event-handling | 易学教程

How to override event handler function of child component from parent component in react.js

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问题 /** @jsx React.DOM */ var Button = React.createClass({ handleClick: function(){ console.log(' FROM BUTTON') }, render: function() { return <input type='button' onClick={this.handleClick} value={this.props.dname}/>; } }); var Text = React.createClass({ render: function() { return <input type='text' onClick={this.handleClick} value={this.props.ival}/>; } }); var search = React.createClass({ handleClick: function() { console.log('searching') }, render: function(){ return ( <div> <Text/> <Button

How are async void event handlers called in C#?

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问题 If I declare my event handlers as async void , will they be called synchronously or asynchronously by the .NET framework? I.e., given the following code: async void myButton_click(object sender, EventArgs e) { do stuff await longRunning() do more stuff } Can I be sure that the "do stuff" line will be executed on the GUI thread? 回答1: Event handlers will be called synchronously and doesn't wait(await) till the event handler completes, but waits till the event handler returns. If previous

How to Add Event Handler with Arguments to an Array of Elements in Javascript?

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问题 I have a three-step process that is entirely reliant upon JavaScript and Ajax to load data and animate the process from one step to the next. To further complicate matters, the transition (forward and backward) between steps is animated :-(. As user's progress through the process anchor's appear showing the current step and previous steps. If they click on a previous step, then it takes them back to the previous step. Right now, the entire process (forward and backward) works correctly, if

javascript internals: how events are implemented?

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问题 My question is related to how the JS engines implement the pattern of asynchronous events when we do something like bind event handlers on a dom for lets say a click event.? Do they have something like a separate thread that is listening to all the click events ? When an event does occur , do they refer the bind list and bubble up the events ? Similar is with Ajax,the asynchronous network call, where the browser spans a new thread that would start listening to the data from the server and

knockoutjs: prevent event bubbling for elements with no handler

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问题 It seems like the binding <event>Bubble: false only works when there's a defined event handler ( see Note 4 ) for <event> . Here's an example fiddle. For elements having native handlers for certain events (e.g. click: <textarea> , <a> , <select> , etc.), where the native handler suffices, I would expect setting the binding, e.g., clickBubble: false on them, without having to bind a "bogus" handler, to work. I guess my question is, is there another knockout way to achieve this without extra

Detach event handler after attaching method with passed parameter

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I need to pass a parameter (in C#) to an event handler and then be able to detach the event handler. I attach the event handler and pass the parameter: _map.MouseLeftButtonUp += (sender, e) => _map_MouseLeftButtonUp2(sender, e, showResultsWindow); The event is called as expected. I try to detach the event handler: _map.MouseLeftButtonUp -= (sender, e) => _map_MouseLeftButtonUp2(sender, e, showResultsWindow); The code executes without error, but does not seem to detach. If I attach the event handler the more conventional way (without passing a parameter): _map.MouseLeftButtonUp+=_map

ListView long click not working when a button is in list

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问题 I have a ListView with custom list adapter. It has OnItemClickListener and OnItemLongClickListner which used to work fine. After then, I had to put a button in the layout of list item and the item click and long click listener stopped working. Here is my sample code: ListView lv=(ListView)findViewbyId(R.id.listview); lv.setAdapter(listviewadapter); lv.setOnItemLongClickListener(new OnItemLongClickListener() { @Override public boolean onItemLongClick(AdapterView<?> parent, View view,int

matplotlib multiple connections to an event handler?

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问题 import sys import matplotlib import matplotlib.pyplot as plt print matplotlib.__version__, matplotlib.get_backend() def hit(event): sys.stderr.write('hit\n') fig = plt.figure() cid0 = fig.canvas.mpl_connect('key_press_event', hit) cid1 = fig.canvas.mpl_connect('button_press_event', hit) print cid0, cid1 plt.show() With the code above, why can't I have both mouse press event and key press events firing hit? It seems in the order above only the key press events work, whereas if I swap the lines

Check if a Key is Down with Qt

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问题 I am playing around with some graphics, and I have implemented simple camera movement with the arrow keys. My first approach was to override keyPressEvent to do something like this: switch(key) { case up: MoveCameraForward(step); break; case left: MoveCameraLeft(step); break; ... } This doesn't work as I wish it would. When I press and hold, for example, the forward key, the camera moves forward "step" units, then halts for a while and then continues moving. I am guessing that this is how the

Is there a way to find the event handlers of an element with Javascript?

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问题 Say you have this div: <div id="foo">bar</div> And you do this: $("#foo").click(someFunction); somewhere inside your javascript code. Once the page has been loaded, is there a way to find out, via firebug or inspect element in chrome, or anything else, that the click event for #foo is bound to someFunction ? I.e, find this out without having to look through all your code? 回答1: Chrome Developer tools does this. right click an element click inspect element in the right hand column, scroll down