event-handling | 易学教程

how to accept/ignore QKeyEvent

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问题 http://qt-project.org/doc/qt-5/qwidget.html#keyPressEvent Note that QKeyEvent starts with isAccepted() == true, so you do not need to call QKeyEvent::accept() - just do not call the base class implementation if you act upon the key. http://qt-project.org/doc/qt-5/qkeyevent.html#details A key event contains a special accept flag that indicates whether the receiver will handle the key event. You should call ignore() if the key press or release event is not handled by your widget. A key event is

Javascript pattern: Conditional event handler

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问题 Given e.g. a class instance of some sort has a state (e.g. 'active', 'inactive', …). The instance also attaches a click event to e.g. a link but the event handler does something different depending on the instance's state. Pseudo code: IF instance state IS 'active' AND link is clicked THEN call function A IF instance state IS 'inactive' AND link is clicked THEN call function B … I'm wondering what's considered good practice to handle this case properly: Which patterns are commonly in use to

Handling events of usercontrols within listview

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问题 I have a simple usercontrol which raises an event on button click Public Class UcPaymentCheque Inherits System.Web.UI.UserControl Public Event OnCancelClick() Private Sub btnCancelPayment_Click(sender As Object, e As System.EventArgs) Handles btnCancelPayment.Click RaiseEvent OnCancelClick() End Sub End Class This usercontrol is used within a listview <asp:ListView ID="lvwNonTpProducts" runat="server" ItemPlaceholderID="ItemPlaceholder"> <LayoutTemplate> <asp:PlaceHolder ID="ItemPlaceholder"

How do you assign an event handler to multiple elements in JavaScript?

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I know how to do so with jQuery, and I know how to do so with event delegation. But how do you do so in plain JavaScript? For example, how do you assign an event handler to a bunch of li s? I see that var li = document.querySelectorAll('li'); . Returns an array-like thing. Do you just loop through and assign handlers? I feel like there must be a better way. If not, what's the best way to loop through the array-like thing (and what is the array-like thing called?)? Yes, you should loop through the collection and assign the handlers individually. jQuery also does this behind the scenes.

Google Analytics Event Tracking on Worpdress

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I am trying to send an Event when clicked on a specific menu item. My header scripts are as follows:  <script async src="https://www.googletagmanager.com/gtag/js?id=UA-124755880-1"></script> <script> window.dataLayer = window.dataLayer || []; function gtag(){dataLayer.push(arguments);} gtag('js', new Date()); gtag('config', 'UA-124755880-1'); </script>  <script> jQuery(document).ready(function($){ function handleOutboundLinkClicks(event) { console.log(event.target.href); ga('send', 'event', {

Point picker event_handler drawing line and displaying coordinates in matplotlib

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I have the following class that draws a vertical line through the y-axis, so that when I click on it a horizontal line gets drawn at the location. My goal is to get the y-coordinate to actually print right at the y-axis where the horizontal line gets drawn. For testing, I am trying to print a title with the y-ccordinate, but it is not working as expected. What I am trying to really accomplish is to make the y-axis on a bar plot clickable so that the user can select a point on the y-axis, and then a bunch of "stuff" happens (including the drawing of a horizontal line). I really see no other way

How to obtain the HttpContext in Event Handler

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问题 I’m trying to obtain the HTTPContext within an Event Handler in a Document Library in MOSS, but all I have is a null value of the HTTPContext.Current, I do the same thing on a List and the HTTPContext is returned. There is a way to obtain the HTTPContext in Document Libraries to access the HTTPContext.Request method? Thanks for your help Here is the code: public class TestContextListItemEventReceiver : SPItemEventReceiver { HttpContext current; static object obj; /// <summary> /// Initializes

How to write event handler in VB.NET?

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问题 I am trying to test out very simple event handling in VB.NET. So far I have: Public Delegate Sub TestEventDelegate() Public Event TestEvent As TestEventDelegate Sub MySub Raise TestEvent End Sub How would you write an event handler for the above event that just displayed a simple MessageBox ? 回答1: Writing the handler method is simple - just write a Sub which takes no parameters and displays a message box. You then need to subscribe the handler to the event, which you can either do adding a

How to override the dragging events in C3.js

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I am currently trying to implement a zooming feature that is slightly different from the one that already exists. Actually, I would like that if a user clicks and drags on the graph it zooms on the so defined domain. I would like to do it that way because with the mouse wheel it prevents the user from the page up/down. As it doesn't seem to be possible with the C3.js API , I tried to implement the drag event by following this little walkthrough on D3.js Drag Behaviour . However, I didn't understand it well as it is not working when I try it on the graph. Here's a sample of my code : function

How to write event handler in VB.NET?

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I am trying to test out very simple event handling in VB.NET. So far I have: Public Delegate Sub TestEventDelegate() Public Event TestEvent As TestEventDelegate Sub MySub Raise TestEvent End Sub How would you write an event handler for the above event that just displayed a simple MessageBox ? Writing the handler method is simple - just write a Sub which takes no parameters and displays a message box. You then need to subscribe the handler to the event, which you can either do adding a Handles clause to the method: Sub ShowMessageBox() Handles foo.TestEvent Or by using an AddHandler statement: