似乎有许多旧的例子表明在Android设备上获得当前的主要方向,但Google提供的官方解决方案似乎并未出现在他们的文档中.
不推荐使用的最旧参考Sensor.TYPE_ORIENTATION,最新的参考文献提到了Sensor.TYPE_ACCELEROMETER和Sensor.TYPE_MAGNETIC_FIELD(我试过但收效甚微 – 准确性根据设备方向快速变化).我一直在尝试使用像this.这样的两个实现,我甚至见过一些TYPE.GRAVITY.
most recent seem to suggest TYPE_ROTATION_VECTOR显然是一个融合传感器(reference),但示例实现似乎并不容易获得.
我需要使用这些位置/运动传感器,而不是GPS,因为在需要进行此测量时,用户不会移动.无论手机是平的还是垂直的(如果你正在拍照),也需要测量稳定
在我们以某种方式拉出度数测量之后,转换到基本方向似乎很容易.(https://stackoverflow.com/a/25349774/1238737)
以前的方案
> How to get Direction in Android (Such as North,West)
> https://stackoverflow.com/a/11068878/1238737
最佳答案
我之前正在研究开源地图项目,如OsmAnd,MapsWithMe和MapBox.我认为这些项目是地图和导航领域中最好的Android开源.我检查了他们的代码,发现当手机垂直然后围绕垂直轴(y)旋转时,显示罗盘的MapBox方法是稳定的.如果旋转矢量传感器可用,它使用TYPE_ROTATION_VECTOR.否则,它使用TYPE_ORIENTATION传感器或TYPE_ACCELEROMETER和TYPE_MAGNETIC_FIELD的组合.在使用TYPE_ACCELEROMETER和TYPE_MAGNETIC_FIELD的情况下,可以通过低通滤波器减少结果的振荡,以实现更平滑的值.
LocationComponentCompassEngine.java:
import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorManager;
import android.os.SystemClock;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.view.Surface;
import android.view.WindowManager;
import timber.log.Timber;
import java.util.ArrayList;
import java.util.List;
/**
* This manager class handles compass events such as starting the tracking of device bearing,or
* when a new compass update occurs.
*/
public class LocationComponentCompassEngine implements SensorEventListener {
// The rate sensor events will be delivered at. As the Android documentation states,this is only
// a hint to the system and the events might actually be received faster or slower then this
// specified rate. Since the minimum Android API levels about 9,we are able to set this value
// ourselves rather than using one of the provided constants which deliver updates too quickly for
// our use case. The default is set to 100ms
private static final int SENSOR_DELAY_MICROS = 100 * 1000;
// Filtering coefficient 0 < ALPHA < 1
private static final float ALPHA = 0.45f;
// Controls the compass update rate in milliseconds
private static final int COMPASS_UPDATE_RATE_MS = 500;
private final WindowManager windowManager;
private final SensorManager sensorManager;
private final ListIoUsNameCombination")
private void updateOrientation() {
if (rotationVectorValue != null) {
SensorManager.getRotationMatrixFromVector(rotationMatrix,rotationVectorValue);
} else {
// Get rotation matrix given the gravity and geomagnetic matrices
SensorManager.getRotationMatrix(rotationMatrix,null,gravityValues,magneticValues);
}
final int worldAxisForDeviceAxisX;
final int worldAxisForDeviceAxisY;
// Remap the axes as if the device screen was the instrument panel,// and adjust the rotation matrix for the device orientation.
switch (windowManager.getDefaultDisplay().getRotation()) {
case Surface.ROTATION_90:
worldAxisForDeviceAxisX = SensorManager.AXIS_Z;
worldAxisForDeviceAxisY = SensorManager.AXIS_MINUS_X;
break;
case Surface.ROTATION_180:
worldAxisForDeviceAxisX = SensorManager.AXIS_MINUS_X;
worldAxisForDeviceAxisY = SensorManager.AXIS_MINUS_Z;
break;
case Surface.ROTATION_270:
worldAxisForDeviceAxisX = SensorManager.AXIS_MINUS_Z;
worldAxisForDeviceAxisY = SensorManager.AXIS_X;
break;
case Surface.ROTATION_0:
default:
worldAxisForDeviceAxisX = SensorManager.AXIS_X;
worldAxisForDeviceAxisY = SensorManager.AXIS_Z;
break;
}
float[] adjustedRotationMatrix = new float[9];
SensorManager.remapCoordinateSystem(rotationMatrix,worldAxisForDeviceAxisX,worldAxisForDeviceAxisY,adjustedRotationMatrix);
// Transform rotation matrix into azimuth/pitch/roll
float[] orientation = new float[3];
SensorManager.getOrientation(adjustedRotationMatrix,orientation);
// The x-axis is all we care about here.
notifyCompassChangeListeners((float) Math.toDegrees(orientation[0]));
}
private void notifyCompassChangeListeners(float heading) {
for (CompassListener compassListener : compassListeners) {
compassListener.onCompassChanged(heading);
}
lastHeading = heading;
}
private void registerSensorListeners() {
if (isCompassSensorAvailable()) {
// Does nothing if the sensors already registered.
