Ambient light sensor

This is a bit of a lie: Apple does not expose any direct ambient light sensing API to developers, so this demo uses screen brightness as a proxy.
This relies on the user having auto brightness enabled, which isn’t always a given (and there’s no easy way to detect if that’s on, either).

ios 不支持获取环境亮度。
androidAPI支持。

<code>
package com.example.testlightambient;
import android.app.Activity;
import android.content.Context;
import android.hardware.Sensor;
import android.hardware.SensorEvent;
import android.hardware.SensorEventListener;
import android.hardware.SensorManager;
import android.os.Bundle;

public class SensorActivity extends Activity implements SensorEventListener {
private SensorManager mSensorManager;
private Sensor mPressure;

@Override
public final void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

//Get an instance of the sensor service, and use that to get an instance of
// a particular sensor.
mSensorManager = (SensorManager) getSystemService(Context.SENSOR_SERVICE);
mPressure = mSensorManager.getDefaultSensor(Sensor.TYPE_LIGHT);
}

@Override
public final void onAccuracyChanged(Sensor sensor, int accuracy) {
// Do something here if sensor accuracy changes.
}

@Override
public final void onSensorChanged(SensorEvent event) {
float millibars_of_pressure = event.values[0];
// Do something with this sensor data.
}

@Override
protected void onResume() {
// Register a listener for the sensor.
super.onResume();
mSensorManager.registerListener(this, mPressure, SensorManager.SENSOR_DELAY_NORMAL);
}

@Override
protected void onPause() {
// Be sure to unregister the sensor when the activity pauses.
super.onPause();
mSensorManager.unregisterListener(this);
}
}
</code>