I wanted to get the type of the control on mouseover. Please help
You can get the type of the UIElement over which the mouse is currently moving using the MouseMove event. Since this is a bubbling event you can attach a handler to the container such as a Canvas.
The UIElement over which the mouse is currently moving can be aquired from the the MouseEventArgs OriginalSource property.
Hence to determine the type over which the mouse is moving you could use code like this:-
void Canvas_MouseMove(object sender, MouseEventArgs e)
{
Type currentType = e.OriginalSource.GetType();
// Make decisions based on value of currentType here
}
However you need be careful, MouseMove fires frequently as the user moves the mouse so you might want to defer any heavy work until there is some time period after the last mouse move.
There is unfortunately no bubbling mouse over event.
The other alternative is to attach the same MouseEnter handler to each child UIElement you add to the Canvas. You could use sender instead of e.OriginalSource in that case. You would have to be careful to remove the handler if the element is removed from the Canvas, else you can create what would appear to be a memory leak.
Add mouse_enter event to the control.
You can get the type with a line of code as follow
var x = sender.GetType();
You can then compare it using something like:
if (x.Equals(typeof(TreeView)))
Related
I've written a Windows Forms app where I do custom drawing on a Panel using Control.CreateGraphics(). Here's what my Form looks like at startup:
The custom drawing is performed on the top panel in the Click event handler of the "Draw!" button. Here's my button click handler:
private void drawButton_Click(object sender, EventArgs e)
{
using (Graphics g = drawPanel.CreateGraphics())
{
g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias;
g.Clear(Color.White);
Size size = drawPanel.ClientSize;
Rectangle bounds = drawPanel.ClientRectangle;
bounds.Inflate(-10, -10);
g.FillEllipse(Brushes.LightGreen, bounds);
g.DrawEllipse(Pens.Black, bounds);
}
}
After a click on drawButton, the form looks like this:
Success!
But when I shrink the form by dragging a corner...
...and expand it back to its original size,
part of what I drew is gone!
This also happens when I drag part of the window offscreen...
...and drag it back onscreen:
If I minimize the window and restore it, the whole image is erased:
What is causing this? How can I make it so the graphics I draw are persistent?
Note: I've created this self-answered question so I have a canonical Q/A to direct users to, as this is a common scenario that's hard to search for if you don't already know the cause of the problem.
TL;DR:
Don't do your drawing in response to a one-time UI event with Control.CreateGraphics. Instead, register a Paint event handler for the control on which you want to paint, and do your drawing with the Graphics object passed via the PaintEventArgs.
If you want to paint only after a button click (for example), in your Click handler, set a boolean flag indicating that the button has been clicked and then call Control.Invalidate(). Then do your rendering conditionally in the Paint handler.
Finally, if your control's contents should change with the size of the control, register a Resize event handler and call Invalidate() there too.
Example code:
private bool _doCustomDrawing = false;
private void drawPanel_Paint(object sender, PaintEventArgs e)
{
if (_doCustomDrawing)
{
Graphics g = e.Graphics;
g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias;
g.Clear(Color.White);
Size size = drawPanel.ClientSize;
Rectangle bounds = drawPanel.ClientRectangle;
bounds.Inflate(-10, -10);
g.FillEllipse(Brushes.LightGreen, bounds);
g.DrawEllipse(Pens.Black, bounds);
}
}
private void drawButton_Click(object sender, EventArgs e)
{
_doCustomDrawing = true;
drawPanel.Invalidate();
}
private void drawPanel_Resize(object sender, EventArgs e)
{
drawPanel.Invalidate();
}
But why? What was I doing wrong, and how does this fix it?
Take a look at the documentation for Control.CreateGraphics:
The Graphics object that you retrieve through the CreateGraphics method should not normally be retained after the current Windows message has been processed, because anything painted with that object will be erased with the next WM_PAINT message.
Windows doesn't take responsibility for retaining the graphics you draw to your Control. Rather, it identifies situations in which your control will require a repaint and informs it with a WM_PAINT message. Then it's up to your control to repaint itself. This happens in the OnPaint method, which you can override if you subclass Control or one of its subclasses. If you're not subclassing, you can still do custom drawing by handling the public Paint event, which a control will fire near the end of its OnPaint method. This is where you want to hook in, to make sure your graphics get redrawn every time the Control is told to repaint. Otherwise, part or all of your control will be painted over to the control's default appearance.
