I am listening for the loaded event of a Page. That event fires first and then all the children fire their load event. I need an event that fires when ALL the children have loaded. Does that exist?
I hear you. I also am missing an out of the box solution in WPF for this.
Sometimes you want some code to be executed after all the child controls are loaded.
Put this in the constructor of the parent control
Dispatcher.BeginInvoke(DispatcherPriority.Loaded, new Action(() => {code that should be executed after all children are loaded} ));
Helped me a few times till now.
Loaded is the event that fires after all children have been Initialized. There is no AfterLoad event as far as I know. If you can, move the children's logic to the Initialized event, and then Loaded will occur after they have all been initialized.
See MSDN - Object Lifetime Events.
You can also use the event: ContentRendered.
http://msdn.microsoft.com/en-us/library/ms748948.aspx#Window_Lifetime_Events
WPF cant provide that kind of an event since most of the time Data is determining whther to load a particular child to the VisualTree or not (for example UI elements inside a DataTemplate)
So if you can explain your scenario little more clearly we can find a solution specific to that.
One of the options (when content rendered):
this.LayoutUpdated += OnLayoutUpdated;
private void OnLayoutUpdated(object sender, EventArgs e)
{
if (!isInitialized && this.ActualWidth != 0 && this.ActualHeight != 0)
{
isInitialized = true;
// Logic here
}
};
Put inside your xaml component you want to wait for, a load event Loaded="MyControl_Loaded" like
<Grid Name="Main" Loaded="Grid_Loaded"...>
<TabControl Loaded="TabControl_Loaded"...>
<MyControl Loaded="MyControl_Loaded"...>
...
and in your code
bool isLoaded;
private void MyControl_Loaded(object sender, RoutedEventArgs e)
{
isLoaded = true;
}
Then, inside the Event triggers that have to do something but were triggering before having all components properly loaded, put if(!isLoaded) return; like
private void OnButtonChanged(object sender, RoutedEventArgs e)
{
if(!isLoaded) return;
... // code that must execute on trigger BUT after load
}
I ended up doing something along these lines.. your milage may vary.
void WaitForTheKids(Action OnLoaded)
{
// After your children have been added just wait for the Loaded
// event to fire for all of them, then call the OnLoaded delegate
foreach (ContentControl child in Canvas.Children)
{
child.Tag = OnLoaded; // Called after children have loaded
child.Loaded += new RoutedEventHandler(child_Loaded);
}
}
internal void child_Loaded(object sender, RoutedEventArgs e)
{
var cc = sender as ContentControl;
cc.Loaded -= new RoutedEventHandler(child_Loaded);
foreach (ContentControl ctl in Canvas.Children)
{
if (!ctl.IsLoaded)
{
return;
}
}
((Action)cc.Tag)();
}
Related
I have many custom controls on my main form that utilize an event to signify they have done processing. They all share this same event (~100 controls or so).
The main form consumes this event but I do not have a clue how to find an efficient way at getting to the one that raised the event without having really inefficient code.
My controls are contained within a List<T> called controlList and are hosted on their own project.
My event looks like so:
public void OnTaskComplete(object sender, custom_control_project.TaskCompleteEventArgs e)
{
foreach (var control in controlList)
{
if (control.Visible) // <--- THIS IS WRONG! WHAT COULD THIS BE???
{
try
{
...// LOTS OF PROCESSING!
}
catch
{
...
}
finally
{
...
}
}
}
}
If I want to use less controls, I make them invisible and disabled, hence the control.Visible.
How can I make it so I only do work on the one control that raised the event without having to process so much unneeded iterations?
The sender parameter is the object that raised the event. You can cast this to a control.
Assuming the all of the controls are wired to the same event (which you indicate):
protected void Button1_Click(object sender, EventArgs e)
{
((Button)sender).Visible = true;
// or more generally:
((WebControl)sender).Visible = true;
}
You will need to cast the sender to a common, base type. If you go with a base type, WebControl will allow you to access the Enabled property while Control will not.
Is there a way to allow Drag and Drop anywhere in a form full of controls?
The idea is to allow user to drag a file anywhere in a form in order to "load" it. I will not need any other DragDrop behavior but this.
By setting AllowDrop=True to the form only, I get DragEnter events but not DragDrop ones.
An idea would be to make a topmost panel visible on DragEnter and handle DragDrop events there, but I wonder if I miss something obvious here since I have little experience in the field.
Another Idea would be to iterate through all controls and subscribe to Drag-related events. I really don't like this approach, though.
Sure, iterating the controls will work, it doesn't take much code:
public Form1() {
InitializeComponent();
WireDragDrop(this.Controls);
}
private void WireDragDrop(Control.ControlCollection ctls) {
foreach (Control ctl in ctls) {
ctl.AllowDrop = true;
ctl.DragEnter += ctl_DragEnter;
ctl.DragDrop += ctl_DragDrop;
WireDragDrop(ctl.Controls);
}
}
void ctl_DragDrop(object sender, DragEventArgs e) {
// etc..
