Test for volume keys, to guard against fixed crash for changing exposure compensation.

        assertEquals(0, seekBar.getProgress());

        assertEquals(mPreview.getCurrentExposure(), mActivity.getExposureSeekbarValue(seekBar.getProgress()));

        // test volume keys

        SharedPreferences settings = PreferenceManager.getDefaultSharedPreferences(mActivity);

        SharedPreferences.Editor editor = settings.edit();

        editor.putString(PreferenceKeys.VolumeKeysPreferenceKey, "volume_exposure");

        editor.apply();

        // volume up

        while( mPreview.getCurrentExposure() < mPreview.getMaximumExposure() ) {

            Log.d(TAG, "use volume key to increase exposure");

            int exposure = mPreview.getCurrentExposure();

            this.getInstrumentation().sendKeyDownUpSync(KeyEvent.KEYCODE_VOLUME_UP);

            assertEquals(exposure+1, mPreview.getCurrentExposure());

        }

        // one more shouldn't change exposure

        this.getInstrumentation().sendKeyDownUpSync(KeyEvent.KEYCODE_VOLUME_UP);

        assertEquals(mPreview.getMaximumExposure(), mPreview.getCurrentExposure());

        // volume down

        while( mPreview.getCurrentExposure() > mPreview.getMinimumExposure() ) {

            Log.d(TAG, "use volume key to decrease exposure");

            int exposure = mPreview.getCurrentExposure();

            this.getInstrumentation().sendKeyDownUpSync(KeyEvent.KEYCODE_VOLUME_DOWN);

            assertEquals(exposure-1, mPreview.getCurrentExposure());

        }

        // one more shouldn't change exposure

        this.getInstrumentation().sendKeyDownUpSync(KeyEvent.KEYCODE_VOLUME_DOWN);

        assertEquals(mPreview.getMinimumExposure(), mPreview.getCurrentExposure());

        // test the exposure button clears and reopens without changing exposure level

        clickView(exposureButton);

        assertEquals(exposureButton.getVisibility(), View.VISIBLE);