Develop Reference

FusedLocationProviderClient doesn't have bearing data

I'm using FusedLocationProviderClient class in android to get user's last location. Everything is fine and I can get latitude and longitude but task.getResult().getBearing() returns 0.0 and task.getResult().hasBearing() returns false. How can I get user's bearing information?
I'm getting ACCESS_FINE_LOCATION and ACCESS_COARSE_LOCATION permissions both in AndroidManifest file and at runtime.
This is the piece of code related to user location I'm using:
#SuppressLint("MissingPermission")
private void getLastLocation() {
fusedLocationClient
.getLastLocation()
.addOnCompleteListener(this, new OnCompleteListener<Location>() {
#Override
public void onComplete(#NonNull Task<Location> task) {
if (task.isSuccessful() && task.getResult() != null) {
onLocationChange(task.getResult());
Log.i(TAG, "lat " + task.getResult().getLatitude() + " lng " + task.getResult().getLongitude());
Log.i(TAG, "bearing? " + task.getResult().hasBearing());
} else {
Toast.makeText(MainActivity.this, "Location Not Found!", Toast.LENGTH_SHORT).show();
}
}
});
}
private void onLocationChange(Location location) {
//do something
}

According to documentation
If this location does not have a bearing then 0.0 is returned.

I solved my problem using accelerometer and magnetic field sensors. This is the Compass class I use to get bearing of my cell phone:
import android.content.Context;
import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorManager;
public class Compass implements SensorEventListener {
private static final String TAG = "Compass";
public interface CompassListener {
void onNewAzimuth(float azimuth);
}
private CompassListener listener;
private SensorManager sensorManager;
private Sensor gsensor;
private Sensor msensor;
private float[] mGravity = new float[3];
private float[] mGeomagnetic = new float[3];
private float[] R = new float[9];
private float[] I = new float[9];
private float azimuth;
private float azimuthFix;
public Compass(Context context) {
sensorManager = (SensorManager) context
.getSystemService(Context.SENSOR_SERVICE);
gsensor = sensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);
msensor = sensorManager.getDefaultSensor(Sensor.TYPE_MAGNETIC_FIELD);
}
public void start() {
sensorManager.registerListener(this, gsensor,
SensorManager.SENSOR_DELAY_GAME);
sensorManager.registerListener(this, msensor,
SensorManager.SENSOR_DELAY_GAME);
}
public void stop() {
sensorManager.unregisterListener(this);
}
public void setAzimuthFix(float fix) {
azimuthFix = fix;
}
public void resetAzimuthFix() {
setAzimuthFix(0);
}
public void setListener(CompassListener l) {
listener = l;
}
#Override
public void onSensorChanged(SensorEvent event) {
final float alpha = 0.97f;
synchronized (this) {
if (event.sensor.getType() == Sensor.TYPE_ACCELEROMETER) {
mGravity[0] = alpha * mGravity[0] + (1 - alpha)
* event.values[0];
mGravity[1] = alpha * mGravity[1] + (1 - alpha)
* event.values[1];
mGravity[2] = alpha * mGravity[2] + (1 - alpha)
* event.values[2];
// mGravity = event.values;
// Log.e(TAG, Float.toString(mGravity[0]));
}
if (event.sensor.getType() == Sensor.TYPE_MAGNETIC_FIELD) {
// mGeomagnetic = event.values;
mGeomagnetic[0] = alpha * mGeomagnetic[0] + (1 - alpha)
* event.values[0];
mGeomagnetic[1] = alpha * mGeomagnetic[1] + (1 - alpha)
* event.values[1];
mGeomagnetic[2] = alpha * mGeomagnetic[2] + (1 - alpha)
* event.values[2];
// Log.e(TAG, Float.toString(event.values[0]));
}
boolean success = SensorManager.getRotationMatrix(R, I, mGravity,
mGeomagnetic);
if (success) {
float orientation[] = new float[3];
SensorManager.getOrientation(R, orientation);
// Log.d(TAG, "azimuth (rad): " + azimuth);
azimuth = (float) Math.toDegrees(orientation[0]); // orientation
azimuth = (azimuth + azimuthFix + 360) % 360;
// Log.d(TAG, "azimuth (deg): " + azimuth);
if (listener != null) {
listener.onNewAzimuth(azimuth);
}
}
}
}
#Override
public void onAccuracyChanged(Sensor sensor, int accuracy) {
}
}
I calibrated the value by adding 352 to bearing received by onNewAzimuth method of this class and used it in my code:
Compass compass = new Compass(this);
Compass.CompassListener cl = new Compass.CompassListener() {
#Override
public void onNewAzimuth(float azimuth) {
// using (360 - (azimuth) + 8) value
}
};
compass.setListener(cl);

How to get only west direction from the Compass Sensor in Android?