}
void ctl_DragEnter(object sender, DragEventArgs e) {
// etc..
}
If you still don't like the approach then use a recognizable single drop target that the user will always hit. Could be as simple as a label that says "Drop here".
I'm not sure what kinds of control you have on your form. But I've tested with a Button, a GroupBox, a PictureBox and a TextBox. All these controls have AllowDrop = false by default. And I can drag-n-drop something from outside onto the form OK. The DragDrop is fired OK. Everything is OK. What is actually your problem? I guess your controls have AllowDrop = true.
In the case the DragDrop event is not fired (which I think only happens if the target is one of your Control with AllowDrop = true). I think the following may work. But if the target is one of your Control with AllowDrop = true, the effect icon is gone away.
public Form1(){
InitializeComponents();
t.Interval = 1;
t.Tick += Tick;
}
IDataObject data;
Timer t = new Timer();
int i = 0;
private void Tick(object sender, EventArgs e)
{
Text = (i++).ToString();
if (ClientRectangle.Contains(PointToClient(new Point(MousePosition.X, MousePosition.Y))) && MouseButtons == MouseButtons.None)
{
t.Stop();
if (data != null)
{
//Process data here
//-----------------
data = null;
}
}
else if (MouseButtons == MouseButtons.None)
{
data = null;
t.Stop();
}
}
private void Form1_DragEnter(object sender, DragEventArgs e)
{
e.Effect = e.AllowedEffect;
if (data == null)
{
data = e.Data;
t.Start();
}
}
And I think you may have to use the loop through all the Controls to add appropriate event handlers. There is no other better way.
In the Drop event.
string[] files = (string[])e.Data.GetData(DataFormats.FileDrop);
foreach (string file in files) Console.WriteLine(file);
In the DragEnter event.
if (e.Data.GetDataPresent(DataFormats.FileDrop)) e.Effects = DragDropEffects.Copy;
I am using the Windows Forms TreeView control.
The way i have it hooked up is as followed (simplified):
TreeView treeView = new TreeView();
treeView.BeforeSelect += beforeSelect;
private void beforeSelect(sender, args)
{
MessageBox.Show("Some msg");
// more code
}
In certain scenarios, the call to MessageBox.Show triggers another raising of the BeforeSelect event, which triggers another, and another, ...
It seems this event is raised PER ITEM in the treeview (i have counted the number of times it is raised).
I have searched all over the internet on more information for why this could occur.
One thing i've found was that TreeView will automatically select the first node when gaining focus.
This does not explain however why the event is fired as the number of treenode items in the tree.
Any help would be appreciated on this. I am considering raising a Microsoft Connect bug for this, as it seems like a very weird behavior that is not consistent with how i think the control should work.
Would it be enough to simply block yourself like the following?
private bool _inside;
private void beforeSelect( object sender, EventArgs args )
{
if ( !_inside )
{
_inside = true;
MessageBox.Show("Some msg");
// more code
_inside = false;
}
}
This would disallow "recursive" calls of your function.
the BeforeSelect event isn't fired multiple times by default.
when you select a node, you show a dialog(here messagebox) which interrupts the selection event or task however and after you close the dialog the selection event fires again based on the interruption. You should use AfterSelect event of the treeview to do things... and BeforeSelect only for validation..
Please look at this code - run it
void treeView1_BeforeSelect(object sender, TreeViewCancelEventArgs e)
{
e.Node.Tag = (int)(e.Node.Tag ?? 0) + 1;
int count = (int)(e.Node.Tag);
e.Node.Text = String.Format("selected {0} Count: {1}", e.Action.ToString(), count);
}
When you define an object,you should write like this;
True Write:
private static TreeView projectagac;
...
...
...
projectagac = new TreeView();
thus you will create only one object.
I'm creating listviews in a flowpanel at run time which later will accept drag and dropped files. the reason being is i want these to act as folders so a user double clicks and gets a window displaying the contents.
i'm having difficulty setting up the events for my listviews as they are added.
how do i create some events (like MouseDoubleClick and DragDrop) dynamically for each added listview? can i create a single function for both of these events and have listview1, listview2, listviewX use it?
i have a button that is adding the listviews, which works fine. please advise, i apologize if this is too conceptual and not exact enough.
private void addNewWOButton_Click(object sender, EventArgs e)
{
ListView newListView = new ListView();
newListView.AllowDrop = true;
flowPanel.Controls.Add(newListView);
}
You would have to have the routine already created in your code:
private void listView_DragDrop(object sender, DragEventArgs e) {
// do stuff
}
private void listView_DragEnter(object sender, DragEventArgs e) {
// do stuff
}
and then in your routine, your wire it up:
private void addNewWOButton_Click(object sender, EventArgs e)
{
ListView newListView = new ListView();
newListView.AllowDrop = true;
newListView.DragDrop += listView_DragDrop;
newListView.DragEnter += listView_DragEnter;
flowPanel.Controls.Add(newListView);
}
You would have to check who the "sender" is if you need to know which ListView control is firing the event.
