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Building Your First App: The List Container
7 November 2009 by Rob Spectre
This entry is part 6 of 9 in the series Building Your First App
/2009/11/boxee.png
Building Your First App

Last time, we finished up the last of the graphics work for our first application. The next step is building the list container. The list container is the primary interface of the application – the control that users browse through to view the content you’re delivering. The good news is they are not very hard to make and they are probably the most complex piece of your whole app.

This one is a little long-winded, I’ll warn you. But not at all as daunting as it might initially seem.

First we start much the same way that we did when building an image control – by setting its position and dimensions:

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<control type="list" id="100">
   <posx>65</posx>
   <posy>235</posy>
   <width>492</width>
   <height>406</height>
</control>

Notice that we set the positioning five pixels to the right of the list.png image control and five pixels down. This will make the list seem indented with list.png as its background. Similarly, we reduced the dimensions both height and width by ten pixels, thus giving us a five pixel margin around our list container. We also assign it the id “100″ – the same value as our the defaultcontrol element we defined earlier.

Next, we define our orientation.

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<control type="list" id="100">
   <posx>60</posx>
   <posy>230</posy>
   <width>502</width>
   <height>416</height>
   <orientation>vertical</orientation>
</control>

This element can have two values – horizontal or vertical. For this particular app, we want a vertical orientation (much like Auto-Tune The News). A horizontal orientation is generally used in panel containers, like those seen in Digg or Revision3.

Third, we need to define our item layout. This is the only part that gets a little tricky. Every item in your RSS feed gets parsed by Boxee and becomes a “ListItem.” The list container we are building will be populated by these ListItems and their appearance must be defined within this control. Consider the following XML:

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<control type="list" id="100">
   <posx>60</posx>
   <posy>230</posy>
   <width>502</width>
   <height>416</height>
   <orientation>vertical</orientation>
   <itemlayout width="502" height="65">
    <control type="label">
        <posx>0</posx>
        <posy>0</posy>
        <width>502</width>
        <height>62</height>
        <font>font40</font>
        <align>left</align>
        <aligny>center</aligny>
        <label>$INFO[ListItem.Label]</label>
        <textcolor>white</textcolor>
    </control>
    </itemlayout>
</control>

The item layout element – like the list control – is a container for all the subelements within it. In this case, we only have one, the ListItem’s Label (read: title). In it you will notice the same position and dimension elements (e.g. posx, width, etc). You will also notice the width and height attributes for the element.

What the item layout attributes do is define the total size of the individual item. In this case, we want to make it as wide as the list container and big enough to have some space between the text. We can then define the dimensions of our label control as slightly shorter, giving us a 3 pixel gap between the labels.

The next step after we define our item layout, is to define our focused item layout. If the item layout defines what all ListItems look like in our app, focused item layout defines how the one focused item in the list should look. This is how we distinguish to the user which piece of content they have selected.

This can be done many ways and fortunately Boxee has some built in features you can use without adding any more graphics assets. Take a look at this addition to our list container:

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<control type="list" id="100">
   <posx>60</posx>
   <posy>230</posy>
   <width>502</width>
   <height>416</height>
   <orientation>vertical</orientation>
   <itemlayout width="502" height="65">
    <control type="label">
        <posx>0</posx>
        <posy>0</posy>
        <width>502</width>
        <height>62</height>
        <font>font40</font>
        <align>left</align>
        <aligny>center</aligny>
        <label>$INFO[ListItem.Label]</label>
        <textcolor>white</textcolor>
    </control>
    </itemlayout>
    <focusedlayout width="502" height="65">
      <control type="image">
           <posx>0</posx>
           <posy>0</posy>
           <width>502</width>
           <height>65</height>
           <texture>white.png</texture>
           <colordiffuse>DD171717</colordiffuse>
       </control>
       <control type="label">
           <visible>!Control.HasFocus(100)</visible>
           <posx>0</posx>
           <posy>0</posy>
           <width>502</width>
           <height>62</height>
           <font>font40</font>
           <align>left</align>
           <aligny>center</aligny>
           <label>$INFO[ListItem.Label]</label>
           <textcolor>white</textcolor>
           <selectedcolor>DD171717</selectedcolor>
       </control>
       <control type="label">
           <visible>Control.HasFocus(100)</visible>
           <posx>0</posx>
           <posy>0</posy>
           <width>502</width>
           <height>62</height>
           <font>font40</font>
           <align>left</align>
           <aligny>center</aligny>
           <label>$INFO[ListItem.Label]</label>
           <textcolor>white</textcolor>
           <selectedcolor>DD171717</selectedcolor>
           <scroll>true</scroll>
           <scrollspeed>30</scrollspeed>
       </control>
    </focusedlayout>
</control>

You’ll notice looks exactly like , only with a few additions. The first addition you will notice is the image control. What this does is give the selected item in the list a tinted background. To accomplish the tint look, we use a default image texture white.png and a colordiffuse element. The colordiffuse element will tint that white with the color you specify, making it in this case just a little more gray. The second difference you’ll notice is that there are two label controls instead of one.

We need two labels in the focused layout to handle two use cases – when the application has focus and when it does not. When Boxee is in focus and the user is actively browsing the list container, he/she sees the label control on the bottom. That label control is set to scroll the text of the label (if it is longer than the width allowed), letting the user preview the content’s full label before selecting it. But, what if that user clicks away into another application or a menu? Obviously we wouldn’t want to continue scrolling, which is what the label control above it does. It stops the scrolling and waits for the user to return his/her focus to the app before scrolling again.

Phew! This is getting long, but we’re almost there.

The final element in your list container is the plumbing to hook your RSS feed up to the application. It can be added easily, like below:

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<control type="list" id="100">
   <posx>60</posx>
   <posy>230</posy>
   <width>502</width>
   <height>416</height>
   <orientation>vertical</orientation>
   <itemlayout width="502" height="65">
    <control type="label">
        <posx>0</posx>
        <posy>0</posy>
        <width>502</width>
        <height>62</height>
        <font>font40</font>
        <align>left</align>
        <aligny>center</aligny>
        <label>$INFO[ListItem.Label]</label>
        <textcolor>white</textcolor>
    </control>
    </itemlayout>
    <focusedlayout width="502" height="65">
       <control type="image">
           <posx>0</posx>
           <posy>0</posy>
           <width>502</width>
           <height>65</height>
           <texture>white.png</texture>
           <colordiffuse>DD171717</colordiffuse>
       </control>
       <control type="label">
           <visible>!Control.HasFocus(100)</visible>
           <posx>0</posx>
           <posy>0</posy>
           <width>502</width>
           <height>62</height>
           <font>font40</font>
           <align>left</align>
           <aligny>center</aligny>
           <label>$INFO[ListItem.Label]</label>
           <textcolor>white</textcolor>
           <selectedcolor>DD171717</selectedcolor>
       </control>
       <control type="label">
           <visible>Control.HasFocus(100)</visible>   
           <posx>0</posx>
           <posy>0</posy>
           <width>502</width>
           <height>62</height>
           <font>font40</font>
           <align>left</align>
           <aligny>center</aligny>
           <label>$INFO[ListItem.Label]</label>
           <textcolor>white</textcolor>
           <selectedcolor>DD171717</selectedcolor>
           <scroll>true</scroll>
           <scrollspeed>30</scrollspeed>
       </control>
    </focusedlayout>
    <content type="url" url="rss://yourdomain.com/yourfeed.rss">
    </content>
</control>

It’s the easy piece of the whole list container puzzle – just plug in the path for your RSS feed into the url attribute, and you’re done-diggy. Once you drop your completed code in the group control after the metadata box image, you can reload the app and see your content now populating. Once you add the container to your app, your main.xml should look like this:

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<?xml version="1.0"?>
   <window type="window" id="14000">
   <defaultcontrol always="true">100</defaultcontrol>
   <allowoverlay>no</allowoverlay>
   <controls>
      <control type="group">
          <control type="image">
             <posx>0</posx>
             <posy>0</posy>
             <width>1280</width>
             <height>720</height>
             <texture>bg.png</texture>
          </control>
          <control type="image">
             <posx>60</posx>
             <posy>230</posy>
             <width>502</width>
             <height>416</height>
             <texture>list.png</texture>
         </control>
         <control type="image">
             <posx>630</posx>
             <posy>255</posy>
             <width>574</width>
             <height>355</height>
             <texture>details.png</texture>
          </control>
          <control type="list" id="100">
	   <posx>60</posx>
	   <posy>230</posy>
	   <width>502</width>
	   <height>416</height>
	   <orientation>vertical</orientation>
	   <itemlayout width="502" height="65">
	    <control type="label">
		<posx>0</posx>
		<posy>0</posy>
		<width>502</width>
		<height>62</height>
		<font>font40</font>
		<align>left</align>
		<aligny>center</aligny>
		<label>$INFO[ListItem.Label]</label>
		<textcolor>white</textcolor>
	    </control>
	    </itemlayout>
	    <focusedlayout width="502" height="65">
	       <control type="image">
		   <posx>0</posx>
		   <posy>0</posy>
		   <width>502</width>
		   <height>65</height>
		   <texture>white.png</texture>
		   <colordiffuse>DD171717</colordiffuse>
	       </control>
	       <control type="label">
		   <visible>!Control.HasFocus(100)</visible>
		   <posx>0</posx>
		   <posy>0</posy>
		   <width>502</width>
		   <height>62</height>
		   <font>font40</font>
		   <align>left</align>
		   <aligny>center</aligny>
		   <label>$INFO[ListItem.Label]</label>
		   <textcolor>white</textcolor>
		   <selectedcolor>DD171717</selectedcolor>
	       </control>
	       <control type="label">
		   <visible>Control.HasFocus(100)</visible>   
		   <posx>0</posx>
		   <posy>0</posy>
		   <width>502</width>
		   <height>62</height>
		   <font>font40</font>
		   <align>left</align>
		   <aligny>center</aligny>
		   <label>$INFO[ListItem.Label]</label>
		   <textcolor>white</textcolor>
		   <selectedcolor>DD171717</selectedcolor>
		   <scroll>true</scroll>
		   <scrollspeed>30</scrollspeed>
	       </control>
	    </focusedlayout>
	    <content type="url" url="rss://yourdomain.com/yourfeed.rss">
	    </content>
	</control>
      </control>
   </controls>
</window>

For more information of the possibilities of the list container, check out Boxee’s developer documentation.

Series Navigation«Building Your First App: Finishing The GraphicsBuilding Your First App: The Metadata Box»

  • Thanks to Greg for catching some errors related to the proper ID of the list container!
  • Max
    Hi there,

    sorry to post somewhat of an unrelated post here but I was wondering, since the my rss feed app is no longer available, if I could use a test app to view an rss video podcast feed I was viewing just fine before. If I can, since I am not a programmer, can I download a template or another test app from somewhere and insert my rss feed?

    I would appreciate you feedback,
    Thanks,
    Max
  • On the last label control (in the last block of example code), <scroll>true</scroll> (line 85), the text will begin to scroll but it also leaves behind the original white text. So in other words it looks like the labels are stacked on top of each other, one is scrolling and the other is not. If I remove the 2nd to last label control (line 60-72) that seems to remedy it. But I'm pretty sure that's not the right solution since you mentioned needing two controls to handle two different cases.

    I cannot browse up and down through the list items. Is that normal at this stage? I didn't know if you were going to cover that in a later tutorial or not.
  • Oooh, good catch. Though it is correct in the first example, the last two examples of the list container did contain a typographical error making the control invisible on object focus. I have correct the examples to make sure only the scrolling label is visible when the ListItem is in focus.

    I also neglected to talk about the importance of an id attribute for your list container - I've add it to all the examples above with a little explanation when we first build it.
  • Thanks again for your great instruction! I have a couple of questions if you don't mind.

    Can you show the complete file? I wasn't quite sure if each section you noted should be appended to the main control group or if you were building on each control, meaning the final code you pasted is the complete bit of code.

    The last bit you posted looks like it didn't come through properly. Meaning I had to view the html source to see the code. Not sure if that was intended or not.

    Again, thanks. Your tuts are by far the best step by step instruction out there.
  • vRobM
    Yes, making sure to mention main.xml and line numbers of intsert at the start of the post would help with the doubt of where the control elements go.
  • Right on - got the complete file shown at the bottom and installed some improved syntax highlighting to make the code examples look a lot better.
  • Very nice man, looks great! Going to check the rest out (as well as the newest tutorial).
  • Hrm... That is definitely not right. I need to find better code
    highlighting.

    Will fix this afternoon.
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