You're refreshing 4x a second, what do you expect to happen?
CellTable constructs a giant HTML string, which requires a lot of string
manipulation and logical code that could take up the CPU. Since javascript
is single threaded, the browser will be unresponsive while CellTable renders
the code, so it makes sense for it to peg the CPU (I'm guessing you have a
dual code system?) and get it over with as quickly as possible. If it
didn't peg the CPU, it would just take longer but still block user input.
Happy as I am that you can update 4x a second, that generally isn't a good
idea because it makes the app unresponsive and harder to use.
Thanks,
John LaBanca
jlaba...@google.com
On Thu, Jan 20, 2011 at 6:28 AM, remuera <brain...@web.de> wrote:
> Hi,
>
> in my web app I have to refresh a table of 6 columns and around 50
> rows to refresh 4 times a second with new data. I'm using CellTable
> for that, since its performance is good, but when I do that, CPU usage
> is at about 60%!
>
> I know that rendering of the HTMl in the browser is expensive, but
> that expensive? Is there any way how I can display the data using
> CellTable? Any other idea?
>
> Here is my test code:
>
> public class Sandbox implements EntryPoint
> {
> public CellTable<Contact> table = null;
> public ArrayList<Contact> list = new ArrayList<Contact>();
>
> public void onModuleLoad()
> {
>
> // Create a CellTable.
> table = new CellTable<Contact>();
>
> table.setKeyboardSelectionPolicy(KeyboardSelectionPolicy.ENABLED);
>
> TextColumn<Contact> nameColumn = new TextColumn<Contact>() {
> @Override
> public String getValue(Contact object)
> {
> return object.name;
> }
> };
> table.addColumn(nameColumn, "Name");
>
> TextColumn<Contact> aColumn = new TextColumn<Contact>() {
> @Override
> public String getValue(Contact object)
> {
> return object.a + "";
> }
> };
> table.addColumn(aColumn, "A");
>
> TextColumn<Contact> bColumn = new TextColumn<Contact>() {
> @Override
> public String getValue(Contact object)
> {
> return object.b + "";
> }
> };
> table.addColumn(bColumn, "B");
>
> TextColumn<Contact> cColumn = new TextColumn<Contact>() {
> @Override
> public String getValue(Contact object)
> {
> return object.c + "";
> }
> };
> table.addColumn(cColumn, "C");
>
> TextColumn<Contact> dColumn = new TextColumn<Contact>() {
> @Override
> public String getValue(Contact object)
> {
> return object.d + "";
> }
> };
> table.addColumn(dColumn, "D");
>
> RootPanel.get().add(table);
>
> Timer timer = new Timer()
> {
> public void run()
> {
> update();
> }};
> timer.scheduleRepeating(250);
>
> }
>
> private void update()
> {
> list.clear();
> for(int i = 0; i < 50; i++)
> {
> list.add(new Contact("abc", Random.nextDouble(),
> Random.nextDouble(), Random.nextDouble(), Random.nextDouble()));
>
> }
> table.setRowCount(list.size(), true);
>
> table.setRowData(list);
> }
> }
>
> class Contact
> {
> public final String name;
> public final double a;
> public final double b;
> public final double c;
> public final double d;
>
>
> public Contact(String name, double a, double b, double c, double d)
> {
> this.name = name;
> this.a = a;
> this.b = b;
> this.c = c;
> this.d = d;
> }
> }
>
> Thanks for any help on that.
>
> Cheers
>
> T
>
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