The Space For App Developers

I’m proud to announce a new release of the as3viewnavigator library. This new release is labeled with a 2.0.0 RC1 version number. Since the previous release the source code has been almost entirely rewritten to provide a host of new features, many bug-fixes and increased extensibility. The changes have likely also introduced some new bugs, so that is why this is an RC1 (Release Candidate 1) even though I think it is feature complete. Before it goes final I want to test it myself in battle and also have others provide input and bug reports. If you used previous versions I’m certain it will break your existing code (for your reference, the previous version is still available in github under the 1.0.0 tag.

So what is new:

• You can use ViewNavigator for Flex (desktop) projects! At least until ViewNavigator from Flex Hero will not be available for desktop projects
• ViewNavigator has become a container (based on the Sprite class for AS3 projects and the UIComponent for Flex) now. Its default behavior in AS3 projects when added to the stage is that it takes 100% of the stage area and it auto-resizes itself. You also have an option to control ViewNavigator width and height values explicitly. When using Flex you can lay it out anywhere in your MXML declaration like any other Flex component.
• Default implementations of the IView interface called View are provided for both AS3 (based on Sprite) and Flex (based on SkinnableContainer) projects.
• When performing actions on ViewNavigator (like pop, push, etc.) a ViewNavigatorEvent.VIEW_CHANGING event is dispatched. This event is cancelable so application logic can prevent the view change. Also the event has additional properties like oldView and newView which enable access to the instances of exchanged views.
• It is now possible to add custom view transitions. This can be done by implementing the IViewTransition interface and setting its implementation instance to the ViewNavigator object’s defaultTransition property or by passing it to the ViewNavigator object’s action functions.
• View instances managed by ViewNavigator can be destructed when they are no longer on the top of the stack. This can be controlled with a new property in IView interface named destructionPolicy. This property has two possible values auto and never that are also available in the ViewDestructionPolicy enum class. Default IView implementations have this property set to auto.

Using it with Flex (desktop) projects:

Actually this is the feature I’m most excited about. You may wonder why this is since Flex already comes with the ViewStack component and ViewNavigator available in Flex Hero mobile projects. The reason is that the ViewStack doesn’t allow two views to be visible at the same time so this type of nice slide transition is not possible (at least the transition in which two views slide in at the same time, I will blog about this in my next post). And as I mentioned already the Flex Hero ViewNavigator is not available for desktop projects, at least not yet. Of course there is a third option, using state transitions, but it doesn’t come with an API as well thought through as the one in ViewNavigator.

Below you can see it working with Flex (right-click to access the example source code):

In the Main MXML document you can see that ViewNavigator can be treated like any other Flex component. It also has the set of properties that set up the first view and register the ViewNavigatorEvent.VIEW_CHANGING event handler. In the snippet below SampleView is registered as firstView and the viewNumber property of the first view instance is set to 1.

// Main.mxml
 
<?xml version="1.0" encoding="utf-8"?>
<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009"
			   xmlns:s="library://ns.adobe.com/flex/spark"
			   xmlns:mx="library://ns.adobe.com/flex/mx"
			   xmlns:vn="http://ns.riaspace.com/as3viewnavigator"
			   width="350" height="350" viewSourceURL="http://riaspace.com/examples/as3viewnavigator/flex/srcview/index.html">
 
	<fx:Script>
		<![CDATA[
			import com.riaspace.as3viewnavigator.demo.SampleView;
			import com.riaspace.as3viewnavigator.events.ViewNavigatorEvent;
 
			protected function navigator_viewChangingHandler(event:ViewNavigatorEvent):void
			{
				txtTrace.appendText(
					"action: " + event.action + 
					", oldView: " + event.oldView + 
					" newView: " +  event.newView +
					"\n"
				);
			}
		]]>
	</fx:Script>
 
	<s:VGroup left="5" top="5" right="5" bottom="5">
		<vn:ViewNavigator id="navigator" firstView="{SampleView}" firstViewProps="{{viewNumber : 1}}"
						  viewChanging="navigator_viewChangingHandler(event)" 
						  width="100%" height="70%" />
		<s:Label id="lblTrace" text="Navigator events:" />
		<s:TextArea id="txtTrace" width="100%" height="30%" />
	</s:VGroup> 
 
</s:Application>

The SampleView MXML document extends the View class that comes with as3viewnavigator for Flex. Within the SampleView there are five buttons declared that let you play with ViewNavigator action functions. The code also declares the public viewNumber property that is set by the view that pushed the current view to the top of the stack. The value of the viewNumber property is 1 more than the viewNumber property from the previous view.