I want to show the west direction in my app using compass. No matter where my user are my compass will always navigate to west direction. I am confused about it that how can i achieve and rotate my image in only one direction . Below is my code -
public class Compass implements SensorEventListener {
private static final String TAG = "Compass";
private SensorManager sensorManager;
private Sensor gsensor;
private Sensor msensor;
private float[] mGravity = new float[3];
private float[] mGeomagnetic = new float[3];
private float azimuth = 0f;
private float currectAzimuth = 0;
private Context context ;
PackageManager packageManager ;
// compass arrow to rotate
public ImageView arrowView = null;
public Compass(Context context) {
this.context = context;
sensorManager = (SensorManager) context
.getSystemService(Context.SENSOR_SERVICE);
gsensor = sensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);
msensor = sensorManager.getDefaultSensor(Sensor.TYPE_MAGNETIC_FIELD);
packageManager = context.getPackageManager();
}
public void start() {
if(packageManager.hasSystemFeature(PackageManager.FEATURE_SENSOR_COMPASS)){
sensorManager.registerListener(this, gsensor,
SensorManager.SENSOR_DELAY_GAME);
sensorManager.registerListener(this, msensor,
SensorManager.SENSOR_DELAY_GAME);
}
else{
Toast.makeText(context,"No Compass Sensor !", Toast.LENGTH_SHORT).show();
}
}
public void stop() {
sensorManager.unregisterListener(this);
}
private void adjustArrow() {
if (arrowView == null) {
Log.i(TAG, "arrow view is not set");
return;
}
Log.i(TAG, "will set rotation from " + currectAzimuth + " to "
+ azimuth);
Animation an = new RotateAnimation(-currectAzimuth, -azimuth,
Animation.RELATIVE_TO_SELF, 0.5f, Animation.RELATIVE_TO_SELF,
0.5f);
currectAzimuth = azimuth;
an.setDuration(500);
an.setRepeatCount(0);
an.setFillAfter(true);
arrowView.startAnimation(an);
}
#Override
public void onSensorChanged(SensorEvent event) {
final float alpha = 0.97f;
synchronized (this) {
if (event.sensor.getType() == Sensor.TYPE_ACCELEROMETER) {
mGravity[0] = alpha * mGravity[0] + (1 - alpha)
* event.values[0];
mGravity[1] = alpha * mGravity[1] + (1 - alpha)
* event.values[1];
mGravity[2] = alpha * mGravity[2] + (1 - alpha)
* event.values[2];
// mGravity = event.values;
// Log.e(TAG, Float.toString(mGravity[0]));
}
if (event.sensor.getType() == Sensor.TYPE_MAGNETIC_FIELD) {
// mGeomagnetic = event.values;
mGeomagnetic[0] = alpha * mGeomagnetic[0] + (1 - alpha)
* event.values[0];
mGeomagnetic[1] = alpha * mGeomagnetic[1] + (1 - alpha)
* event.values[1];
mGeomagnetic[2] = alpha * mGeomagnetic[2] + (1 - alpha)
* event.values[2];
// Log.e(TAG, Float.toString(event.values[0]));
}
float R[] = new float[9];
float I[] = new float[9];
boolean success = SensorManager.getRotationMatrix(R, I, mGravity,
mGeomagnetic);
if (success) {
float orientation[] = new float[3];
SensorManager.getOrientation(R, orientation);
Log.d(TAG, "azimuth (rad): " + azimuth);
azimuth = (float) Math.toDegrees(orientation[0]); // orientation
azimuth = (azimuth + 360) % 360;
Log.d(TAG, "azimuth (deg): " + azimuth);
adjustArrow();
}
}
}
#Override
public void onAccuracyChanged(Sensor sensor, int accuracy) {
}
}

Why don't you use trigonometry to calculate the correct angle for the image based on north being at 0 degrees.
If north is 0 degrees, west would be -90 degrees or 270 degrees in comparison. So simply set the rotation of the image to north + 270 degrees?

