I've tried using all the usual techniques to figure out how to get to that moment when the content of a user control is fully displayed. The only way I've managed to to it so far is using the LayoutUpdated event and count the number of calls to this event until I know that sufficient controls are now visible to enable me to (in this example, turn off the waiting cursor). Here is a code sample.
private void PortfolioDesignerGridPage_Loaded(object sender, RoutedEventArgs e)
{
Mouse.OverrideCursor = Cursors.Wait;
LayoutUpdated += PortfolioDesignerGridPage_LayoutUpdated;
}
int renderCounts = 0;
private void PortfolioDesignerGridPage_LayoutUpdated(object sender, System.EventArgs e)
{
renderCounts += 1;
if(renderCounts > 19)
{
LayoutUpdated -= PortfolioDesignerGridPage_LayoutUpdated;
renderCounts = 0;
Mouse.OverrideCursor = Cursors.Arrow;
}
}
This if course is very unsatisfactory. Surely there is a more precise way to do this?
Related
So I have a user control with six textboxes and a few buttons. One of those buttons is 'clear'. When I click the clear button, in the btnClear_Click handler, I want to find all the textboxes in my user control (and ONLY in my user control). And then set them to an empty string. That's it. That's all.
This is turning out to be a herculean, insurmountably difficult thing to do. Finding an answer is like trying to map the human genome. I just want to ITERATE THROUGH THE CONTROLS. Nothing more.
I'm not interested in hearing about the merits of what I'm trying to do. Just the mechanics of how to do it. Something like this:
public partial class myUserControl: UserControl
{
private void btnClear_Click(object sender, RoutedEventArgs e)
{
var allMyControls = SomeMiraculousOperationToGetAllControlsThatOnlyExistInMyUserControl();
foreach (var control in allMyControls)
{
if (control is TextBox)
((TextBox)control).Text = string.Empty;
}
}
}
You can use the VisualTreeHelper to enumerate the child controls of your user control.
You can find an extension method base on this class here
public static T GetChildOfType<T>(this DependencyObject depObj)
where T : DependencyObject
{
if (depObj == null) return null;
for (int i = 0; i < VisualTreeHelper.GetChildrenCount(depObj); i++)
{
var child = VisualTreeHelper.GetChild(depObj, i);
var result = (child as T) ?? GetChildOfType<T>(child);
if (result != null) return result;
}
return null;
}
I've attached the KeyDown event to a ListView in my Win 10 UWP app. I want to make VirtualKey.Enter have a special effect, but the event is not firing for this particular key. Neither does it for Space, Arrow up or down. This I guess because the listview already has defined a special behaviour for those keys.
I'd like to override some of those keys though, or at least trigger additional actions. Even attaching events to those key with modifiers (e.g. Shift+ArrowDown) would not work because the events still are not firing.
I read that for WPF that there is a PreviewKeyDown-event which one can attach to. I can't find that event for UWP though. Are there any other options?
Stephanie's answer is a good one and it works in the general case. However, as Nilzor observed it will not work in the case of a ListView for the Enter key. For some reason the ListView handles the KeyDown event in case Enter is pressed.
A better way to handle key events when dealing with a ListView, as the question asks, is this.
private void ListView_Loaded(object sender, RoutedEventArgs e)
{
(sender as ListView).AddHandler(UIElement.KeyDownEvent, new KeyEventHandler(ListView_KeyDown), true);
}
private void ListView_KeyDown(object sender, KeyRoutedEventArgs args)
{
if (args.Key == Windows.System.VirtualKey.Enter)
{
}
}
Notice the last argument in the AddHandler function. This specifies whether we want to handle events already handled by a previous element in the visual tree.
Of course don't forget to unsubscribe from the event when appropriate
Here is one way to do it : subscribe to the global Window.Current.CoreWindow.KeyDown event.
Then save the focus state of your listview and react accordingly.
Here is the code :
public sealed partial class MainPage : Page
{
bool hasFocus = false;
public MainPage()
{
this.InitializeComponent();
Window.Current.CoreWindow.KeyDown += CoreWindow_KeyDown;
}
private void CoreWindow_KeyDown(Windows.UI.Core.CoreWindow sender, Windows.UI.Core.KeyEventArgs args)
{
if(hasFocus)
{
Debug.Write("Key down on list");
}
}
private void myList_GotFocus(object sender, RoutedEventArgs e)
{
hasFocus = true;
}
private void myList_LostFocus(object sender, RoutedEventArgs e)
{
hasFocus = false;
}
You will also need to subscribe to the focus events in xaml, for your ListView :
<ListView .... GotFocus="myList_GotFocus" LostFocus="myList_LostFocus"/>
Corcus's solution doesn't work for me. What is working is handling PreviewKeyDown directly from XAML. Works well for SPACE or ENTER key:
XAML:
<ListView PreviewKeyDown="BookmarksListView_PreviewKeyDown">
Code behind:
private void BookmarksListView_PreviewKeyDown(object sender, KeyRoutedEventArgs e)
{
if (e.Key == Windows.System.VirtualKey.Enter)
{
// DO YOUR STUFF...