// com/riaspace/as3viewnavigator/demo/SampleView.as
 
<?xml version="1.0" encoding="utf-8"?>
<vn:View xmlns:fx="http://ns.adobe.com/mxml/2009" 
		 xmlns:s="library://ns.adobe.com/flex/spark" 
		 xmlns:mx="library://ns.adobe.com/flex/mx" 
		 xmlns:vn="http://ns.riaspace.com/as3viewnavigator">
 
	<fx:Script>
		<![CDATA[
			import mx.utils.NameUtil;
 
			override public function toString():String
			{
				return NameUtil.createUniqueName(this);
			}
 
		]]>
	</fx:Script>
 
	<fx:Declarations>
		<fx:Number id="viewNumber" />
	</fx:Declarations>
 
	<s:Rect width="100%" height="100%">
		<s:fill>
			<s:SolidColor color="#f0f0f0" />
		</s:fill>
	</s:Rect>
 
	<s:Label id="lblViewNumber" text="{viewNumber}" fontSize="55" 
			 top="10" horizontalCenter="0" />
 
	<s:VGroup bottom="10" horizontalCenter="0">
		<s:Button id="btnPushView" label="push view" width="100" 
				  click="navigator.pushView(SampleView, {viewNumber : (viewNumber + 1)})" />
 
		<s:Button id="btnPopView" label="pop view" width="100" 
				  click="navigator.popView()" />
 
		<s:Button id="btnPopAll" label="pop all" width="100" 
				  click="navigator.popAll()" />
 
		<s:Button id="btnPopToFirst" label="pop to first" width="100" 
				  click="navigator.popToFirstView()" />
 
		<s:Button id="btnReplace" label="replace" width="100" 
				  click="navigator.replaceView(SampleView, {viewNumber : (viewNumber + 1)})" />
	</s:VGroup>
 
</vn:View>

Using it with AS3 projects:

The example below shows the AS3 version in action. You can also right-click it to access the full source code.

In this example, the ViewNavigator is instantiated and added as a child of the Main class (the Main class listing is below this paragraph). The ViewNavigator constructor receives two parameters: the class type of the first view (SampleView) to display and an Object with view properties to be set (in this case, this is my custom viewNumber property, which will be displayed in the view label). Before ViewNavigator is added as a child to the Main class it also registers a ViewNavigatorEvent.VIEW_CHANGING event handler that traces out info about ViewNavigator actions. Another thing to note here is that the ViewNavigator size is set explicitly in the layoutComponents function using setSize function. It is important to understand that in this situation ViewNavigator will not auto-size itself anymore to the size of the stage. That is why layoutComponents function is also called by stage Event.RESIZE event handler.

// Main.as
 
package
{
	import com.adobe.viewsource.ViewSource;
	import com.riaspace.as3viewnavigator.ViewNavigator;
	import com.riaspace.as3viewnavigator.demo.SampleView;
	import com.riaspace.as3viewnavigator.events.ViewNavigatorEvent;
 
	import fl.controls.TextArea;
 
	import flash.display.Sprite;
	import flash.display.StageAlign;
	import flash.display.StageScaleMode;
	import flash.events.Event;
 
	[SWF(width="350", height="350", frameRate="30")]
	public class Main extends Sprite
	{
		private var navigator:ViewNavigator;
 
		private var txtTrace:TextArea;
 
		public function Main()
		{
			// Adding source code view
			ViewSource.addMenuItem(this, "http://riaspace.com/examples/as3viewnavigator/as3/srcview/index.html");
 
			stage.align = StageAlign.TOP_LEFT;
			stage.scaleMode = StageScaleMode.NO_SCALE;
 
			// Adding trace area
			txtTrace = new TextArea;
 
			// Creating instance of ViewNavigator
			navigator = new ViewNavigator(SampleView, {viewNumber : 1});
			// Registering view navigator event handler 
			navigator.addEventListener(ViewNavigatorEvent.VIEW_CHANGING, navigator_viewChangingHandler);
 
			// Setting components dimenstions and positions
			layoutComponents();
 
			// Adding txtTrace component
			addChild(txtTrace);
			// Adding navigator to the current sprite
			addChild(navigator);
 
			// Adding resize handler to handle components layout
			stage.addEventListener(Event.RESIZE, function(event:Event):void { layoutComponents() });
		}
 
		protected function layoutComponents():void
		{
			// Resizing txtTrace component
			txtTrace.width = stage.stageWidth;
			// Setting fixed height of txtTrace component
			txtTrace.height = 60;
			// Positioning txtTrace component below navigator
			txtTrace.y = stage.stageHeight - txtTrace.height; 
 
			// Setting navigator size to be over txtTrace component
			navigator.setSize(stage.stageWidth, stage.stageHeight - txtTrace.height);
		}
 
		protected function navigator_viewChangingHandler(event:ViewNavigatorEvent):void
		{
			txtTrace.appendText(
				"action: " + event.action + 
				", oldView: " + event.oldView + 
				" newView: " +  event.newView +
				"\n"
			);
		}
	}
}

The SampleView class extends View, which is a default implementation of the IView interface. Because the View class extends Sprite you can add/remove child DisplayObjects to/from it and work with it as with a standard Sprite. Worth mentioning here is overridden function resize. Doing so allows to scale and layout child elements of the view whenever the owning ViewNavigator size changes.

// com/riaspace/as3viewnavigator/demo/SampleView.as
 
...
	override public function resize():void
	{
		for (var element:Object in _elements)
		{
			var coordinates:Object = _elements[element];
			position(DisplayObject(element), coordinates.horizontalCenter, 
				coordinates.verticalCenter);
		}
	}
 
...