Sometimes being a software engineer can be very frustrating. It has been one of those days, despite the fact that things started out in the right direction.
I got a request from a creative director on my current project to add a dashed line to a layout. According the official Google documentation, this is out of the box functionality. After a brief scan of the SDK guide, I was ready to rock and roll.
I'd define a simple XML drawable, like so:
<?xml version="1.0" encoding="utf-8"?> <shape xmlns:android="http://schemas.android.com/apk/res/android" android:shape="line"> <stroke android:color="#FF0000FF" android:dashWidth="4dp" android:dashGap="8dp" /> </shape>
Then apply it to a view in a simple layout:
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" > <View android:layout_centerInParent="true" android:layout_width="match_parent" android:layout_height="8dp" android:layout_margin="20dp" android:background="@drawable/dotted_line"/> </RelativeLayout>
In minutes, I'd spun up an Android Virtual Device and validated my assumptions (Figure A).
However, after applying the same technique to my production code, I discovered something troublesome: The line showed up completely solid on an actual device (Figure B).
I racked my brain and the brains of my colleagues and eventually ended up asking the all-knowing Google. After over an hour of reading Android-related blogs and forums posts, I came across this little gem on the official Android issue tracker: Issue 29944: DashPathEffect/drawLine not working properly when hardwareAccelerated="true". I wasn't explicitly setting hardware acceleration to true in my manifest, but a quick glance back to the Google documentation confirms that as of API 14 hardware acceleration is true by default on all views.
Like I said, it was one of those days. Fortunately, the workaround is rather simple: You add the following line to the affected view in your layout:
The result was exactly what I wanted (Figure C).
I remember my grandfather coming home from work some days looking like he'd been through the mill. I'd ask him how his day went, and his response would be: "Some days you get the bear, and other days the bear gets you." I'd like to think today I got the bear -- even if the bear did get in a few good licks.
William J Francis began programming computers at age eleven. Specializing in embedded and mobile platforms, he has more than 20 years of professional software engineering under his belt, including a four year stint in the US Army's Military Intelligence Corps. Throughout his career William has published numerous technical articles, as well as the occasional short story.