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)
	    {
	    }
   }