如何定期更改页面标题并打开/关闭更改？

Question

I want to change the title of my page periodically, ie add a (*) in front of the current page title and remove it after a couple of seconds. I want to turn this title change on and off in code.

I get and set the page title from:

    public static native void setPageTitle(String title) /*-{
    $doc.title = title;
    }-*/;


public static native String getPageTitle() /*-{
    return $doc.title;
}-*/;

But how should I write a function that will change the page title every 300 miliseconds while adding and removing a prefix?

What I tried was:

private void changePageTitle(final String prefix) {

    new Timer() {
        @Override
        public void run() {
            String pageTitle =getPageTitle();

            if (pageTitle.startsWith(prefix)) {
                    pageTitle = pageTitle.substring(prefix.length());
                }
                else {
                    pageTitle = pageTitle + prefix;
                }
            setPageTitle(pageTitle);

        }
        }
    }.schedule(300);
}

This does not work. And I do not know how to switch the process on and off?

The Effect should be like in Facebook. When a new message arrive and you are not on the Facebook browser tab, then the tab shows a notification which is blinking.

Answer 1

You have to change schedule(300) by scheduleRepeating(300) .

You should use just one instance of Timer or save the last timer to cancel it before creating a new one.

BTW: you dont need to write any JSNI to access the window title, just use Window.getTitle() and Window.setTitle(String)

EDITED:

This should work:

// create just an instance of the timer
final MyUpdateTitleTimer mytimer = new MyUpdateTitleTimer();
// To Start the updater
mytimer.setPrefix("> ");
// To Stop set the prefix to null
mytimer.setPrefix(null);


class MyUpdateTitleTimer extends Timer {
  private String prefix;
  private String title;
  private boolean b;

  public void run() {
    String s = (b = !b) ? prefix + title : title;
    Window.setTitle(s);
  }

  public void setPrefix(String prefix) {
    if (title != null) {
      Window.setTitle(title);
    }
    this.prefix = prefix;
    if (prefix == null) {
      cancel();
    } else {
      title = Window.getTitle();
      scheduleRepeating(300);
    }
  }
}