You can also just use a lambda function for simple things:
newListView.DragEnter += (s, de) => de.Effect = DragDropEffects.Copy;
Just make sure to unwire the events with -= if you also remove the ListViews dynamically.
To answer the other half of your question, you can use a single handler for any event, from any source, that has the handler's signature. In the body of the handler, you just have to check the sender argument to determine which control raised the event.
You need a way to tell one control from a different one of the same class, however. One way to do this is to make sure to set the Name property on each control when you create it; e.g., newListView.Name = "FilesListView".
Then, before you do anything else in your event handler, check the sender.
private void listView_DragDrop(object sender, DragEventArgs e) {
ListView sendingListView = sender as ListView;
if(sendingListView == null) {
// Sender wasn't a ListView. (But bear in mind it could be any class of
// control that you've wired to this handler, so check those classes if
// need be.)
return;
}
switch(sendingListView.Name) {
case "FilesListView":
// do stuff for a dropped file
break;
case "TextListView":
// do stuff for dropped text
break;
.....
}
}
I have a WinForms app that contains many NumericUpDown controls. In a nutshell, if my users enter a value into the control and then delete the text, I want to restore it (the text) when the control loses focus. So I decided that I'd check .Text when the control loses focus and if it's empty, I set .Text = .Value.ToString().
I'm doing this in the Leave event handler and it works just fine. But as I said, I have many of these controls (18, to be exact). I don't like creating 18 Leave event handlers that all do the same thing so I created a generic one like this:
private void numericUpDown_GenericLeave(object sender, EventArgs e)
{
if (string.IsNullOrEmpty(((NumericUpDown)sender).Text))
((NumericUpDown)sender).Text = ((NumericUpDown)sender).Value.ToString();
}
I started to hook up all of the controls to this generic event handler but I quickly got tired of doing this:
numericUpDown1.Leave += numericUpDown_GenericLeave;
numericUpDown2.Leave += numericUpDown_GenericLeave;
numericUpDown3.Leave += numericUpDown_GenericLeave;
...
numericUpDown18.Leave += numericUpDown_GenericLeave;
So I thought I'd create a function that would return a list of all the controls of a specified type and then loop through that list and hookup the event handlers. That function looks like this:
public static List<Control> GetControlsOfSpecificType(Control container, Type type)
{
var controls = new List<Control>();
foreach (Control ctrl in container.Controls)
{
if (ctrl.GetType() == type)
controls.Add(ctrl);
controls.AddRange(GetControlsOfSpecificType(ctrl, type));
}
return controls;
}
I call the function like this:
var listOfControls = GetControlsOfSpecificType(this, typeof(NumericUpDown));
foreach (var numericUpDownControl in listOfControls)
{
numericUpDownControl.Leave += numericUpDown_GenericLeave;
}
When I run my app, however, I don't see the expected behavior that occurs when I manually hookup each control to the generic event handler. This code is currently in the constructor of my form and I've tried calling it before as well as after the call to InitializeComponent() but neither one seems to be working. I get no error of any kind, I just don't see the behavior that I was expecting. I have a breakpoint set inside the generic event handler but the debugger never breaks so it seems like the event handler isn't being hooked up correctly. Does anyone know why this might be or how I can troubleshoot it further? Thanks!
EDIT
I just realized that the call to:
var listOfControls = GetControlsOfSpecificType(this, typeof(NumericUpDown));
was happening before the call to InitializeComponent() so of course the list of controls being returned was empty. DOH! Thanks for all the replys. I apologize for wasting everyones time. :-(
You're passing this to your method, which is presumably a reference to your form. Your method will only catch the controls that are placed directly on your form. Any NumericUpDown controls that are not directly on the form (i.e. they're sitting on a panel or something) will be missed.
Why not create a user control that has a NumericUpDown control in it.
Then handle this is in the user control events.
This worked for me:
private decimal _previous = 0;
private void numericUpDown1_ValueChanged(object sender, EventArgs e)
{
if (((NumericUpDown)sender).Text.Length > 0)
{
_previous = this.numericUpDown1.Value;
}
}
private void UserControl1_Leave(object sender, EventArgs e)
{
if (this.numericUpDown1.Text == "")
{
this.numericUpDown1.Value = _previous;
this.numericUpDown1.Text = System.Convert.ToString(_previous);
}
}
Just note that the Leave event is on the user control not on the updown control itself.
Question answered. See Edit above. Thanks to bsegraves for pointing me in the right direction.