I am working on an Android app wherein I want to scroll a large image horizontally. I used the accelerometer (Sensor.TYPE_ACCELEROMETER) and magnetic field (Sensor.TYPE_MAGNETIC_FIELD) data to get the angle of rotation. This data being to frequent infested with noise I am not able to implement a smooth motion effect.
#Override
public void onSensorChanged(SensorEvent event) {
switch (event.sensor.getType()) {
case Sensor.TYPE_MAGNETIC_FIELD:
mags = event.values.clone();
break;
case Sensor.TYPE_ACCELEROMETER:
accels = event.values.clone();
break;
}
if (mags != null && accels != null) {
gravity = new float[16];
boolean success = SensorManager.getRotationMatrix(gravity, null, accels, mags);
if (success) {
float[] outGravity = new float[16];
SensorManager.remapCoordinateSystem(gravity, SensorManager.AXIS_X, SensorManager.AXIS_Z, outGravity);
SensorManager.getOrientation(outGravity, values);
rollingAverage[0] = roll(rollingAverage[0], values[0]);
rollingAverage[1] = roll(rollingAverage[1], values[1]);
rollingAverage[2] = roll(rollingAverage[2], values[2]);
azimuth = Math.toDegrees(values[0]);
pitch = Math.toDegrees(values[1]);
roll = Math.toDegrees(values[2]);
mags = null;
accels = null;
double diffRoll = lastRoll - roll;
double diffPitch = lastPitch - pitch;
long curTime = System.currentTimeMillis();
if (Math.abs(diffRoll) >= 2) {
if (diffRoll > 0)
imageView.panLeft();
else
imageView.panRight();
lastRoll = roll;
}
}
}
}
Any ideas on achieving this using other methods?
You have to implement sensor fusion techniques based on Kalman filter or other filters. You can use open source libraries if needed. Refer this bitbucket repository. If you want to do yourself, read the tutorial.
Related
I'm building an augmented reality app with POI.
Most of the app is done but now I am trying to find a better stabilization of my sensors, in particular the Accelerometer. I have used low pass filter, but POI are still bouncing to much. The thing I was trying to do is get 5 or more readings of accelerometer and then divide it by n. That should give me better readings but i have no idea how to make it. I can make a for loop but I can't just make for(int i=0; i<n; i++) , because i++ should be done only when the value of accelerometer has changed. If I do it with a simple for loop, I will get an error because the loop is done faster then the sensors are changed. The thing i was looking for is a timer that will changed only when the sensors are changed too.
This is what i have done so far:
static final float ALPHA = 0.15f; // if ALPHA = 1 OR 0, no filter applies.
// low level pass filter, so i can get steadier reading of mobile sensors
// using only accelerometer and compass
protected float[] lowPass(float[] input, float[] output) {
if (output == null) return input;
for (int i = 0; i < input.length; i++) {
output[i] = output[i] + ALPHA * (input[i] - output[i]);
// output[i] = input[i]*ALPHA + output[i]*(1.0f-ALPHA);
}
return output;
}
public void onSensorChanged(SensorEvent event) {
StringBuilder msg = new StringBuilder(event.sensor.getName())
.append(" ");
for (float value : event.values) {
msg.append("[").append(String.format("%.3f", value)).append("]");
}
switch (event.sensor.getType()) {
case Sensor.TYPE_ACCELEROMETER:
lastAccelerometer = lowPass(event.values.clone(), lastAccelerometer);
accelData = msg.toString();
break;
case Sensor.TYPE_GYROSCOPE:
gyroData = msg.toString();
break;
case Sensor.TYPE_MAGNETIC_FIELD:
lastCompass = lowPass(event.values.clone(), lastCompass);
compassData = msg.toString();
break;
}
this.invalidate();
}
I found the solution :
protected float[] getMovingAvg() {
float [] output = new float [3];
for( int i = 0; i< moveVector.size(); i++) {
output[0] += moveVector.get(i)[0];
output[1] += moveVector.get(i)[1];
output[2] += moveVector.get(i)[2];
}
output[0] = output[0]/moveVector.size();
output[1] = output[1]/moveVector.size();
output[2] = output[2]/moveVector.size();
if(moveVector.size() >= 70) {
moveVector.remove(0);
}
return output;
}
For an application I'm making, I need to have a camera and a compass. The application is set to be at landscape mode in the manifest.