Repainting happens when all or part of a control is invalidated. You can invalidate the entire control, requesting a full repaint, by calling Control.Invalidate(). Other situations may require only a partial repaint. If Windows determines that only part of a Control needs to be repainted, the PaintEventArgs you receive will have a non-empty ClipRegion. In this situation, your drawing will only affect the area in the ClipRegion, even if you try to draw to areas outside that region. This is why the call to drawPanel.Invalidate() was required in the above example. Because the appearance of drawPanel needs to change with the size of the control and only the new parts of the control are invalidated when the window is expanded, it's necessary to request a full repaint with each resize.
I'm working with WPF.
My visual tree hierarchy as the following:
RadDiagram > RadDiagramShape > MyControl
The content of RadDiagramShape is mycontrol.
In myControl class, I have handled (MouseLeftButtonDown) Event, I put drag-drop code inside it(which I need it in another place). So, it's Direct Event not Tunneling or Bubbling!
While I'm moving my Custom Control which is the content of the RadDiagramShape, in RadDiagram, it doesn't move (It's trying to be dragged) because the MouseLeftButtonDown has been handled inside MyControl.
It prevents the event from bubbling up the Visual tree, preventing any parent handlers from being notified of the event.
I tried to handled the Event for the RadDiagramShape and for the RadDiagram as e.Handled = true;
but it did nothing because It's MouseLeftButtonDown and it's handled inside the root element so, it won't bubble or tunnel and I didn't override movement code, which I don't want to override it. Because I tried it before and it didn't give me the same slightly move that built-in in WPF.
How can I block MouseLeftButtonDown event in root element and let the event fired in the container(parent) level?
Please check in your control handler if 'OriginalSource' is the same control that you want or not.
if ((e.OriginalSource is TextBox) && (e.OriginalSource as TextBox).Name == "TextBoxName")
{
//Do every thing you want
}
Thank you leila karimi. You gave me the orientation, the condition itself didn't work. But I put another condition and it worked
void MyLabel_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
MyLabel dc = (MyLabel)sender;
if (dc.Parent.GetType() != typeof(RadDiagramShape))
{///....drop it}
}
I'm using WPF to design a borderless, movable application window.
In order to manually perform the ability to drag and drop the window, I've added an OnMouseDown event to the <Window> element, that executes a corresponding C# function (this.DragMove()).
Additionally, I need an <Image> button to allow some operation (with the OnMouseUp event this time). Note that it has to be an Image tag, and not a Button.
Unfortunately, the Image event fired only when the right mouse button is clicked, probably because the left button is held to the window event. Am I right?
When someone clicks the Image button, I want only the Image event to be triggered. How can I do it?
Problem you're facing is most probably related to event routing. The idea is that if your handler doesn't mark event as a Handled it will be routed to the next listener unless reach end of chain or one of listeners/handlers will set it as Hadnled.
So if you have MouseDown event handler for both Window and Image you should keep in mind that routing will stop at a point when you will set e.Handled = true;:
private void Window_OnMouseDown(object sender, KeyEventArgs e)
{
e.Handled = false; // will NOT break event chain;
}
You can always check a type of sender so it will make possible for you to differ Image and Window events:
private void Image_OnMouseDown(object sender, KeyEventArgs e)
{
if (sender is Image)
{
// Handle Image.MouseDown
e.Handled = true; // we don't need to push event further;
}
}
Its because of WPF bubbling and tunnelling events. so what u can do is whenever u handle event on button use bubbling for that means you can use previewevents for that for both button and window and whenever you just want to handle event for button then after last line of code in button click just write down like this.
e.handled=true;
// here e is the event argument which u will get in your preview event.so now window dragging event will not work.
i would just suggest first clear the idea of bubbling(preview mouse event) and tunneling in wpf.
Difference between Bubbling and Tunneling events
and go through some of the example of bubbling and tunnelling. you will get better idea.
http://www.codeproject.com/Articles/464926/To-bubble-or-tunnel-basic-WPF-events
I am trying to make a nice "drag and drop zone" in WPF that is displayed in the adorner layer when something is being dragged into the main application. The problem is that I do not get any events from my adorner, even though it according to documentation should receive all input events since it is in a higher z-order.
To debug my problem I created a really simple example where I have a user control with only a button in it. This user control is displayed in the adorner layer, but I cannot click the button. Why? What have I done wrong?