unable to make 2nd circle follow its own path

I am unable to create more circles which follows its own path with drawCircle .
I have used the code below which creates another circle but follows the path along the lines of 1st circle but not independent .How do I move both circles independent of each other?
I have added
c.drawCircle(ballX-100, ballY-100, 50, ballPaintyellow);
How do I make the above circle independent from the 1st circle?. I really appreciate any help.Thanks in Advance.
BouncingBallActivity.java
package com.stuffthathappens.games;
import static android.hardware.SensorManager.DATA_X;
import static android.hardware.SensorManager.DATA_Y;
import static android.hardware.SensorManager.SENSOR_ACCELEROMETER;
import static android.hardware.SensorManager.SENSOR_DELAY_GAME;
import java.util.concurrent.TimeUnit;
import android.app.Activity;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.hardware.SensorListener;
import android.hardware.SensorManager;
import android.os.Bundle;
import android.os.Vibrator;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.view.SurfaceHolder.Callback;
/**
* This activity shows a ball that bounces around. The phone's
* accelerometer acts as gravity on the ball. When the ball hits
* the edge, it bounces back and triggers the phone vibrator.
*/
#SuppressWarnings("deprecation")
public class BouncingBallActivity extends Activity implements Callback, SensorListener {
private static final int BALL_RADIUS =20;
private SurfaceView surface;
private SurfaceHolder holder;
private final BouncingBallModel model = new BouncingBallModel(BALL_RADIUS);
private GameLoop gameLoop;
private Paint backgroundPaint;
private Paint ballPaint;
private SensorManager sensorMgr;
private long lastSensorUpdate = -1;
private Paint ballPaintyellow;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.bouncing_ball);
surface = (SurfaceView) findViewById(R.id.bouncing_ball_surface);
holder = surface.getHolder();
surface.getHolder().addCallback(this);
backgroundPaint = new Paint();
backgroundPaint.setColor(Color.WHITE);
ballPaint = new Paint();
ballPaint.setColor(Color.BLUE);
ballPaint.setAntiAlias(true);
ballPaintyellow = new Paint();
ballPaintyellow.setColor(Color.YELLOW);
ballPaintyellow.setAntiAlias(true);
}
#Override
protected void onPause() {
super.onPause();
model.setVibrator(null);
sensorMgr.unregisterListener(this, SENSOR_ACCELEROMETER);
sensorMgr = null;
model.setAccel(0, 0);
}
#Override
protected void onResume() {
super.onResume();
sensorMgr = (SensorManager) getSystemService(SENSOR_SERVICE);
boolean accelSupported = sensorMgr.registerListener(this,
SENSOR_ACCELEROMETER,
SENSOR_DELAY_GAME);
if (!accelSupported) {
// on accelerometer on this device
sensorMgr.unregisterListener(this, SENSOR_ACCELEROMETER);
// TODO show an error
}
// NOTE 1: you cannot get system services before onCreate()
// NOTE 2: AndroidManifest.xml must contain this line:
// <uses-permission android:name="android.permission.VIBRATE"/>
Vibrator vibrator = (Vibrator) getSystemService(Activity.VIBRATOR_SERVICE);
model.setVibrator(vibrator);
}
public void surfaceChanged(SurfaceHolder holder, int format, int width,
int height) {
model.setSize(width, height);
}
public void surfaceCreated(SurfaceHolder holder) {
gameLoop = new GameLoop();
gameLoop.start();
}
private void draw() {
// thread safety - the SurfaceView could go away while we are drawing
Canvas c = null;
try {
// NOTE: in the LunarLander they don't have any synchronization here,
// so I guess this is OK. It will return null if the holder is not ready
c = holder.lockCanvas();
// this needs to synchronize on something
if (c != null) {
doDraw(c);
}
} finally {
if (c != null) {
holder.unlockCanvasAndPost(c);
}
}
}
private void doDraw(Canvas c) {
int width = c.getWidth();
int height = c.getHeight();
c.drawRect(0, 0, width, height, backgroundPaint);
float ballX, ballY;
synchronized (model.LOCK) {
ballX = model.ballPixelX;
ballY = model.ballPixelY;
}
c.drawCircle(ballX, ballY, BALL_RADIUS, ballPaint);
c.drawCircle(ballX-100, ballY-100, 50, ballPaintyellow);
}
public void surfaceDestroyed(SurfaceHolder holder) {
try {
model.setSize(0,0);
gameLoop.safeStop();
} finally {
gameLoop = null;
}
}
private class GameLoop extends Thread {
private volatile boolean running = true;
public void run() {
while (running) {
try {
// don't like this hardcoding
TimeUnit.MILLISECONDS.sleep(5);
draw();
model.updatePhysics();
} catch (InterruptedException ie) {
running = false;
}
}
}
public void safeStop() {
running = false;
interrupt();
}
}
public void onAccuracyChanged(int sensor, int accuracy) {
}