First I've implemented the compass. As suggested in Android Developers, I used two sensors - Accelerometer and Magnetic Field. This is how I've done it:
I have my activity implement SensorEventListener. In onCreate() I initialize my sensorManager using:
sManager = (SensorManager) getSystemService(SENSOR_SERVICE);
I register my listeners in onResume() like so:
sManager.registerListener(this, sManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER),SensorManager.SENSOR_DELAY_NORMAL);
sManager.registerListener(this, sManager.getDefaultSensor(Sensor.TYPE_MAGNETIC_FIELD),SensorManager.SENSOR_DELAY_NORMAL);
and of course unregister them in onPause().
I don't use onAccuracyChanged(). this is what I do in onSensorChanged():
#Override
public void onSensorChanged(SensorEvent event) {
switch (event.sensor.getType()) {
case Sensor.TYPE_MAGNETIC_FIELD:
mags = event.values.clone();
break;
case Sensor.TYPE_ACCELEROMETER:
accels = event.values.clone();
break;
}
if (mags != null && accels != null) {
gravity = new float[9];
magnetic = new float[9];
SensorManager.getRotationMatrix(gravity, magnetic, accels, mags);
float[] outGravity = new float[9];
float inclination = (float) Math.acos(gravity[8]);
if (inclination < Math.toRadians(25)
|| inclination > Math.toRadians(155)) {
// device is close to flat. Remap for landscape.
SensorManager.remapCoordinateSystem(gravity, SensorManager.AXIS_Y,SensorManager.AXIS_MINUS_X, outGravity);
SensorManager.getOrientation(outGravity, values);
} else {
// device is not flat. Remap for landscape and perpendicular
SensorManager.remapCoordinateSystem(gravity, SensorManager.AXIS_X,SensorManager.AXIS_Z, outGravity);
SensorManager.getOrientation(outGravity, values);
}
azimuth = Math.round(Math.toDegrees(values[0]));
}
}
As you can see, I differentiate between when the phone is lying flat on the table, and when the user holds it (as you would when taking a picture). When I use this code alone, everything works great more or less. I'm getting correct azimuth values both when phone is lying on the table and when holding it perpendicular to the table (about 5-10 degrees difference, but I can live with that).
The problem starts when adding the camera preview to the application.
I have my activity implement SurfaceHolder.Callback. I initialize my camera in onCreate():
SurfaceView cameraView = (SurfaceView)findViewById(R.id.camera_view);
surfaceHolder = cameraView.getHolder();
surfaceHolder.addCallback(this);
if (Build.VERSION.SDK_INT < Build.VERSION_CODES.HONEYCOMB) {
surfaceHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
}
This is how I implement the interface:
#Override
public void surfaceCreated(SurfaceHolder surfaceHolder) {
camera = Camera.open();
camera.setDisplayOrientation(0);
}
#Override
public void surfaceChanged(SurfaceHolder surfaceHolder, int i, int i1, int i2) {
if (isCameraOn) {
camera.stopPreview();
isCameraOn = false;
}
if (camera != null) {
try {
camera.setPreviewDisplay(surfaceHolder);
camera.startPreview();
isCameraOn = true;
} catch (IOException e) {
e.printStackTrace();
}
}
}
#Override
public void surfaceDestroyed(SurfaceHolder surfaceHolder) {
camera.stopPreview();
camera.release();
camera = null;
}
When I add the camera code to my project, and show the camera on the phone's screen, my sensors dont work properly when phone is perpendicular suddenly. If phone is lying flat on the table, the azimuth values I'm getting are correct. When phone is being held perpendicular to the table, my azimuth values are off by about 40 degrees (though stable).
I've tried looking for a solution (both by myself and online), but so far my efforts were in vain. I would love to get some direction on how to tackle this problem.Thanks!
First TYPE_MAGNETIC_FIELD sensor will not available in all devices.
You can use TYPE_ACCELEROMETER sensor alone to accomplish your requirement.
