Android传感器之方向传感器Orientation功能实现与源码

先明确一下空间坐标系的三个方向：
x 方向就是手机的水平方向，右为正；
y 方向就是手机的水平垂直方向，前为正；
z 方向就是手机的空间垂直方向，天空的方向为正，地球的方向为负。
方向角的定义是手机y轴水平面上的投影与正北方向的夹角。（值得范围是 0 ~ 359 其中0=North, 90=East, 180=South, 270=West）
倾斜角的定义是手机y轴与水平面的夹角（手机z轴向y轴方向移动为正 ,值得范围是 -180 ~ 180）
旋转角的定义是手机x轴与水平面的夹角（手机x轴离开z轴方向为正，值得范围是 -90 ~ 90）
也就是说，当你把手机水平放置在桌面上(屏幕向上)且手机指向正北(Y轴方向)，此时传感器获得的xyz三个值应该都为0。

基于Rexsee对于方向传感器Orientation的扩展，我们可以很快的实现传感器功能，比如读取X/Y/Z方向角度值：rexseeOrientation.getLastKnownX()；读取响应速度：rexseeOrientation.getRate()；设置传感器检测周期：rexseeOrientation.setCycle(1000)等。具体的函数介绍可以在Rexsee社区的手册与源码中查阅：http://www.rexsee.com/CN/helpReference.php

如下是Rexsee用Java封装的的方向传感器功能详细源码。感兴趣的也可以直接去Rexsee社区查阅：http://www.rexsee.com。
但是首先需要知道，并不是所有的Android手机都支持方向传感器。。比如说乐Phone，好像就是加速度、重力和光线，方向和磁场貌似都不支持。

[java]
/*
* Copyright (C) 2011 The Rexsee Open Source Project
*
* Licensed under the Rexsee License, Version 1.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
*      http://www.rexsee.com/CN/legal/license.html
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/

package rexsee.sensor;

import rexsee.core.browser.JavascriptInterface;
import rexsee.core.browser.RexseeBrowser;
import android.content.Context;
import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorManager;

public class RexseeSensorOrientation implements JavascriptInterface {

       public static final String INTERFACE_NAME = "Orientation";
       @Override
       public String getInterfaceName() {
               return mBrowser.application.resources.prefix + INTERFACE_NAME;
       }
       @Override
       public JavascriptInterface getInheritInterface(RexseeBrowser childBrowser) {
               return this;
       }
       @Override
       public JavascriptInterface getNewInterface(RexseeBrowser childBrowser) {
               return new RexseeSensorOrientation(childBrowser);
       }

       public static final String EVENT_ONORIENTATIONCHANGED = "onOrientationChanged";

       private final Context mContext;
       private final RexseeBrowser mBrowser;
       private final SensorManager mSensorManager;
       private SensorEventListener mSensorListener;
       private final Sensor mSensor;

       private int mRate = SensorManager.SENSOR_DELAY_NORMAL;
       private int mCycle = 100; //milliseconds
       private int mEventCycle = 100; //milliseconds

       private float mAccuracyX = 0;
       private float mAccuracyY = 0;
       private float mAccuracyZ = 0;

       private long lastUpdate = -1;
       private long lastEvent = -1;

       private float x = -999f;
       private float y = -999f;
       private float z = -999f;

       public RexseeSensorOrientation(RexseeBrowser browser) {
               mContext = browser.getContext();
               mBrowser = browser;
               browser.eventList.add(EVENT_ONORIENTATIONCHANGED);

               mSensorManager = (SensorManager) mContext.getSystemService(Context.SENSOR_SERVICE);

               mSensor = mSensorManager.getDefaultSensor(Sensor.TYPE_ORIENTATION);
               mSensorListener = new SensorEventListener() {
                       @Override
                       public void onAccuracyChanged(Sensor sensor, int accuracy) {
                       }
                       @Override
                       public void onSensorChanged(SensorEvent event) {
           &n

补充：移动开发 , Android ,