I'd like to tell if a certain key is being held down around the startup of my AIR (desktop) application, and I'd like to tell if a specific key (ALT in this case) is being held down. Unfortunately, flex seems to be so event based that there is no way poll the keyboard directly. Can anyone verify this?
I know that it's possible to take the keyboard events and keep track manually. However, this won't work if the user presses the key right before startup, so it isn't a solution for my specific problem.
In my app I track ctrl pressed via listening stage MOUSE_MOVE, MOUSE_DOWN and KEY_DOWN. MouseEvent has ctrlKey and altKey properties. I store state in some static variable . When I longer need this I unsubscribe from these events.
If you listen for key up, then you should hear this if the key was down. So you won't actually know right at startup, but when they release the key. You can unsubscribe from that event at some point that you determine is "after startup."
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My team is developing an UI for an apparatus with touch screen and we would like it to emit a sound (from a buzzer) each time the user correctly presses a button (so using the release event). Notice that I don't want to play the sound after each click on the interface, but only when the click is over a button.
We use many types of button, sometimes QPushButton and most of the times customized buttons derived from QAbstractButton. In most cases these buttons get an objectName.
So I supposed in order to do that, I would have to catch the MouseButtonRelease event and since I'm already working with a subclass of QApplication to handle excetions, I decided to do this in the notify function.
I tried, then, some methods to recognized when the MouseButtonRelease was related to a button but none of them were successfull. The best one, verifying the receiver's objectName was still not good enought not only because not all buttons had an objectName (which, of course, can be handled), but specially because not always the event was caught for buttons with names set. In other words, sometimes I would click in a button and it recognizes the event and sometimes I would click in the same button and the event is not recognized.
I did some research and another method I found was to set an event filter in the MainWindow, but not all widgets have the MainWindow as their parent which means I would have to Ctrl+c / Ctrl+V the same code time after time when I obviously want something more localized (i.e. in only one spot).
So why it happens that the notify not always handles the events? And how could I do this? Any suggestions are appreciated specially one that is less heavier then handling the events globally.
As info, the other two ways I tried to catch the events with similar or even worst results inside notify were with receiver->inherits("...") and qobject_cast< QAbstractButton* >(receiver).
From what I see, QApplication::mouseButtons() may return no buttons even when a button is held down. This happens when you have clicked a side of a window for re-sizing. It's coherent with the docs because mouseButtons() reflects the state from the flow of QEvent::mouseButtonPress, etc. However, I need just to know if the button is held down. Does any one know if it's possible through the Qt API?
I think it's not possible. Mouse events outside an application's window are not passed to its event handlers. Dragging mouse borders is one of such events, it's processed by the window system. Another example is clicking on other windows. Usually an application doesn't know what the user does with other windows. You need to install system-wide event listener or use native API features(e.g. GetAsyncKeyState on Windows) to determine that. This behavior is unusual and possibly dangerous. In most cases it's not useful, and it seems that Qt doesn't have this ability.
I'd like to create a semi-transparent information window that doesn't get in the way of the user's other activities. Any clicks on the window should just pass through as if the window wasn't there.
How would you recommend implementing such behavior? Is there an easy way to do it or do I have to follow a clumsy workaround? I'm thinking of hiding the window, re-executing the click, then making the window visible again. But this would still screw up drag'n'drop gestures.
Take a look at an enum value of Qt::WidgetAttribute: Qt::WA_TransparentForMouseEvents:
When enabled, this attribute disables the delivery of mouse events to
the widget and its children. Mouse events are delivered to other
widgets as if the widget and its children were not present in the
widget hierarchy; mouse clicks and other events effectively "pass
through" them. This attribute is disabled by default.
I did a little more research into "mouse event transparency" (didn't know the exact terminology) and I found this.
I don't think there is a general and easy approach to your problem. You will probably have to dig into the native API. Once events reach an application they are not forwarded to other applications on their own.
What do you guys think? Am I doomed to work with the native APIs of each OS?
Looking through the documentation, it seems that the new advanced gestures API doesn't determine the direction of a swipe beyond the basic { left, right, up, down }.
I need the start point of the swipe and the direction.
Is there anyway to retrieve this other than coding my own advanced gesture library from scratch out the basic gestures?
And if this is my only option, could anyone point me to some open source code that does this?
Got it! Documentation is here, under 'Creating Custom Gesture Recognizers' at the bottom.
Basically the six gestures Apple provides all derive from UIGestureRecognizer, and you can make your own gesture recogniser in the same way.
then, inside your view's init, you hook up your recogniser. and just the act of hooking it up automatically reroutes incoming touch events.
Actually, the default behaviour is to make your recogniser an Observer of these events. Which means your view gets them as it used to, and in addition if your recogniser spots a gesture it will trigger your myCustomEventHandler method inside your view (you passed its selector when you hooked up your recogniser).
But sometimes you want to prevent the original touch events from reaching the view, and you can fiddle around in your recogniser to do that. so it's a bit misleading to think of it as an ' observer '.
There is one other scenario, where one gesture needs to eat another. Like you can't just send back a single click if your view is also primed to receive double clicks. You have to wait for the double-click recogniser to report failure. and if it is successful, you need to fail the single click -- obviously you don't want to send both back!
One of our application is implemented in flex and adobe air. We want to have the user press combination of keys, say 'ABC', and have the keyboard return a different character, 'FOG', to whatever app is in focus. This should work even if app has no focus.
Will it possible in Adobe Air/Flex? If yes, provide me some examples?
Thanks in advance
That won't work. Flash/AIR can only listen to keyboard events when it has focus, so as a background application it won't be able to manipulate the key codes that come directly from the driver.
Even if it was possible to notice when a key was pressed, it is not possible to change that value. So if you want to change which key codes are returned, you should rather write a driver for it, or try to get access to it with a lower level approach (C & WinAPI maybe).