Hi Marc,
I tried something slightly differently, seems to work out:
I removed the button.setCommand(this._command) line in _getMenu(), but
instead added a listener
button.addListener("execute", function(e){
this.toggleShowLabel();
}, this);
in the same place.
With this tiny modification, the removeListener() line seems obsolete.
Maybe you give it a try,
HTH,
greetings
Stefan
On 11.07.2010 13:39, Marc Puts wrote:
> Hi all,
>
> I have a command object which toggles the value of a boolean property
> "showLabel".
> I also have a qx.ui.menu.CheckBox, which toggles "showLabel" indirectly
> by using the command object.
>
> Whenever the property value is changed, whether that's done by the
> command object, the checkbox or some external source, I need the
> checkbox state to reflect the new value. Obviously, this is easy to do
> using data binding. Everything is fine when the property change is
> initiated from the command object, or from the outside world.
>
> But trouble arises when the change is initiated from the CheckBox. The
> CheckBox automatically changes its checked state whenever its execute
> event is fired. However, since the CheckBox uses the command object, the
> execute itself changes the value of "showLabel", which (due to the data
> binding) changes the checked state of the CheckBox. Chicken or the egg?
> Not surprisingly, this results in strange/unwanted behaviour.
>
> To prevent this the unwanted behaviour, I want to suppress the checkbox
> behaviour of changing its checked state on execution. This can be done
> by removing its internal "execute" listener right after creating the
> checkbox:
>
> button.removeListener("execute", button._onExecute, button, false);
>
> This works, but since this makes use of unexposed CheckBox interiors: is
> there's a better way of handling it?
>
>
>
>
> Code example below:
> ********************************************************
>
>
> qx.Class.define("test.Window", {
>
> extend : qx.ui.window.Window,
>
> construct : function() {
> this.base(arguments);
>
> this.setLayout(new qx.ui.layout.Canvas());
> this.setWidth(300);
> this.setHeight(200);
>
> this._label = new qx.ui.basic.Label("Rightclick or press L to hide
> this text.");
> this.add(this._label);
>
> this._command = new qx.ui.core.Command("L");
> this._command.addListener("execute", this.toggleShowLabel, this);
>
> this.initShowLabel(true);
>
> this.setContextMenu(this._getMenu());
> },
>
> properties :
> {
> showLabel : {
> deferredInit: true,
> check: "Boolean",
> apply: "_applyShowLabel",
> event: "showLabelChanged"
> }
> },
>
> members :
> {
> _label: null,
> _command : null,
>
> _applyShowLabel : function(value, old) {
> this._label.setVisibility(value ? "visible" : "excluded");
> },
>
> _getMenu : function() {
> var menu = new qx.ui.menu.Menu;
>
> var button = new qx.ui.menu.CheckBox("Show label");
>
> //suppress default behaviour of toggling checked value on execute
> button.removeListener("execute", button._onExecute, button, false);
>
> button.setCommand(this._command);
> this.bind("showLabel", button, "value");
>
> menu.add(button);
> return menu;
> }
> }
> });
>
> ********************************************************
>
> If you comment out the removeListener line, you will notice that the
> checkbox state will not be updated on the first "showLabel" change. All
> subsequent showLabel changes will be passed to the checkbox, but its
> state will be inverted.
>
>
> Thanks,
>
> Marc
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