相机预览2.1版本一下兼容setDisplayOrientation

protected void setDisplayOrientation(Camera camera, int angle){    Method downPolymorphic;    try    {        downPolymorphic = camera.getClass().getMethod("setDisplayOrientation", new Class[] { int.class });        if (downPolymorphic != null)            downPolymorphic.invoke(camera, new Object[] { angle });    }    catch (Exception e1)    {    }   }