37 posts tagged “apple”

UITableView scrolling performance gotcha

Sep 30, 2009
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After a few months of .NET reporting/SSIS development work, I'm back to an iPhone project this week. One enhancement I added yesterday was a better formatted table section title in a UITableView. Before, the section title is either a bunch of unformatted (also incorrectly by locale) dates (e.g. 2009-09-30), or times (e.g. 14:58) straight from the data source. The enhancement/bug fix is to format the date or time to be locale aware so the title would either be "Wed Sep, 30 2009" or "2:58 PM" if you are in the US.

Pretty straightforward I thought, and after a couple of trips to NSDateFormatter and use the output in UITableView's titleForHeaderInSection:section method, it was all working very well in the simulator. That was until I put the app onto my iPhone for some real in-device testing.

The scrolling performance in the table was horrible! My first thought was that it had to do with the background view I added to the custom table cell view for colouring the table cell background. But after nearly an hour of debugging through the code I still couldn't find anything wrong.

Turns out that the titleForHeaderInSection:section method is not just called once per controller instantiation. It is called once per table cell display!

Once I moved the code to format the section title into viewDidLoad and cached a copy of the nicely formatted titles in an array, the scrolling is back to normal speed.

How safe do you feel?

Aug 16, 2009
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Most people I know do not have any plan to backup their data. Somehow they put their trust to a piece of 3.5" glass disc, spinning at 5400 times a second or more with a sharp metal spike fraction of a hair above it. Me? I like to spread my risk and backup my data, especially after suffering a total data lost about 12 years ago. As Alex Lindsay from the PixelCorps often says on podcasts, "Unless the data is stored in 3 different places, it doesn't exist". This may sound over the top but with all the online file sharing or storage services available it is actually pretty easy to have decent backup strategy with minimum cost. To achieve comprehensive backup coverage, it would definitely cost a few dollars.

Like computer security, any backup strategy should be constructed in layers. This applies to both time, location, and accessibility. Let me use my backup strategy as an example.

The least time consuming (in terms of setup and maintenance) backup component in my setup is Time Machine that comes with OS X. I setup Time Machine to backup to an external drive (more on that later) that is the same size as my main bootup drive and that's it. Time Machine will then backup everything on the drive and updates the backup copy with any changes every hour. This provides the first layer in my backup strategy; files that are used most will always be backed up and available to restore quickly.

In the event of my bootup hard disk fails, I can restore from the Time Machine backup. But that can take a while given most hard disk is rather large nowadays. So to keep down time to the minimum, every week I also clone the entire hard disk to an external disk (separated from the one Time Machine uses). I use Carbon Copy Cloner for this and while it is not a 'set and forget' setup like Time Machine, it only requires 5-10 minutes of actual effort every week on my part to clone the hard disk. This copy will allow me to boot my Mac up from the external drive within minutes of any internal hard disk failure. At the most, I'll have 6 days of data to catch up using Time Machine and that would not take long at all.

So I have two copies of my internal hard disk on two different external drives, e.g. data in two places. Pretty safe, right? Yes, pretty safe but not very safe. What if any of these two external drives fails? Then I can easily back to having no backup at all.

Drobe on Mac Pro - 3

To mitigate that, the external drive that Time Machine uses is actually a Drobo. Drobo is a fully redundant disk array so data will be stored in a way that only all the drives fail at the same time in order to loss the data. This means my Time Machine copy is actually safer than just being stored on a regular external drive. The problem is that the Drobo drive is still sitting right where my machine is. What if someone break into my apartment and steals my computer, the clone external drive, and the Drobo? What if there is a fire in the building and all my computer equipment are lost?

For that eventuality, only an offsite backup will save my data. Again, time, location, and accessibility guide which services I choose to use. For files that I access and save often, I store them on Dropbox. It is ultra fast (way faster to sync to the cloud than MobileMe, for example) which makes it a pleasure to use. The free option let you store up to 2GB of data and it is more than adequate for my day-to-day data. This also have the added advantage of allow me to access files on different computers, e.g. my work laptop. For files that I need less often and larger (for example, video files that I want to share online), I store them on MobileMe's iDisk. Data syncing is nowhere as fast as Dropbox but it provides more data storage.

