在我的应用程序中，我想显示设备方向，如北，南，东，西。为此，我正在使用加速度计和磁传感器，并尝试使用以下代码。
public class MainActivity extends Activity implements SensorEventListener
{
public static float swRoll;
public static float swPitch;
public static float swAzimuth;
public static SensorManager mSensorManager;
public static Sensor accelerometer;
public static Sensor magnetometer;
public static float[] mAccelerometer = null;
public static float[] mGeomagnetic = null;
public void onAccuracyChanged(Sensor sensor, int accuracy) {
}
@Override
public void onSensorChanged(SensorEvent event)
{
// onSensorChanged gets called for each sensor so we have to remember the values
if (event.sensor.getType() == Sensor.TYPE_ACCELEROMETER)
{
mAccelerometer = event.values;
}
if (event.sensor.getType() == Sensor.TYPE_MAGNETIC_FIELD)
{
mGeomagnetic = event.values;
}
if (mAccelerometer != null && mGeomagnetic != null)
{
float R[] = new float[9];
float I[] = new float[9];
boolean success = SensorManager.getRotationMatrix(R, I, mAccelerometer, mGeomagnetic);
if (success)
{
float orientation[] = new float[3];
SensorManager.getOrientation(R, orientation);
// at this point, orientation contains the azimuth(direction), pitch and roll values.
double azimuth = 180 * orientation[0] / Math.PI;
//double pitch = 180 * orientation[1] / Math.PI;
//double roll = 180 * orientation[2] / Math.PI;
Toast.makeText(getApplicationContext(), "azimuth: "+azimuth, Toast.LENGTH_SHORT).show();
//Toast.makeText(getApplicationContext(), "pitch: "+pitch, Toast.LENGTH_SHORT).show();
//Toast.makeText(getApplicationContext(), "roll: "+roll, Toast.LENGTH_SHORT).show();
}
}
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mSensorManager = (SensorManager)getSystemService(SENSOR_SERVICE);
accelerometer = mSensorManager.getDefaultSensor(Sensor.TYPE_ACCELEROMETER);
magnetometer = mSensorManager.getDefaultSensor(Sensor.TYPE_MAGNETIC_FIELD);
}
@Override
protected void onResume() {
super.onResume();
mSensorManager.registerListener(this, accelerometer, SensorManager.SENSOR_DELAY_GAME);
mSensorManager.registerListener(this, magnetometer, SensorManager.SENSOR_DELAY_GAME);
}
@Override
protected void onPause() {
super.onPause();
mSensorManager.unregisterListener(this, accelerometer);
mSensorManager.unregisterListener(this, magnetometer);
}
}
我读了一些艺术品并且知道方位角值用于获取方向。但它没有显示正确的值，即它总是在任何方向上显示103到140之间的值。我正在使用三星galaxy s进行测试。哪里出错了 任何帮助将不胜感激......谢谢
答案 0 :(得分：6)
这是我为自己使用而编写的指南针传感器。它有点起作用。实际上它需要更好的过滤 - 来自传感器的结果非常嘈杂，我在它上面构建了一个过滤器以减缓更新并改进了一些东西，但如果要在生产中使用它需要更好的过滤器
package com.gabesechan.android.reusable.sensor;
import java.lang.ref.WeakReference;
import java.util.HashSet;
import android.content.Context;
import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorManager;
import android.os.Handler;
import android.os.Message;
public class CompassSensor {
SensorManager sm;
int lastDirection = -1;
int lastPitch;
int lastRoll;
boolean firstReading = true;
HashSet<CompassListener> listeners = new HashSet<CompassListener>();
static CompassSensor mInstance;
public static CompassSensor getInstance(Context ctx){
if(mInstance == null){
mInstance = new CompassSensor(ctx);
}
return mInstance;
}
private CompassSensor(Context ctx){
sm = (SensorManager) ctx.getSystemService(Context.SENSOR_SERVICE);
onResume();
}
public void onResume(){
sm.registerListener(sensorListener, sm.getDefaultSensor(Sensor.TYPE_ACCELEROMETER), SensorManager.SENSOR_DELAY_NORMAL);
sm.registerListener(sensorListener, sm.getDefaultSensor(Sensor.TYPE_MAGNETIC_FIELD), SensorManager.SENSOR_DELAY_UI);
firstReading = true;
//Restart the timer only if we have listeners
if(listeners.size()>0){
handler.sendMessageDelayed(Message.obtain(handler, 1),1000);
}
}
public void onPause(){
sm.unregisterListener(sensorListener);
handler.removeMessages(1);
