Android4.2距离感应器

   先说现象，现象就是来电话，接通电话，把手机屏幕靠近脸部，遮挡住P-sensor，屏幕变黑了，不遮挡住P-sensor,屏幕就点亮了。接着我们来看看代码流程。

距离感应器与屏幕休眠可参考

http://blog.csdn.net/wds1181977/article/details/42125699

     先来说说靠近P-sensor，不灭屏的正常的现象：

1. 插入耳机
2. 打开扬声器
3. 打开蓝牙耳机
4. 链接蓝牙键盘

   步骤一： 在PhoneGlobals.java文件中onCreate()方法中：

。。。 。。。

 // lock used to keep the processor awake, when we don't care for the display.
             mPartialWakeLock = mPowerManager.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK
                     | PowerManager.ON_AFTER_RELEASE, LOG_TAG);
             // Wake lock used to control proximity sensor behavior.
             if (mPowerManager.isWakeLockLevelSupported(
                     PowerManager.PROXIMITY_SCREEN_OFF_WAKE_LOCK)) {
                 mProximityWakeLock = mPowerManager.newWakeLock(
                         PowerManager.PROXIMITY_SCREEN_OFF_WAKE_LOCK, LOG_TAG);
             }

。。。 。。。

  注意这个private PowerManager.WakeLock mProximityWakeLock;这个初始化变量，

这个mProximityWakeLock就是所说的P-Sensor锁，它是用来唤醒屏幕和使屏幕睡眠的锁。

步骤二：在PhoneGlobals.java文件中的onCreate()方法中：

 // create mAccelerometerListener only if we are using the proximity sensor
             if (proximitySensorModeEnabled()) {
                 mAccelerometerListener = new AccelerometerListener(this, this);
             }

创建加速度感应器。

步骤三：在更新Phone的状态的时候确定这个加速度的P-sensor感应器起作用；

 <span style="font-size:18px;">/**
      * Notifies the phone app when the phone state changes.
      *
      * This method will updates various states inside Phone app (e.g. proximity sensor mode,
      * accelerometer listener state, update-lock state, etc.)
      */
     /* package */ void updatePhoneState(PhoneConstants.State state) {
         if (state != mLastPhoneState) {
             mLastPhoneState = state;
             if (state == PhoneConstants.State.IDLE)
                 PhoneGlobals.getInstance().pokeUserActivity();
             updateProximitySensorMode(state);

             // Try to acquire or release UpdateLock.
             //
             // Watch out: we don't release the lock here when the screen is still in foreground.
             // At that time InCallScreen will release it on onPause().
             if (state != PhoneConstants.State.IDLE) {
                 // UpdateLock is a recursive lock, while we may get "acquire" request twice and
                 // "release" request once for a single call (RINGING + OFFHOOK and IDLE).
                 // We need to manually ensure the lock is just acquired once for each (and this
                 // will prevent other possible buggy situations too).
                 if (!mUpdateLock.isHeld()) {
                     mUpdateLock.acquire();
                 }
             } else {
                 if (!isShowingCallScreen()) {
                     if (!mUpdateLock.isHeld()) {
                         mUpdateLock.release();
                     }
                 } else {
                     // For this case InCallScreen will take care of the release() call.
                 }
             }

             if (mAccelerometerListener != null) {
                 // use accelerometer to augment proximity sensor when in call
                 mOrientation = AccelerometerListener.ORIENTATION_UNKNOWN;
                </span><span style="color:#ff0000;"><strong><span style="font-size:24px;"> </span><span style="font-size:18px;">mAccelerometerListener.enable(state == PhoneConstants.State.OFFHOOK);</span></strong></span><span style="font-size:18px;">
             }
             // clear our beginning call flag
             mBeginningCall = false;
             // While we are in call, the in-call screen should dismiss the keyguard.
             // This allows the user to press Home to go directly home without going through
             // an insecure lock screen.
             // But we do not want to do this if there is no active call so we do not
             // bypass the keyguard if the call is not answered or declined.
             if (mInCallScreen != null) {
         if (VDBG) Log.d(LOG_TAG, "updatePhoneState: state = " + state);
         if (!PhoneUtils.isDMLocked())
                     mInCallScreen.updateKeyguardPolicy(state == PhoneConstants.State.OFFHOOK);
             }
         }
     }</span>

