I have a CheckBox that is set to CheckState.Indeterminate. When a timer expires it will be set to CheckState.Unchecked and turn off an external output signal. So far so good.
With the current code when the user clicks on the Indeterminate CheckBox it will become an Unchecked CheckBox. I would like to intercept it and make it a Checked CheckBox.
The effect for the user would be to cancel the timer and leave the output on until the user unchecks the box or the user starts a separate process that takes over and the Indeterminate CheckBox` is set again.
As it is he turns off the output and has to explicitly turn it on again.
I tried the validating event, but that doesn't happen until I leave the box.
Update 1: To clarify a little bit what the user wants to see.
When the lights are off the box is always unchecked.
When the automated part of the system is running, the light is on. If the user looks at the control it is in the indeterminate state because the user did not activate it it, but it is on.
When the process stops a timer is started leaving the lights on for 2 minutes. The user still sees the indeterminate state during this time.
If the user needs the light to remain on he will check the box removing the indeterminate state. When he is through he will manually uncheck the box turning off the light or restart the automated process which will make it indeterminate again.
I wasn't aware of the AutoCheck property
There is no need for anything drastic, you just don't like the way that Checkbox implemented its AutoCheck property. So select the control and set its AutoCheck property to False. That let's you control the check state the way you want it.
Add the Click event handler to allow the user to flip the state straight from Indeterminate to Checked with a mouse click or spacebar press:
private void checkBox1_Click(object sender, EventArgs e) {
checkBox1.CheckState = checkBox1.CheckState == CheckState.Checked ?
CheckState.Unchecked : CheckState.Checked;
}
I'm advising against changing the behavior of standard controls, but if this is what you need, you can subclass the CheckBox and override the Onclick method.
This is where you can see what the standard behavior is.
All you need to do is rework that logic in the switch statement and call the base. We need to suppress the base's checkstate logic by setting AutoCheck to false, then restore it to its previous value afterwards:
public class MyCheckBox : CheckBox
{
protected override void OnClick(EventArgs e)
{
if (AutoCheck)
switch (CheckState)
{
case CheckState.Indeterminate:
CheckState = CheckState.Checked;
break;
case CheckState.Unchecked:
if (ThreeState)
{
CheckState = CheckState.Indeterminate;
}
else
{
CheckState = CheckState.Checked;
}
break;
default:
CheckState = CheckState.Unchecked;
break;
}
var oldAutoCheckValue = AutoCheck;
AutoCheck = false;
base.OnClick(e);
AutoCheck = oldAutoCheckValue;
}
}
As an alternative solution, you should consider using radio buttons to improve UX.
I think you need CheckStateChanged event.
Try this and let me know:
//mark the process as running (check box is Indeterminate state)
private bool processIsRunning = true;
private void chkState_CheckStateChanged(object sender, EventArgs e)
{
//the user clicks the indeterminate checkbox
if (processIsRunning && chkState.CheckState == CheckState.Unchecked)
{
processIsRunning = false;
chkState.CheckState = CheckState.Checked;
}
}
Related
I am trying to disable the thin and crispy checkbox when traditional checkbox is clicked. I have these in a group due to me enabling the whole group when the numericUpDown value is set to 1. When I click traditional checkbox, it doesn't disable the thin and crispy checkbox. I am using windows form application
Code
private void NudQuantity1_ValueChanged(object sender, EventArgs e)
{
if (NudQuantity1.Value == 0)
{
gbCheesePizza.Enabled = false;
}
else
{
gbCheesePizza.Enabled = true;
}
if (CBXTraditional1.Checked == true)
{
CBXthinandcrispy1.Enabled = false;
}
}
When I run this code outside of a groupbox, it works perfectly.
I don't think this block should be inside the event handler
if (CBXTraditional1.Checked == true)
{
CBXthinandcrispy1.Enabled = false;
}
It means that, provided you've got no other event handling for the checkboxes, this code will only be executed when you change the value of NudQuantity1 so it won't execute anything when you click the checkboxes afterwards.