Retrieve accelerometer sensor
Sensor accelerometer = mSensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);
Just compare and copy values when sensor change event call
#Override
public void onSensorChanged(SensorEvent event) {
if (event.sensor.getType() == Sensor.TYPE_ACCELEROMETER)
mGravity = event.values;
}
Then you can use below function to get sensor values of all axis.
public int[] getDeviceAngles() {
float[] g = mGravity.clone();
double normOfG = Math.sqrt(g[0] * g[0] + g[1] * g[1] + g[2] * g[2]);
// Normalize the accelerometer vector
g[0] = (float) (g[0] / normOfG);
g[1] = (float) (g[1] / normOfG);
g[2] = (float) (g[2] / normOfG);
int x = (int) Math.round(Math.toDegrees(Math.atan2(g[1], g[0])));
int pitch = (int) Math.round(Math.toDegrees(Math.atan2(g[1], g[2])));
int rollValue = (int) Math.round(Math.toDegrees(Math.atan2(g[2], g[0])));
int pitchValue = pitch * -1;
int[] values = new int[3];
values[0] = x;
values[1] = pitchValue;
values[2] = rollValue;
//values contains: azimut, pitch and roll
return values;
}
My app is locked into portrait orientation only, however in one fragment I have a camera preview where I would like to rotate captured images based on the device orientation. I believe that because my app is portrait only, the following code always logs zero.
Display display = ((WindowManager)getActivity().getSystemService(Context.WINDOW_SERVICE)).getDefaultDisplay();
int rotation = display.getRotation();
Log.i(TAG, "Rotation: " + rotation );
Is it possible to get the actual orientation of the device while locking the app to portrait?
I am targeting android 4.0+ so I'm not concerned if the solution won't work on older devices.
you could implement a SensorEventListener, then look at the Roll in onSensorChanged:
#Override
public void onSensorChanged(SensorEvent event) {
synchronized(this)
{
if (event.sensor.getType() == Sensor.TYPE_ACCELEROMETER) {
mAccelerometerValues = event.values;
}
if (event.sensor.getType() == Sensor.TYPE_MAGNETIC_FIELD) {
mGeomageneticValues = event.values;
}
if ((mAccelerometerValues != null) && (mGeomageneticValues != null))
{
boolean success = SensorManager.getRotationMatrix(R, I, mAccelerometerValues, mGeomageneticValues);
if (success)
{
SensorManager.remapCoordinateSystem(R, SensorManager.AXIS_X, SensorManager.AXIS_Z, outR);
SensorManager.getOrientation(outR,orientation);
mYaw = orientation[0] * MathX.toDegreesF;
mPitch = orientation[1] * MathX.toDegreesF;
mRoll = orientation[2] * MathX.toDegreesF;
String sText = String.format("a:%1.4f\np:%1.4f\nr:%1.4f", yaw,pitch,roll);
}
}
}
}
In my 2d game I have the following code which is responsible for game entity control (flying plane). It all seems to be working fine when it comes for phones, but unfortunately I've getting some information that on Android tablets the steering is completely unreliable (axis are messed up, or it doesn't work at all). Unfortunately I don't have a tablet of my own, so I cannot investigate it closer. So.. what's wrong with the following code? (for the clarity I put only the code related to sensors)
// ...
private float[] accelerometerValues;
private float[] magneticFieldValues;
private float[] R;
private float[] I;
private float[] outR;
private float[] sensorValues;
private Sensor accelerometer;
private Sensor magneticField;
// ...
// ... sensor initialization
sensorManager = (SensorManager)activity.getSystemService(Context.SENSOR_SERVICE);
if(sensorManager == null)
return;
accelerometer = sensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);
magneticField = sensorManager.getDefaultSensor(Sensor.TYPE_MAGNETIC_FIELD);
// ...
// ... onPause() sensor is being unregistered
public void onResume() {
if(!sensorManager.registerListener(sensorListener, accelerometer, SensorManager.SENSOR_DELAY_GAME) ||
!sensorManager.registerListener(sensorListener, magneticField, SensorManager.SENSOR_DELAY_GAME))
// ...
// ...
sensorListener = new SensorEventListener() {
public void onAccuracyChanged(Sensor arg0, int arg1) {
}
public void onSensorChanged(android.hardware.SensorEvent event) {
synchronized(InputMgr.this) {
switch(event.sensor.getType()) {
case Sensor.TYPE_ACCELEROMETER:
System.arraycopy(event.values, 0, accelerometerValues, 0, 3);
break;
case Sensor.TYPE_MAGNETIC_FIELD:
System.arraycopy(event.values, 0, magneticFieldValues, 0, 3);
break;
}
}
}
};
// ...