sensorManager.registerListener(this,compassSensor,SENSOR_DELAY_MICROS);
} else {
sensorManager.registerListener(this,gravitySensor,SENSOR_DELAY_MICROS);
sensorManager.registerListener(this,magneticFieldSensor,SENSOR_DELAY_MICROS);
}
}
private void unregisterSensorListeners() {
if (isCompassSensorAvailable()) {
sensorManager.unregisterListener(this,compassSensor);
} else {
sensorManager.unregisterListener(this,gravitySensor);
sensorManager.unregisterListener(this,magneticFieldSensor);
}
}
private boolean isCompassSensorAvailable() {
return compassSensor != null;
}
/**
* Helper function,that filters newValues,considering prevIoUs values
*
* @param newValues array of float,that contains new data
* @param smoothedValues array of float,that contains prevIoUs state
* @return float filtered array of float
*/
private float[] lowPassFilter(float[] newValues,float[] smoothedValues) {
if (smoothedValues == null) {
return newValues;
}
for (int i = 0; i < newValues.length; i++) {
smoothedValues[i] = smoothedValues[i] + ALPHA * (newValues[i] - smoothedValues[i]);
}
return smoothedValues;
}
/**
* Pulls out the rotation vector from a SensorEvent,with a maximum length
* vector of four elements to avoid potential compatibility issues.
*
* @param event the sensor event
* @return the events rotation vector,potentially truncated
*/
@NonNull
private float[] getRotationVectorFromSensorEvent(@NonNull SensorEvent event) {
if (event.values.length > 4) {
// On some Samsung devices SensorManager.getRotationMatrixFromVector
// appears to throw an exception if rotation vector has length > 4.
// For the purposes of this class the first 4 values of the
// rotation vector are sufficient (see crbug.com/335298 for details).
// Only affects Android 4.3
System.arraycopy(event.values,truncatedRotationVectorValue,4);
return truncatedRotationVectorValue;
} else {
return event.values;
}
}
public static float shortestRotation(float heading,float prevIoUsHeading) {
double diff = prevIoUsHeading - heading;
if (diff > 180.0f) {
heading += 360.0f;
} else if (diff < -180.0f) {
heading -= 360.f;
}
return heading;
}
}
CompassListener.java:
/**
* Callbacks related to the compass
*/
public interface CompassListener {
/**
* Callback's invoked when a new compass update occurs. You can listen into the compass updates
* using {@link LocationComponent#addCompassListener(CompassListener)} and implementing these
* callbacks. Note that this interface is also used internally to to update the UI chevron/arrow.
*
* @param userHeading the new compass heading
*/
void onCompassChanged(float userHeading);
/**
* This gets invoked when the compass accuracy status changes from one value to another. It
* provides an integer value which is identical to the {@code SensorManager} class constants:
*
MainActivity.java:
import android.content.Context;
import android.hardware.SensorManager;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v7.app.AppCompatActivity;
import android.view.WindowManager;
import android.widget.TextView;
import java.util.Locale;
public class MainActivity extends AppCompatActivity {
private LocationComponentCompassEngine compassEngine;
private float prevIoUsCompassBearing = -1f;
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
final TextView textView = findViewById(R.id.textView);
CompassListener compassListener = new CompassListener() {
@Override
public void onCompassChanged(float targetCompassBearing) {
if (prevIoUsCompassBearing < 0) {
prevIoUsCompassBearing = targetCompassBearing;
}
float normalizedBearing =
LocationComponentCompassEngine.shortestRotation(targetCompassBearing,prevIoUsCompassBearing);
prevIoUsCompassBearing = targetCompassBearing;
String status = "NO_CONTACT";
switch (compassEngine.getLastAccuracySensorStatus()) {
case SensorManager.SENSOR_STATUS_NO_CONTACT:
status = "NO_CONTACT";
break;
case SensorManager.SENSOR_STATUS_UNRELIABLE:
status = "UNRELIABLE";
break;
case SensorManager.SENSOR_STATUS_ACCURACY_LOW:
status = "ACCURACY_LOW";
break;
case SensorManager.SENSOR_STATUS_ACCURACY_MEDIUM:
status = "ACCURACY_MEDIUM";
break;
case SensorManager.SENSOR_STATUS_ACCURACY_HIGH:
status = "ACCURACY_HIGH";
break;
}
textView.setText(String.format(Locale.getDefault(),"CompassBearing: %f\nAccuracySensorStatus: %s",normalizedBearing,status));
}
@Override
public void onCompassAccuracyChange(int compassStatus) {
}
};
WindowManager windowManager = (WindowManager) getSystemService(Context.WINDOW_SERVICE);
SensorManager sensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);
compassEngine = new LocationComponentCompassEngine(windowManager,sensorManager);
compassEngine.addCompassListener(compassListener);
compassEngine.onStart();
}
@Override
protected void onDestroy() {
super.onDestroy();
compassEngine.onStop();
}
}