Hi,
You need to account for Gravity, see
http://developer.android.com/reference/android/hardware/SensorEvent.html
Regards
Sensor.TYPE_ACCELEROMETER:
All values are in SI units (m/s^2)
values[0]: Acceleration minus Gx on the x-axis
values[1]: Acceleration minus Gy on the y-axis
values[2]: Acceleration minus Gz on the z-axis
A sensor of this type measures the acceleration applied to the device
(Ad). Conceptually, it does so by measuring forces applied to the
sensor itself (Fs) using the relation:
Ad = - ∑Fs / mass
In particular, the force of gravity is always influencing the measured
acceleration:
Ad = -g - ∑F / mass
For this reason, when the device is sitting on a table (and obviously
not accelerating), the accelerometer reads a magnitude of g = 9.81 m/
s^2
Similarly, when the device is in free-fall and therefore dangerously
accelerating towards to ground at 9.81 m/s^2, its accelerometer reads
a magnitude of 0 m/s^2.
It should be apparent that in order to measure the real acceleration
of the device, the contribution of the force of gravity must be
eliminated. This can be achieved by applying a high-pass filter.
Conversely, a low-pass filter can be used to isolate the force of
gravity.
public void onSensorChanged(SensorEvent event)
{
// alpha is calculated as t / (t + dT)
// with t, the low-pass filter's time-constant
// and dT, the event delivery rate
final float alpha = 0.8;
gravity[0] = alpha * gravity[0] + (1 - alpha) *
event.values[0];
gravity[1] = alpha * gravity[1] + (1 - alpha) *
event.values[1];
gravity[2] = alpha * gravity[2] + (1 - alpha) *
event.values[2];
linear_acceleration[0] = event.values[0] - gravity[0];
linear_acceleration[1] = event.values[1] - gravity[1];
linear_acceleration[2] = event.values[2] - gravity[2];
}
Examples:
When the device lies flat on a table and is pushed on its left side
toward the right, the x acceleration value is positive.
When the device lies flat on a table, the acceleration value is +9.81,
which correspond to the acceleration of the device (0 m/s^2) minus the
force of gravity (-9.81 m/s^2).
When the device lies flat on a table and is pushed toward the sky with
an acceleration of A m/s^2, the acceleration value is equal to A+9.81
which correspond to the acceleration of the device (+A m/s^2) minus
the force of gravity (-9.81 m/s^2).
On Jul 21, 4:20 pm, sandeep agrawal <[email protected]> wrote:
> Hi All,
>
> I am developing one application in which i want to paint using
> accelerometer sensor, this is my code,
>
> this is my drawmainactivity
>
> package com.drawline;
>
> import android.app.Activity;
> import android.os.Bundle;
> import android.view.Window;
> import android.view.WindowManager;
>
> public class DrawMainActivity extends Activity {
>
> DrawlineActivity drawView;
> @Override
> protected void onCreate(Bundle savedInstanceState) {
> // TODO Auto-generated method stub
> super.onCreate(savedInstanceState);
>
> // Set full screen view
>
> getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
>
> WindowManager.LayoutParams.FLAG_FULLSCREEN);
> requestWindowFeature(Window.FEATURE_NO_TITLE);
>
> drawView = new DrawlineActivity(this);
> setContentView(drawView);
> drawView.requestFocus();
> }
>
> }
>
> This is the code in which i am trying to paint
>
> package com.drawline;
>
> import java.util.ArrayList;
> import java.util.List;
>
> import android.app.Activity;
> import android.content.Context;
> import android.graphics.Canvas;
> import android.graphics.Color;
> import android.graphics.Paint;
> import android.graphics.drawable.shapes.ArcShape;
> import android.hardware.Sensor;
> import android.hardware.SensorEvent;
> import android.hardware.SensorEventListener;
> import android.hardware.SensorManager;
> import android.os.Bundle;
> import android.util.Log;
> import android.view.MotionEvent;
> import android.view.View;
> import android.view.View.OnTouchListener;
> import android.widget.LinearLayout;
>
> public class DrawlineActivity extends View implements
> SensorEventListener {
> private static final String TAG = "DrawView";
> float startx=40,starty=40,oldx,oldy,x,y;
> List<Point> points = new ArrayList<Point>();
> Paint paint = new Paint();
> SensorManager mSensorManager;
> public DrawlineActivity(Context context) {
> super(context);
> setFocusable(true);
> setFocusableInTouchMode(true);
>
> mSensorManager =
> (SensorManager)context.getSystemService(context.SENSOR_SERVICE);
> mSensorManager.registerListener(this,
>
> mSensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER),
> SensorManager.SENSOR_DELAY_NORMAL);
> paint.setColor(Color.WHITE);
> paint.setAntiAlias(true);
> }
>
> @Override
> public void onDraw(Canvas canvas) {
> for (Point point : points) {
> canvas.drawCircle(point.x+100, point.y +100, 5, paint);
>
> //canvas.drawLine(startx,starty, startx,starty, paint);
> // Log.d(TAG, "Painting: "+point);
> Log.d("SANDEEP", "Inside ondraw " + point.x+ point.y);
> }
> }
>
> // public boolean onTouch(View view, MotionEvent event) {
> // // if(event.getAction() != MotionEvent.ACTION_DOWN)
> // // return super.onTouchEvent(event);
> // Point point = new Point();
> // point.x = event.getX();
> // point.y = event.getY();
> // points.add(point);
> // invalidate();
> // Log.d(TAG, "point: " + point);
> // return true;
> // }
>
> @Override
> public void onAccuracyChanged(Sensor sensor, int accuracy) {
> // TODO Auto-generated method stub
>
> }
>
> @Override
> public void onSensorChanged(SensorEvent event) {
> // TODO Auto-generated method stub
> Point point = new Point();
>
> point.x= event.values[0] *5;
> point.y = event.values[1]*5;
>
> // point.x=(int) (x + point.x);
> // point.y= (int) (y+ point.y);
> points.add(point);
> invalidate();
> Log.d(TAG, "point: " + startx + starty);
> // startx= startx + oldx;
> // starty = starty + oldy;
> oldx = startx;
> oldy = starty ;
> }
> }
>
> class Point {
> float x=40, y=40;
>
> @Override
> public String toString() {
> return x + ", " + y;
> }
>
> }
>
> Can anyone of you please correct it what i am doing wrong.
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