结合重力感应器来计算手机移动的方位

public void onSensorChanged( SensorEvent event ) {

    // If we don't have a Location, we break out
    if ( LocationObj == null ) return;

    float azimuth = event.values[0];
    float baseAzimuth = azimuth;

    GeomagneticField geoField = new GeomagneticField( Double
        .valueOf( LocationObj.getLatitude() ).floatValue(), Double
        .valueOf( LocationObj.getLongitude() ).floatValue(),
        Double.valueOf( LocationObj.getAltitude() ).floatValue(),
        System.currentTimeMillis() );

    azimuth -= geoField.getDeclination(); // converts magnetic north into true north

    // Store the bearingTo in the bearTo variable
    float bearTo = LocationObj.bearingTo( destinationObj );

    // If the bearTo is smaller than 0, add 360 to get the rotation clockwise.
    if (bearTo < 0) {
        bearTo = bearTo + 360;
    }

    //This is where we choose to point it
    float direction = bearTo - azimuth;

    // If the direction is smaller than 0, add 360 to get the rotation clockwise.
    if (direction < 0) {
        direction = direction + 360;
    }

    rotateImageView( arrow, R.drawable.arrow, direction );

    //Set the field
    String bearingText = "N";

    if ( (360 >= baseAzimuth && baseAzimuth >= 337.5) || (0 <= baseAzimuth && baseAzimuth <= 22.5) ) bearingText = "N";
    else if (baseAzimuth > 22.5 && baseAzimuth < 67.5) bearingText = "NE";
    else if (baseAzimuth >= 67.5 && baseAzimuth <= 112.5) bearingText = "E";
    else if (baseAzimuth > 112.5 && baseAzimuth < 157.5) bearingText = "SE";
    else if (baseAzimuth >= 157.5 && baseAzimuth <= 202.5) bearingText = "S";
    else if (baseAzimuth > 202.5 && baseAzimuth < 247.5) bearingText = "SW";
    else if (baseAzimuth >= 247.5 && baseAzimuth <= 292.5) bearingText = "W";
    else if (baseAzimuth > 292.5 && baseAzimuth < 337.5) bearingText = "NW";
    else bearingText = "?";

    fieldBearing.setText(bearingText);

}

PS,用这种方式，如果手机的方向和移动的方向不一致，那就会不准。