I’m currently in the process to implement a preview window in ReadNow. One of my ideas was to implement a sliding text at the bottom of the window, because lots of websites have a title that is longer than the window. The view should slide the text to the right side till the end of the text and then back to the beginning of the text. Another requirement was that it should be very easy to change the text.
First I thought it will be not so much complicated to implement that, but I was wrong. I tried several of options, like to slide a text within a NSScrollView, but no one of that fit my needs.
After a while of searching , I read a post in a forum that mentioned a implementation of a sliding text view with a Custom NSView and Core Animation. Unfortunately no sample code was given. Due to I don’t use Core Animation before, I decided to dive a little bit into Core Animation.

The plan was:

1. Create a NSView subclass
2. Say the NSView that he needs a layer.
Core Animation is layer based, it’s like the view hierarchy with NSView and subviews. Basically a NSView don’t have a layer attached, you must explicitly say that he needs a layer in the Interface Builder. You see the necessary setting in the following screenshot:

3. Create a CAScrollLayer and set it as the layer of the NSView subclass
4. Add a CATextLayer to our CAScrollLayer
5. Attach a animation to the CATextLayer that scrolls the text within the CAScrollLayer.
In detail, it changes the position property of the CATextLayer that results in a sliding effect.

The result code is at the following:

Header file:

Implementation file:

You will find a sample Xcode project on my github-profile.

In the last weekend I tried to dive a little bit into the Google Data APIs Objective-C Client Library. Unfortunately it wasn’t so easy to integrate the Library into my iPhone project as I thought at the beginning.

If you would like to integrate the Google Data APIs Library in one of your iPhone Projects, I wrote the necessary steps, down which you can read at the following:

First of all we have to add the necessary frameworks to the iPhone Project.
This are the Security.framework and the SystemConfiguration.framework. For each of the frameworks we have to do the following:
We make a right click on the “Frameworks” folder in the “Group & Files” list and choose the “Add->Existing Frameworks…” menu item.

We scroll to the respective framework, click on it, and click the “Add” button.

Next, we download the source of the Google Data APIs Objective-C Client Library from the URL: http://code.google.com/p/gdata-objectivec-client and make some necessary preparations.
After unzipping the archive we open the GData.xcodeproj file in the “Source” directory.

After Xcode opened the GData.xcodeproj file we click on the left triangle besides the “Targets” entry. Then we make a double click on the GDataTouchStaticLib and substitute the Base SDK entry from “iPhone Device 3.0″ to “iPhone Device 4.0″.

At the end we have to open the project settings for the GData.xcodeproj file (Project -> Edit Project Settings) and delete all entries in “Other warning flags”.

Back to the iPhone Project.
The GData library project includes a target for building a static library for iPhone and iPod Touch apps; this avoids dragging individual library source files into the iPhone application’s project. To build the iPhone poject with the static library we have to make a cross project reference.
There are two ways, choose on of it:

• drag the GData.xcodeproj file itself from the Finder into “Groups & Files” in the iPhone project
• add the GData.xcodeproj file with “Project->Add to Project…” to the iPhone project

In the next step, we add the GDataTouchStaticLib target as a dependency for building the iPhone project: We have to do a click on the triangle besides the Target entry, a right mouse click on the Target in the targets list and a click on the “Get info” menu item.

Now you switch to the “General” pane on the top of the target editor. To add a target dependency, click the plus-sign button. The list of targets shown includes all the other targets in the current project, as well as the targets in any referenced projects. Due to we have the GData.xcodeproj as a cross reference we see the GDataTouchStaticLib in the list of targets. Now we click on the GDataTouchStaticLib and “Add Target” Button to add it as a target dependency. After that we close the target editor window.

The next step is to drag the static library target (libGDataTouchStaticLibrary) from under the GData.xcodeproj cross-project reference in our iPhone project to the target’s “Link Binary With Libraries” build phase from our iPhone project. You will see the “Link Binary With Libraries” build phase if you click on the triangle besides you Target.

Next we have to add some “Other Linker Flags” to the iPhone project preferences. In Xcode, double-click the target’s name under “Targets” in the project window. Choose the “Build” pane from the ensuing “Info” window. Scroll down to the “Other Linker Flags” build setting under the Linking collection and open it with a double click. Add “-ObjC” in line 1 and “-lxml2″ in line 2 to the table view.

After that, we will have problems to build the Project, because Xcode can’t find the lxml library. To solve this problem we add to the “Header Search Paths” build setting the entry: /usr/include/libxml2

Now we have to build the iPhone project to create header files of the static library. Click (Build->build). After the build have been finished, the static library build creates the necessary directory of header files (in its build products directory) that should be dragged into the iPhone project.

So go to the the GData Project Folder and change the folder to “Source -> build -> Debug-iphonesimulator” and you will see a directory called “Headers”. We drag the hole directory to our iPhone project.

Thats all, with the static library linked into your project, refer directly to the headers by omitting the framework name, like

in your source files.

Further informations you will find at the following links:

• http://code.google.com/p/gdata-objectivec-client/
• Google Data APIs for
  Cocoa Applications
• GDataObjCIntroduction
• Google Data Protocol