{"id":1869,"date":"2013-10-10T18:17:40","date_gmt":"2013-10-10T06:17:40","guid":{"rendered":"https:\/\/www.deltics.co.nz\/blog\/?p=1869"},"modified":"2014-08-03T17:14:16","modified_gmt":"2014-08-03T05:14:16","slug":"developing-an-appwidget-part-4","status":"publish","type":"post","link":"https:\/\/www.deltics.co.nz\/blog\/posts\/1869\/","title":{"rendered":"Developing an AppWidget – Part 4"},"content":{"rendered":"[Estimated Reading Time: <\/span> 3<\/span> minutes]<\/span><\/span>

Keep On Running…<\/h2>\n

Some may have noticed that I updated my previous post<\/a> with a footnote describing an issue with my battery widget not resuming it’s updates after the phone went into (and came out of) deep sleep. I got to the bottom of that and can now happily report that my widget seems 100% reliable and the solution is not contributing to any additional battery drain.<\/p>\n

This is what I did…<\/p>\n

<\/p>\n

Specialised Services<\/h3>\n

I think I may have mentioned near the beginning of this series<\/a>, that Services<\/strong> were a potentially complex area on Android. Even with this simple widget exercise I have learned quite a bit about them and still I think I have only scratched the surface.<\/p>\n

I already refactored my code once to avoid using a deprecated method that I inadvertently adopted from an out of date example. I have now learned that for my needs, I should in fact be using a different Service<\/strong> class<\/strong> entirely!<\/p>\n

Specifically, an IntentService<\/strong>.<\/p>\n

The main difference between this and the Service<\/strong> class I was using previously, is that an IntentService<\/a><\/strong> does not run on the main application thread, but on it’s own worker thread, created by the system automatically when any intents are passed to it for handling.<\/p>\n

Something led me to believe that an IntentService is “long lived<\/em>” which, is the key to ensuring that my update schedule survived the device going into “deep sleep”.<\/p>\n

To switch to an IntentService was relatively straightforward.<\/p>\n

Update:<\/strong> Everything that follows is indeed how I switched to an IntentService<\/strong>. But it turns out this created a different problem which leads me to suspect that an IntentService does not function how I was led to believe and issn’t actually appropriate. Just bear that in mind.<\/em><\/p>\n

First of all of course, I needed to derive from the IntentService<\/strong> class itself.<\/p>\n

Then I again had to change the method being used to implement the service call. Previously I was using onStartCommand()<\/code>. This now needs to change to onHandleIntent()<\/code>.<\/p>\n

There was one other change that I needed to make but I didn’t discover this until trying to install my updated widget. Had I read the guide to implementing services<\/a> I would have known about it. But I hadn’t.<\/p>\n

That other thing is that the service requires a parameterless constructor to be implemented. Why this is the case for an IntentService and not for a Service, I haven’t yet thought about. I am sure there is an explanation. But for now, all I need to know is that I need to implement such a constructor and it must call the inherited constructor that takes a service name as a parameter.<\/p>\n