public void onSensorChanged(int sensor, float[] values) {
if (sensor == SENSOR_ACCELEROMETER) {
long curTime = System.currentTimeMillis();
// only allow one update every 50ms, otherwise updates
// come way too fast
if (lastSensorUpdate == -1 || (curTime - lastSensorUpdate) > 50) {
lastSensorUpdate = curTime;
model.setAccel(values[DATA_X], values[DATA_Y]);
}
}
}
}
Bouncingballmodel.java
package com.stuffthathappens.games;
import java.util.concurrent.atomic.AtomicReference;
import android.os.Vibrator;
/**
* This data model tracks the width and height of the playing field along
* with the current position of a ball.
*/
public class BouncingBallModel {
// the ball speed is meters / second. When we draw to the screen,
// 1 pixel represents 1 meter. That ends up too slow, so multiply
// by this number. Bigger numbers speeds things up.
private final float pixelsPerMeter = 10;
private final int ballRadius;
// these are public, so make sure you synchronize on LOCK
// when reading these. I made them public since you need to
// get both X and Y in pairs, and this is more efficient than
// getter methods. With two getters, you'd still need to
// synchronize.
public float ballPixelX, ballPixelY;
private int pixelWidth, pixelHeight;
// values are in meters/second
private float velocityX, velocityY;
// typical values range from -10...10, but could be higher or lower if
// the user moves the phone rapidly
private float accelX, accelY;
/**
* When the ball hits an edge, multiply the velocity by the rebound.
* A value of 1.0 means the ball bounces with 100% efficiency. Lower
* numbers simulate balls that don't bounce very much.
*/
private static final float rebound = 0.8f;
// if the ball bounces and the velocity is less than this constant,
// stop bouncing.
private static final float STOP_BOUNCING_VELOCITY = 2f;
private volatile long lastTimeMs = -1;
public final Object LOCK = new Object();
private AtomicReference<Vibrator> vibratorRef =
new AtomicReference<Vibrator>();
public BouncingBallModel(int ballRadius) {
this.ballRadius = ballRadius;
}
public void setAccel(float ax, float ay) {
synchronized (LOCK) {
this.accelX = ax;
this.accelY = ay;
}
}
public void setSize(int width, int height) {
synchronized (LOCK) {
this.pixelWidth = width;
this.pixelHeight = height;
}
}
public int getBallRadius() {
return ballRadius;
}
/**
* Call this to move the ball to a particular location on the screen. This
* resets the velocity to zero, but the acceleration doesn't change so
* the ball should start falling shortly.
*/
public void moveBall(int ballX, int ballY) {
synchronized (LOCK) {
this.ballPixelX = ballX;
this.ballPixelY = ballY;
velocityX = 0;
velocityY = 0;
}
}
public void updatePhysics() {
// copy everything to local vars (hence the 'l' prefix)
float lWidth, lHeight, lBallX, lBallY, lAx, lAy, lVx, lVy;
synchronized (LOCK) {
lWidth = pixelWidth;
lHeight = pixelHeight;
lBallX = ballPixelX;
lBallY = ballPixelY;
lVx = velocityX;
lVy = velocityY;
lAx = accelX;
lAy = -accelY;
}
if (lWidth <= 0 || lHeight <= 0) {
// invalid width and height, nothing to do until the GUI comes up
return;
}
long curTime = System.currentTimeMillis();
if (lastTimeMs < 0) {
lastTimeMs = curTime;
return;
}
long elapsedMs = curTime - lastTimeMs;
lastTimeMs = curTime;
// update the velocity
// (divide by 1000 to convert ms to seconds)
// end result is meters / second
lVx += ((elapsedMs * lAx) / 1000) * pixelsPerMeter;
lVy += ((elapsedMs * lAy) / 1000) * pixelsPerMeter;
// update the position
// (velocity is meters/sec, so divide by 1000 again)
lBallX += ((lVx * elapsedMs) / 1000) * pixelsPerMeter;
lBallY += ((lVy * elapsedMs) / 1000) * pixelsPerMeter;
boolean bouncedX = false;
boolean bouncedY = false;
if (lBallY - ballRadius < 0) {
lBallY = ballRadius;
lVy = -lVy * rebound;
bouncedY = true;
} else if (lBallY + ballRadius > lHeight) {
lBallY = lHeight - ballRadius;
lVy = -lVy * rebound;
bouncedY = true;
}
if (bouncedY && Math.abs(lVy) < STOP_BOUNCING_VELOCITY) {
lVy = 0;
bouncedY = false;
}
if (lBallX - ballRadius < 0) {
lBallX = ballRadius;
lVx = -lVx * rebound;
bouncedX = true;
} else if (lBallX + ballRadius > lWidth) {
lBallX = lWidth - ballRadius;
lVx = -lVx * rebound;
bouncedX = true;
}
if (bouncedX && Math.abs(lVx) < STOP_BOUNCING_VELOCITY) {
lVx = 0;
bouncedX = false;
}
// safely copy local vars back to object fields
synchronized (LOCK) {
ballPixelX = lBallX;
ballPixelY = lBallY;
velocityX = lVx;
velocityY = lVy;
}
if (bouncedX || bouncedY) {
Vibrator v = vibratorRef.get();
if (v != null) {
v.vibrate(20L);
}
}
}
public void setVibrator(Vibrator v) {
vibratorRef.set(v);
}
}