e.Handled = true;
}
}
You can use AddHandler method.
private void KeyEnterEventHandler(object sender, KeyRoutedEventArgs e)
{
if (e.OriginalKey == Windows.System.VirtualKey.Enter)
{
PlayFromListView();
}
}
private void LoadListView()
{
foreach (var music in playListStorageFile.PlayList)
{
ListViewItem item = new ListViewItem();
item.AddHandler(FrameworkElement.KeyDownEvent, new KeyEventHandler(KeyEnterEventHandler), true);
TextBlock mytext = new TextBlock();
mytext.Text = music.Nro.ToString() + " - " + music.Name;
mytext.Tag = music.Nro;
item.Content = mytext;
lvMusics.Items.Add(item);
}
}
https://learn.microsoft.com/en-us/uwp/api/windows.ui.xaml.uielement.addhandler?view=winrt-18362
I was making a program and I stumbled across this two-in-one problem, where the first problem leads to the other. I have not yet found a question where someone had both problems leading into eachother. I'm still learing, and have learned a lot from other problems I had, but I can't find a solution to this problem.
It has to do with threading. I want to make a thread, that can place something in a rich textbox every second or so, while I can still press buttons to start and stop it. But to make a function that a thread can run, I need to make the function static. Otherwise I'll get the error "A field initializer cannot reference the non-static field, method, or property". But when a function is static, it cannot acces any of the created items, like richTextBox1. Because if I try to change it's text, I get the error "Error 1 An object reference is required for the non-static field, method, or property". And if I fix this by removing static, the thread will not work.
I made a demo program that is smaller than the full one, but has the same problem. Button1 is the button to start the thread, Button2 is the one to stop it.
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Threading;
namespace threading_non_static_problem_demo
{
public partial class Form1 : Form
{
static Thread thr = new Thread(new ThreadStart(demofunc));
int checkthr = 0; //int to check if the thread has been running before (I like to do things like this)
int ifthrrun = 0; //int to check if the thread is running
public Form1()
{
InitializeComponent();
button2.Enabled = false; // so you can't click the "stop" button if nothing is running
}
private void richTextBox1_TextChanged(object sender, EventArgs e)
{
}
static void demofunc()
{
while (true)
{
Thread.Sleep(1000);
richTextBox1.Text = richTextBox1.Text + "text added"; // <-- here's the problem
MessageBox.Show("tried to add text"); // you can use this messagebox to check if the thread is working correctly
}
}
private void button1_Click(object sender, EventArgs e)
{
if (checkthr == 0) // check if the thread has run before, 0 is no, 1 is yes, and then start or resume it
{
thr.Start();
ifthrrun = 1;
button2.Enabled = true;
button1.Enabled = false;
}
else if (checkthr == 1)
{
thr.Resume();
ifthrrun = 1;
button2.Enabled = true;
button1.Enabled = false;
}
}
private void button2_Click(object sender, EventArgs e)
{
thr.Suspend();
checkthr = 1;
ifthrrun = 0;
button2.Enabled = false;
button1.Enabled = true;
}
protected override void OnFormClosing(FormClosingEventArgs e) // if the program is closing, check the thread's state and act accordingly
{
if (ifthrrun == 0)
{
if (checkthr == 1)
{
thr.Resume();
thr.Abort();
}
else if (checkthr == 0)
{
}
}
else if (ifthrrun == 1)
{
thr.Abort();
}
}
}
}
To use this code just creat a forms application, add two buttons, and a rich text box, it should work.
Thank you in advance for you answers.
But to make a function that a thread can run, I need to make the
function static.
Get rid of the static declarations and move initialization of your "thr" variable to the constructor like this:
Thread thr;
public Form1()
{
InitializeComponent();
button2.Enabled = false; // so you can't click the "stop" button if nothing is running
thr = new Thread(new ThreadStart(demofunc));
Control.CheckForIllegalCrossThreadCalls = false;
}
private void demofunc()
{
while (true)
{
Thread.Sleep(1000);
richTextBox1.Text = richTextBox1.Text + "text added"; // <-- problem "solved" by disabling Control.CheckForIllegalCrossThreadCalls
}
}
But ignore the above "fix" because using Suspend()/Resume() is not recommended.
See Pausing and Resuming Threads:
Important
Starting with the .NET Framework version 2.0, the Thread.Suspend and
Thread.Resume methods are marked obsolete and will be removed in a
future release.