// used somewhere in the game
public void getSensorValues(float values[]) {
synchronized(InputMgr.this) {
SensorManager.getRotationMatrix(R, I, accelerometerValues, magneticFieldValues);
SensorManager.remapCoordinateSystem(R, SensorManager.AXIS_Y, SensorManager.AXIS_X, outR);
SensorManager.getOrientation(outR, sensorValues);
System.arraycopy(sensorValues, 0, values, 0, sensorValues.length);
}
}
This wont cheer you up much but I have a similar problem. I can see a TYPE_MAGNETIC_FIELD sensor, I can add a an event listener to it but I never get any data from it. Other sensors work fine. This is on a Galaxy Tab 7.
onSensorChanged(SensorEvent event) never fires a case Sensor.TYPE_MAGNETIC_FIELD:
As such I get no data from the Magnetic Field Sensor.
if you solve it let us know =)
On devices whose default orientation is landscape (-> most tablets), the sensor values are kind of 'wrong' (I don't know why). So you need to catch those devices and remap your Rotation Matrix.
To check whether the matrix needs to be remapped, you can use this code:
public boolean needToRemapOrientationMatrix;
// compute once (e.g. in onCreate() of your Activity):
Display display = ((WindowManager)getSystemService(Context.WINDOW_SERVICE)).getDefaultDisplay();
int orientation;
if(display.getWidth() < display.getHeight()) orientation = Configuration.ORIENTATION_PORTRAIT;
else if(display.getWidth() > display.getHeight()) orientation = Configuration.ORIENTATION_LANDSCAPE;
else orientation = Configuration.ORIENTATION_SQUARE;
int rotation = display.getRotation();
needToRemapOrientationMatrix =
(orientation==Configuration.ORIENTATION_LANDSCAPE && (rotation==Surface.ROTATION_0 || rotation==Surface.ROTATION_180)) ||
(orientation==Configuration.ORIENTATION_PORTRAIT && (rotation==Surface.ROTATION_90 || rotation==Surface.ROTATION_270));
And when you read the sensor values, remap the matrix if needed:
public void getSensorValues(float values[]) {
synchronized(InputMgr.this) {
SensorManager.getRotationMatrix(R, I, accelerometerValues, magneticFieldValues);
if(needToRemapOrientationMatrix)
SensorManager.remapCoordinateSystem(R, SensorManager.AXIS_MINUS_Y, SensorManager.AXIS_X, R);
SensorManager.remapCoordinateSystem(R, SensorManager.AXIS_Y, SensorManager.AXIS_X, outR);
SensorManager.getOrientation(outR, sensorValues);
System.arraycopy(sensorValues, 0, values, 0, sensorValues.length);
}
}
This worked for me, I hope it helps.
I'm getting my phone orientation with help of
SensorManager.getOrientation
but the results are very unstable, something like +-8 degrees, is there some good way fo filtering the results?
this is how I get the values:
public void onSensorChanged(SensorEvent event)
{
switch (event.sensor.getType ()){
case Sensor.TYPE_ACCELEROMETER:
aValues = event.values.clone();
break;
case Sensor.TYPE_MAGNETIC_FIELD:
mValues = event.values.clone();
break;
}
float[] R = new float[16];
float[] orientationValues = new float[3];
if( aValues == null || mValues == null )
return;
if( !SensorManager.getRotationMatrix (R, null, aValues, mValues) )
return;
float[] outR = new float[16];
SensorManager.remapCoordinateSystem(R, SensorManager.AXIS_Z, SensorManager.AXIS_MINUS_X, outR);
SensorManager.getOrientation (outR, orientationValues);
orientationValues[0] = (float)Math.toDegrees (orientationValues[0]);
orientationValues[1] = (float)Math.toDegrees (orientationValues[1]);
orientationValues[2] = (float)Math.toDegrees (orientationValues[2]);
}
Just buffer the values by calculating the average (there are many different calculation possibilities: http://en.wikipedia.org/wiki/Average#Types ). Also consider that the more you buffer the slower the app will react to changes!