[android-beginners] Re: How to (properly) get device orientation data?
On Jun 17, 11:56 am, lawrizy lawr...@gmail.com wrote: Hi, I wanna thank you very much for your explanation. The official documentation was very difficult to understand. And the example in the api sample (the compass) does use a depreciated methods (with sensorlistener). Nice, I'm glad it's been useful. Just remember, this is definitely not definitive. I don't understand what does remapCoordinateSystem and his parameters, could you help? Hmm, not sure where is the difficulty, but in my example it demonstrates remapping to camera's line of view (Y axis along the camera's axis instead of the device length) as used in augmented reality applications. I think that on this one the documentation is pretty extensive try looking it up again at: http://developer.android.com/reference/android/hardware/SensorManager.html#remapCoordinateSystem(float[],%20int,%20int,%20float[]) For what it worth, Rick Deckard. -- You received this message because you are subscribed to the Google Groups Android Beginners group. NEW! Try asking and tagging your question on Stack Overflow at http://stackoverflow.com/questions/tagged/android To unsubscribe from this group, send email to android-beginners+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/android-beginners?hl=en
[android-beginners] Re: How to (properly) get device orientation data?
Thank you for your answer. I will try on a device. On 22 juin, 11:17, repDetect() n6mba50...@gmail.com wrote: On Jun 17, 11:56 am, lawrizy lawr...@gmail.com wrote: Hi, I wanna thank you very much for your explanation. The official documentation was very difficult to understand. And the example in the api sample (the compass) does use a depreciated methods (with sensorlistener). Nice, I'm glad it's been useful. Just remember, this is definitely not definitive. I don't understand what does remapCoordinateSystem and his parameters, could you help? Hmm, not sure where is the difficulty, but in my example it demonstrates remapping to camera's line of view (Y axis along the camera's axis instead of the device length) as used in augmented reality applications. I think that on this one the documentation is pretty extensive try looking it up again at:http://developer.android.com/reference/android/hardware/SensorManager...[],%20int,%20int,%20float[]) For what it worth, Rick Deckard. -- You received this message because you are subscribed to the Google Groups Android Beginners group. NEW! Try asking and tagging your question on Stack Overflow at http://stackoverflow.com/questions/tagged/android To unsubscribe from this group, send email to android-beginners+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/android-beginners?hl=en
[android-beginners] Re: How to (properly) get device orientation data?
Hi,
Thanks for the explanation. It was very useful. I am trying to get 2
variables to store the lat/lon. Can we do that continuously? As in
have 3 variables. One each for current azimuth, Lat and lon. What
changes would we need to make in the code you provided here?
implementing LocationListener along with the this listener should do I
guess? But I tried and am unable to get both location and orientation
at the 'same time'.
thanks
Ricky
On Jun 17, 9:56 am, lawrizy lawr...@gmail.com wrote:
Hi,
I wanna thank you very much for your explanation. The official
documentation was very difficult to understand. And the example in the
api sample (the compass) does use a depreciated methods (with
sensorlistener).
I don't understand what does remapCoordinateSystem and his parameters,
could you help?
Thank you.
On 16 juin, 06:28, repDetect() n6mba50...@gmail.com wrote:
Hi,
While trying to retrieve orientation data I found some pretty straight
forward code making use of SensorEventListener for
Sensor.TYPE_ORIENTATION and it works fine, but the
Sensor.TYPE_ORIENTATION constant has been deprecated recently - I
believe it was on 8 (API level) - which I understand to mean that
while I can still use it, I shouldn't.
The documentation [1] only says use SensorManager.getOrientation()
instead. [2] but as a newbie, I had difficulties following that
detailed instruction.
So the question is:
How to properly get device orientation data?
In an attempt to make this discussion constructive, here is what I
managed to figure out, hopefully it will attract corrections relevant
to my limitations and not just general pointers to material I already
read (and misunderstood) and perhaps also benefit other newbies
struggling with this task.
So please fix any misconceptions or errors you find below.
The most important thing to realize is that
SensorManager.getOrientation() doesn't get the orientation from the
sensors (as with SensorEvent for Sensor.TYPE_ORIENTATION), it merely
Computes the device's orientation based on the rotation matrix which
you must provide as the first parameter.
In a similar fashion SensorManager.getRotationMatrix() doesn't read
sensors data to produce the rotation matrix, it depends on you to
provide the data through the third and forth arguments (gravity,
geomagnetic), also note that the values of these arguments must be
within expected limits or the method will fail. This holds in
particular for the case where these are initialized to zeros, as this
will imply free fall for gravity and something even more disturbing
for geomagnetic.
Don't take my word on it look it up for yourself in the source [3],
for the Java end at list.
Once that was digested it appears the only way to get sensor data is
through registering a sensor event listener (I thought it would be
really nice if I could query the sensors's readings at will and that
what I naively assumed was done by the get methods in SensorManager,
could anyone comment why this is not made available?), then that data
may be used to calculate the orientation as outlined below:
1) Retrieve sensor data from accelerometer and magnetic field sensor
as required by getRotationMatrix():
This actually involves a number of steps in the Activity class:
1.1) Obtain a sensor manager.