步骤四：用AccelerometerListener.java类中的监听事件来处理一些这个覆盖的改变，一共有2个状态，一个是

horizontal，一个是vertical的状态。在上述步骤三红色的调用部分注册这个监听事件:

 public void enable(boolean enable) {
        if (DEBUG) Log.d(TAG, "enable(" + enable + ")");
        synchronized (this) {
            if (enable) {
                mOrientation = ORIENTATION_UNKNOWN;
                mPendingOrientation = ORIENTATION_UNKNOWN;
                mSensorManager.registerListener(mSensorListener, mSensor,
                        SensorManager.SENSOR_DELAY_NORMAL);
            } else {
                mSensorManager.unregisterListener(mSensorListener);
                mHandler.removeMessages(ORIENTATION_CHANGED);
            }
        }
    }

步骤五：监听事件的相应的过程如下：

 SensorEventListener mSensorListener = new SensorEventListener() {
         public void onSensorChanged(SensorEvent event) {
             onSensorEvent(event.values[0], event.values[1], event.values[2]);
         }

         public void onAccuracyChanged(Sensor sensor, int accuracy) {
             // ignore
         }
     };

 private void onSensorEvent(double x, double y, double z) {
         if (VDEBUG) Log.d(TAG, "onSensorEvent(" + x + ", " + y + ", " + z + ")");

         // If some values are exactly zero, then likely the sensor is not powered up yet.
         // ignore these events to avoid false horizontal positives.
         if (x == 0.0 || y == 0.0 || z == 0.0) return;

         // magnitude of the acceleration vector projected onto XY plane
         double xy = Math.sqrt(x*x + y*y);
         // compute the vertical angle
         double angle = Math.atan2(xy, z);
         // convert to degrees
         angle = angle * 180.0 / Math.PI;
         int orientation = (angle >  VERTICAL_ANGLE ? ORIENTATION_VERTICAL : ORIENTATION_HORIZONTAL);
         if (VDEBUG) Log.d(TAG, "angle: " + angle + " orientation: " + orientation);
         setOrientation(orientation);
     }


 private void setOrientation(int orientation) {
         synchronized (this) {
             if (mPendingOrientation == orientation) {
                 // Pending orientation has not changed, so do nothing.
                 return;
             }

             // Cancel any pending messages.
             // We will either start a new timer or cancel alltogether
             // if the orientation has not changed.
             mHandler.removeMessages(ORIENTATION_CHANGED);

             if (mOrientation != orientation) {
                 // Set timer to send an event if the orientation has changed since its
                 // previously reported value.
                 mPendingOrientation = orientation;
                 Message m = mHandler.obtainMessage(ORIENTATION_CHANGED);
                 // set delay to our debounce timeout
                 int delay = (orientation == ORIENTATION_VERTICAL ? VERTICAL_DEBOUNCE
                                                                  : HORIZONTAL_DEBOUNCE);
                 mHandler.sendMessageDelayed(m, delay);
             } else {
                 // no message is pending
                 mPendingOrientation = ORIENTATION_UNKNOWN;
             }
         }
     }

然后发送消息ORIENTATION_CHANGED这个改变的消息;这个消息会调用一个回调函数，然后根据状态判断，调用acquire和release（）方法；

 Handler mHandler = new Handler() {
         public void handleMessage(Message msg) {
             switch (msg.what) {
             case ORIENTATION_CHANGED:
                 synchronized (this) {
                     mOrientation = mPendingOrientation;
                     if (DEBUG) {
                         Log.d(TAG, "orientation: " +
                             (mOrientation == ORIENTATION_HORIZONTAL ? "horizontal"
                                 : (mOrientation == ORIENTATION_VERTICAL ? "vertical"
                                     : "unknown")));
                     }
                     mListener.orientationChanged(mOrientation);
                 }
                 break;
             }
         }
     };

步骤五：回调到PhoneGlobals.java这个类的 orientationChanged（）

 @Override
     public void orientationChanged(int orientation) {
         mOrientation = orientation;
         updateProximitySensorMode(mCM.getState());
     }

 <pre name="code" class="java">/**
      * Updates the wake lock used to control proximity sensor behavior,
      * based on the current state of the phone.  This method is called
      * from the CallNotifier on any phone state change.
      *
      * On devices that have a proximity sensor, to avoid false touches
      * during a call, we hold a PROXIMITY_SCREEN_OFF_WAKE_LOCK wake lock
      * whenever the phone is off hook.  (When held, that wake lock causes
      * the screen to turn off automatically when the sensor detects an
      * object close to the screen.)
      *
      * This method is a no-op for devices that don't have a proximity
      * sensor.
      *
      * Note this method doesn't care if the InCallScreen is the foreground
      * activity or not.  That's because we want the proximity sensor to be
      * enabled any time the phone is in use, to avoid false cheek events
      * for whatever app you happen to be running.
      *
      * Proximity wake lock will *not* be held if any one of the
      * conditions is true while on a call:
      * 1) If the audio is routed via Bluetooth
      * 2) If a wired headset is connected
      * 3) if the speaker is ON
      * 4) If the slider is open(i.e. the hardkeyboard is *not* hidden)
      *
      * @param state current state of the phone (see {@link Phone#State})
      */
     /* package */ void updateProximitySensorMode(PhoneConstants.State state) {

         boolean isRingingWhenActive = false;//MTK81281 add isRingingWhenActive for Cr:ALPS00117091

         if (VDBG) Log.d(LOG_TAG, "updateProximitySensorMode: state = " + state);

         if (proximitySensorModeEnabled()) {
             synchronized (mProximityWakeLock) {
                 // turn proximity sensor off and turn screen on immediately if
                 // we are using a headset, the keyboard is open, or the device
                 // is being held in a horizontal position.
                 boolean screenOnImmediately = (isHeadsetPlugged()
                                                || PhoneUtils.isSpeakerOn(this)
                                                || isBluetoothHeadsetAudioOn()
                                                || mIsHardKeyboardOpen);

                 if (FeatureOption.MTK_VT3G324M_SUPPORT) {
                     screenOnImmediately = screenOnImmediately ||
                             ((!VTCallUtils.isVTIdle()) && (!VTCallUtils.isVTRinging()));
                 }

                 // We do not keep the screen off when the user is outside in-call screen and we are
                 // horizontal, but we do not force it on when we become horizontal until the
                 // proximity sensor goes negative.

                 // this horizontal is not the same portrait.
                  boolean horizontal =
                         (mOrientation == AccelerometerListener.ORIENTATION_HORIZONTAL);
                  screenOnImmediately |= !isShowingCallScreenForProximity() && horizontal;
                 if (VDBG) Log.d(LOG_TAG, "updateProximitySensorMode: mBeginningCall = " + mBeginningCall);
                 if (VDBG) Log.d(LOG_TAG, "updateProximitySensorMode: screenOnImmediately = " + screenOnImmediately);
            //MTK81281 add isRingingWhenActive for Cr:ALPS00117091 start
            //when a call is activeand p-sensor turn off the screen,
            //another call or vtcall in we don't release the lock and acquire again
            //(the prowermanagerservice will turn on and off the screen and it's a problem)
            //instead ,we don't release the lock(prowermanagerservice will not turn on and off the screen)
                 isRingingWhenActive = (state == PhoneConstants.State.RINGING)
                     && (mCM.getActiveFgCallState() == Call.State.ACTIVE)
                     && (mCM.getFirstActiveRingingCall().getState() == Call.State.WAITING);

                 if (VDBG) Log.d(LOG_TAG, "updateProximitySensorMode: isRingingWhenActive = " + isRingingWhenActive);
            //MTK81281 add  isRingingWhenActive for Cr:ALPS00117091 end

                 //MTK81281 add isRingingWhenActive for Cr:ALPS00117091
                 if (((state == PhoneConstants.State.OFFHOOK) || mBeginningCall || isRingingWhenActive)
                         && !screenOnImmediately) {
                     // Phone is in use!  Arrange for the screen to turn off
                     // automatically when the sensor detects a close object.
                     if (!mProximityWakeLock.isHeld()) {
                         if (DBG) Log.d(LOG_TAG, "updateProximitySensorMode: acquiring...");
                         <span style="color:#ff0000;"><strong>mProximityWakeLock.acquire();</strong></span>
                     } else {
                         if (VDBG) Log.d(LOG_TAG, "updateProximitySensorMode: lock already held.");
                     }
                 } else {
                     // Phone is either idle, or ringing.  We don't want any
                     // special proximity sensor behavior in either case.
                     if (mProximityWakeLock.isHeld()) {
                         if (DBG) Log.d(LOG_TAG, "updateProximitySensorMode: releasing...");
                         // Wait until user has moved the phone away from his head if we are
                         // releasing due to the phone call ending.
                         // Qtherwise, turn screen on immediately
                         int flags =
                             (screenOnImmediately ? 0 : PowerManager.WAIT_FOR_PROXIMITY_NEGATIVE);
                         <strong><span style="color:#ff0000;">mProximityWakeLock.release(flags);</span></strong>
                     } else {
                         if (VDBG) {
                             Log.d(LOG_TAG, "updateProximitySensorMode: lock already released.");
                         }
                     }
                 }
             }
         }
     }</pre><br><br>

到这已经把Phone层的P-sensor的亮屏和灭屏说完了，回头再来屡屡这个mProximityWakeLock在framework层怎么具体实现的亮屏和灭屏的；敬请期待。。。 。。。

    更正：上述的讲解是不正确的，后来经过打log，发现，这个mProximityWakeLock.acquire();和mProximityWakeLock.release(flags);只是申请这个锁，和释放这个锁，防止其他的调用，

其实，在4.2以前Phone模块的P-Sensor在PowerManagerServer.java中处理的，而Android4.2的时候，谷歌对代码进行了一些调整，所以Phone的模块的P-Sensor的控制的类在DisplayPowerController.java

路径:framework/base/services/java/com/android/server/power/DisplayPowerController.java中的：

 private final SensorEventListener mProximitySensorListener = new SensorEventListener() {
        @Override
        public void onSensorChanged(SensorEvent event) {
            if (mProximitySensorEnabled) {
                final long time = SystemClock.uptimeMillis();
                final float distance = event.values[0];
                boolean positive = distance >= 0.0f && distance < mProximityThreshold;
                if (DEBUG) {
                    Slog.d(TAG, "P-Sensor Changed: " + positive);
                }
                handleProximitySensorEvent(time, positive);
            }
        }

 <span style="color: rgb(255, 0, 0);"><strong></strong></span>

这个onSensorChanged（）就是距离感应器的；这个log：

P-Sensor Changed:true  表示：靠近手机，P-sensor被遮挡住；

P-Sensor Changed:false 表示：离开手机，P-sensor没有被遮挡住；

通过这个log也能帮我们分析一些问题；这个mProximitySensorListener的注册和反注册，大家可以自己在这个类中搜索就可以了；

       补充：在PowserManagerServerice.java这个类中，  private LightsService.Light mButtonLight;这个变量申请的就是按键灯，像：home，返回键，menu键的灯，申请这个灯的代码：

 private LightsService mLightsService;
 。。。 。。。

 mButtonLight = mLightsService.getLight(LightsService.LIGHT_ID_BUTTONS);

通过LightService可以获得键盘灯的实例，

打开灯的方法：mButtonLight.setBrightness(120);//120可以是（0～255）任意数字；

关闭灯的方法：mButtonLight.turnOff();

     需求：要想使Phone通话界面的P-Sensor亮灭屏幕和按键灯同步，当屏幕灭的时候，按键灯也灭，屏幕亮的时候，按键灯也亮；其实做法很简单了，在onSensorChanged（）的时候处理，扩一些接口，

具体设计的类我列举一下：

•   PowerManager.java
•   PowerManagerService.java
•   BridgetPowerManager.java
•   IPowerManager.adil
•   DisPlayPowerController.java

     具体代码就不详细赘述了，还是“觉知此事要躬行”；

     注意在

 mLastUserActivityButtonTime = SystemClock.uptimeMillis();
         mButtonLight.setBrightness(102);

在设置打开按键灯的时候，设置一下最后一次用户触摸按钮的时间；至于为什么？？大家自已到时候打log就明白了。。。 。。。

 mLastUserActivityButtonTime