feat(android): add QRScanner class and majority of its methods

Created the QRScanner and CameraPreview classes. The majority of the methods are now functional,
excluding the scan functions.

src/android/CameraPreview.java

@@ -0,0 +1,103 @@
+package com.bitpay.cordova.qrscanner;
+
+import android.app.Activity;
+import android.content.Context;
+import android.content.res.Configuration;
+import android.util.Log;
+import android.view.Surface;
+import android.view.SurfaceHolder;
+import android.view.SurfaceView;
+import java.io.IOException;
+import android.hardware.Camera;
+import android.hardware.Camera.*;
+import android.view.WindowManager;
+
+@SuppressWarnings("deprecation")
+
+public class CameraPreview extends SurfaceView implements SurfaceHolder.Callback {
+    private SurfaceHolder mHolder;
+    private Camera mCamera;
+
+
+    public CameraPreview(Context context, Camera camera) {
+        super(context);
+        mCamera = camera;
+        // Install a SurfaceHolder.Callback so we get notified when the
+        // underlying surface is created and destroyed.
+        mHolder = getHolder();
+        mHolder.addCallback(this);
+        // deprecated setting, but required on Android versions prior to 3.0
+        mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
+    }
+    public void surfaceCreated(SurfaceHolder holder) {
+        // The Surface has been created, now tell the camera where to draw the preview.
+        try {
+            mCamera.setDisplayOrientation(90);
+            mCamera.setPreviewDisplay(holder);
+            mCamera.startPreview();
+        } catch (IOException e) {
+        }
+    }
+
+    public void surfaceDestroyed(SurfaceHolder holder) {
+        // empty. Take care of releasing the Camera preview in your activity.
+    }
+
+    public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) {
+        // If your preview can change or rotate, take care of those events here.
+        // Make sure to stop the preview before resizing or reformatting it.
+
+        if (mHolder.getSurface() == null){
+            // preview surface does not exist
+            return;
+        }
+
+        // stop preview before making changes
+        try {
+            mCamera.stopPreview();
+        } catch (Exception e){
+            // ignore: tried to stop a non-existent preview
+        }
+
+        // set preview size and make any resize, rotate or
+        // reformatting changes here
+        android.hardware.Camera.CameraInfo info = new android.hardware.Camera.CameraInfo();
+
+        android.hardware.Camera.getCameraInfo(QRScanner.getCurrentCameraId(), info);
+
+        WindowManager windowService = (WindowManager) getContext().getSystemService(Context.WINDOW_SERVICE);
+        int rotation = windowService.getDefaultDisplay().getRotation();
+        int degrees = 0;
+        switch (rotation) {
+            case Surface.ROTATION_0:
+                degrees = 0;
+                break;
+            case Surface.ROTATION_90:
+                degrees = 90;
+                break;
+            case Surface.ROTATION_180:
+                degrees = 180;
+                break;
+            case Surface.ROTATION_270:
+                degrees = 270;
+                break;
+        }
+        int result;
+        if (info.facing == Camera.CameraInfo.CAMERA_FACING_FRONT) {
+            result = (info.orientation + degrees) % 360;
+            result = (360 - result) % 360; // compensate the mirror
+        } else { // back-facing
+            result = (info.orientation - degrees + 360) % 360;
+        }
+        mCamera.setDisplayOrientation(result);
+
+        // start preview with new settings
+        try {
+            mCamera.setPreviewDisplay(mHolder);
+            mCamera.startPreview();
+
+        } catch (Exception e){
+
+        }
+    }
+}