双后摄切换

M810项目配置了两个后摄，需要实现双后摄切换：

vendor/mediatek/proprietary/packages/apps/Camera2/feature/setting/cameraswitcher/src/com/mediatek/camera/feature/setting/CameraSwitcher.java

+       private static final String CAMERA_FACING_BACK2 = "back2";

................
+       private void switchCameraInNormal() {
+        //String nextFacing = mFacing.equals(CAMERA_FACING_BACK) ? CAMERA_FACING_FRONT
+        //        : CAMERA_FACING_BACK;
+        String nextFacing = CAMERA_FACING_BACK;
+               String newCameraId;
+               if(mFacing.equals(CAMERA_FACING_BACK)){
+                       nextFacing = CAMERA_FACING_BACK2;
+                       newCameraId = CameraUtil.getCamIdsByFacing(true, mApp.getActivity()).get(1);
+               }else if(mFacing.equals(CAMERA_FACING_BACK2)){
+                       nextFacing = CAMERA_FACING_FRONT;
+                       newCameraId = CameraUtil.getCamIdsByFacing(false, mApp.getActivity()).get(0);
+               }else{
+                       nextFacing = CAMERA_FACING_BACK;
+                       newCameraId = CameraUtil.getCamIdsByFacing(true, mApp.getActivity()).get(0);
+               }
+        boolean success = mApp.notifyCameraSelected(newCameraId);
+        if (success) {
+            android.util.Log.d("wangqing","[switchCameraInNormal], switch camera success.");
+            mFacing = nextFacing;
+            mDataStore.setValue(KEY_CAMERA_SWITCHER, mFacing,
+                    getStoreScope(), true);
+        }else{
+                       android.util.Log.d("wangqing","failed");
+        }
+        mSwitcherView.setContentDescription(mFacing);
+    }

 用上述代码替换原有的switchCameraInNormal()方法。