My adorner class is constructed like this:
public ShellOverlayAdorner(UIElement element, AdornerLayer adornerLayer)
:base(element)
{
_adornerLayer = adornerLayer;
_overlayView = new AdornedElement();
_overlayView.AllowDrop = true;
_adornerLayer.Add(this);
}
and is created in the main window by
private void Window_Loaded(object sender, RoutedEventArgs e)
{
adornerLayer = AdornerLayer.GetAdornerLayer(MyTopGridWithButtonInIt);
ShellOverlayAdorner shell = new ShellOverlayAdorner(MyTopGridWithButtonInIt, adornerLayer);
}
I do not get any events at all from my control, i.e. no mouse clicks, mouse over, button clicks. I cannot even click the button in the adorner layer. What have I done wrong?
I don't know if you already tried that:
If you want the element added to react to events, I think that the element must be bound to the visual tree of the adorner.
The way to do it is to use a VisualCollection, intitialized to the adorner itself, or at least, this way it seems to be working:
VisualCollection visualChildren;
FrameworkElement #object;
public CustomAdorner(UIElement adornedElement) :
base(adornedElement)
{
visualChildren = new VisualCollection(this);
#object = new Button {Content = "prova"};
visualChildren.Add(#object);
}
protected override Visual GetVisualChild(int index)
{
return visualChildren[index];
}
This way the events are correctly routed.
I just had the same issue. Following the advice from MSDN sorted it for me:
Adorners receive input events just
like any other FrameworkElement.
Because an adorner always has a higher
z-order than the element it adorns,
the adorner receives input events
(such as Drop or MouseMove) that may
be intended for the underlying adorned
element. An adorner can listen for
certain input events and pass these on
to the underlying adorned element by
re-raising the event.
To enable pass-through hit testing of
elements under an adorner, set the hit
test IsHitTestVisible property to
false on the adorner.
i.e In the adorner itself, make sure IsHitTestVisible = false
During a drag in Wpf, how can the mouse cursor (or perhaps using an adorner) be changed to indicate that the droptarget will not accept the dragged item?
I've tried to set e.Effects = DragDropEffects.None during the DragEnter event but this isn't working and I suspect that I've misunderstood what that feature should be used for. I've tried using the GiveFeedback event but don't see how the droptarget can influence it.
Just setting the DragDropEffects in DragEnter of the drop target should work. Is your DragEnter even getting called. Have you set AllowDrop on the drop target control?
This is the sequence of events during a drag & drop in WPF (taken from MSDN) which might help work out what's going on...
Dragging is initiated by calling the DoDragDrop method for the source control.
The DoDragDrop method takes two parameters:
* data, specifying the data to pass
* allowedEffects, specifying which operations (copying and/or moving) are allowed
A new DataObject object is automatically created.
This in turn raises the GiveFeedback event. In most cases you do not need to worry about the GiveFeedback event, but if you wanted to display a custom mouse pointer during the drag, this is where you would add your code.
Any control with its AllowDrop property set to True is a potential drop target. The AllowDrop property can be set in the Properties window at design time, or programmatically in the Form_Load event.
As the mouse passes over each control, the DragEnter event for that control is raised. The GetDataPresent method is used to make sure that the format of the data is appropriate to the target control, and the Effect property is used to display the appropriate mouse pointer.
If the user releases the mouse button over a valid drop target, the DragDrop event is raised. Code in the DragDrop event handler extracts the data from the DataObject object and displays it in the target control.
I had a similar problem because I changed the cursor in the GiveFeedback handler.
This cursor was used even the drop target did reject the data.
After switching back to the default cursor (e.UseDefaultCursors = true) the cursor shape did change propely to "not allowed".
You didn't say if you use the DragOver even. Maybe you're setting e.Effect = DragDropEffects.All; in this even and it will be fired repeatedly after you enter the target control instead of DragEnter that will be fired just once.
private void arbol_DragOver(object sender, DragEventArgs e)
{
if (some_reason)
e.Effect = DragDropEffects.None;
else
e.Effect = DragDropEffects.All;
}
If you didn't use this event or didn't modify e.Effect within, then it's hard to say. Code is needed.
If you want the app to take your change in account,
you should set Handled property to true:
private void OnDragOver(object sender, DragEventArgs e)
{
if (your_test)
e.Effects = DragDropEffects.Link;//or other effect you want
else
e.Effects = DragDropEffects.None;
e.Handled = true;
}