Hello,
Firstly,You need 2 important Dataconnections ;
ProcessFlexiTaskResponse
GetrunningWorkflowTaskforCurrentuserid
In the form Of course you need to create 2 buttons; 1- Approve 2-Reject
So We have to a write a rule for these buttons;
For Approve button;The rule is Action type
set a field's value:SpTaskID=SharePointTaskId (SptaskID comes from ProcessFlexiTaskResponse Query fields) and (SharePointTaskID comes from GetrunningWorkflowTaskForCurrentUserid under UserTask )
set filed's value:outcome='Approve'
set field's value:taskListName='WorkFlow Tasks'
Query Using Data Connections:ProcessFlexiTaskResponse
Submit using DataConnection
For "Reject" Button The rule is same as "Approve"'s rule just change;
outcome='Reject'