public class SpeedometerActivity extends ActionBarActivity {
SensorManager sensors;
TextView tvSpeed;
float velocity = 0f ;
float currentAcceleration = 0f;
float appliedAcceleration = 0f;
Date lastUpdated;
Handler handler = null;
Timer timer = null;
private final SensorEventListener sensorEventListener =
new SensorEventListener(){
double calibrator = Double.NaN;
@Override
public void onAccuracyChanged(Sensor sensor, int accuracy){
}
@SuppressWarnings("deprecation")
@Override
public void onSensorChanged(SensorEvent event){
double x = event.values[SensorManager.DATA_X];
double y = event.values[SensorManager.DATA_Y];
double z = event.values[SensorManager.DATA_Z];
double a =
(-1)* Math.sqrt(Math.pow(x, 2) + Math.pow(y, 2) +
Math.pow(z, 2));
if(calibrator == Double.NaN){
calibrator =a;
}
else {
computeVelocity();
currentAcceleration = (float)a;
}
}
};
@SuppressLint("ServiceCast")
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_speedometer);
tvSpeed = (TextView)findViewById(R.id.text_meter);
lastUpdated = new Date(System.currentTimeMillis());
sensors =
(SensorManager)getSystemService(Context.SEARCH_SERVICE);
sensors.registerListener(sensorEventListener,
sensors.getDefaultSensor(Sensor.TYPE_ACCELEROMETER),
SensorManager.SENSOR_DELAY_FASTEST);
timer = new Timer("updateVelocity");
timer.scheduleAtFixedRate(new TimerTask(){
public void run(){
updateScreen();
}
}, 0, 1000);
if (savedInstanceState == null) {
getSupportFragmentManager().beginTransaction()
.add(R.id.container, new PlaceholderFragment()).commit();
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.speedometer, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
/**
* A placeholder fragment containing a simple view.
*/
public static class PlaceholderFragment extends Fragment {
public PlaceholderFragment() {
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_speedometer,
container, false);
return rootView;
}
}
private void computeVelocity(){
Date now = new Date(System.currentTimeMillis());
long timeGap = now.getTime() - lastUpdated.getTime();
lastUpdated.setTime(now.getTime());
float velocityGap = appliedAcceleration*(timeGap/1000);
appliedAcceleration = currentAcceleration;
velocity += velocityGap;
double kmh =(Math.round(100*velocity*3.6)) / 100;
tvSpeed.setText(String.valueOf(kmh) + "" +
getString(R.string.speed_unit));
}
private void updateScreen(){
final double kmh = (Math.round(100* velocity *3.6)) /100;
handler.post(new Runnable(){
public void run(){
tvSpeed.setText(String.valueOf(kmh) + " " + getString(R.string.speed_unit));
}
});
}
}
