Refactor Raspberry Pi GPIO and add GPIO mock

samples/raspberry_pi/basic/knight-rider.dart

 // Copyright (c) 2015, the Fletch project authors. Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE.md file.
 //
 // Remember those red running lights KITT had in Knight Rider?
 // https://www.youtube.com/watch?v=Mo8Qls0HnWo
 //
 // This sample recreates those with a chain of LEDs running right and left:
 // https://storage.googleapis.com/fletch-archive/images/knight-rider.mp4
 //
 // For breadboard layout and connections to the Pi, see:
 // https://storage.googleapis.com/fletch-archive/images/k-r-schematic.png
 
 import 'package:gpio/gpio.dart';
+import 'package:raspberry_pi/raspberry_pi.dart';
 import 'package:os/os.dart';
 
 main() {
+  // Initialize Raspberry Pi
+  RaspberryPi pi = new RaspberryPi();
+
   // Array constant containing the GPIO pins of the connected LEDs.
   // You can add more LEDs simply by extending the list. Make sure
   // the pins are listed in the order the LEDs are connected.
   List<int> leds = [26, 19, 13, 6];
 
   // Initialize the lights controller class.
-  Lights lights = new Lights(leds);
+  Lights lights = new Lights(pi.memoryMappedGPIO, leds);
   lights.init();
 
   // Alternate between running left and right in a continuous loop.
   const int waitTime = 100;
   while (true) {
     lights.runLightLeft(waitTime);
     lights.runLightRight(waitTime);
   }
 }
 
 class Lights {
-  List<int> leds;
-  PiMemoryMappedGPIO _gpio = new PiMemoryMappedGPIO();
+  final GPIO _gpio;
+  final List<int> leds;
 
-  Lights(this.leds);
+  Lights(this._gpio, this.leds);
 
   // Initializes GPIO and configures the pins.
   void init() {
     leds.forEach((pin) => _gpio.setMode(pin, Mode.output));
     leds.forEach((pin) => _gpio.setPin(pin, false));
   }
 
   // Iterates though the lights in increasing order, and sets the LEDs using
   // a helper function. Pauses [waitTime] milliseconds before returning.
   void runLightLeft(int waitTime) {
@@ skipping 15 matching lines @@
   // Sets LED [ledToEnable] to true, and all others to false.
   void _setLeds(int ledToEnable) {
     var state;
 
     for (int i = 0; i < leds.length; i++) {
       bool state = (i == ledToEnable);
       _gpio.setPin(leds[i], state);
     }
   }
 }