I also use a separate online service to store my code. cvsdude provides online storage of code using CVS or Subversion. I also use GitHub for my latest code project. Eventually all of my code will be stored on GitHub once my subscription with cvsdude expires.

But what about all the music, photos, and videos files that I own? Their large size make it difficult to backup to the cloud. Right now I store all of them on the Drobo so they are protected against disk failure but that means they exist only in one place (strictly speaking more than one copy is stored by Drobo). To guard against total loss, I am currently in the process of using Mozy to backup all of the media files which come to about 600+GB. The MozyHome Unlimited plan is not free but it will be tough to ask someone to provide that amount of backup storage at no cost! The issue with Mozy is the time requires to upload that much data to their data centre. Even with a decent upload connection of ~2Mbps I am expecting the upload to take at least 3-4 months to complete.

To recap, here is where my data exists:

1) Files (e.g. documents, emails, applications, etc.) - Internal hard disk, Time Machine on Drobo, clone on USB external drive = 3 places

2) Important/Frequent use documents (subset of #1) - Internal hard disk, Time Machine, clone drive, Dropbox, MobileMe's iDisk = 4 places

3) Code files - Internal hard disk, Time Machine, clone drive, MobileMe's iDisk, cvsdude/GitHub = 5 places

3) Media files (iTunes library, iPhoto library, iMovie Events & Projects) - Drobo, Mozy = 2 places

Am I crazy? Ask me again when you have a hard disk failure and want some advice on how to recover your precious data.

Inoperative Cancel button in UIActionSheet

May 9, 2009
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Let's say you want to use UIActionSheet to show three buttons to the user with a cancel buttons in a UIView, which itself is managed by a UITabBarController:

UIAlertSheet

Your code would probably look like this:

UIActionSheet *actionSheet = [[UIActionSheet alloc] initWithTitle:@"Action Title" delegate:self cancelButtonTitle:@"Cancel" destructiveButtonTitle:nil otherButtonTitles:@"Option 1", @"Option 2", @"Option 3", nil];

actionSheet.actionSheetStyle = UIActionSheetStyleDefault;

[actionSheet showInView:self.view];

[actionSheet release];

And you'll also probably find that all the 3 option buttons works, but the Cancel one doesn't!

It is because the UIView which the UIAlertSheet belongs to is behind the UITabBarController, and the TabBar's hitTest method gets called before the UIAlertSheet's.

To fix this, it is just a simple matter of using the view from the UITabBarController in the showInView method. Like this:

UIActionSheet *actionSheet = [[UIActionSheet alloc] initWithTitle:@"Action Title" delegate:self cancelButtonTitle:@"Cancel" destructiveButtonTitle:nil otherButtonTitles:@"Option 1", @"Option 2", @"Option 3", nil];

actionSheet.actionSheetStyle = UIActionSheetStyleDefault;

ApplicationDelegate *appDelegate = (ApplicationDelegate *)[[UIApplication sharedApplication] delegate];

UITabBarController *tabBarController = appDelegate.tabBarController_;

[actionSheet showInView:tabBarController.view];

[actionSheet release];

iMovie needs batch export

Feb 1, 2009
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Since I was a teenager, I have been fascinated by the process of video production but purely from the technical point of view. The complexity of capturing video, editing (the process not the artistic element), video effects, etc. drove my curiosity. A few years ago I worked with someone who also really into video as well. He captured videos for lots of family events and learnt to use professional tools and techniques. While I get really excited as I discussed the ins and outs of the equipment and setup my friend has, I was definitively unable to find a reason to take video for personal use. Capturing family memory is great but who actually would sit down and watch hours upon hours of family videos, apart from the family themselves?

It all changed when I started organising the NY ALT.NET events last September. We decided that we would video tape each meeting so members who were unable to attend would have a chance to participate, albeit in a passive form. As a result, I started learning to use iMovie '08 as a tool to process approximately 2 hours of video from each monthly meeting.