Which view you are using has nothing to do with it ....
At the moment you have only one BouncingBallModel
private final BouncingBallModel model = new BouncingBallModel(BALL_RADIUS);
This is the one you see when you draw something. Now if you want to draw multiple balls, you will need many BouncingBallModel. So either create a BouncingBallModel model2 or make it dynamic using an array.
Then iterate over the array and draw each ball.

Android: Using the accelerometer to detect a flick

I'm trying to develop an app where the user can hit an invisible drum using the motion of the phone. So that when the phone is flicked downwards a drum is sounded at the end of the flick.
I have managed to get 90% of this working, by detecting when a large, quick movement suddenly stops. But although the drum is being sounded after a flick (good) it's also being sounded at the end of a pull (not desirable).
By flick I mean the phone is being flicked forwards and downwards, as if you are striking a drum with it, and by pull I mean you are returning your arm back to the starting position.
Does anyone know an efficient way of determining when a flick occurs but not a push?
Any ideas will be gratefully received.
Thanks
EXISTING CODE:
package com.example.testaccelerometer;
import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorListener;
import android.hardware.SensorManager;
import android.os.Bundle;
import android.app.Activity;
import android.content.Context;
import android.view.Menu;
import android.widget.TextView;
public class MainActivity extends Activity implements SensorEventListener{
public static TextView results;
public static TextView clickresults;
StringBuilder builder = new StringBuilder();
private float mAccelNoGrav;
private float mAccelWithGrav;
private float mLastAccelWithGrav;
public static boolean shakeIsHappening;
public static int beatnumber = 0;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
results = (TextView) findViewById(R.id.results);
clickresults = (TextView) findViewById(R.id.clickresults);
SensorManager manager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);
Sensor accelerometer = manager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);
if(!manager.registerListener(this, accelerometer, SensorManager.SENSOR_DELAY_FASTEST)){
builder.append("Problem with Accelerometer - Shaking will not work");
};
mAccelNoGrav = 0.00f;
mAccelWithGrav = SensorManager.GRAVITY_EARTH;
mLastAccelWithGrav = SensorManager.GRAVITY_EARTH;
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
#Override
public void onAccuracyChanged(Sensor sensor, int accuracy) {
// TODO Auto-generated method stub
}
#Override
public void onSensorChanged(SensorEvent event) {
builder.setLength(0);
builder.append("X " + event.values[0] + "\nY " + event.values[1] + "\nZ " + event.values[2]);
results.setText(builder.toString());
float x = event.values[0];
float y = event.values[1];
float z = event.values[2];
mLastAccelWithGrav = mAccelWithGrav;
mAccelWithGrav = android.util.FloatMath.sqrt(x*x + y*y + z*z);
float delta = mAccelWithGrav - mLastAccelWithGrav;
mAccelNoGrav = mAccelNoGrav * 0.9f + delta;
if (mAccelNoGrav >8.5) {
shakeIsHappening = true;
//clickresults.append(" click " + mAccel);
}
if (shakeIsHappening == true && mAccelNoGrav <2) {
beatnumber++;
clickresults.append(" click number: " + beatnumber + "\n" + "PA: " + mLastAccelWithGrav + " CA:" + mAccelNoGrav + "\n ");
shakeIsHappening = false;
}
}
#Override
protected void onResume() {
super.onResume();
// YOU DO NEED TO TRY AND REREGISTER IT NOW
}
#Override
protected void onPause() {
// YOU DO NEED TO TRY AND UNREGISTER IT NOW
super.onPause();
}
}

You can use the geo-magnet sensor in conjunction with your accelerometer sensor to determine which edge of the device is facing toward the ground, and then exclude any acceleration events in the opposite direction
http://developer.android.com/reference/android/hardware/SensorManager.html#getOrientation(float[], float[])

