Andorid code snippet for acquiring an accelerometer sensor data without gravity data. Also removes noise by using a low pass filter. 重力の影響を省いた加速度値を取得するためのアンドロイドのサンプルコード。 ローパスフィルタでノイズも除去。

SensorAdapter.java

//Acquiring an accelerometer sensor data without gravity data

import java.util.List;

import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorManager;

public class SensorAdapter implements SensorEventListener{
	
	//THRESHOLD ある値以上を検出するための閾値
	protected final static double THRESHOLD=4.0;
	protected final static double THRESHOLD_MIN=1;
	
	//low pass filter alpha ローパスフィルタのアルファ値
	protected final static float alpha= 0.8;
	
	//端末が実際に取得した加速度値。重力加速度も含まれる。This values include gravity force.
	private float[] currentOrientationValues = { 0.0f, 0.0f, 0.0f };
	//ローパス、ハイパスフィルタ後の加速度値 Values after low pass and high pass filter
	private float[] currentAccelerationValues = { 0.0f, 0.0f, 0.0f };

	//diff 差分
	private float dx=0.0f;
	private float dy=0.0f;
	private float dz=0.0f;
	
	//previous data 1つ前の値
	private float old_x=0.0f;
	private float old_y=0.0f;
	private float old_z=0.0f;
	
	//ベクトル量
	private double vectorSize=0;
	
	//カウンタ
	long counter=0;
	
	//一回目のゆれを省くカウントフラグ（一回の端末の揺れで2回データが取れてしまうのを防ぐため）
	//count flag to prevent aquiring data twice with one movement of a device
	boolean counted=false;
	
	// X軸加速方向
	boolean vecx = true;
	// Y軸加速方向
	boolean vecy = true;
	// Z軸加速方向
	boolean vecz = true;
	
	
	//ノイズ対策
	boolean noiseflg=true;
	//ベクトル量(最大値)
	private double vectorSize_max=0;
	
	
	public float getx(){return this.dx;}
	public float gety(){return this.dy;}
	public float getz(){return this.dz;}
	public long getcounter(){return this.counter;}
	public double getVectorMax(){return this.vectorSize_max;}

	public SensorAdapter(SensorManager manager) {
		// construct sensor
		List<Sensor> sensors =manager.getSensorList(Sensor.TYPE_ACCELEROMETER);
		
		if(sensors.size()>0){
			Sensor s =sensors.get(0);
			manager.registerListener(this, s,SensorManager.SENSOR_DELAY_UI);
		}


	}
	
    
    public void stopSensor(SensorManager manager) {
    	
        // センサー停止時のリスナ解除 Stopping Listener
        if ( manager != null )
            manager.unregisterListener(this);
        manager = null;
      
    }

	@Override
	public void onAccuracyChanged(Sensor arg0, int arg1) {
		// TODO 自動生成されたメソッド・スタブ
		
	}

	@Override
	public void onSensorChanged(SensorEvent event) {

		if (event.sensor.getType() == Sensor.TYPE_ACCELEROMETER) {
			// 取得 Acquiring data

      // ローパスフィルタで重力値を抽出　Isolate the force of gravity with the low-pass filter.
			currentOrientationValues[0] = event.values[0] * 0.1f + currentOrientationValues[0] * (1.0f - 0.1f);
			currentOrientationValues[1] = event.values[1] * 0.1f + currentOrientationValues[1] * (1.0f - 0.1f);
			currentOrientationValues[2] = event.values[2] * 0.1f + currentOrientationValues[2] * (1.0f - 0.1f);
			
			// 重力の値を省くRemove the gravity contribution with the high-pass filter.
			currentAccelerationValues[0] = event.values[0] - currentOrientationValues[0];
			currentAccelerationValues[1] = event.values[1] - currentOrientationValues[1];
			currentAccelerationValues[2] = event.values[2] - currentOrientationValues[2];

			// ベクトル値を求めるために差分を計算　diff for vector
			dx = currentAccelerationValues[0] - old_x;
			dy = currentAccelerationValues[1] - old_y;
			dz = currentAccelerationValues[2] - old_z;

			vectorSize = Math.sqrt((double) (dx * dx + dy * dy + dz * dz));

			// 一回目はノイズになるから省く
			if (noiseflg == true) {
				noiseflg = false;
			} else {

				if (vectorSize > THRESHOLD /* && dz <0.0f */) {
					if (counted == true) {
						System.out.println(dx + "," + dz + "," + vectorSize);
						counter++;
						counted = false;
						// System.out.println("count is "+counter);
						// 最大値なら格納
						if (vectorSize > vectorSize_max) {
							vectorSize_max = vectorSize;
						}
					} else if(counted== false) {
						counted = true;

					}

				}
			}

			// 状態更新
			//vectorSize_old = vectorSize;
			old_x = currentAccelerationValues[0];
			old_y = currentAccelerationValues[1];
			old_z = currentAccelerationValues[2];

		}

	}
	
	// 指定ミリ秒実行を止めるメソッド
	public synchronized void sleep(long msec) {
		try {
			wait(msec);
		} catch (InterruptedException e) {
		}
	}

}