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Icons on iOS and OS X

Sometime I need some small table to resume quickly the artwork required for the iOS and OsX applications. They are often the same image, but in different resolutions. Here they are:

OsX

	Resolution	Notes
Icons	1024 x 1024 pixels 512 x 512 pixels 256 x 256 pixels 128 x 128 pixels 32 x 32 pixels 16 x 16 pixels
Toolbar icons (inside control)	19 x 19 pixels	Outline style, recommanded to be black
Toolbar icon buttons	32 x 32 pixels	Color with antialiasing
Sidebar icons	16 x 16 pixels 18 x 18 pixels 32 x 32 pixels	Black and white with alpha, all three resolutions required

More information for Os X here: Icon Design Guidelines

iOS

	Resolution	Notes
Icon for iPhone	57 x 57 pixels	Suggested name: Icon.png. No shadow or round corners required.
Icon for iPhone with Retina Display	114 x 114 pixels	Suggested name: Icon@2x.png. No shadow or round corners required.
Icon for iPad	72 x 72 pixels	Suggested name: Icon-72.png. No shadow or round corners required.
Small icons iPhone (Spotlight and settings)	29 x 29 pixels
Small icons iPhone High Resolution (Spotlight and settings)	58 x 58 pixels
Small icons iPad (Spotlight)	50 x 50 pixels	It trims the side pixels (safe area 48x48)
Small icons iPhone (settings)	29 x 29 pixels
Toolbar icons for iPhone	20 x 20 pixels	Approximately
Toolbar icons for iPhone High Resolution	40 x 40 pixels	Approximately
Toolbar icons iPad	20 x 20 pixels	Approximately
Tab bar icons iPhone	30 x 30 pixels	Approximately
Tab bar icons iPhone High resolution	60 x 60 pixels	Approximately
Tab bar icons iPad	30 x 30 pixels	Approximately

More information for iOS here: Custom Icon and Image Creation Guidelines

Open source/free toolbar icon sets

Some link to free/open source iPhone toolbar icon set:

• TWG Retina Icons
• PP Free iPhone Toolbar Icons
• Glyphish

How to take a screenshot with the Android SDK

You can take a screenshot in Android using one of the several Market's application, or using "ddms", a tool you can find in the tools directory of the sdk.

So, go to that directory and start it:

cd [sdkdir]/tools
./ddms

Then go on the Device menu ant click on Screen capture. Then save the image file.






If you want to take a screenshot from Eclipse, it is even simpler.
Just set the DDMS perspective:

Look for the camera button, and click on it to show the following menu:

Here you can find the "Screen Capture" command.

How to check if our app is running on an iPad or iPhon

The easiest way is using the UI_USER_INTERFACE_IDIOM macro. Only SDKs 3.2 an later support it. Here an example:

if (UI_USER_INTERFACE_IDIOM()==UIUserInterfaceIdiomPad) 
{
  NSLog(@"I'm on iPad");
}

In the same way:

if (UI_USER_INTERFACE_IDIOM()==UIUserInterfaceIdiomPhone) {
  NSLog(@"I'm on iPhone or on an iPod touch"); 
}

The macro uses the [[UIDevice currentDevice] userInterfaceIdiom] method. If you are sure that your SDK supports the userInterfaceIdiom selector, you can also use something like this:

[[UIDevice currentDevice] userInterfaceIdiom]==UIUserInterfaceIdiomPad

Android's services

Android uses services to perform long running jobs, or background tasks (think to a network interaction or an mp3 player). How can we start a service?

We should begin extending the android.app.Service class:

public class TestService extends Service {

     @Override

     public IBinder onBind(Intent arg0) {

          return null;

     }

     public void onCreate () {

       Log.i("onCreate", "onCreate");   

     }

    

     @Override

     public int onStartCommand(Intent intent, int flags, int startId) {

           Log.i("onStartCommand", "onStartCommand");  

           Toast.makeText(this, "Hi, this is a service!",

                           Toast.LENGTH_LONG).show();

           return START_STICKY;

      }

}

The two most important methods, for the purposes of this post, are onCreate and onStartCommand. Android invokes the first, when the service is created, and the second one, when it is executed. The Toast.makeText(…) command is a nice way to give notifications to the users.

Please note that the onStartCommand callback exists only in the versions 2.0 and later. In older versions you should override the onStart method (now deprecated).

Once you have you service’s skeleton, you can register with the operating system, adding a line to the manifest:

 <service android:name="TestService" android:enabled="true" >service>

Or in a easier way, using the Eclipse interface:

At the end is time to start our service, using two instructions:

Intent intent = new Intent(this, TestService.class);

     startService(intent);

We create an android.content.Intent instance, and then we use it in the startService method. The Intent, ask you for a context (your calling Activity is fine), and the implementation class. He will take care of the instantiation. The startService will call your onStartCommand procedure, passing it also the intent instance. A nice place to do it could be in the onClick method:

     public void onClick(View v) {

          switch (v.getId()) {

          case R.id.buttonStart:

               Intent intent = new Intent(this, TestService.class);

               startService(intent);

               break;

          }

     }

How to take screenshots directly on the iPhones

If you want to take a screen-shot directly from your iPhone/iPod touch/iPad, and find it directly in your photo library, there is a simple procedure:

1. Press the Home button, without releasing it;
2. Press and release the Sleep button;
3. Release the Home button.

That's all! Now go in your camera roll, and enjoy the image of screen. Some more thing on screen-shots here!
The (so called) Home and Sleep buttons are marked in red in the picture.

Load an XML file in Mac Os X using Cocoa: NSXMLDocument

Here another snippet on how to load an XML file using the NSXMLDocument class. Our goal is to show an “Open File” dialog box (as said in the last post), chose an xml file, and put it in a data structure (NSXMLDocument)

Here’s the code:

-(BOOL) LoadXml : (NSError **)err
{
    NSURL *fileUrl = nil;
    
    NSOpenPanel* openDlg = [NSOpenPanel openPanel];
    [openDlg setCanChooseFiles:YES];
    [openDlg setCanChooseDirectories:NO];
    [openDlg setAllowsMultipleSelection: NO];
    [openDlg setAllowedFileTypes:[NSArray arrayWithObjects:@"xml", 
             nil]];
    if ( [openDlg runModal] == NSOKButton )
    {
        fileUrl = [openDlg URL];
    }
    if (fileUrl==nil)
    {
        return NO;
    }
    
    xmlDoc = [[NSXMLDocument alloc] initWithContentsOfURL:fileUrl 
       options:(NSXMLNodePreserveWhitespace|NSXMLNodePreserveCDATA)
       error:err];
    if (xmlDoc == nil) {
        xmlDoc = [[NSXMLDocument alloc] initWithContentsOfURL:fileUrl
           options:NSXMLDocumentTidyXML error:&err];
    }
    if (xmlDoc == nil) 
  return NO;
    
    ...
}

The only “strange” thing suggested by the Apple’s example and reported here, is the double initialization of NSXMLDocument, with different parameters: the first one with NSXMLNodePreserveWhitespace|NSXMLNodePreserveCDATA, the second one with NSXMLDocumentTidyXML.

We are trying to recover from parsing errors. NSXMLDocumentTidyXML reformats the document before the parsing. Hopefully it can correct some error, but it modifies the original file (take a look at the documentation).

More information is in the “Introduction to Tree-Based XML Programming Guide for Cocoa” on the Apple Devveloper web site.