There might be times when ADF Region content should not be displayed on a runtime page. Instead, the page should appear blank where the region was previously located. This is really easy to implement, but it’s not really the region that’s “empty”. It’s actually the task flow definition associated with the region that’s “empty”. But, no need to go to the trouble of creating metadata for a task flow definition containing a view activity associated with a blank page. All you need to do is just set the region or dynamic region taskFlow binding taskFlowId=””. The open-quote closed-quote convention MUST be used as defined by ADF Controller. Setting the taskFlowId to “null” or using parse commands will not work.
This same “empty” task flow approach is often used when region content is hidden and shown as part of an ADF Faces popup or panelTab. It’s important to swap an “empty” task flow into a dynamic region when it’s hidden from view. This ensures memory and recourses for the associated task flow definition are allocated and released appropriately.
For example, the following Java class can be used to swap an “empty” task flow into a dynamic region contained within an ADF Faces popup. Note two VERY IMPORTANT things about the code sample: 1) getDynamicTaskFlowId() returns a String, not a TaskFlowId (currently there is not a formalized TaskFlowId="") 2) the parse() command will NOT work for "".
public class popupDynamicRegion {
private String taskFlowId = "";
private String popupTaskFlowId = "/WEB-INF/employee-update.xml#employee-update";
private String emptyTaskFlowId = "";
public PopupDynamicRegion() {
}
public String getDynamicTaskFlowId() {
if (taskFlowId != null)
return taskFlowId;
else
return getEmptyTaskFlowId();
}
public String getEmptyTaskFlowId() {
return emptyTaskFlowId;
}
public void swapEmptyTaskFlow(ClientEvent event) {
setDynamicTaskFlowId("");
// if event delivery set to immediate="true", short-circuit to renderResponse.
// Forcing an empty taskflow releases the bindings and view port.
Boolean immediate = (Boolean)event.getParameters().get("immediate");
if (immediate != null && immediate) {
FacesContext context = FacesContext.getCurrentInstance();
context.renderResponse();
}
String popupId = (String)event.getParameters().get("popupId");
System.out.println("**** Swapping Empty Taskflow on popupClosed for " +
popupId + " ****");
}
public void setDynamicTaskFlowId(String newTaskFlowId) {
taskFlowId = newTaskFlowId;
// For HA Applications
//if (taskFlowId != null)
//{
// ControllerContext.getInstance().markScopeDirty(pageFlowScope);
//}
}
}
