sensor：gsensor的流程以及优化分析

一 概述

frameworks\base\core\java\android\view\WindowOrientationListener.java

监听sensor是否有数据变化

 

首先看看芯片方向（x,y,z）：

补充流程：

PhoneWindowManager调用updateOrientationListenerLp去SensorManager里面去注册一个Listener，

当Sensor发生变化的时候，PhoneWindowManager就可以监听到并且调用回调onProposeRotationChanged。

Callback 如下：

1 MyOrientationListener.onProposeRotationChange  PhoneWindowManager.java

-------------》

    class MyOrientationListener extends WindowOrientationListener {

       

        @Override

        public void onProposedRotationChanged(introtation) {

            if (localLOGV) Log.v(TAG,"onProposedRotationChanged, rotation=" + rotation);

            updateRotation(false);

        }

    }

--------》

2. PhoneWindowManager.updateRotation(booleanalwaysSendConfiguration)

    void updateRotation(booleanalwaysSendConfiguration) {

        try {

            //set orientation on WindowManager

            mWindowManager.updateRotation(alwaysSendConfiguration, false);、、WindowManagerService的对象

        } catch (RemoteException e) {

            // Ignore

        }

    }

3. WindowManagerService.updateRotation(booleanalwaysSendConfiguration, boolean forceRelayout)

 

 

二代码分析

public void onSensorChanged(SensorEvent event) {

            // The vector given in theSensorEvent points straight up (towards the sky) under ideal

            // conditions (the phone is notaccelerating).  I'll call this up vectorelsewhere.

            float x =event.values[ACCELEROMETER_DATA_X];

            float y =event.values[ACCELEROMETER_DATA_Y];

            float z =event.values[ACCELEROMETER_DATA_Z];

 

            if (LOG) {

                Slog.v(TAG, "Rawacceleration vector: "

                        + "x=" + x +", y=" + y + ", z=" + z

                        + ",magnitude=" + FloatMath.sqrt(x * x + y * y + z * z));

            }

 

            // Apply a low-pass filter to theacceleration up vector in cartesian space.

            // Reset the orientation listenerstate if the samples are too far apart in time

            // or when we see values of (0, 0,0) which indicates that we polled the

            // accelerometer too soon afterturning it on and we don't have any data yet.

            final long now = event.timestamp;

            final long then =mLastFilteredTimestampNanos;

            final float timeDeltaMS = (now -then) * 0.000001f;

            final boolean skipSample;

            if (now < then

                    || now > then +MAX_FILTER_DELTA_TIME_NANOS

                    || (x == 0 && y ==0 && z == 0)) {

                if (LOG) {

                    Slog.v(TAG, "Resettingorientation listener.");

                }

                reset();

                skipSample = true;

            } else {

                final float alpha = timeDeltaMS/ (FILTER_TIME_CONSTANT_MS + timeDeltaMS);

                x = alpha * (x -mLastFilteredX) + mLastFilte