Monday, July 01, 2013

Ultimate Stopwatch version 6.0.4

Fresh from being used to demo Android Studio at Google I/O, the Ultimate Stopwatch version 6.0.4 is rolling out with a couple more tweaks and bug fixes. This has also given me the opportunity to try the Google Play staged rollout feature.

First up, overdraw has been reduced again, this time by removing the background drawable for the window. 


Resulting in an almost totally green/blue layout, the only remaining red section is in the overlap of the minute and second hands. The screen was already drawing in a fraction of the time needed to maintain 60fps, so at this point it is really just optimizing for the sake of optimizing. Removing the window background had the side effect of a lap time screen without a background at all, leaving a hole in the UI and some freaky results. That was quickly resolved by setting a background color on that view.

I've gone one step further in an experimental version, which results in 0 overdraw for most of the app, but there are still a few margins left with no background color, so it needs a little more work and testing.

Another minor change in 6.0.4 was in the animation timing code. The animation runnable was already using postInvalidateOnAnimation() for JB+ devices, an optimization to cause redraws to happen on the next display frame:

    if(JELLYBEAN_OR_ABOVE) postInvalidateOnAnimation();
    else invalidate();

However, +ChrisBanes pointed out that there is a version of this in ViewCompat. ViewCompat is a backwards compatible helper provided in the Support Library for accessing View features introduced after API level 4. So, the custom view animation runnable now looks like this:

    //Stopwatch animation runnable
    private final Runnable animator = new Runnable() {
        public void run() {

                ViewCompat.postOnAnimation(StopwatchCustomView.this, this);

Which is more pleasing to the eye, easier to understand for devs reading the code and would benefit from any future advances in ViewCompat.

There are also a couple of other bug fixes in this release:

Issue #42: Fixed - Hands don't reset on Stopwatch when hand animations turned off.
Issue #47: Fixed - Ticking sounds go wrong during onPause onResume cycle.

As always the full source code to Ultimate Stopwatch is available at

Saturday, February 23, 2013

Custom Paint Job: Accelerating the Ultimate Stopwatch

(Edit - 1st July 2013: Animator runnable updated again and one more layer of overdraw removed, details in new blog post)

Creating a custom Android view in 2013 isn't exactly breaking new ground, but the time was long overdue to relegate the old SurfaceView to history and move on; a task I was looking forward to but had kept putting off. Anyway, +Marie Schweiz's great new Ultimate Stopwatch designs deserved a hardware accelerated home.

The Android Developers training class breaks down the job of developing a Custom view into a few simple steps:
  1. Subclass a View
  2. Implement custom drawing
  3. Make the view interactive
In practice, when it came to the animations I also grabbed a couple of hints from Anders Ericsson's post at JayWay, as the mental model is also slightly different and I'd seen his related talk at Droidcon London 2012. In the SurfaceView I had a thread constantly looping to call the update/draw methods, however in a custom view it will redraw each time you call invalidate(). So, instead of a looping thread I can just call invalidate() after each cycle completes to start the next paint. This is done by posting a runnable to the View's message queue, I'm aiming for 15ms update cycles for just over 60fps.

    private Runnable animator = new Runnable() {
        public void run() {

            if (mIsRunning) postDelayed(this, 15);
The onDraw() methods from my SurfaceView and Custom view are identical, so just a copy and paste job there. The onTouch() and Activity communications handler also remained untouched. So in the end the Custom view is considerably simpler as there is no surface creation/destruction to worry about or separate thread to maintain.

A really nice feature of a Custom view is the ability to configure your own XML attributes. Previously I had to instantiate the SurfaceView and pass in details on whether it should represent the Stopwatch or Countdown view, with a Custom view I can add the following into attrs.xml

        <declare-styleable name="StopwatchCustomView">
            <attr name="watchType" format="enum">
                <enum name="stopwatch" value="1"/>
                <enum name="countdown" value="0"/>

Then by adding the name space xmlns:custom="" in my layout, I can use the attribute custom:watchType="stopwatch" in the layout file and retrieve it in the code during instantiation. Being able to configure the custom view in XML can really simplify code and make the source easier to understand. Here is the code to retrieve the value:

    TypedArray a = context.getTheme().obtainStyledAttributes(
         0, 0);
        isStopwatch = a.getBoolean(R.styleable.StopwatchCustomView_watchType,true);

That's it. The view is hardware accelerated where available and due to some optimizations the refresh rate has also increased when h/w acceleration is absent.

Some small improvements were gained by refactoring, but the main increases were delivered using the 'Show GPU overdraw' feature of Android's Developer Options, which is now available as I'm using the GPU to draw. It's immediately clear that before optimization there's excessive overdraw, highlighted by the red areas. This was almost entirely down to background colours being set on layers that weren't visible; the ViewPager, the layout of the custom view and also in the onDraw() of the Custom View. Eliminating these unseen, but still drawn, background colours reduced the graphics load and improved performance.

Now we have a wondrous, hardware accelerated Custom view we're in a much better position to add some final flourishes to improve the application. Later I'll write about some custom animations I've added, as suggested by +Nick Butcher to not only improve the perceived quality but also the usability.

The Ultimate Stopwatch and Timer is open source at, designed by +Marie Schweiz and makes use of the awesome ActionBarSherlock by Jake Wharton.