I eventually figured out how to work this out, simply using the z axis to work out whether the motion is towards the ground or not.
The z axis data is fed into the z array (minus the force of gravity). When acceleration goes over a certain level, we record the highest number, highZ and the lowest number, lowZ. These mark out the range of the hand movement between high and low points. When the acceleration goes below 2, we check to see if the latest bit of data in the Z array is equal to the high point or the low point, and this tells us whether the movement was a flick or a pull.
It's probably not the most efficient way to work this out, but it's working now so I'm happy. Thanks for all your help, everyone.
Here's my finished code:
public class MainActivity extends Activity implements SensorEventListener {
private float mAccelNoGrav;
private float mAccelWithGrav;
private float mLastAccelWithGrav;
ArrayList<Float> z = new ArrayList<Float>();
public static float finalZ;
public static boolean shakeIsHappening;
public static int beatnumber = 0;
public static float highZ;
public static float lowZ;
public static boolean flick;
public static boolean pull;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
results = (TextView) findViewById(R.id.results);
clickresults = (TextView) findViewById(R.id.clickresults);
SensorManager manager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);
Sensor accelerometer = manager
.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);
if (!manager.registerListener(this, accelerometer,
SensorManager.SENSOR_DELAY_FASTEST)) {
builder.append("Problem with Accelerometer - Shaking will not work");
}
;
mAccelNoGrav = 0.00f;
mAccelWithGrav = SensorManager.GRAVITY_EARTH;
mLastAccelWithGrav = SensorManager.GRAVITY_EARTH;
}
#Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
#Override
public void onAccuracyChanged(Sensor sensor, int accuracy) {
// TODO Auto-generated method stub
}
#Override
public void onSensorChanged(SensorEvent event) {
float x = event.values[0];
float y = event.values[1];
z.add((event.values[2])-SensorManager.GRAVITY_EARTH);
mLastAccelWithGrav = mAccelWithGrav;
mAccelWithGrav = android.util.FloatMath.sqrt(x * x + y * y + z.indexOf(z.size()-1) * z.indexOf(z.size()-1));
float delta = mAccelWithGrav - mLastAccelWithGrav;
mAccelNoGrav = mAccelNoGrav * 0.9f + delta; // Low-cut filter
if (mAccelNoGrav > 8.5) {
shakeIsHappening = true;
z.clear();
if (z.indexOf(z.size()-2) > z.indexOf(z.size()-1)) {
clickresults.append(" Z shrinking" + z);
} else if (z.indexOf(z.size()-2) < z.indexOf(z.size()-1)) {
clickresults.append(" Z growing" + z);
}
}
if (shakeIsHappening == true && mAccelNoGrav < 2) {
finalZ = z.get(z.size()-1);
highZ= z.get(z.size()-1);
lowZ= z.get(z.size()-1);
for (int i = 0; i < z.size(); i++) {
if (z.get(i) > highZ) {
highZ = z.get(i);
} else if ((z.get(i) < lowZ)) {
lowZ = z.get(i);
}
if (highZ==finalZ) {
flick = true;
pull = false;
} else if (lowZ==finalZ) {
flick = false;
pull = true;
}
if (flick) {
beatnumber++;
clickresults.append(" click number: " + beatnumber + "\n" + "PA: "
+ mLastAccelWithGrav + " CA:" + mAccelNoGrav + "\n " + "Lz " + z.indexOf(z.size()-2) +"z " + z.indexOf(z.size()-1) + "\n" + "\n");
shakeIsHappening = false;
}
z.clear();
} }
}
#Override
protected void onResume() {
super.onResume();
// YOU DO NEED TO TRY AND REREGISTER IT NOW
}
#Override
protected void onPause() {
// YOU DO NEED TO TRY AND UNREGISTER IT NOW
super.onPause();
}
}

How to detect movement of an android device?

I need suggestion about how to detect the amount of movement of an android device. Suppose I have put the phone on a table or bed and then if somebody taps the table or sits or laydown on the bed then I want to detect the movement of the android device.
Actually I know that android has motion sensors APIs but I don't know which sensor to use and what sensor type is best for this type of movement detection.
I would be glad if someone can share some basic demo code.