When Apple rebuilt iMovie from the ground up for the '08 version, lots of complains were raised because many features from iMovie '06 were dropped. What the user gained, however, was a much simpler user interface that makes editing movies a snap. Without any preparation and little learning time, I was able to import, pick video clips, add title and transition, and export videos within minutes. Literally. And the new version iMovie '09 added new features that were missing from iMovie '06, such as Precision Editor, themes, more transitions, etc. I especially love the Precision Editor because I can easily control the entry and exit points of each clip with ease.

But, and there's always a but, all these great time-saving features come to nothing when I need to export the video for people to consume. Because Apple is targeting the consumer market with iMovie (Final Cut Express for prosumer, and Final Cut Studio for pros), there is no facility to batch up video export.

Why is it important? Let's look at the typical time I spent working on videos for a monthly meeting:

~2-2.5 hours importing from camcorder. This is fixed time because it is a MiniDV tape camcorder and the only way to get from tape to hard disk is to replay all the footage in realtime.
~20-30 minutes editing each part. I break down the 2 hours meeting into around 30 minutes parts (actual length depends on the nature stopping point of the conversation). I then change the opening credit, make some adjustment to the audio (boast volume) and video (colour correction).
~2 hours exporting each final video to hard disk for uploading. This result in a 640x480 H.264 QuickTime video file around 550MB.
~1 hours uploading to Vimeo.

Now, there is no way for me to multi-task step #1. There is only one camcorder and thus I can only do one import at a time. Not a big problem as I can do other things once the import has started.

Step #4 is a background process. Once I kicked it off in the browser, I can do other things on the computer. For example, step #2.

The problem is with step #3. iMovie does not have the ability to export video in the background. What it means is that once the exporting process has started, I can't use iMovie to work on my next clip and thus save time. It would not be that bad if iMovie uses all the CPU power my computer has. My Mac Pro has two CPUs, each CPU has two cores, making it a total of four cores. That's a lot of computing power. But iMovie can only take advantage of one CPU at a time! So instead of a reasonable export time of around an hour, I have to wait for two before I can work on the next clip.

Now, if iMovie is able to export in the background, then at least I can work on the next clip using one CPU while exporting uses the other CPU. Alternatively, if iMovie has the facility to batch up videos for export in a queue, then I can work on editing all the clips and export them in a single batch while I sleep, or do whatever. But iMovie has neither and so the process of producing four 30 minutes video clips basically takes up most of my weekend instead of a few hours. Granted most of the time is spent waiting but still...

Of course one can argue that background or batch exporting is a pro feature and I agree. But when should I sacrifice the ease of use of iMovie, learn a completely different editing paradigm (arguably more difficult to use), just so I can save a few hours each months when my hardware is more than capable? I am more than willing to pay extra for iMoviePlus or plug-ins to achieve what I need but unfortunately I don't think either would be available any time soon.

iPhone Developer's Cookbook review

Dec 30, 2008
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The iPhone Developer's Cookbook: Building Applications with the iPhone SDK (Developer's Library)

Erica Sadun

When learning a new language/platform/framework, sometimes learning from a book is a good approach. But that depends heavily on picking the 'right' book. What I mean is that the book contains the 'right' amount of content for the reader's skill level. So when I looked for book to learn more about iPhone development, I have something specific in my mind already.

With Apple's original rather restrictive NDA placed on iPhone developers, all the iPhone development books were placed on hold until Apple changed of mind a few months back. One of the book that I received good recommendation from fellow ThoughtWorkers who were also interested in iPhone development was Erica Sudan's iPhone Developer's Cookbook. I bought it earlier this month along with Christmas presents so I can read it during the holiday vacation.

The book is not thick at all, coming just under 340 pages, and took me couple of afternoons to read through. It is written half in traditional cover-to-cover manner and half in 'recipe' manner where developers can find solutions to problem quickly. Perhaps because I've been part of the iPhone SDK program since the beginning and had seen the evolution from the first beta, most of the book content (I'd say 90%) is not new to me. Particularly the sections on table, advanced table, and UI controls are areas that I am already very familiar with after poking around the SDK for over 6 months. I did learn some valuable tips on media and animation, which I've not spent any time on yet.

I'm kind of disappointed by the book because I was hoping I would learn how to create great iPhone app. Particular I was looking for code examples of common application requirements (e.g. how to implement options screen) with in-depth discussion on the limitations imposed by the public API, alternative ways to work around them using legitimate means, as well as undocumented API. I am also hoping to see some mention of unit testing with OCUnit or Google's unit testing framework, profiling using Instrument, and other libraries that would fill in the API gaps. Instead, the book only provides isolated information on each topic and spends to my mind, a disproportion amount of time on undocumented API thus giving it an implicit approval. (On the topic of private/undocumented API, I am in the camp of John Gruber of Daring Fireball)

In the end, I would give this book 3 out of 5 because it provides a lot of valuable information for any one starting out with iPhone development. But it does not provide any insight into building great iPhone application, which I think is sorely missing in this area.

Birthday weekend

Dec 16, 2008
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After some prodding from me, Missus H. organised a birthday dinner for me on Saturday this year. Bunch of my friends came and we ate lots of delicious food cooked by Missus H. herself. The cherry coca cola ham was soft and sweet, the roasted potatoes disappeared within minutes, so were the creamed spinach. Dan, my fellow TWer, bought me a bottle of port as birthday gift and we all enjoyed it from the blue plastic cups!

Then on Sunday, Missus H. decided that I was 'allowed' to have my birthday present from her a day early. It turned out she bought me a iPhone 3G! So without further ado, we got out of bed, had breakfast, hopped onto the PATH train and visited Apple SoHo store to pick up my new phone.

Finally, last night we went to see David Sedaris at the Lincoln Center. He was as funny in person as he was in This American Life. He was not the skinny guy that I imagined him to be from listening to his voice alone, which proves the power of the radio.

A bit of contrast from last year when I was working in London and all I did on my birthday was to go to the Race of Champions at Wembley in below freezing temperature! I thoroughly enjoyed the racing but would much prefer to be not frozen solid in the process. And by the time I got back to central London, almost all the restaurants (i.e. not pub, Italian/pizza, or Subway) that I wanted to go were shut. Closed at the weekend by 9PM!

Spit and Polish

Dec 7, 2008
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A few months back, I started working on an iPhone app using the beta version of the iPhone SDK. Since then various things got in the way (not to mention the restriction of the old TOS placed on developers so everyone were working in the dark) and I didn't spend any time on it to really finish the app. My interest was revived when I attended the iPhone Tech Talk event in NYC last Tuesday. The sessions were interesting but nothing technical or coding. I learnt a lot more about the process of provisioning an iPhone for development testing and distribution, as well as how to submit app to the iTunes App Store. Most importantly though were that I was able to resolve issues around my personal's Standard and ThoughtWorks' Enterprise applications to the iPhone Developer Program. Now I am able to distribute and test my app on actual phone(s)!

Since Tuesday, I've been spending lots of my free time on polishing up the CCPhone app so I can start distributing it to the masses. One main change from the original vision is the colour theme change. This stems from the advice in the "iPhone User Interface Design" session, where dark colour theme is the preferred colour for apps that people use for short period of time (and possibly under the table/desk).

Another I've found is that the SDK has improved in many ways since the 2.0 days. Now it is easy to find the relevant sample code from the API reference documentation since the links to the sample apps are hyperlinked! There are also a lot more documentation on how to use various type of controls/classes in an advanced manner, much more than just the simple basis stuff. And from talking to all the Apple staff in the Tech Talk, I was impressed by how receptive they are to feedback. Even the really stupid stuff that they shouldn't have released in the first place.

And get this. I ran across a problem with the iPhone Developer Portal on Wednesday when I tried to set myself up with both my personal account and the ThoughtWorks' enterprise account. Somehow I was not able to switch between the two and when I un-assigned myself from the TW's account, I no longer had access to my personal one! With no recourse, I ended up sending an email to Apple and waited. That evening around 5PM, I got a surprise phone call from Apple inquiring about my problem. By that time, the problem had mysteriously resolved itself so I gave the lady on the phone my feedback on the Portal instead. Imagine that, someone actually calls the developer to resolve an issue!

