Basically title of form item also takes one column. If you do want to show the title also then it will double the column count.
For more info have a look at DynamicForm#setColWidths().
As per you comment:
//filling the list with one CheckboxItem, one TextItem and one SelectItem?
Try this one:
final DynamicForm df = new DynamicForm();
// FormItem[] fi = new FormItem[3];
// filling the list with one CheckboxItem, one TextItem and one SelectItem
CheckboxItem ci = new CheckboxItem();
ci.setShowTitle(false);
ci.setTitle("");
TextItem ti = new TextItem();
ti.setShowTitle(false);
SelectItem si = new SelectItem();
si.setShowTitle(false);
si.setValues("PDF");
df.setItems(ci, ti, si);
df.setColWidths("20", "250", "*");
df.setNumCols(3);
// df.setFields(fi);
RootPanel.get().add(df);
Snapshot:
As per your snapshot:
Try this one
final DynamicForm df = new DynamicForm();
// FormItem[] fi = new FormItem[3];
CheckboxItem ci = new CheckboxItem();
ci.setShowTitle(false);
ci.setTitle("");
SelectItem si = new SelectItem();
si.setTitle("LANGUAGE");
si.setValues("PDF");
df.setItems(ci, si);
df.setColWidths("20", "250", "*");
df.setNumCols(3);
// df.setFields(fi);
RootPanel.get().add(df);
Snapshot: