android - 使用传感器的方向

Question

在我的应用程序中，我想显示设备方向，例如北、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);
}
}

我阅读了一些文章，了解到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 samsung galaxy s 进行测试。我哪里出错了。 任何帮助将不胜感激...谢谢

Answer 1

编辑:我将保留这个答案，因为这里没有其他答案，但我再次查看这段代码时的直觉是它可能效果不佳。使用风险自负，如果有人给出了合适的答案，我会删除它

这是我为自己使用而编写的罗盘传感器。它的工作原理，有点。实际上它需要更好的过滤——传感器的结果非常嘈杂，我在它上面构建了一个过滤器来减慢更新速度并改进了一些东西，但如果要在生产中使用它需要一个更好的过滤器

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);
}

}