[sensors] Android platform adaptation for Generic Sensor API

device/generic_sensor/android/java/src/org/chromium/device/sensors/PlatformSensor.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.sensors;
+
+import org.chromium.base.annotations.CalledByNative;
+import org.chromium.base.annotations.JNINamespace;
+
+import java.nio.ByteBuffer;
+import java.nio.ByteOrder;
+
+/**
+ * Base class that is wrapped by device::PlatformSensorAndroid and should be used to implement
+ * concrete sensors. Lifetime is controlled by the device::PlatformSensorAndroid.
+ */
+@JNINamespace("device")
+public abstract class PlatformSensor {

[Ted C, 2016/09/01 00:12:36]

seeing that we are in the generic_sensor directory, do we ever see any classes
that extend this other than GenericPlatformSensor?

If we don't see that happening in the coming month, then I feel this is doing
more abstraction/indirection than is useful.

[shalamov, 2016/09/06 12:36:43]

Agree, removed abstraction, if in the future non Sensor Framework, sensors would
be needed, can be added back.

+    protected long mNativePlatformSensorAndroid;

[Ted C, 2016/09/01 00:12:36]

I think this should be private.  Then expose helper functions that call the
native code.  Ideally, native pointers are isolated to just the one file that
does native calls.

[shalamov, 2016/09/06 12:36:43]

Done.

+    protected ByteBuffer mBuffer;
+    protected ByteBuffer mSensorReadingData;
+
+    protected PlatformSensor() {}

[Ted C, 2016/09/01 00:12:36]

you want this protected to prevent sensors from being created outside of this
package?

[shalamov, 2016/09/06 12:36:43]

added public static create() that returns null in case sensor cannot be created,
will keep it as protected.

+
+    @CalledByNative
+    private void initPlatformSensorAndroid(long nativePlatformSensorAndroid, ByteBuffer buffer) {
+        mNativePlatformSensorAndroid = nativePlatformSensorAndroid;
+        mBuffer = buffer;

[Ted C, 2016/09/01 00:12:36]

I would just have another abstract method that exposes buffer and
sensorReadingData to subclasses (unless we combine them)

[shalamov, 2016/09/06 12:36:43]

not needed, since I merged classes.

+        mSensorReadingData = ByteBuffer.allocate(mBuffer.capacity());
+        mSensorReadingData.order(ByteOrder.nativeOrder());
+    }
+
+    @CalledByNative
+    protected abstract int getReportingMode();

[Ted C, 2016/09/01 00:12:36]

javadoc for all non-private methods

[shalamov, 2016/09/06 12:36:43]

Done.

+
+    @CalledByNative
+    protected abstract PlatformSensorConfiguration getDefaultConfiguration();
+
+    @CalledByNative
+    protected abstract boolean startSensor(PlatformSensorConfiguration configuration);
+
+    @CalledByNative
+    protected abstract void stopSensor();
+
+    @CalledByNative
+    protected abstract boolean checkSensorConfiguration(PlatformSensorConfiguration configuration);
+
+    protected native void nativeNotifyPlatformSensorReadingChanged(
+            long nativePlatformSensorAndroid);
+    protected native void nativeNotifyPlatformSensorError(long nativePlatformSensorAndroid);
+}