Monday, July 30, 2012

Android: Swipe Image Viewer

EDIT: I have a much simpler implementation with ViewPager, and the github project has been updated. See post here.

I have a GrideView of images, which enlarges to full screen when you tap on any image. When I showed it to my friend he swiped to get to the next image, but that did not do anything because I was just using a plain old ImageView. I looked around for a standard widget to do that, and couldn't find any. So I unwillingly rolled my own solution:

I show the image in an ImageSwitcher. It contains two views, one displays the current image, and the other one holds the image to swap in. I lifted the gesture listener code from the Android Gallery app:

private class SwipeListener extends SimpleOnGestureListener {
  private static final int SWIPE_MIN_DISTANCE = 75;
  private static final int SWIPE_MAX_OFF_PATH = 250;
  private static final int SWIPE_THRESHOLD_VELOCITY = 200;

  public boolean onFling(MotionEvent e1, MotionEvent e2, 
      float velocityX, float velocityY) {
    try {
      if (Math.abs(e1.getY() - e2.getY()) > SWIPE_MAX_OFF_PATH)
        return false;
      // right to left swipe
      if (e1.getX() - e2.getX() > SWIPE_MIN_DISTANCE
          && Math.abs(velocityX) > SWIPE_THRESHOLD_VELOCITY) {
      } else if (e2.getX() - e1.getX() > SWIPE_MIN_DISTANCE
          && Math.abs(velocityX) > SWIPE_THRESHOLD_VELOCITY) {
    } catch (Exception e) {
      // nothing
    return false;

moveNextOrPrevious() swaps in the previous or next image with the appropriate animation:

private void moveNextOrPrevious(int delta) {
  int nextImagePos = mCurrentPosition + delta;
  if (nextImagePos < 0) {
  if (nextImagePos >= mImages.length) {

    delta > 0 ? mSlideInRight : mSlideInLeft);
    delta > 0 ? mSlideOutLeft : mSlideOutRight);

  mCurrentPosition = nextImagePos;

Notice how I show an overscroll grow when the user reaches the start or the end of the list of images. I make it visible immediately, and then use an animation to fade it away.

Right now all the logic is in MainActivity. I thought about encapsulating the viewer code into a custom view and bundling it into a jar file, but I am not sure how many people will find it useful, so laziness got the better of me. If you want to get a jar file to reuse this code, please let me know.

Until then, here is the source code:

Tuesday, July 24, 2012

#weareallawesome for public speaking

Every Tuesday at 1pm Pacific Time We Are All Awesome holds office hours on #weareallawesome on freenode. This week I asked Lorna Mitchell to share her experience at OSCON.

lornajane: I have never been to OSCON before, and I got two talks accepted that were kinda out of my league (I just submitted in the vague hope that something would happen)
chiuki: What do you mean by out of your league?
lornajane: both were scheduled on the same day - and they both went well!!! One of them was so full they shut the doors 5 minutes early
lornajane: chiuki: they were topics I didn't feel expert on
chiuki: ah
chiuki: but topics people want to hear
lornajane: yes, exactly
chiuki: what are the topics?
lornajane: I am very good at writing abstracts now - I have lots of practice at that! It was a PHP 5.4 talk (which actually was quite fun) and one about REST
lornajane: I am expert in REST but I hate speaking about it because it's contraversial and that part of the industry seems to make a habit of flaming and then I get upset
lornajane: the rest of my week was amazing, I've never been to Portland before and I loved it
chiuki: were there pointed questions at the REST talk?
lornajane: I met new friends and caught up with old ones, attended talks and tutorials in all kinds of technologies that I know nothing about, met loads of exhibitors and had fun at the parties
lornajane: chiuki: almost none. I mean, I got some questions laid down as a challenge, but I gave my (not-the textbook-version) opinion and the guy thanked me for my input
chiuki: cool
chiuki: so no flaming, then
lornajane: none!
lornajane: actually the OSCON crowd were all very friendly. I didn't know what to expect which was maybe fuelling my fears

I was curious about topics to submit, and Lorna has some insights:

chiuki: Any tips on submitting proposals to OSCON? What kind of topics go well?
lornajane: chiuki: it seems to be complicated, because there are tracks, so you're sort of submitting to subconferences
lornajane: so I aimed my talks firmly at the PHP track, and I know those people (and I stalked them on twitter!)
chiuki: That's a good way to look at it, to treat each track as a subconference
chiuki: I bet each track has its own review committee too
lornajane: chiuki: it exactly does
lornajane: I'm well-known in the PHP community so I pitched two talks to them (which they took) and one more general one (which didn't get in)
chiuki: the general one for a different track?
lornajane: yeah, it was like "algorithms for a geek lifestyle" or something like that
chiuki: oh I remember now
chiuki: I actually submitted something
lornajane: because I saw a few lifehacker type talks
chiuki: for being an indie developer
chiuki: but got rejected
lornajane: but mostly it was just good, clean tech all the way through
chiuki: next year I'll submit some hardcore Android talks for the mobile track
lornajane: chiuki: definitely do that!
chiuki: I think I got confused by the OS part of OSCON
chiuki: focusing too much on open source
chiuki: Android is open source, but that's not the part I work with
lornajane: they aren't militant about open source
chiuki: so I was trying too hard to cater to the OS part
chiuki: I'm looking at the program
chiuki: my existing Android talks will go really well

chiuki: I wonder if the twitter stalking helped you got your proposals accepted, lornajane :-)
cczona: what was the twitter stalking?
lornajane: chiuki: I don't know! I figured it didn't hurt :) Laura told me though that they had loved my proposals and that it was unusual to take two
lornajane: cczona: I know who runs the PHP track at OSCON so I tweeted at her when I submitted, just a little touch to remind her
cczona: Good idea.
chiuki: yeah, it's good to get your name in front of people

