David Janes' Code Weblog

After a brutal day of running into many Android bugs and misdocumentations, I’ve finally figured out how to create a slideshow of images for Android, with each imaging fading to the next. This is not unlike AnimationDrawable, except with a smoother and slower transition between images.

First, you need a resource file with something like this in it. The FrameLayout is the clever bit: it stacks everyone of its children on top of each other.

<FrameLayout
 android:id="@+id/frame"
 android:layout_width="wrap_content"
 android:layout_height="wrap_content"
>
 <ImageView
 android:id="@+id/slide_1"
 android:layout_gravity="center_vertical"
 android:layout_width="wrap_content"
 android:layout_height="wrap_content"
 />
 <ImageView
 android:id="@+id/slide_2"
 android:layout_gravity="center_vertical"
 android:layout_width="wrap_content"
 android:layout_height="wrap_content"
 />
</FrameLayout>

Then you need code that looks like this:

public class TopListActivity
  extends Activity
{
  private static class AnimationAlphaTimer
    extends TimerTask
    implements Animation.AnimationListener
  {
    TopListActivity topList;
    Vector<BitmapDrawable> images;
    int count = 0;

    public AnimationAlphaTimer(TopListActivity _topList)
    {
      this.topList = _topList;

      this.images = new Vector<BitmapDrawable>();
      for (int i = 0; ; i++) {
      // LOAD IMAGES HERE
      }

      if (this.images.size() > 0) {
        this.topList.slide_0.setBackgroundDrawable(this.images.get(0));

        if (this.images.size() > 1) {
          this.topList.slide_1.setBackgroundDrawable(this.images.get(1));
        }
      }

      this.count = 1;
    }

    public void launch()
    {
      if (this.images.size() >= 2) {
        (new Timer(false)).schedule(this, 100);
      }
    }

    @Override
    public void run()
    {
      this.doit();
      this.cancel();
    }

    private void doit()
    {
      if ((this.count % 2) == 0) {
        AlphaAnimation animation = new AlphaAnimation(1.0f, 0.0f);
        animation.setStartOffset(3000);
        animation.setDuration(3000);
        animation.setFillAfter(true);
        animation.setAnimationListener(this);

        this.topList.slide_1.startAnimation(animation);
      } else {
        AlphaAnimation animation = new AlphaAnimation(0.0f, 1.0f);
        animation.setStartOffset(3000);
        animation.setDuration(3000);
        animation.setFillAfter(true);
        animation.setAnimationListener(this);

        this.topList.slide_1.startAnimation(animation);
      }
    }

    public void onAnimationEnd(Animation animation)
    {
      if ((this.count % 2) == 0) {
        this.topList.slide_1.setBackgroundDrawable(
          this.images.get((this.count + 1) % (this.images.size()))
        );
      } else {
        this.topList.slide_0.setBackgroundDrawable(
          this.images.get((this.count + 1) % (this.images.size()))
        );
      }

      this.count++;
      this.doit();
    }

    public void onAnimationRepeat(Animation animation)
    {
    }
    public void onAnimationStart(Animation animation)
    {
    }
  }

  @Override
  public void onResume()
  {
    super.onResume();

    (new AnimationAlphaTimer(this)).launch();
  }
}

The “create a Timer trick” in onResume is courtesy of Diego Torres. If you just try to run the animation, it’s likely just to choke.

CNET has a very detailed article on JavaFX, Sun’s better-late-than-never-maybe-hopefully answer to Adobe’s Flash / AIR and Microsoft’s Silverlight:

With a back-to-the-future technology called JavaFX to be launched Thursday, Sun Microsystems hopes to attract a new class of developer while building a much-needed new revenue source.

JavaFX 1.0 returns to the sales pitch that Sun used during Java’s launch more than 13 years ago: a foundation for software on a wide variety of computing “clients” such as desktop computers or mobile phones. JavaFX builds on current Java technology but adds two major pieces.

First is a new software foundation designed to run so-called rich Internet applications–network-enabled programs with lush user interfaces. Second is a new programming language called JavaFX Script that’s intended to be easier to use than traditional Java.

The benefit for me (and maybe you) is that most web shops have three different classes of developers: backend programmers, HTML/CSS coders, and The Flash Guy. The problem with The Flash Guy is that they have to be involved to make any changes to Flash components; JavaFX instead provides components that can easily be manipulated by coders and by web designers (with a little training I think).

The JavaFX site looks a hell of a lot better than anything Sun’s produced in the past too, so maybe they’re learning that looks matter too. Here’s some examples to play with.