CCPhone is just my way of dipping my toes in the water, testing the temperature. Now I need some more ideas for apps that I can work on.

Build there, check status everywhere

Jun 29, 2008
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I've been using the iPhone SDK since its original release way back in March. Many frustrating moment in the beginning but the recent beta 7 and beta 8 release proved to be ready for prime time. Apple has added many helper classes or helper methods to classes to make it far easier to work with the UI components, which is by far the most frustrating things I encountered. I am still having problem wrapping my head around the idea of Interface Builder but since the apps that I am building do not involve very complex UI, I just hand coded all the UI instead.

To illustrate, the original iPhone app idea I had that I started developing using the original SDK is a mobile application for Mingle. The application would consist of a series of table views showing projects, cards, and card details, along with some network code to talk to the Mingle server through REST API. At that time, progress was slow because of many factors. First, learning Cocoa/Cocoa Touch API and Xcode at the same time was tough. Second, the Cocoa Touch API was a bit 'primitive' in the beginning. What I mean is that while the API provides all the necessary hooks for developers to create an iPhone app it does not provide many pre-build components, making it difficult and required lots more work from developers to re-create the look and feel of the built-in iPhone apps.

I was so put off by the initial experience that I skipped beta 4-6 and did not open up Xcode until last weekend. And what a refreshing change with beta 7! Now it is straightforward to make an app that looks and feels just like an Apple's one. I was so fired up that last Sunday evening I decided that I would try to create an app for an idea that one of my fellow ThoughtWorker suggested to me. Instead of days of tearing my hair out and got no where, I was able to create a almost features completed app within hours, using beta 8.

So what is this app? It checks the build status on the CruiseControl server. Just like CCTray (Windows) or CCMenu (OS X), it allows users to monitor their software build status. Following the convention, I am calling it CCPhone. The app isn't more complex than the Mingle app but the fact that I was able to almost match the productivity I normally get on my Windows development environment means that I was excited about working on the app rather than dreading it.

Now here are couple of screen shots:

To-do:

Fix the build time being 1 hours off (probably day time saving bug)
Better status icons
Create application icon (currently it uses icon from CCMenu)
Finish coding the 'Force Build' functionality
Add startup screen bitmap (so it won't be just a black screen)
Add auto detect of CruiseControl server (Java, .Net, or Ruby)

Windy tennis

May 18, 2008
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My Flip Video (I have the 2GB/60 min, black) arrived last week and I finally got the chance to play with it today. Unfortunately the weather didn't cooperate. Dan and I had to deal with 15-20 mph wind while trying to film our tennis swings. You can hear the wind noise in the background, it's kind of hard to miss! Here is a short clip of what we did:

Tennis - Ground Strokes

You can see the full version (17:07) on Vimeo.

Transferring the video clips from the Flip to my Mac was a breeze. The Flip appears as a USB drive when plugged in so I can just copy the files across to my hard drive. Editing is a little tricky. The Flip uses a DivX MP4 encoder so the video files are not recognized by iMovie '08. After some Googling and experimentation, I decided to fork out some hard earned cash and got a license for QuickTime Pro. QTPro exports the clip to standard MP4 easily and quickly, utilizing all 4 of my MacPro cores. And editing in iMovie '08 pretty easy too. I was able to put this short clip together in about 5 minutes, even though I have no prior experience with iMovie '08 or video editing. It would be perfect if Apple fixes iMovie so that in the future it would just recognize the Flip video without any transcoding.

Dev Chair : iPhone SDK experience - Download Squad

Mar 28, 2008
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Dev Chair : iPhone SDK experience - Download Squad

http://www.downloadsquad.com/2008/03/...

The iPhone SDK has been out for couple of weeks now and I've been using it to develop an application for my work as a technology demonstrator. My experience thus far has been largely positive. I wasn't surprised by how well-made the SDK is, even at this beta stage. The amount of work involved in releasing any SDK, let alone one that is so tightly scrutinized, cannot be underestimated.Consider that I am learning three new things simultaneously: programming in Objective-C, learning how to use Xcode, and what is available in the iPhone SDK, I am going to describe the whole experience instead of just confined to the SDK...