What is the complete flow of events when touching the screen in Android?
As per my understanding, when user touches the screen:
Touch driver will find the co-ordinates and pass them to kernel
Kernel will pass it to framework
Framework will ask the graphic library to perform zoom and render (after it determines how much to zoom)
How do the drivers, kernel, native libraries, framework and application interact to achieve a desired action? I'd be great to have some light shed on this.
Please take a look at [diagram here]. In nutshell it is system calls and they are handled by OS
Hope this is will help you out
Touch Event Flow in Android
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I want to make a drawing app using Flutter. There is this widget called CustomPaint that allows you to easily have a Canvas and draw on it with you fingers.
Let's say that I want to use a tablet with a dedicated stylus will CustomPaint take into account the pressure sensitivity automatically.
If not, what should I do for my app to support the stylus.
I've been looking around for example apps and the only ones I found don't even mention the possibility of pressure sensitivity or even just plain usage with stylus.
Example apps
https://github.com/vemarav/signature
https://github.com/psuzn/draw-it
For basic input handling you would use the GestureDetector widget.
For low level input detection you can use the Listener widget that has onPointerDown, onPointerMove, onPointerHover and onPointerUp event listeners (and much more), which you can use to get the information of your stylus.
The information you can get from the listeners can be found under the according PointerEvent given by each event listener. One of the information you can get from PointerEvent is the pressure.
You can find a basic introduction to input detection under Taps, drags, and other gestures.
Is it possible to determine if a device (non-rooted) is in use at the moment, even if my app is not in the foreground? Precisely "in use" means the user made touch events in the last 5 seconds or display is on.
If so, what specific rights are required?
Thanks
AFAIK, android security model would not allow you to record touches if your app in not in the foreground.
There are some crude workarounds like overlaying a transparent screen to record touches. Not sure if these work now though.
"in use" means the user made touch events in the last 5 seconds
In Android, that's not practical, short of writing your own custom ROM.
or display is on
In Android, you can find out if the device is in an "interactive" mode or not. This does not strictly align with screen-on/screen-off, as the whole notion of screen-on/screen-off has pretty much fallen by the wayside.
I'm with not much experience in Android development.
I'm considering a big project and before getting deeply into it, I want to check whether my requirements are even possible:
My goal is to manipulate the system by changing the coordinates of a user's touch on the touchscreen. For example: If a user is touching the screen on point (X,Y), I want any opened application to act like the user touched (X+5,Y-3).
I have thought on a few levels that this may be possible to be defined in:
Touch-screen's driver level, OS level, application level (i.e. background application).
A big advantage will be to built it in a way that will allow as much compatibility as possible.
What is the best/right way to do it?
I'm not looking for a full solution, only a hint regarding the best direction to start digging...
Thanks in advance.
Is there any technique to differentiate between finger touch and palm rest on surface while drawing on touch surface in iOS touch based os?
Edit : Added android tag as question is relevant for any touch based os.
Thanks
I can't speak for Android systems, but on iOS I do not believe there is any definitive distinction as all touches, regardless of surface area' are resolved to individual points.
That said, there are ways you could determine whether a specific touch is a palm or finger. If you are making a hand-writing App for instance, if you ask the user whether they are left or right handed then you could ignore all touches to the right/left of the touch that would logically be the finger/stylus. Your method for eliminating the "palm touches" would be specific to the App you are writing.
Something else I have noticed (although I hasten to add this is not particularly reliable!) is that a palm touch will often result in many small touches around the palm area rather than a single touch due to the shape of the palm, small palm movement/rolling, etc. If you know you only ever need to receive and use one touch, this may be something you can manipulate.
In the end, any technique you use to differentiate a palm touch from a finger touch will probably be logical, rather than API/hardware-available. Again, this is iOS specific I am not at all familiar with Android's touch system.
I am looking into developing a new input method on the Android platform that would emulate the touch input of the screen, is it possible to create a service that can interact directly or indirectly with the touch API to achieve this?
Specifics:
The interactions will come in the form of colour tracking from the camera which is processed into x/y coordinates and touch:0/1 events. Is it possible to have these interact with the touchscreen just as if it were a touch on the screen itself?
I understand that there may be permission problems with this approach of 'injection' control or piggybacking?
Also this is a technical exercise for an experimental report rather than a distributable app/piece of software so root/modifications are not a problem.
I have searched to no avail on the subject (at least not on the android platform) and i would like to find out the feasibility/difficulty of the project before undertaking it so any input would be much appreciated!
I'm sort of guessing here, but MotionEvent has some set...-functions like setLocation(float x, float y). There is also MotionEvent.Pointer to play with.