Rebecca Murphey, Carina Zona and Estelle Weyl chimed in when we discussed speaker packages:

lornajane: the main thing with oscon is that they have no speaker package
lornajane: so unless you work for a big company, it's hard to go
chiuki: no financial aid whatsoever?
lornajane: officially, not at all. In fact they can help out if you ask them, sometimes, but it seems a bit hit and miss
rmurphey: how much are oscon tickets and oscon sponsorships?
lornajane: rmurphey: I am not sure, I think the tickets are 1200 USD
chiuki: 1200USD????
chiuki: OMG
rmurphey: i am a tad bit puzzled as to why they can't cover speaker costs
rmurphey: sell one ticket per speaker, done
lornajane: rmurphey: the speakers are confused about that too
lornajane: rmurphey: most of them are big company people so it's no pain to them
lornajane: OSCON did cover my flight when I asked them to (I'm coming in from Europe and I'm self-employed)
rmurphey: good for you for asking lornajane :)
lornajane: rmurphey: actually, estellevw told me to
lornajane: and the devchix helped me find somewhere cheap to stay
lornajane: then the phpwomen helped me with my slides because it was all quite short notice
lornajane: hurrah for women in tech, is all I can say!
cczona: yeah
chiuki: hurray!
cczona: that's a great testament to the support available in the community
lornajane: *and* the systers had a lunch while we were there and I met more cool ladies doing amazing things. I felt so inspired by everyone's support
cczona: :-)
lornajane: oscon gives a pass, I should have said that. But nothing else
estellevw: O'Reilly does pay for some speakers. I assume if they want you to speak and don't think you can fund it thru a company.
rmurphey: if you would like to read a host of opinions on the topic,
rmurphey: but be warned
rmurphey: there are 181 comments

This is just a sample of the things we discuss on #weareallawesome. What do you want to talk about? Come join us some time!

Wednesday, July 18, 2012

Sony Smart Wireless Headset

I got a Sony SmartWatch from AnDevCon, and published two apps on Google Play:

Slideshow for SmartWatch

Fake Call for SmartWatch

I told Sony about my apps, and as a result they sent me a Sony Smart Wireless Headset to develop more apps!

I went to Google Play to get some apps for the headset, and there aren't many available. Here is the Twitter app:

The headset has a display, a microphone, and comes with an SD card to store your music. Besides playing music from the SD card, you can listen to the radio, and stream music from your phone or computer. It also has quite a few buttons:

  • Back key/Menu key
  • Previous key
  • Music key/Select key
  • Next key
  • Action key
  • Power key
  • Volume controls

With earphones and microphone, a display, and all these buttons, I'm sure there is a cool app waiting to be written. Guess it's time to study the SDK!

Sunday, July 1, 2012

Public speaking mid-year score card

Can you believe it's July already? I started the year with a resolution to be a public speaker, with the specific goal of giving 5 lightning talks and 3 full-length lectures. Let's see the mid-year score card!

Lightning talks

  1. April 2, 2012: Ignite Where 2012, San Francisco, CA
  2. June 28, 2012: Ignite Google I/O, San Francisco, CA

Full-length lectures

  1. April 6, 2012: Fluid Android Layouts, WindyCityGo, Chicago, IL
  2. April 11, 2012: Caching Strategies for Mobile Apps, Philly ETE, Philadelphia, PA
  3. April 17, 2012: Mobile Caching Strategies, Twitter Engineering Submit, San Francisco, CA
  4. May 16, 2012: Reusable Custom Components, AnDevCon III, Burlingame, CA
  5. June 8, 2012: Progressive enhancement for Android web apps, Dutch Mobile Conference, Amsterdam, the Netherlands

Looks like I'm coming short on the lightning talk side, which is quite surprising. I thought it would be more difficult to get accepted to give lectures. Also interesting that all my lightning talks were in Ignite talks, which is way more challenging than the speak-at-a-meetup quick talks I had in mind when I came up with the goals.

Ignite at Google I/O

Ignite talks are challenging because it follows a very specific format: 5 minutes, 20 slides, auto advancing. The auto-advancing slides is the trickiest bit, since you don't control the rhythm any more. I rehearse way more for Ignite than my full-length lectures, because I need to internalize the timing to sync my speech to my slides. It's almost like lip-syncing!

The first time I gave an Ignite talk was at Where 2012, to a crowd of 30 people or so. I was rather scared of the auto-advancing slides, but I found that I just need to wait until the next slide to appear before transitioning to a new topic.

Ironically, because I felt I did pretty well at my first Ignite, I was more nervous when preparing for my second one. I kept thinking that it was not quite as good. I mentioned that to my friend Julia, and did a practice run with her. She loved it! I notice that I really feed off the energy from the audience, even if only one person was listening. So the practice run was all I need to get back my confidence.

Ah, confidence is such a fragile thing. I walked into the room, and wow, it's big! It probably seats a thousand people. A thousand people! Plus the event was live streamed. I never spoke to such a large crowd, and I was so ridiculously nervous while waiting for the show to start. Fortunately once I got on stage I was back to my elements.

Here is the recording of the Ignite show at Google I/O. Let me know what you think!