}
private final SensorEventListener sensorListener = new SensorEventListener(){
float accelerometerValues[] = null;
float geomagneticMatrix[] = null;
public void onSensorChanged(SensorEvent event) {
if (event.accuracy == SensorManager.SENSOR_STATUS_UNRELIABLE)
return;
switch (event.sensor.getType()) {
case Sensor.TYPE_ACCELEROMETER:
accelerometerValues = event.values.clone();
break;
case Sensor.TYPE_MAGNETIC_FIELD:
geomagneticMatrix = event.values.clone();
break;
}
if (geomagneticMatrix != null && accelerometerValues != null && event.sensor.getType() == Sensor.TYPE_MAGNETIC_FIELD) {
float[] R = new float[16];
float[] I = new float[16];
float[] outR = new float[16];
//Get the rotation matrix, then remap it from camera surface to world coordinates
SensorManager.getRotationMatrix(R, I, accelerometerValues, geomagneticMatrix);
SensorManager.remapCoordinateSystem(R, SensorManager.AXIS_X, SensorManager.AXIS_Z, outR);
float values[] = new float[4];
SensorManager.getOrientation(outR,values);
int direction = normalizeDegrees(filterChange((int)Math.toDegrees(values[0])));
int pitch = normalizeDegrees(Math.toDegrees(values[1]));
int roll = normalizeDegrees(Math.toDegrees(values[2]));
if((int)direction != (int)lastDirection){
lastDirection = (int)direction;
lastPitch = (int)pitch;
lastRoll = (int)roll;
}
}
}
public void onAccuracyChanged(Sensor sensor, int accuracy) {
}
};
//Normalize a degree from 0 to 360 instead of -180 to 180
private int normalizeDegrees(double rads){
return (int)((rads+360)%360);
}
//We want to ignore large bumps in individual readings. So we're going to cap the number of degrees we can change per report
private static final int MAX_CHANGE = 3;
private int filterChange(int newDir){
newDir = normalizeDegrees(newDir);
//On the first reading, assume it's right. Otherwise NW readings take forever to ramp up
if(firstReading){
firstReading = false;
return newDir;
}
//Figure out how many degrees to move
int delta = newDir - lastDirection;
int normalizedDelta = normalizeDegrees(delta);
int change = Math.min(Math.abs(delta),MAX_CHANGE);
//We always want to move in the direction of lower distance. So if newDir is lower and delta is less than half a circle, lower lastDir
// Same if newDir is higher but the delta is more than half a circle (you'd be faster in the other direction going lower).
if( normalizedDelta > 180 ){
change = -change;
}
return lastDirection+change;
}
public void addListener(CompassListener listener){
if(listeners.size() == 0){
//Start the timer on first listener
handler.sendMessageDelayed(Message.obtain(handler, 1),1000);
}
listeners.add(listener);
}
public void removeListener(CompassListener listener){
listeners.remove(listener);
if(listeners.size() == 0){
handler.removeMessages(1);
}
}
public int getLastDirection(){
return lastDirection;
}
public int getLastPitch(){
return lastPitch;
}
public int getLastRoll(){
return lastPitch;
}
private void callListeners(){
for(CompassListener listener: listeners){
listener.onDirectionChanged(lastDirection, lastPitch, lastRoll);
}
}
//This handler is run every 1s, and updates the listeners
//Static class because otherwise we leak, Eclipse told me so
static class IncomingHandler extends Handler {
private final WeakReference<CompassSensor> compassSensor;
IncomingHandler(CompassSensor sensor) {
compassSensor = new WeakReference<CompassSensor>(sensor);
}
@Override
public void handleMessage(Message msg)
{
CompassSensor sensor = compassSensor.get();
if (sensor != null) {
sensor.callListeners();
}
sendMessageDelayed(Message.obtain(this, 1), 1000);
}
}
IncomingHandler handler = new IncomingHandler(this);
public interface CompassListener {
void onDirectionChanged(int direction, int pitch, int roll);
}
}