NOTE: Context.getSystemService needs a Context, typically called
within an Activity's context.
mSensMan = (SensorManager) getSystemService(SENSOR_SERVICE);
1.2) Register a sensor event listener for each of the above sensor
types.
mSensMan.registerListener(this,
mSensMan.getDefaultSensor(Sensor.TYPE_MAGNETIC_FIELD),
SensorManager.SENSOR_DELAY_UI);
mSensMan.registerListener(this,
mSensMan.getDefaultSensor(Sensor.TYPE_ACCELEROMETER),
SensorManager.SENSOR_DELAY_UI);
1.3) In the listener's onSensorChanged method copy the data from the
SensorEvent.values.
NOTE: The data must be copied off the event.values as the system is
reusing that array in all SensorEvents, simply assigning won't work.
public void onSensorChanged(SensorEvent event) {
switch (event.sensor.getType()) {
case Sensor.TYPE_ACCELEROMETER:
System.arraycopy(event.values, 0, mGravs, 0, 3);
break;
case Sensor.TYPE_MAGNETIC_FIELD:
System.arraycopy(event.values, 0, mGeoMags, 0, 3);
break;
default:
return;
}
}
2) Pass the copied sensor data as arrays to
SensorManager.getRotationMatrix() to receive the rotation matrix.
SensorManager.getRotationMatrix(mRotationM, null, mGravs, mGeoMags)
Optionally transform the returned rotation matrix through
SensorManager.remapCoordinateSystem() or
[android-beginners] Re: How to (properly) get device orientation data?
Hi,
I wanna thank you very much for your explanation. The official
documentation was very difficult to understand. And the example in the
api sample (the compass) does use a depreciated methods (with
sensorlistener).
I don't understand what does remapCoordinateSystem and his parameters,
could you help?
Thank you.
On 16 juin, 06:28, repDetect() n6mba50...@gmail.com wrote:
Hi,
While trying to retrieve orientation data I found some pretty straight
forward code making use of SensorEventListener for
Sensor.TYPE_ORIENTATION and it works fine, but the
Sensor.TYPE_ORIENTATION constant has been deprecated recently - I
believe it was on 8 (API level) - which I understand to mean that
while I can still use it, I shouldn't.
The documentation [1] only says use SensorManager.getOrientation()
instead. [2] but as a newbie, I had difficulties following that
detailed instruction.
So the question is:
How to properly get device orientation data?
In an attempt to make this discussion constructive, here is what I
managed to figure out, hopefully it will attract corrections relevant
to my limitations and not just general pointers to material I already
read (and misunderstood) and perhaps also benefit other newbies
struggling with this task.
So please fix any misconceptions or errors you find below.
The most important thing to realize is that
SensorManager.getOrientation() doesn't get the orientation from the
sensors (as with SensorEvent for Sensor.TYPE_ORIENTATION), it merely
Computes the device's orientation based on the rotation matrix which
you must provide as the first parameter.
In a similar fashion SensorManager.getRotationMatrix() doesn't read
sensors data to produce the rotation matrix, it depends on you to
provide the data through the third and forth arguments (gravity,
geomagnetic), also note that the values of these arguments must be
within expected limits or the method will fail. This holds in
particular for the case where these are initialized to zeros, as this
will imply free fall for gravity and something even more disturbing
for geomagnetic.
Don't take my word on it look it up for yourself in the source [3],
for the Java end at list.
Once that was digested it appears the only way to get sensor data is
through registering a sensor event listener (I thought it would be
really nice if I could query the sensors's readings at will and that
what I naively assumed was done by the get methods in SensorManager,
could anyone comment why this is not made available?), then that data
may be used to calculate the orientation as outlined below:
1) Retrieve sensor data from accelerometer and magnetic field sensor
as required by getRotationMatrix():
This actually involves a number of steps in the Activity class:
1.1) Obtain a sensor manager.
NOTE: Context.getSystemService needs a Context, typically called
within an Activity's context.
mSensMan = (SensorManager) getSystemService(SENSOR_SERVICE);
1.2) Register a sensor event listener for each of the above sensor
types.
mSensMan.registerListener(this,
mSensMan.getDefaultSensor(Sensor.TYPE_MAGNETIC_FIELD),
SensorManager.SENSOR_DELAY_UI);
mSensMan.registerListener(this,
mSensMan.getDefaultSensor(Sensor.TYPE_ACCELEROMETER),
SensorManager.SENSOR_DELAY_UI);
1.3) In the listener's onSensorChanged method copy the data from the
SensorEvent.values.
NOTE: The data must be copied off the event.values as the system is
reusing that array in all SensorEvents, simply assigning won't work.
public void onSensorChanged(SensorEvent event) {
switch (event.sensor.getType()) {
case Sensor.TYPE_ACCELEROMETER:
System.arraycopy(event.values, 0, mGravs, 0, 3);
break;
case Sensor.TYPE_MAGNETIC_FIELD:
System.arraycopy(event.values, 0, mGeoMags, 0, 3);
break;
default:
return;
}
}
2) Pass the copied sensor data as arrays to
SensorManager.getRotationMatrix() to receive the rotation matrix.
SensorManager.getRotationMatrix(mRotationM, null, mGravs, mGeoMags)
Optionally transform the returned rotation matrix through
SensorManager.remapCoordinateSystem() or multiplying by a
transformation matrix.
3) Pass the rotation matrix to SensorManager.getOrientation() to
receive the orientation as yaw, pitch and roll expressed in radians.
SensorManager.getOrientation(mRotationM, mOrientation);
Voila.
Below the relevant code is wrapped with a complete Activity to allow
for testing and to get the whole picture, once again - corrections and
remarks are requested - the TODO: tags would also indicate areas where
knowledge is lacking.
Please handle with care, this newbie is still a little wet and
slippery!
