Suppose that my display consists of numbers 1-9 displayed via a 3x3 grid of Buttons, like on num-pad, where one number is placed on each button. I want to be able to detect complex movements, such as the tracing of a Z, which would yield [7 8 9 5 1 2 3] or top-left to bottom-right swipe, which would yield [7 5 3]. I read that I could accomplish this via overriding boolean onTouchEvent(MotionEvent event), but I'm not certain that I understand how this works. From what I can tell from the Android API for MotionEvents, whenever an object is touched on the screen, whether or not one's finger is still tracing or lifting up, it is captured by ACTION_UP. If that is true,
How do I get the history or stack trace, if you will? Can I do this in real time, or do I have to wait for the drag to complete?
How do I actually highlight/ draw the path that their finger/ stylus is tracing (in real time)? I don't want their precise, trace, but rather, I'd like to be able to normalize it via straight-line paths, like Android implements in their pattern-lock system.
Thanks in advance.
Related
I'm working on an android application on tablet to draw every points touched by the finger or the hand. It is very important for the application to track not only the fingers but also the palm (even if it's not drawing the exact touched area but only a thin path, as long as we can see the movement of the palm it's fine). A good example of what I want to do is the "show pointer location" in the Android developer menu : if the drawing could be exactly like this, that would be perfect.
I managed to code a multi-touch drawing app, but the problem I have here is that every time the touched area is too wide (for example when I touch the screen with my entire palm), the application stops drawing (even the fingers drawings stops) and I have this error in the log : [ViewRootImpl] action cancel - 1, eccen:1.4225352 (the number after "eccen" changes depending on the size of my palm touch).
I'm quite new to android, I spent a lot of time searching how I could prevent this action_cancel but I couldn't find anything that makes it work... I tried to prevent the parent views from taking control of the onTouch events, but it didn't work. So if you have any idea of how I can manage that, it would be great :)
Thanks !
(English is not my native language, so don't hesitate to ask me to reformulate is something is not clear)
As a hobby and to learn, whether this is possible, I'm trying to implement a simple first-person shooter for Android. Unfortunately, I ran into a dead end when dealing with mouse event processing.
I already have an onGenericMotion()-Listener, which processes MotionEvent objects generated by the system framework. The problem is, that MotionEvent objects, generated by a mouse merely contain absolute coordinates, which tend to get "stuck", once the cursor reaches an edge or a corner of the screen. So I'm thinking relative mouse coordinates. While I found no feature on MotionEvent that could deliver relative movements, using
adb shell su -- getevent -lt /dev/input/event3
and examining its output revealed that the kernel generates distinct relative motion events when one tries to move the cursor, even when it is stuck in a corner of the screen. So, given that my shooter has su access, I could obtain relative movements.
And now the question: A little bit of Google-fu revealed, that in many first-person shooters, the typical mouse movement is achieved by
using relative mouse coordinates and
by re-positioning the mouse cursor in the center of the screen.
So, the question really is two-folded:
Is it possible to re-position the mouse cursor in the center of the screen on Android? and
If not, can the typical "first-person-shooter" mouse movement be realised by using relative mouse movement information alone?
This is now possible without root permissions, with the pointer capture API in Android 8.0+ (released August 2017). In summary:
To request pointer capture, call the requestPointerCapture() method on the view.
Once the request to capture the pointer is successful, Android calls onPointerCaptureChange(true), and starts delivering the mouse events.
Your focused view can handle the events by performing one of the following tasks:
If you're using a custom view, override onCapturedPointerEvent(MotionEvent).
Otherwise, register an OnCapturedPointerListener.
The view in your app can release the pointer capture by calling releasePointerCapture().
It turns out that this completely answers my question. Never mind then.
One thing I find many Android games and emulators get wrong is when the user presses multiple (on-screen) buttons simultaneously. I'm wondering how one could fix that.
Imagine a game like Super Mario World. You have two buttons on the right side (simplified): Y is for running and B is for jumping. Typically, you hold Y most of the time with the tip of your thumb, and when you want to jump you lay down your thumb and press B, too.
