activiti工作流引擎如何获取bmpn的布局信息啊？

[TuskueNeko]

以下是我获取的代码 但是拿到的activity是空的

 ProcessDefinition processDefinition = repositoryService.createProcessDefinitionQuery().processDefinitionId(task.getProcessDefinitionId()).singleResult();
		  //获取到流程定义
		  ProcessDefinitionEntity pd = (ProcessDefinitionEntity)processDefinition;
		  //此处我断点看了下 processDefinition 发现processDefinition里面的activitys属性是空的，那么下面的findActivity毫无疑问也是空
                //
		  
		  ProcessInstance processInstance = runtimeService.createProcessInstanceQuery().processInstanceId(processInstanceId).singleResult();  
		  String activityId = processInstance.getActivityId();
		 // 使用流程定义通过currentActivitiId得到活动对象

		  ActivityImpl ai = pd.findActivity(activityId);  
//		  /获取活动的坐标
		  request.setAttribute("x",ai.getX());  //
		  request.setAttribute("y",ai.getY());
		  request.setAttribute("wdith",ai.getWidth());
		  request.setAttribute("height",ai.getHeight());