Try use radio buttons as Steve mentioned. They do this for you.
I am writing a Xamarin forms application which checks whether or not a user is in a specific geo-location. When a user walks inside an area, a XAML switch is toggled from the off to on position.
farmSwitch.toggled = true;
This calls this function
farmSwitch.Toggled += (object sender, ToggledEventArgs e) => {
manualOnFarm = true;
Console.WriteLine("Switch.Toggled event sent");
changeOnFarmStatus(e);
};
I also need functionality where a user manually clicks the switch, which need to be differentiated from when the code automatically toggles farmSwitch
The reason is that I have a boolean that should only be true when the user manually clicks farmSwitch, and should be false when the switch is toggled automatically
What are my options? Ideally there would be a farSwtich.clicked() function I could call for when a user manually clicks farmSwitch, but no such luck
I don't see how you can't just differentiate between this by using some kind of marker in the code you've written that programatically toggles the switch?
So you call this programatically but you also set a boolean marker to say this is a programatic change:
private bool HasBeenProgrammaticallyToggled = false;
public void ThisIsAProgrammaticToggle()
{
HasBeenProgrammaticallyToggled = true;
farmSwitch.toggled = true;
}
and in your little on toggled event just do:
farmSwitch.Toggled += (object sender, ToggledEventArgs e) => {
if(HasBeenProgrammaticallyToggled)
{
//This has been toggled programmatically, so reset our bool
HasBeenProgrammaticallyToggled = false;
}
else
{
// I am assuming this is what you use to determine a manual toggle?
manualOnFarm = true;
}
Console.WriteLine("Switch.Toggled event sent");
changeOnFarmStatus(e);
};
Wouldn't this work?
Use #digitalsa1nt 's suggestion or, use "-=" the method before you switch it manually and use "+=" again.
I have a simple Winform example that demonstrates what happens.
There is a GroupBox with two RadioButtons. The two buttons share a validating event handler. Also on the form is a Button that does nothing. No events are connected. Finally there is a CheckBox that controls the state of a passing validation. Checked it passes and unchecked it fails.
When the program starts and the user clicks on either RadioButton the validating event does not fire. Then when I click on any control other than the current button the Validating Event fires. The NOP button gives me something to click besides the CheckBox.
In this test the CheckBox represents the status of passing the validation.
This will not work because once I uncheck the CheckBox and then click a radio button the focus is forever stuck. You can't get the focus to the CheckBox to change its state.
The reason is the Validating event is always called when the focus is leaving and not when the RadioButton is clicked. It sees that "valdating" fails and cancels the event.
This is obviously the wrong approach. What should I be doing to test at the time of the initial click? The Click event happens after the state has changed.
What event should I use so that I can test validation before changing the RadioButton state? Then I can leave the button and fix the issue before trying again.
This example is a simplified test that shows my dead end. My real world example is the two RadioButtons select one of two similar tables in a DataGridView. The two tables are related and I want them to be on the same TabPage. When the user selects the alternate table I want to do a validation/confirmation before switching away. If the confirmation fails I want to cancel the radio button.
// Validate is called when the radio button is clicked and when it leaves the box
using System.ComponentModel;
using System.Windows.Forms;
namespace ValidateRadioButton
{
public partial class Form1 : Form
{
int count;
public Form1()
{
InitializeComponent();
}
private void radiobutton_Validating(object sender, CancelEventArgs e)
{
if (sender is RadioButton) {
// If box not checked, cancel radioButton change
// This becomes a Hotel California test, once unchecked you
// can never leave the control
e.Cancel = !chkAllowChange.Checked;
}
count++;
//Display the number of times validating is called in the title bar
//Demonstrates when the event is called
Text = count.ToString();
}
}
}
I have reproduced your form in a test project and I think I see what is going on.
Setting the Checked property of CancelEventArgs to true will prevent whatever control set it from losing focus until input is "corrected". As you are aware, the Validating event is triggered whenever a control loses focus. The user becomes "stuck" as you say because the only way they can "correct" their input is to modify the check box, which they cannot get to because of the Validating event which fires on the radio button.
