Added autofocus feature

Updated with Mobile Vision API fix for missing autofocus feature.
Thanks to @Gericop fix
https://gist.github.com/Gericop/7de0b9fdd7a444e53b5a

Author: Gnzlt

AndroidVisionQRReader/src/main/java/com/gnzlt/AndroidVisionQRReader/camera/CameraSourcePreview.java

@@ -17,6 +17,7 @@
 
 import android.content.Context;
 import android.content.res.Configuration;
+import android.hardware.Camera;
 import android.util.AttributeSet;
 import android.util.Log;
 import android.view.SurfaceHolder;
@@ -78,6 +79,7 @@ public void release() {
     private void startIfReady() throws IOException {
         if (mStartRequested && mSurfaceAvailable) {
             mCameraSource.start(mSurfaceView.getHolder());
+            VisionApiCameraFix.cameraFocus(mCameraSource, Camera.Parameters.FOCUS_MODE_CONTINUOUS_PICTURE);
             mStartRequested = false;
         }
     }

AndroidVisionQRReader/src/main/java/com/gnzlt/AndroidVisionQRReader/camera/VisionApiCameraFix.java

@@ -0,0 +1,93 @@
+package com.gnzlt.AndroidVisionQRReader.camera;
+
+import android.hardware.Camera;
+import android.support.annotation.NonNull;
+import android.support.annotation.StringDef;
+
+import com.google.android.gms.vision.CameraSource;
+
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.reflect.Field;
+
+public class VisionApiCameraFix {
+    /*
+     * IF YOU WANT TO JUST ACCESS THE CAMERA INSTANCE SO THAT YOU CAN SET ANY OF THE PARAMETERS, VISIT THE FOLLOWING LINK:
+     * https://gist.github.com/Gericop/364dd12b105fdc28a0b6
+     */
+
+    /**
+     * Custom annotation to allow only valid focus modes.
+     */
+    @StringDef({
+            Camera.Parameters.FOCUS_MODE_CONTINUOUS_PICTURE,
+            Camera.Parameters.FOCUS_MODE_CONTINUOUS_VIDEO,
+            Camera.Parameters.FOCUS_MODE_AUTO,
+            Camera.Parameters.FOCUS_MODE_EDOF,
+            Camera.Parameters.FOCUS_MODE_FIXED,
+            Camera.Parameters.FOCUS_MODE_INFINITY,
+            Camera.Parameters.FOCUS_MODE_MACRO
+    })
+    @Retention(RetentionPolicy.SOURCE)
+    private @interface FocusMode {
+    }
+
+    /**
+     * <p>
+     * Sets the Mobile Vision API provided {@link com.google.android.gms.vision.CameraSource}'s
+     * focus mode. Use {@link Camera.Parameters#FOCUS_MODE_CONTINUOUS_PICTURE} or
+     * {@link Camera.Parameters#FOCUS_MODE_CONTINUOUS_VIDEO} for continuous autofocus.
+     * </p>
+     * <p>
+     * Note that the CameraSource's {@link CameraSource#start()} or
+     * {@link CameraSource#start(SurfaceHolder)} has to be called and the camera image has to be
+     * showing prior using this method as the CameraSource only creates the camera after calling
+     * one of those methods and the camera is not available immediately. You could implement some
+     * kind of a callback method for the SurfaceHolder that notifies you when the imaging is ready
+     * or use a direct action (e.g. button press) to set the focus mode.
+     * </p>
+     * <p>
+     * Check out <a href="https://github.com/googlesamples/android-vision/blob/master/face/multi-tracker/app/src/main/java/com/google/android/gms/samples/vision/face/multitracker/ui/camera/CameraSourcePreview.java#L84">CameraSourcePreview.java</a>
+     * which contains the method <code>startIfReady()</code> that has the following line:
+     * <blockquote><code>mCameraSource.start(mSurfaceView.getHolder());</code></blockquote><br>
+     * After this call you can use our <code>cameraFocus(...)</code> method because the camera is ready.
+     * </p>
+     *
+     * @param cameraSource The CameraSource built with {@link com.google.android.gms.vision.CameraSource.Builder}.
+     * @param focusMode    The focus mode. See {@link android.hardware.Camera.Parameters} for possible values.
+     * @return true if the camera's focus is set; false otherwise.
+     * @see com.google.android.gms.vision.CameraSource
+     * @see android.hardware.Camera.Parameters
+     */
+    public static boolean cameraFocus(@NonNull CameraSource cameraSource, @FocusMode @NonNull String focusMode) {
+        Field[] declaredFields = CameraSource.class.getDeclaredFields();
+
+        for (Field field : declaredFields) {
+            if (field.getType() == Camera.class) {
+                field.setAccessible(true);
+                try {
+                    Camera camera = (Camera) field.get(cameraSource);
+                    if (camera != null) {
+                        Camera.Parameters params = camera.getParameters();
+
+                        if (!params.getSupportedFocusModes().contains(focusMode)) {
+                            return false;
+                        }
+
+                        params.setFocusMode(focusMode);
+                        camera.setParameters(params);
+                        return true;
+                    }
+
+                    return false;
+                } catch (IllegalAccessException e) {
+                    e.printStackTrace();
+                }
+
+                break;
+            }
+        }
+
+        return false;
+    }
+}