Guys I think cursors are the best choice for paging ... It is also
safe to send a cursor to the client and this is exactly what i am
doing ... I am saving all cursors on the client in an ArrayList and
using them to page forward and backward ... of coarse u have to start
by page 1 and move forward to be able to move backward ... I have 3
Buttons (First-Page, Previous-Page and Next Page) ... No Last-Page
because I did not implement any global Counters :) Tell me what u
think ... This is sample code:
//
----------------------------------------------------------------------------------
public enum CursorEnum {
START, PREVIOUS, NEXT, CURRENT;
}
//
----------------------------------------------------------------------------------
public class Counter {
private int count = 0;
...
}
//
----------------------------------------------------------------------------------
public class Page implements IsSerializable {
private ArrayList<DataObject> objects; // DataObject = Parent of all
Objects ...
private String cursorNext;
... // getter & setters
}
//
----------------------------------------------------------------------------------
private final ArrayList<String> cursors = new ArrayList<String>();
private final Counter cursorPosition = new Counter();
.....
// Select cursor to use ...
String cursorString = null;
switch (cursor) { // read CursorEnum cursor
case START:
break;
case PREVIOUS:
if (cursors.size() > 2) {
cursorString = cursors.get(cursors.size() - 3);
}
break;
case NEXT:
if (!cursors.isEmpty()) {
cursorString = cursors.get(cursors.size() - 1);
}
break;
case CURRENT:
if (cursors.size() > 1) {
cursorString = cursors.get(cursors.size() - 2);
}
break;
}
//
----------------------------------------------------------------------------------
final String startingAt = cursorString;
// Call AsyncCallback ...
...getPage(className, startingAt, limit, filters, sortFields,
new AsyncCallback<Page>() {
@Override
public void onFailure(Throwable caught) {
...
}
@Override
public void onSuccess(Page page) {
...
objects = page.getObjects();
if (objects.isEmpty()) {
label_Range.setText("( Empty )");
cursors.clear();
cursorPosition.setCount(0);
} else {
switch (cursor) {
case START:
cursors.clear();
cursorPosition.setCount(0);
break;
case PREVIOUS:
if (cursors.size() > 2) {
cursors.remove(cursors.size() - 1);
cursors.remove(cursors.size() - 1);
cursorPosition.subtract(limit);
} else {
cursors.clear();
cursorPosition.setCount(0);
}
break;
case NEXT:
if (cursors.size() > 0) {
cursorPosition.add(limit);
}
break;
case CURRENT:
if (cursors.size() > 0) {
cursors.remove(cursors.size() - 1);
}
break;
}
cursors.add(page.getCursorNext());
label_Range.setText("("
+
(cursorPosition.getCount() + 1)
+ " - "
+
(cursorPosition.getCount() + objects
.size()) + ")");
}
... // render objects
}
});
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