A solution which I came up with was moving the Validated event to the GroupBox, instead of the radio buttons:
private void groupBox_Validating(object sender, CancelEventArgs e)
{
if (sender is RadioButton)
{
e.Cancel = !checkBox1.Checked;
}
count++;
//Display the number of times validating is called in the title bar
//Demonstrates when the event is called
Text = count.ToString();
}
Be sure to remove the Validating event handler from the radio buttons.
For clarity, I have set my form up in this manner:
The result is now I cannot click the 'OK' until I have ticked the check box. I have preserved your Text = count.ToString() assignment so that you can see that the form now calls Validating only as it should.
I ended up using the CheckChanged and Click events for the RadioButtons.
I track the currently active RadioButton and do the validation in the CheckChanged event. Then in the Click event, if the validation failed I restore the previous active RadioButton. Otherwise we can continue to the purpose of the RadioButton.
This solution works for two or more RadioButtons in a group and it works when using the keyboard.
using System.ComponentModel;
using System.Windows.Forms;
namespace ValidateRadioButton
{
public partial class Form1 : Form
{
// RadioButton that is currently active
RadioButton ActiveRadioButton;
bool cancelingChange;
public Form1()
{
InitializeComponent();
activeRadioButton = this.radioButton1;
}
private void radioButton_CheckedChanged(object sender, System.EventArgs e)
{
// Each click fires two events
// One for the RadioButton loosing its check and the other that is gaining it
// We are interested in the one gaining it
if (sender is RadioButton) {
RadioButton radioButton = (RadioButton)sender;
if (radioButton.Checked) {
// If this button is changing because of a canceled check
// do not validate
if (!cancelingChange) {
cancelingChange = !ValidateData();
if (!cancelingChange) {
// Mark this as the active value
activeRadioButton = radioButton;
}
}
}
}
}
private void radioButton_Click(object sender, System.EventArgs e)
{
// This is called after the RadioButton has changed
if (cancelingChange) {
// Check theRadioButton that was previously checked
activeRadioButton.Checked = true;
cancelingChange = false;
}
else {
// Do the thing the RadioButton should do
// If using separate events they all must start with the condition above.
this.Text = ((RadioButton)sender).Name;
}
}
/// <summary>
/// Validate state of data
/// </summary>
/// <returns></returns>
private bool ValidateData()
{
bool result = chkAllowChange.Checked;
if (!result) {
result = MessageBox.Show("Do you want to save your data?", "CheckBox unchecked", MessageBoxButtons.OKCancel, MessageBoxIcon.Exclamation) == DialogResult.OK;
if (result) {
// This is where I would save the data
chkAllowChange.Checked = true;
}
}
return result;
}
}
}
I have been trying to make a matching game and I recently learned that the following is possible:
if (checkBox1.checked = true)
{
MessageBox.Show("For Example.")'
}
Then why is the following not possible?
private void pictureBox1_Click(object sender, EventArgs e)
{
MessageBox.Show("Now Pick Another Hidden Picture!");
pictureBox1.Visible = false;
if (pictureBox13.Click = true)
{
MessageBox.Show("Great!");
pictureBox13.Visible = false;
double score = score + 1;
textBox1.Text = (score).ToString();
}
else
{
MessageBox.Show("Try Again!");
pictureBox13.Visible = true;
pictureBox1.Visible = true;
}
}
There is a error line under .Click , and the error is :
The event 'system.Windows.Forms.Control.Click' can only appear on the left hand side of += or -=.
What does this mean? And why does this work for checking checkboxes, but not for clicking pictureboxes? Thank in advance.
Checked is the state of a checkbox. At any given time, a checkbox is either checked or unchecked. Reading myCheckBox.Checked immediately returns the current state of the checkbox.