Definitely work with the accelerometer:
// Start with some variables
private SensorManager sensorMan;
private Sensor accelerometer;
private float[] mGravity;
private float mAccel;
private float mAccelCurrent;
private float mAccelLast;
// In onCreate method
sensorMan = (SensorManager)getSystemService(SENSOR_SERVICE);
accelerometer = sensorMan.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);
mAccel = 0.00f;
mAccelCurrent = SensorManager.GRAVITY_EARTH;
mAccelLast = SensorManager.GRAVITY_EARTH;
// And these:
#Override
public void onResume() {
super.onResume();
sensorMan.registerListener(this, accelerometer,
SensorManager.SENSOR_DELAY_UI);
}
#Override
protected void onPause() {
super.onPause();
sensorMan.unregisterListener(this);
}
#Override
public void onSensorChanged(SensorEvent event) {
if (event.sensor.getType() == Sensor.TYPE_ACCELEROMETER){
mGravity = event.values.clone();
// Shake detection
float x = mGravity[0];
float y = mGravity[1];
float z = mGravity[2];
mAccelLast = mAccelCurrent;
mAccelCurrent = FloatMath.sqrt(x*x + y*y + z*z);
float delta = mAccelCurrent - mAccelLast;
mAccel = mAccel * 0.9f + delta;
// Make this higher or lower according to how much
// motion you want to detect
if(mAccel > 3){
// do something
}
}
}
#Override
public void onAccuracyChanged(Sensor sensor, int accuracy) {
// required method
}

I used the following class:
public class MovementDetector implements SensorEventListener {
protected final String TAG = getClass().getSimpleName();
private SensorManager sensorMan;
private Sensor accelerometer;
private MovementDetector() {
}
private static MovementDetector mInstance;
public static MovementDetector getInstance() {
if (mInstance == null) {
mInstance = new MovementDetector();
mInstance.init();
}
return mInstance;
}
//////////////////////
private HashSet<Listener> mListeners = new HashSet<MovementDetector.Listener>();
private void init() {
sensorMan = (SensorManager) GlobalData.getInstance().getContext().getSystemService(Context.SENSOR_SERVICE);
accelerometer = sensorMan.getDefaultSensor(Sensor.TYPE_LINEAR_ACCELERATION);
}
public void start() {
sensorMan.registerListener(this, accelerometer, SensorManager.SENSOR_DELAY_NORMAL);
}
public void stop() {
sensorMan.unregisterListener(this);
}
public void addListener(Listener listener) {
mListeners.add(listener);
}
/* (non-Javadoc)
* #see android.hardware.SensorEventListener#onSensorChanged(android.hardware.SensorEvent)
*/
#Override
public void onSensorChanged(SensorEvent event) {
if (event.sensor.getType() == Sensor.TYPE_LINEAR_ACCELERATION) {
float x = event.values[0];
float y = event.values[1];
float z = event.values[2];
float diff = (float) Math.sqrt(x * x + y * y + z * z);
if (diff > 0.5) // 0.5 is a threshold, you can test it and change it
Log.d(TAG,"Device motion detected!!!!");
for (Listener listener : mListeners) {
listener.onMotionDetected(event, diff);
}
}
}
/* (non-Javadoc)
* #see android.hardware.SensorEventListener#onAccuracyChanged(android.hardware.Sensor, int)
*/
#Override
public void onAccuracyChanged(Sensor sensor, int accuracy) {
// TODO Auto-generated method stub
}
public interface Listener {
void onMotionDetected(SensorEvent event, float acceleration);
}
}
Usage:
On my activity onCrate():
MovementDetector.getInstance().addListener(new MovementDetector.Listener() {
#Override
public void onMotionDetected(SensorEvent event, float acceleration) {
mMotionDetectionTextView.setText("Acceleration: ["+String.format("%.3f",event.values[0])+","+String.format("%.3f",event.values[1])+","+String.format("%.3f",event.values[2])+"] "+String.format("%.3f", acceleration));
if (acceleration > SettingsHelper.getInstance().getMotionDetectionThreshold()){
mMotionDetectionTextView.setTextColor(Color.RED);
} else {
mMotionDetectionTextView.setTextColor(Color.WHITE);
}
}
});
On my activity onResume():
MovementDetector.getInstance().start();
On my activity onPause():
MovementDetector.getInstance().stop();

