Developing Android Clock Widgets

I recently created a tutorial series for Mobiletuts+ on creating an Android clock widget. It was the first time I had attempted the task, so I thought I'd share a couple of the things I discovered.

Analog or Digital

First, the process for creating analog and digital clocks is totally different. For an analog clock widget, the process is pretty straightforward, in fact the most time consuming part is probably creating your clock design. The basic tasks in creating a simple analog clock widget are as follows:

• Create a widget project, setup the properties in the Manifest and XML resource file.
• Create images for the dial, minute and hour hands for each density.
• Add an AnalogClock element to your layout file.
• Extend AppWidgetProvider and receive updates.

For a digital clock widget, more programming is involved. There is a DigitalClock class/ View, but unlike the AnalogClock, the DigitalClock cannot be used within the layout for a widget, only within standard apps. This means that you need to implement the details yourself, for example using a Service or AlarmManager for updating the widget appearance - there are potentially serious performance issues.

XML Layout

The following code outlines including an AnalogClock element within your widget layout file:

<AnalogClock
android:id="@+id/AnalogClockID"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:dial="@drawable/your_dial_image"
android:hand_hour="@drawable/your_hour_hand_image"
android:hand_minute="@drawable/your_minute_hand_image"
/>

Just replace the dial, minute and hour hand references with the names of your own drawable image files. The minute and hour hands should be included as though pointing at 12 o'clock, with the hands placed centrally horizontally within the dial image.

Clicks

If you do develop an Android clock widget, you need to decide what will happen on user clicks. Users have now come to expect certain behaviour as standard on clicking clock widgets, such as launching the device alarm clock (although there is as yet no standard way of doing this). Another option is to allow the user to configure the clock, choosing between designs - this is what I did in the tutorial series.

Launcher

Although widgets are of course accessed from the device homescreen, there is invariably the issue of users attempting to launch a widget app from the device menu. To accommodate this, you can add a launcher Activity to your widget app, which contains instructions on how to add the widget.

Conclusion

If you haven't attempted any Android widgets yet, don't be afraid to have a go, they are generally not too tough to implement. For clock widgets, it's easy enough as long as you go for analog, a little trickier for digital.

Related Info

• Android AnalogClock class
• Android DigitalClock class
• Developer Guide: App Widgets
• App Widget Design Guidelines
• Vogella on Android Widgets
• DroidDraw: Visual Guide to Android GUI Widgets

Google's Project Glass

When Project Glass hit the headlines earlier this year following Sergey Brin's demo at Google I/O I must admit I wasn't massively interested. I've never thought much about Augmented Reality/ wearable computing other than finding the concept vaguely scary.

However, following the London Olympics/ Paralympics I found myself thinking about the role of technology in sport. It looks as though sport is going to be one of the main areas developers will look to target with Project Glass apps - there are already projects under development to that end.

Although I'm not competitive, I love to swim and started to think about the possibility of smart swimming goggles. Since Project Glass runs Android, I thought about how I would love to come up with some swimming apps. I'm a big fan of swimming techniques including the Shaw Method and Total Immersion, so initial app ideas would probably focus on the quality of the swimming experience rather than exclusively on competitive/ high performance aspects. Following a cursory Google search on the topic, I was pleased to find that the company has indeed acquired a patent for swimming goggles.

Anyway, this development has basically got me excited about programming for the first time in a while. Although I love developing applications, I haven't felt too creatively stimulated recently, mainly because I don't spend enough time working on my own projects. I've got a lot to learn if I do want to target these devices, as I know virtually nothing about AR or wearable computing at the moment. I'll be posting on the topic as I learn more about it, and keep my fingers crossed that the smart goggles do become a reality.

Here are some related links:

Hacking for Fun: Programming a Wearable Android Device
Could Google Glass Change Pro Sports Forever?
Google Googles For The Open Water?
Google Acquires Swimming Goggle Patent
Wikipedia: Project Glass
Project Glass on Google+

Using the Android Crop Intent and Action

Recently I discovered that using standard intents and actions to capture and crop an image was not as straightforward as I had expected. I had assumed there would be a standard, reliable way to launch any apps that can perform a cropping action on images but was unfortunately wrong. Launching the camera is pretty consistent, but cropping an image you have either allowed the user to capture with the camera or choose from the device, for example with a file explorer app or the standard gallery app, is not so easy.

There is a generic action you can use for cropping that is supported on many user devices, but not all of them. The following represents the closest we have to a standard approach to launching a cropping Activity:

Intent croppingIntent = 
 new Intent("com.android.camera.action.CROP"); 

You need to pass various additional data values to the Intent before starting it, and if you want the cropped image to return to your code you need to call the Intent using startActivityForResult, then implement onActivityResult to process the returned cropped image.

So far so good, but unfortunately there are lots of Android vendors whose devices do not support this action. You have two broad options:

• Only provide your cropping functionality to users whose devices support this Intent
• Query the user device in order to target specific cropping Activities

If you opt for the first approach, you can include the code in which you call the Intent in a try block, with a catch block outputting an informative error message letting the user know why they can't complete the cropping action. If you opt for the second approach, you have a more complex task in front of you.

See this Stack Overflow post for an example of how to handle differing device crop Activities:
Android Camera Intent with Crop

For an overview of using the basic crop action above, see my tutorial on Mobiletuts+ for more details:
Capture and Crop an Image with the Device Camera

It seems the Android system is plagued a little by this type of issue. When approaching another task recently I found there is a similar problem when attempting to launch the alarm clock app on a user device - a common aim, particularly for clock widget apps.