So first, the parameterless constructor:<\/p>\n

\r\n  constructor UpdateService;\r\n  begin\r\n    inherited constructor('UpdateService');\r\n  end;\r\n<\/pre>\n
Note that constructors are not named in Java.  The token constructor<\/strong>, as opposed to the usual method<\/strong> declaration is all that we need.  As I think I may have mentioned, you have the option of using Create<\/strong> (but only<\/em> Create) to name your constructors if you wish (and this may be important for classes intended for cross-platform use) but in this case, I chose not.<\/p>\n
The change of onStartCommand<\/code> to onHandleIntent<\/code> involves only changing the method signatures.  The implementation is not affected at all:<\/p>\n
\r\n  method UpdateService.onHandleIntent(aIntent: Intent);\r\n<\/pre>\n
As far as I can tell, this deals with the issue of my widget updates surviving deep sleep, and importantly, without any adverse affect on battery drain that I have observed.<\/p>\n
Update:<\/strong> This seems to be true, but is not actually functioning how I intended and so I shall revisit this change.<\/em><\/p>\n
But there is something else that I haven’t yet taken care of (Update:<\/strong> which the IntentService had an adverse affect on – i.e. it broke it!<\/em>), that I left a hint about in that previous post, and I shall be making that the subject of my truly final post in this series later this evening<\/del> another post soon.<\/p>\n
UPDATE<\/h2>\n
Take everything above with a pinch of salt.<\/strong><\/p>\n
In preparing the next post I discovered that things were not behaving quite as I thought and I need to do some more research before I can say definitively that I have found the correct approach for dealing with both the issue of surviving sleep and the subject of what was to be my next post.<\/p>\n
Hey ho.  It’s all learning, right ?  \ud83d\ude42<\/p>\n","protected":false},"excerpt":{"rendered":"
[Estimated Reading Time: <\/span> 3<\/span> minutes]<\/span><\/span> Keep On Running… Some may have noticed that I updated my previous post with a footnote describing an issue with my battery widget not resuming it’s updates after the phone went into (and came out of) deep sleep. I got to the bottom of that and can now happily report that my widget seems 100% […]<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"jetpack_post_was_ever_published":false,"jetpack_publicize_message":"","jetpack_is_tweetstorm":false,"jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":[]},"categories":[212,205,4,180],"tags":[153,233,181,232],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_shortlink":"https:\/\/wp.me\/p1TKYv-u9","jetpack_sharing_enabled":true,"jetpack-related-posts":[{"id":1791,"url":"https:\/\/www.deltics.co.nz\/blog\/posts\/1791\/","url_meta":{"origin":1869,"position":0},"title":"Developing and Debugging an AppWidget – Part 2","date":"30 Sep 2013","format":false,"excerpt":"In the first instalment of this series, I implemented the basic framework of a new appwidget and established a means by which I could debug the widget code. Now it's time to add some code worth debugging. You may recall that the aim of my widget is to display the\u2026","rel":"","context":"In "Android"","img":{"alt_text":"","src":"https:\/\/i0.wp.com\/www.deltics.co.nz\/blog\/wp-content\/uploads\/Screenshot_2013-09-30-20-03-27.jpg?resize=350%2C200&ssl=1","width":350,"height":200},"classes":[]},{"id":1873,"url":"https:\/\/www.deltics.co.nz\/blog\/posts\/1873\/","url_meta":{"origin":1869,"position":1},"title":"Developing an AppWidget – Part 5","date":"13 Oct 2013","format":false,"excerpt":"In my previous post I explained how I believed I had solved a problem with my widget, only to discover that it created a different problem in the process. I had believed that IntentService based services were long-lived, but in fact this is not the case. However, the change remains\u2026","rel":"","context":"In "Android"","img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":1774,"url":"https:\/\/www.deltics.co.nz\/blog\/posts\/1774\/","url_meta":{"origin":1869,"position":2},"title":"Developing and Debugging an AppWidget – Part 1","date":"29 Sep 2013","format":false,"excerpt":"With my external HDD trials and tribulations behind me, I have finally been able to complete a project I started last weekend - implementing an Android AppWidget. 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Indeed, the impressive specifications are part\u2026","rel":"","context":"In "Android"","img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":1896,"url":"https:\/\/www.deltics.co.nz\/blog\/posts\/1896\/","url_meta":{"origin":1869,"position":4},"title":"Getting Published in the Play Store (Google Apps)","date":"14 Oct 2013","format":false,"excerpt":"Well, this went far more smoothly than I had anticipated. At the XE5 World Tour event in Auckland, Brian Hamilton, creator of the iWD app, told us that getting his approved took about a week (if I recall correctly), and he had to submit a video showing how his app\u2026","rel":"","context":"In "Android"","img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":1817,"url":"https:\/\/www.deltics.co.nz\/blog\/posts\/1817\/","url_meta":{"origin":1869,"position":5},"title":"Getting the Battery Level on Android With Delphi","date":"01 Oct 2013","format":false,"excerpt":"Over the past few days I posted a two part series showing how to obtain the current battery level as part of the implementation of an Android AppWidget using Oxygene. 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