Situations like this understandably confuse Android. Instead of detecting two presses, it just moves the one from the Y button down a bit.
What I'd need to fix this is one of the following:
Raw touch data as a bitmap (but probably too computationally expensive, and doesn't leave the touchscreen anyway)
The detected touch points in more detail, e.g. as best-fit ellipses or polygons
The ability to define touch regions. If a finger overlaps such a region a certain amount, the region fires.
(The points are from low- to high level, e.g. if I had the first I could emulate the other ones.)
Any ideas?
Is it possible to detect every pixel being touched? More specifically, when the user touches the screen, is it possible to track all the x-y coordinates of the cluster of points touched by the user? How can I tell the difference between when users are drawing with their thumb and when they are drawing with the tip of a finger? I would like to reflect the brush difference depending on how users touch the screen, and would also like to track x-y coordinates of all the pixels being touched over time. Thanks so much in advance for any help.
This would be very tricky primarily because every android phone is going to behave differently. There are some touch screen devices that are very, very sensitive and some that are basically "dull" by comparison.
It also sounds more like you are wanting to track pressure - how hard is the user pushing on the screen - which is actually supported on android devices.
I think some of your answer may be found by monitoring all of the touch events - in practice, most applications ignore a great number of events or perform some kind of "smoothing" of the events since there is literally a deluge of touch events when the user is manipulating the screen. Doing this may negatively impact your applications performance though.
I would recommend that you look into pressure sensitivity and calculate a circular region around the primary touch point based on pressure, then build your brush around that.
Another idea would be to incorporate more of a gesture approach to what you are trying to do - for example, visualize touching the screen with the tip of two fingers together (index and middle) and rolling the middle finger around the index finger or simply moving the middle finger up and down in relation to the index finger. Both fingers would be moved together for painting. This could be used to manipulate drawing angle on the fly or perhaps even toggle between a set of pre-selected brushes or could change brush size on the fly as you are painting.
Some of the above ideas I would love to see implemented - let me know when you have your app ready.
Good luck!
Rodney
If you have a listener on your image it will respond that there was a touch within that bounding box, basically.
So, to get what you want, you could, but, I would never do this, create a box around every pixel, or small group of pixels, and listen for a touch.
Wherever you get a touch, it may fire off an event, then you can react accordingly.
I can't think of any other solution that will give you each pixel that a person touched, at one time.
You may want to read up on multitouch though, as there are some suggestions in here that my help you:
http://android-developers.blogspot.com/2010/06/making-sense-of-multitouch.html
If you're looking for a way to get your content view as a View after Activity#setContentView(int), then you can set an id on the outer-most element of your layout:
android:id="#+id/entire_view" and reference it in your onCreate() method after setContentView:
View view = getViewById(R.id.entire_view);
view.setOnTouchListener( ... );
I am recently getting into Android programming and want to make a simple game using 2D canvas drawing. I have checked out the Lunar Lander example and read up on some gestures, but it looks like I can only detect if a gesture occurred. I am looking to do a little more complicated detection on a swipe:
I want to make a simple game where a user can drag their finger through one or more objects on the screen and I want to be able to detect the objects that they went over in their path. They may start going vertically, then horizontally, then vertically again, such that at the end of a contiguous swipe they have selected 4 elements.
1) Are there APIs that expose the functionality of getting the full path of a swipe like this?
2) Since I am drawing on a Canvas, I don't think I will be able to access things like "onMouseOver" for the items in my game. I will have to instead detect if the swipe was within the bounding box of my sprites. Am I thinking about this correctly?
If I have overlooked an obvious post, I apologize. Thank you in advance!
I decided to implement the
public boolean onTouchEvent(MotionEvent event)
handler in my code for my game. Instead of getting the full path, I do a check to see which tile the user is over each time the onTouchEvent fires. I previously thought this event fired only once on the first touch, but it fires as long as you are moving along the surface of the screen, even if you haven't retouched.