没有地磁的Android设备方向 [英] Android device orientation without geomagnetic

问题描述

我需要确定设备方向.据我所知，通常使用TYPE_ACCELEROMETER和TYPE_MAGNETIC_FIELD传感器.我的问题是SensorManager.getDefaultSensor返回我null的地磁传感器.它也为TYPE_ORIENTATION传感器返回null.

I need to get device orientation. As I know usually used TYPE_ACCELEROMETER and TYPE_MAGNETIC_FIELD sensors. My problem is that SensorManager.getDefaultSensor returns me null for geomagnetic sensor. It returns null for TYPE_ORIENTATION sensor too.

manager = (SensorManager) getSystemService(SENSOR_SERVICE);
Sensor sensorAcc = manager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER), //normal object
        sensorMagn = manager.getDefaultSensor(Sensor.TYPE_MAGNETIC_FIELD); //null
orientationListener = new OrientationSensorListener();
manager.registerListener(orientationListener, sensorAcc, 10);
manager.registerListener(orientationListener, sensorMagn, 10);

我需要另一种获取设备方向的方法.

I need another ways to get device orientation.

推荐答案

方向可以分解为三个欧拉角:俯仰，侧倾和方位角.

Orientation can be decomposed in three Euler angle : Pitch, Roll and Azimuth.

仅使用加速度计数据，就无法计算方位角，也不能计算音高的符号.

With only accelerometer datas, you cannot compute your Azimuth, neither the sign of your pitch.

您可以尝试以下方法来了解有关俯仰和横滚的信息:

You can try something as this to know something about your pitch and roll :

    private final float[] mMagnet = new float[3];               // magnetic field vector
    private final float[] mAcceleration = new float[3];         // accelerometer vector
    private final float[] mAccMagOrientation = new float[3];    // orientation angles from mAcceleration and mMagnet
    private float[] mRotationMatrix = new float[9];             // accelerometer and magnetometer based rotation matrix

    public void onSensorChanged(SensorEvent event) {
    switch (event.sensor.getType()) {
        case Sensor.TYPE_ACCELEROMETER:
            System.arraycopy(event.values, 0, mAcceleration, 0, 3);   // save datas
            calculateAccMagOrientation();                       // then calculate new orientation
            break;
        case Sensor.TYPE_MAGNETIC_FIELD:
            System.arraycopy(event.values, 0, mMagnet, 0, 3);         // save datas
            break;
        default: break;
    }
}
public void calculateAccMagOrientation() {
    if (SensorManager.getRotationMatrix(mRotationMatrix, null, mAcceleration, mMagnet))
        SensorManager.getOrientation(mRotationMatrix, mAccMagOrientation);
    else { // Most chances are that there are no magnet datas
        double gx, gy, gz;
        gx = mAcceleration[0] / 9.81f;
        gy = mAcceleration[1] / 9.81f;
        gz = mAcceleration[2] / 9.81f;
        // http://theccontinuum.com/2012/09/24/arduino-imu-pitch-roll-from-accelerometer/
        float pitch = (float) -Math.atan(gy / Math.sqrt(gx * gx + gz * gz));
        float roll = (float) -Math.atan(gx / Math.sqrt(gy * gy + gz * gz));
        float azimuth = 0; // Impossible to guess

        mAccMagOrientation[0] = azimuth;
        mAccMagOrientation[1] = pitch;
        mAccMagOrientation[2] = roll;
        mRotationMatrix = getRotationMatrixFromOrientation(mAccMagOrientation);
    }
}
public static float[] getRotationMatrixFromOrientation(float[] o) {
    float[] xM = new float[9];
    float[] yM = new float[9];
    float[] zM = new float[9];

    float sinX = (float) Math.sin(o[1]);
    float cosX = (float) Math.cos(o[1]);
    float sinY = (float) Math.sin(o[2]);
    float cosY = (float) Math.cos(o[2]);
    float sinZ = (float) Math.sin(o[0]);
    float cosZ = (float) Math.cos(o[0]);

    // rotation about x-axis (pitch)
    xM[0] = 1.0f;xM[1] = 0.0f;xM[2] = 0.0f;
    xM[3] = 0.0f;xM[4] = cosX;xM[5] = sinX;
    xM[6] = 0.0f;xM[7] =-sinX;xM[8] = cosX;

    // rotation about y-axis (roll)
    yM[0] = cosY;yM[1] = 0.0f;yM[2] = sinY;
    yM[3] = 0.0f;yM[4] = 1.0f;yM[5] = 0.0f;
    yM[6] =-sinY;yM[7] = 0.0f;yM[8] = cosY;

    // rotation about z-axis (azimuth)
    zM[0] = cosZ;zM[1] = sinZ;zM[2] = 0.0f;
    zM[3] =-sinZ;zM[4] = cosZ;zM[5] = 0.0f;
    zM[6] = 0.0f;zM[7] = 0.0f;zM[8] = 1.0f;

    // rotation order is y, x, z (roll, pitch, azimuth)
    float[] resultMatrix = matrixMultiplication(xM, yM);
    resultMatrix = matrixMultiplication(zM, resultMatrix);
    return resultMatrix;
}
public static float[] matrixMultiplication(float[] A, float[] B) {
    float[] result = new float[9];

    result[0] = A[0] * B[0] + A[1] * B[3] + A[2] * B[6];
    result[1] = A[0] * B[1] + A[1] * B[4] + A[2] * B[7];
    result[2] = A[0] * B[2] + A[1] * B[5] + A[2] * B[8];

    result[3] = A[3] * B[0] + A[4] * B[3] + A[5] * B[6];
    result[4] = A[3] * B[1] + A[4] * B[4] + A[5] * B[7];
    result[5] = A[3] * B[2] + A[4] * B[5] + A[5] * B[8];

    result[6] = A[6] * B[0] + A[7] * B[3] + A[8] * B[6];
    result[7] = A[6] * B[1] + A[7] * B[4] + A[8] * B[7];
    result[8] = A[6] * B[2] + A[7] * B[5] + A[8] * B[8];

    return result;
}

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