Actions

Actions define the behaviours of Commands, i.e. the code that executed when a button, menu-item etc. is pressed. The Actions can then be used to build the buttons, menu items etc.

For example, we define Commands like so :

object MyApplicationCommands : Commands( myIcons ) {
    val FILE_OPEN = define( "file_open", "Open", Key.O.control() )
    val FILE_SAVE = define( "file_save", "Save", Key.S.control() )
}

Each Command has a key (such as file_open), which is never seen by the end-user. Next is the text that will appear in the menu-item, button etc. We can optionally add a keyboard shortcut and tooltip text.

Notice that Commands do NOT define the behavior. This is where Actions come in.

val action = Actions().apply {
    // Attach to a node (often the root node) for keyboard-shortcuts.
    // When input focus is elsewhere, the keyword-shortcuts won't apply.
    attachTo( aNode )

    MyApplicationCommands.FILE_OPEN { println( "Not implemented!" ) }
    MyApplicationCommands.FILE_SAVE { println( "Not implemented!" ) }
}

Simple behaviours can be written in-line, but longer behaviours are usually function calls.

Now, we can start building our GUI :

fun myToolBar( actions : Action ) = toolBar {
    actions.build {
       + button( MyApplicationCommands.FILE_OPEN )
       + button( MyApplicationCommands.FILE_SAVE )
    }
}

fun myMenuBar( action : Actions ) = menuBar {
    actions.build {
        + menuItem( MyApplicationCommands.FILE_OPEN )
        + menuItem( MyApplicationCommands.FILE_SAVE )
    }
}

Note, it is tiresome to keep including MyApplicationCommands., so you could wrap them in a with block instead.

It is typical for the GUI components (i.e. myToolBar() and myMenuBar()) to be in a separate source files, which is why I declared them as functions, and passed actions to them.

See DemoActions.kt in glok-demos subproject for real example code.

Missing from the example code :

• Setting the size of icons. See NodeBuilder.iconSizeProperty

• Enabling/disabling buttons/menu items. See Action.disable

Some applications have a single instance of Actions, but more complex application may have many (one for each part of the application).

For shortcuts to work, you must attachTo a node. The shortcuts will only work when the input focus is one of that node's descendants (or itself). Therefore, Scene.root is often a good choice.