep(50);
OnUI(() => Character.Left -= XSpeed);
if (XSpeed == 0)
{
break;
}
}});
}
private void Character_KeyUp(object sender, KeyEventArgs e)
{
Task.Factory.StartNew(() =>
{
if (e.KeyCode == Keys.Left)
{
OnUI(() => XSpeed = 0);
}
}
}
here's a sample for OnUI:
private void OnUi (Action action)
{
if (_dispatchService == null)
_dispatchService = ServiceLocator.Current.GetInstance<IDispatchService>();
//or _dispatchService = Application.Current.Dispatcher - whatever is suitable
if (_dispatchService.CheckAccess())
action.Invoke ();
else
_dispatchService.Invoke(action);
}

How can I catch both single-click and double-click events on WPF FrameworkElement?

I can catch a single-click on a TextBlock like this:
private void TextBlock_MouseDown(object sender, MouseButtonEventArgs e)
{
MessageBox.Show("you single-clicked");
}
I can catch a double-click on a TextBlock like this:
private void TextBlock_MouseDown(object sender, MouseButtonEventArgs e)
{
if (e.LeftButton == MouseButtonState.Pressed)
{
if (e.ClickCount == 2)
{
MessageBox.Show("you double-clicked");
}
}
}
But how do I catch them both on a single TextBlock and differentiate between the two?

You need to fire the event after the click sequence is over... when is that? I suggest using a timer. The MouseDown event would reset it and increase the click count. When timer interval elapses it makes the call to evaluate the click count.
private System.Timers.Timer ClickTimer;
private int ClickCounter;
public MyView()
{
ClickTimer = new Timer(300);
ClickTimer.Elapsed += new ElapsedEventHandler(EvaluateClicks);
InitializeComponent();
}
private void TextBlock_MouseDown(object sender, MouseButtonEventArgs e)
{
ClickTimer.Stop();
ClickCounter++;
ClickTimer.Start();
}
private void EvaluateClicks(object source, ElapsedEventArgs e)
{
ClickTimer.Stop();
// Evaluate ClickCounter here
ClickCounter = 0;
}
Cheers!

If you need to detect the difference, I suggest you use a control such as Label that does the work for you:
label.MouseDown += delegate(object sender, MouseEventArgs e)
{
if (e.ClickCount == 1)
{
// single click
}
};
label.MouseDoubleClick += delegate
{
// double click
};
EDIT: My advice was following from documentation on MSDN:
The Control class defines the
PreviewMouseDoubleClick and
MouseDoubleClick events, but not
corresponding single-click events. To
see if the user has clicked the
control once, handle the MouseDown
event (or one of its counterparts) and
check whether the ClickCount property
value is 1.
However, doing so will give you a single click notification even if the user single clicks.

You must use a timer to differentiate between the two. Add a timer to your form in the GUI (easiest that way - it will automatically handle disposing etc...). In my example, the timer is called clickTimer.
private bool mSingleClick;
private void TextBlock_MouseUp(object sender, MouseButtonEventArgs e)
{
if (e.Button == MouseButtons.Left)
{
if (e.ClickCount < 2)
{
mSingleClick = true;
clickTimer.Interval = System.Windows.Forms.SystemInformation.DoubleClickTime;
clickTimer.Start();
}
else if (e.ClickCount == 2)
{
clickTimer.Stop();
mSingleClick = false;
MessageBox.Show("you double-clicked");
}
}
}
private void clickTimer_Tick(object sender, EventArgs e)
{
if (mSingleClick)
{
clickTimer.Stop();
mSingleClick = false;
MessageBox.Show("you single-clicked");
}
}

I did it this Way and it works perfectly
If e.Clicks = 2 Then
doubleClickTimer.Stop()
ElseIf e.Clicks = 1 Then
doubleClickTimer.Enabled = True
doubleClickTimer.Interval = 1000
doubleClickTimer.Start()
End If
Private Sub doubleClickTimer_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles doubleClickTimer.Tick
OpenWebPage("abc")
doubleClickTimer.Stop()
End Sub

You are simply can use MouseDown event and count click number, like this:
if (e.ChangedButton == MouseButton.Left && e.ClickCount == 2)
{
// your code here
}

My suggestion, implemented in a UserControl by simply using a Task:
private int _clickCount = 0;
protected override void OnPreviewMouseDown(MouseButtonEventArgs e)
{
_clickCount = e.ClickCount;
}
protected override async void OnPreviewMouseUp(MouseButtonEventArgs e)
{
if (_clickCount > 1)
{
//apparently a second mouse down event has fired => this must be the second mouse up event
//no need to start another task
//the first mouse up event will be handled after the task below
return;
}
await Task.Delay(500);
if (_clickCount == 1)
{
//single click
}
else
{
//double (or more) click
}
}
The drawback of all these solutions is, of course, that there will be a delay before actually responding to the user's action.

You could do it on MouseUp instead of MouseDown. That way you can ask the ClickCount property for the total number of clicks, and decide what to do from that point.

It's my working solution :)
#region message label click --------------------------------------------------------------------------
private Timer messageLabelClickTimer = null;
private void messageLabel_MouseUp(object sender, MouseButtonEventArgs e)
{
Debug.Print(e.ChangedButton.ToString() + " / Left:" + e.LeftButton.ToString() + " Right:" + e.RightButton.ToString() + " click: " + e.ClickCount.ToString());
// in MouseUp (e.ClickCount == 2) don't work!! Always 1 comes.
// in MouseDown is set e.ClickCount succesfully (but I don't know should I fire one clicked event or wait second click)
if (e.ChangedButton == MouseButton.Left)
{
if (messageLabelClickTimer == null)
{
messageLabelClickTimer = new Timer();
messageLabelClickTimer.Interval = 300;
messageLabelClickTimer.Elapsed += new ElapsedEventHandler(messageLabelClickTimer_Tick);
}
if (! messageLabelClickTimer.Enabled)
{ // Equal: (e.ClickCount == 1)
messageLabelClickTimer.Start();
}
else
{ // Equal: (e.ClickCount == 2)
messageLabelClickTimer.Stop();
var player = new SoundPlayer(ExtraResource.bip_3short); // Double clicked signal
player.Play();
}
}
}
private void messageLabelClickTimer_Tick(object sender, EventArgs e)
{ // single-clicked
messageLabelClickTimer.Stop();
var player = new SoundPlayer(ExtraResource.bip_1short); // Single clicked signal
player.Play();
}
#endregion

My issue was with single/double-clicking rows in a DataGrid in WPF. For some reason the ButtonDown events weren't firing, only the OnMouseLeftButtonUp event was. Anyway, I wanted to handle the single-click differently from the double-click. It looks me a little time (I'm sure the solution isn't perfect, but it appears to work) to distill the problem down until I got it down to the below. I created a Task which calls an Action and that Action's target can be updated by a second click. Hope this helps someone!
private Action _clickAction;
private int _clickCount;
private void Grid_OnMouseLeftButtonUp(object sender, MouseButtonEventArgs e)
{
Debug.WriteLine("Button Click Occurred");
_clickCount++;
if (_clickCount == 1)
{
_clickAction = SingleClick;
}
if (_clickCount > 1)
{
_clickAction = DoubleClick;
}
if (_clickCount == 1)
{
Task.Delay(200)
.ContinueWith(t => _clickAction(), TaskScheduler.FromCurrentSynchronizationContext())
.ContinueWith(t => { _clickCount = 0; });
}
}
private void DoubleGridClick()
{
Debug.WriteLine("Double Click");
}
private void SingleGridClick()
{
Debug.WriteLine("Single Click");
}