Click is an event. What do you expect if (pictureBox.Click == true) to do? Tell you if the pictureBox has been clicked within the last X seconds? Wait X seconds for the user to click (or not click) on the pictureBox?
In other words: If you check a checkbox, it stays checked until it is unchecked. Thus, it makes sense to check the current state of the checkbox. On the other hand, if you click a button, it is "clicked" for only an instant and then returns to being "unclicked". Thus, it just does not make sense to query the "clicked" state of a button.
PS: Comparisons are done with ==, not with =. The latter is an assigment. And, as Hugh correctly points out in the comments, if (boolean) is enough, if (boolean == true) is redundant.
I have a Winform application I'm modifying for a friend. It has a listview and wants me to add a checkbox to each row and make them mutually exclusive. So in my testing of how to make it work I found a strange behavior and as hopping someone could tell me what I'm missing.
If I display the List view with no checkbox checked. When I click right on the checkbox I cannot get it to check, but the row dose get selected. If I click on the item (the name in this case) in the column it does get checked and selected.
No matter where I click on a row, any checkboxes in rows not selected will be uncheck. Here is my little test program. I’m using .NET 4
public partial class Form1 : Form {
public Form1() {
InitializeComponent();
}
private void Form1_Load(object sender, EventArgs e) {
TestListView.Items.Add("Bob");
TestListView.Items.Add("Ann");
TestListView.Items.Add("Frank");
}
void TestListView_MouseClick(object sender, System.Windows.Forms.MouseEventArgs e) {
ListViewItem currentItem = TestListView.GetItemAt(e.X, e.Y);
if (currentItem != null) {
foreach (ListViewItem item in TestListView.Items) {
if (item.Text == currentItem.Text) {
item.Checked = true;
item.Selected = !currentItem.Selected;
}
else
item.Checked = false;
}
}
}
}
Seems that WinForms is checking the checkbox when you click on the checkbox directly, and then your code immediately undoes the checking, so you never see it.
Perhaps instead of MouseClick you should use the ItemCheck or ItemChecked event. The first is fired before the Checked property changes, the second after.
I'm currently having a very similar issue as well, however in response to Timwi it's not the code doing the unchecking. I've been stepping through it very slowly and as the code fires when clicking on a checkbox, it states that it has checked it. But when the form resumes, it is unchecked again. After reading Timwi post, he lead me onto the answer. It's not the code doing the unchecked, but the winforms event firing afterwards that unchecks the box. This fixes it:
My code is:
private bool allowCheck = false;
private bool preventOverflow = true;
private void lstvwRaiseLimitStore_MouseClick(object sender, MouseEventArgs e)
{
preventOverflow = false;
ListViewItem item = lstvwRaiseLimitStore.HitTest(e.X, e.Y).Item;
if (item.Checked)
{
allowCheck = true;
item.Checked = false;
}
else
{
allowCheck = true;
item.Checked = true;
}
}
private void lstvwRaiseLimitStore_ItemChecked(object sender, ItemCheckedEventArgs e)
{
if (!preventOverflow)
{
if (!allowCheck)
{
preventOverflow = true;
e.Item.Checked = !e.Item.Checked;
}
else
allowCheck = false;
}
}
So what it is doing, first I have to set a flag to prevent overflow, otherwise when the form is built or when you uncheck windows checking the box, it keeps looping the code and will eventually stack overflow. Next flag is the actual allow checking of the checkbox via your code and not via another method.
Clicking on them item, it locates where the click was and then sets the flag to allow a check to be done. The code then checks the box and the item checked section kicks off, becuase it was done by our code, it does nothing but reset the allowcheck flag.
If you clicked on a line, it does nothing else, however if it was a checkbox, at the end of our code, the Windows function kicks off and tries to check the box, becuase the allowcheck flag is false, the code first sets a flag to say I'm already preventing a check and then resets the check back to it's intial status. Becuase this is done, the itemchecked event kicks off again, but the code has set the flag to prevent it from doing anything. Then the code finishes and it has prevented windows from checking the check box and only allowed our code.
Hope it helps!