This code is for walking detection (Modified from #anthropomo code)
to get smoother value.
// initialize
private SensorManager sensorMan;
private Sensor accelerometer;
private float[] mGravity;
private double mAccel;
private double mAccelCurrent;
private double mAccelLast;
private boolean sensorRegistered = false;
// onCreate
sensorMan = (SensorManager) context.getSystemService(Context.SENSOR_SERVICE);
accelerometer = sensorMan.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);
mAccel = 0.00f;
mAccelCurrent = SensorManager.GRAVITY_EARTH;
mAccelLast = SensorManager.GRAVITY_EARTH;
sensorMan.registerListener(this, accelerometer,
SensorManager.SENSOR_DELAY_NORMAL);
sensorRegistered = true;
// onSensorChanged
private int hitCount = 0;
private double hitSum = 0;
private double hitResult = 0;
private final int SAMPLE_SIZE = 50; // change this sample size as you want, higher is more precise but slow measure.
private final double THRESHOLD = 0.2; // change this threshold as you want, higher is more spike movement
#Override
public void onSensorChanged(SensorEvent event) {
if (event.sensor.getType() == Sensor.TYPE_ACCELEROMETER) {
mGravity = event.values.clone();
// Shake detection
double x = mGravity[0];
double y = mGravity[1];
double z = mGravity[2];
mAccelLast = mAccelCurrent;
mAccelCurrent = Math.sqrt(x * x + y * y + z * z);
double delta = mAccelCurrent - mAccelLast;
mAccel = mAccel * 0.9f + delta;
if (hitCount <= SAMPLE_SIZE) {
hitCount++;
hitSum += Math.abs(mAccel);
} else {
hitResult = hitSum / SAMPLE_SIZE;
Log.d(TAG, String.valueOf(hitResult));
if (hitResult > THRESHOLD) {
Log.d(TAG, "Walking");
} else {
Log.d(TAG, "Stop Walking");
}
hitCount = 0;
hitSum = 0;
hitResult = 0;
}
}
}

I have been working with a similar idea to measure the displacement of the phone. I have found that the LINEAR ACCELERATION (and ACCELERATION) are not accurate enough to correctly measure the displacement.
This code should work a little better:
(ititialize)
private SensorManager sensorManager;
private Sensor accelerometer;
double[] maxAccelerations = new double[3];
double[] position = new double[3];
long[] times = new long[3];
// time combined with maxAcceleration can approximate the change in position,
// with the formula Δpos = (maxAcceleration * time ^ 2) / 6
long currentTime;
(onCreate)
sensorManager = (SensorManager) getSystemService(SENSOR_SERVICE);
if (sensorManager.getDefaultSensor(Sensor.TYPE_LINEAR_ACCELERATION) != null) {
accelerometer = sensorManager.getDefaultSensor(Sensor.TYPE_LINEAR_ACCELERATION);
sensorManager.registerListener(this, accelerometer, sensorManager.SENSOR_DELAY_FASTEST);
}
currentTime = System.currentTimeMillis();
for(int i=0;i<3;i++){
times[i]=currentTime;
}
else{
throw "Error";
//Which will throw an error, if not the error that is expected. 😉
}
(onSensorChanged and onAccuracyChanged)
#Override
public void onAccuracyChanged(Sensor ignore, int thisFunction) {
}
#Override
public void onSensorChanged(SensorEvent event) {
if (event.sensor.getType() == Sensor.TYPE_LINEAR_ACCELERATION) {
for(int i=0;i<3;i++){
if(Math.abs(event.values[i])<0.01){
// Note: this is to try to prevent accelerating time from being counted when the phone is stationary. 0.01 should be
// changed to an appropriate sensitivity level that can be calculated by finding an average noise level when the phone is stationary.
times[i]=System.currentTimeMillis();
}
if(event.values[i]>maxAccelerations[i] && maxAccelerations[i]>=0){
maxAccelerations[i]=event.values[i];
}
else if(event.values[i]<maxAccelerations[i] && maxAccelerations[i]<=0){
maxAccelerations[i]=event.values[i];
}
else if(event.values[i]>0 && maxAccelerations[i]<0){
currentTime = System.currentTimeMillis();
position[i]+=maxAccelerations[i] * (times[i]-currentTime)*(times[i]-currentTime) / 6;
times[i]=currentTime;
maxAccelerations[i]=event.values[i];
}
else if(event.values[i]<0 && maxAccelerations[i]>0){
currentTime = System.currentTimeMillis();
position[i]+=maxAccelerations[i] * (times[i]-currentTime)*(times[i]-currentTime) / 6;
times[i]=currentTime;
maxAccelerations[i]=event.values[i];
}
}
}
}

While I don't have demo code (since you aren't specific enough), a good start is here: http://developer.android.com/guide/topics/sensors/sensors_motion.html (and other items on the left).

if you are trying to find the displacement of your phone, you need to find the
Linear acceleration acting on your phone rather than the acceleration due to gravity
android has a built in converter to find the LINEAR ACCELERATION acting on your mobile phone
https://github.com/yuvaramsingh94/AndroidSensorTestCode/tree/master
this is a code where you can see how to get the raw value of LINEAR ACCELERATION