Generic Sensor API : Ambient Light Sensor API.

device/sensor/android/java/src/org/chromium/device/sensor/AmbientLightSensorImpl.java

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package org.chromium.device.sensor;
+
+import android.content.Context;
+import android.hardware.Sensor;
+import android.hardware.SensorEvent;
+import android.hardware.SensorEventListener;
+import android.hardware.SensorManager;
+
+import org.chromium.base.Log;
+import org.chromium.mojo.system.MojoException;
+import org.chromium.mojom.device.AmbientLightSensor;
+import org.chromium.mojom.device.AmbientLightSensorReading;
+
+import java.util.Date;
+
+/**
+ * Android implementation of Ambient Light Sensor service as defined in
+ * device/sensor/sensor.mojom.
+ */
+public class AmbientLightSensorImpl implements AmbientLightSensor, SensorEventListener {
+    private static final String TAG = "AmbientLightSensor";
+    private QueryNextReadingResponse mResponse;
+    // A reference to the application context in order to acquire the SensorService.
+    private final Context mAppContext;
+    private final SensorManager mSensorManager;
+    private final Sensor mAmbientLightSensor;
+    private boolean mHasNewValue;
+    private AmbientLightSensorReading mLastUpdate;
+
+    public AmbientLightSensorImpl(Context context) {
+        mAppContext = context.getApplicationContext();
+
+        mSensorManager = (SensorManager) mAppContext.getSystemService(Context.SENSOR_SERVICE);
+        mAmbientLightSensor = mSensorManager.getDefaultSensor(Sensor.TYPE_LIGHT);
+        if (mSensorManager == null) {
+            Log.w(TAG, "Sensor service not supported");
+        } else {
+            mHasNewValue = false;
+            mLastUpdate = new AmbientLightSensorReading();
+        }
+    }
+
+    @Override
+    public void queryNextReading(QueryNextReadingResponse callback) {
+        if (mResponse != null) {
+            Log.e(TAG, "Overlapped call to queryNextReading!");
+            return;
+        }
+
+        mResponse = callback;
+        if (mHasNewValue) reportReading();
+    }
+
+    @Override
+    public void startReading() {
+        mLastUpdate.timeStamp = new Date().getTime();
+        mLastUpdate.illuminance = Double.POSITIVE_INFINITY;
+        mSensorManager.registerListener(
+                this, mAmbientLightSensor, SensorManager.SENSOR_DELAY_NORMAL);
+    }
+
+    @Override
+    public void stopReading() {
+        mHasNewValue = false;
+        mLastUpdate.illuminance = Double.POSITIVE_INFINITY;
+        mSensorManager.unregisterListener(this);
+    }
+
+    void reportReading() {
+        mResponse.call(mLastUpdate);
+        mResponse = null;
+        mHasNewValue = false;
+    }
+
+    @Override
+    public void close() {
+        mSensorManager.unregisterListener(this);
+    }
+
+    @Override
+    public void onConnectionError(MojoException e) {}
+
+    @Override
+    public void onAccuracyChanged(Sensor sensor, int accuracy) {}
+
+    @Override
+    public void onSensorChanged(SensorEvent event) {

[riju_, 2016/05/16 16:58:51]

TODO(riju) : Use event.timestamp here.

+        if (event.sensor.getType() == Sensor.TYPE_LIGHT) {
+            mLastUpdate.illuminance = event.values[0];
+            mHasNewValue = true;
+
+            reportReading();
+            if (mResponse != null) reportReading();
+        }
+    }
+}