The Thread.Suspend and Thread.Resume methods are not
generally useful for applications and should not be confused with
synchronization mechanisms. Because Thread.Suspend and Thread.Resume
do not rely on the cooperation of the thread being controlled, they
are highly intrusive and can result in serious application problems
like deadlocks (for example, if you suspend a thread that holds a
resource that another thread will need).
One way to be able to pause/resume your loop would be to use a ManualResetEvent like this:
Thread thr;
ManualResetEvent mre = new ManualResetEvent(false);
public Form1()
{
InitializeComponent();
button2.Enabled = false; // so you can't click the "stop" button if nothing is running
thr = new Thread(new ThreadStart(demofunc));
}
private void demofunc()
{
while (!this.IsDisposed && !this.Disposing)
{
Thread.Sleep(1000);
if (!this.IsDisposed && !this.Disposing)
{
this.Invoke((MethodInvoker)delegate {
richTextBox1.AppendText("text added");
});
}
mre.WaitOne();
}
}
private void button1_Click(object sender, EventArgs e)
{
button1.Enabled = false;
mre.Set();
if (!thr.IsAlive)
{
thr.Start();
}
button2.Enabled = true;
}
private void button2_Click(object sender, EventArgs e)
{
button2.Enabled = false;
mre.Reset();
button1.Enabled = true;
}
protected override void OnFormClosing(FormClosingEventArgs e) // if the program is closing, check the thread's state and act accordingly
{
mre.Set(); // make sure the loop continues so it can drop out
}
}
I am dynamically creating a RadGrid and adding GridTemplateColumns to it. Those columns have textbox in them.
After binding datatable to the grid, after user makes changes to the textboxes and on clicking save button, I would like to access the textbox values. But I am stuck at getting hold of the textbox instance. I couldn't even get hold of GridItems!
To add more complexity, my RadGrid is in a UserControl, which is in a (multi)view.
Heres the code.
protected void Page_Init(object sender, EventArgs e)
{
DefineGridStructure();
}
protected void Page_Load(object sender, EventArgs e)
{
if (RadGrid1 != null && RadGrid1.Items.Count > 0)
{
string strtxt = ((TextBox)RadGrid1.Items[1]["ProductGroup1"].Controls[0]).Text;//For starters, load one control and check it's state
}
}
private void DefineGridStructure()
{
RadGrid1 = new RadGrid();
RadGrid1.AutoGenerateColumns = false;
RadGrid1.ShowHeader = true;
RadGrid1.NeedDataSource += RadGrid1_NeedDataSource;
foreach(GridColumn qtyColumn in BuildGridQtyColumns(PaxColumnCount))
{
RadGrid1.MasterTableView.Columns.Add(qtyColumn);
}
//Add grid to page
phRadGrid.Controls.Add(RadGrid1);
}
private List<GridColumn> BuildGridQtyColumns(int count)
{
List<GridColumn> qtyColumns = new List<GridColumn>();
for (int i = 1; i <= count; i++)
{
string qtyColumnName = string.Format("ProductGroup{0}", i);
GridTemplateColumn qtyColumn = new GridTemplateColumn();
qtyColumn.ItemTemplate = new GridNumberTemplate(qtyColumnName);//Creates a textbox control
qtyColumn.UniqueName = qtyColumnName;
qtyColumn.HeaderText = "Qty";
qtyColumn.HeaderStyle.Width = Unit.Pixel(60);
qtyColumn.HeaderStyle.HorizontalAlign = HorizontalAlign.Center;
qtyColumns.Add(qtyColumn);
}
return qtyColumns;
}
Since my control is in view, it's Page_Init is called more than once for each action that involves this view.
For a dynamically generated radgrid, it should be created in page_init method and viewstate for this grid will be restored for us automatically which we can get hold of in page_load method.
I have 20 TextBoxes in a form. And I have a Common KeyPress Event for all of that Textboxes.
So I try to declare the keypress event like the following manner... is it possible?
for (int Cnl = 1; Cnl < 21; Cnl++)
{
((RichTextBox)Cnl).KeyPress += new KeyPressEventHandler(this.Comn_KeyPress);
}
Correct idea; but casting an int to a RichTextBox will never work. Try this:
foreach (var control in this.Controls)
{
var text = control as RichTextBox;
if (text != null)
text.KeyPress += new KeyPressEventHandler(this.Comn_KeyPress);
}
For a WPF application you can register global event handlers using the methods on the EventManager static class:
// Register the following class handlers for the TextBox XxFocus events.
EventManager.RegisterClassHandler(typeof(TextBox), TextBox.GotKeyboardFocusEvent,
new RoutedEventHandler(HandleTextBoxFocus));
Then add whatever logic you need on the event handler, for ex.:
private void HandleTextBoxFocus(Object sender, RoutedEventArgs e)
{
(sender as TextBox).SelectAll();
}