[英] Delphi 编写 Android 服务

原文链接:http://blog.blong.com/2013/11/delphi-and-android-services-part-2.html(国外)

原文标题:Delphi 和 Android 服务

注:本来想翻译给大家,但感觉我这英语太差,实在无法精准的将老外的这篇文章翻译出来,所以原文输出吧。谁要是能翻译的不错,请联系我,我会将您的翻译放出来。

第一部分:

Delphi and Android services

Since Delphi’s introduction of Android support with the release of XE5, there have been many questions posted hither and thither regarding whether and how you can build service applications with it. The pervading suggestion or suspicion is that maybe Delphi isn’t cut out to build such exotic Android creations.

Well, if your goal is to just build some sort of a service app I wouldn’t particularly recommend Delphi for the job right now, simply because it hasn’t got the wherewithal to support you in that endeavour in its current guise, and consequently it’s quite difficult. Really, if you just want to build a service app you’d probably have an easier time using Java or Oxygene for Java in conjunction with the Android SDK.

However if you are invested in building a Delphi Android app, are in the midst of building a FireMonkey application for mobile deployment, and need an Android service as part of that, well it’s quite possible. But as I may have mentioned, it’s neither particularly easy nor especially straightforward.

I am aware that I have (at this time of writing) yet to write up the business of adding Android menus to Delphi apps, employing a splash screen and launching Android activities and getting results back (as demo’d in my CodeRage 8 talk, albeit with code samples available in that linked post)*.

Now I can add to the list of things I have yet to write up the steps for creating a service application. If you take a look at this Google Play Store listing you’ll see I’ve built an app that, as well as a splash screen, also implements a service.

ServiceApp_thumb ServiceAppProcess_thumb

So yes, it’s quite feasible to build a service and a broadcast receiver in a Delphi app. That said, I’ve had to be a little creative on exiting the app to avoid a failure being evident on the screen.

As mentioned, these Android aspects that fall outside the standard simple business app paradigm haven’t factored into what is readily supported currently in Delphi’s Android support. Hopefully this will be improved as time goes on to allow all sorts of Android features and facets to be surfaced in Delphi Android code. In the mean time a certain degree of spelunking and skulduggery is needed to achieve certain ends.

I know quite a few people are clamouring for knowledge on how to build service apps. Hopefully in the near future I’ll write it up, but certainly in the nearer future I’ll release the code sample, once I’ve exhausted possibilities to clean up the wrinkle around app shutdown. That should satisfy the keener of you out there. In the mean time, be satisfied that it’s been proved to be possible at all.

【第二部分】

It’s been a while now since I posted up the link to my Delphi service example on Google Play.

I mentioned at the time that it was not a trivial exercise and was somewhat imperfect in implementation (although I’d done my best to disguise this fact). Indeed you only really see an issue if you are looking at the logcat output from the app (either using the command-line adb logcat command, or using the deprecated DDMS tool or the replacement Monitor tool). Alas the app dies while endeavouring to tidy up for exit…

I also mentioned at the time that I was hoping to work out some scheme to remedy the situation before releasing the example source, something to do with pride or perfectionism or some such… Anyway, with the day job, the evening job, the prep work for last week’sBe-Delphi 3.0 event in Belgium my plans haven’t been accomplished and I have still to work out if it’s feasible to clean up the shutdown part of the sample. All my current efforts have come to little in resolving it.

So, given that there have been a number of requests for the source I have now made it available at this download link. This is the same as the sample online other than it has no splash screen. This example is free of a splash screen to simplify the example and leave it clearer. There are a couple of examples that incorporate a splash screen and have similar custom build steps available in my CodeRage 8 session files.

Please note that the archive has a Readme file in it, and you should take the time to read through this file carefully as it explains the non-standard build steps required to get the sample successfully built for deployment. If you don’t follow the Readme file, then you’re unlikely to get any joy with the sample at all.

For your convenience I include the text of the ReadMe file below.

As you will see, since Delphi has no catering for building Delphi services or broadcast receivers, I’ve had to go “round the houses” to do it, using Java stubs, and pertinent thread-switching between the Java and Delphi threads.

As you will also perhaps appreciate, I don’t recommend this as a productive way of building an Android service. However if you need to add a service to a Delphi Android application, then this approach allows you to do so.

But… as of the time of posting there is a still the small matter of a (slightly brushed under the carpet) death-by-tombstoning bug on shutdown. If any keen reader can work out a clean way of closing I’d be most obliged to hear of it!

[Update]

When the small Java source files get compiled, the Android dx tool expects them to be compiled by the JDK 1.6.x compiler as opposed to the JDK 1.7.x compiler. If you have JDK 1.7.x installed, you hit a problem with dx reporting:

bad class file magic (cafebabe) or version (0033.0000)

However, to avoid forcing a reinstall of JDK 1.6 you might like to modify my build.bat batch files and add in extra command line switches to the javac.exe command-lines. You need to insert this after the javac.exe command to force Java 1.6 byte code output, which is digestible by the Android dx command:

-source 1.6 -target 1.6


第三部分:

Once upon a time I uploaded a Delphi sample app to the Google Play Store, written in Delphi XE5 and implementing an Android service. I wrote about the published app in this post and supplied the source in this follow-up post.

There was an issue that’s been hanging around with that sample project. When pulled into Delphi XE7 and updated so it all compiled nicely, it didn’t play ball when deployed. Instead it hung.

I’ve eventually worked through the to-do list enough to take a look at the problem. For one reason or another starting the service in the OnCreate event handler caused an issue thanks to some required thread synchronisation, which no longer functions as I wanted it to.

I’ve worked around the problem by very slightly delaying the service starting by use of a one-shot timer. Then the form setup is done and dusted by the time the service is invoked and all seems to be well.

An updated download archive is available here, which contains the original Delphi XE5 project and a Delphi XE7 equivalent, which should now be functionally equivalent.

分享到: