I am working on a library that ideally will have a strictly-Java component and added functionality for Android-specific projects, with the intent to be most useful for Android apps, but also work with other Java apps.
But my question is: how should this be designed? I do not plan on needing resources, so I want to compile it into a JAR, but would I need to make two JARs, one of the Java stuff and another for the Android stuff? Or would a Java-only application be able to use a single JAR so long as it does not use the Android components?
If you make a library that uses pure java and does not use any android apis. It will work on both standard java and android java. However if the library uses any android apis it can't be used in a standard java project.
As far as I know, the JAR would be good for both types of aplications. It seems to mee that both JARs (just Java and android) are totally identical and thus equally compatible. If you don't use any of the android components, including Resources there should not be a problem at all.
You should still check whether you depend on libraries which are available on android and any normal Java distribution or -if not- either tell the user to preinstall the depending libraries or ship them whitin your JAR package and build path. Be carefull not to use libraries which are not available on android because the user has no or really few options to install them on himself.
What I don't understand is why you think your library is more usefull to android developers. I can not think of any example where this could happen. If the problem is really specific for android, you should consider developing the library android-only. If the problem is more general the lib will be usefull to all developers that might come to this problem, not just android.
Related
I want to make a java library (so I can compile it into a jar) that makes calls to a server. I then want to share this amongst android application projects so that I can access those simple calls.
Is using HTTPRequest the best way to do this?
http://docs.oracle.com/javase/7/docs/api/java/net/HttpURLConnection.html
Something about making web calls in the java way and sharing them in android apps seems odd to me. should this be an Android Library instead? (I believe those should only be used when resources are involved)
Sorry for the potentially simple question.
You can develop a common Java library that you can use with both android , and regular java projects.
Take a look at OkHttp , it shows you how to achieve this. It is related to HTTP client, may be it already provides everything you need. You can extend it where needed.
For a simpler example (~20 java classes), take look at Okio , the underlying io library used by OkHttp.
I am currently attempting to port an android app to desktop. I realize that the majority of the android based code cannot be reused, but what about "smaller parts" which dont depend on the android architecture?
I am mostly talking about support or math related classes like SparseArray, Matrix and so on.
Those may work. But you will have a rough time figuring out what works and what doesn't. Even once you do that you will need to create a whitelist somewhere like in your IDE that doesn't auto-complete classes you don't want or can't use and you will also want to fail your build. Maybe you should create a jar containing only the classes you want to use that you determine are usable.
is it possible to create java libraries the apps can use shared?
It is totally clear to me how to create a library project and how to use it while shared between several another projects, compile each project into different apps.
But in this case the library gets compiled into each app separated.
What I want is to create a library, compile it, install it into the device (or emulator) and several apps calling into this library.
And when it is needed to change something the apps use shard in this library, I just re-work the library, re-compile it, replace it on device (or emulator), and the apps use the new library, all apps use the new functions.
Is it possible?
I googled it, but I couldn't find the solution.
I am using Win + Eclipse, I can't use native code (since I know only Java).
Thanks
UPDATE: Thank you for your suggestions, I know about using Services and Activities started explicitly in order to share functionality.
I asked about libraries because I am investigating the possibilites. If there is no way to use common library, what is the purpose of uses-library... in the app manifest?
Thank you
It's more likely that you need a service as a library. Have you considered this possibility? You can create it as a separate application, define an interface for your service and use it in other apps. So as the interface does not change this will not influence on other apps that depends on this service.
The Android model installs each application as a separate user (UID) on the device and the users have no access to other application's/user's files. Therefore, you can't share libraries as such.
As Yury suggested, you might need a service or an activity that can be invoked from multiple applications.
not to create an Android project but just a common Java program, can i import packages from Android SDK in order to use some interesting methods and compile it using java compiler in JDK.
Thanks.
If the package uses Android-specific SDK's then no (without some porting). If it's generic Java then probably yes. I have imported packages I wrote for BlackBerry to Android and vice-versa, but any Android-specific API calls have to be rewritten.
There are Android SDK JARs under
android-sdk/platorms/android-3/android.jar
In this case it is API Level 3. I used to copy this .jar to the buildpath of a framework that I am coding recently.
You can use those in Java since they are java bytecodes and your jvm can execute it. Your classes may use classes of Android SDK, however I think since most of them do need an Android environment, they will not just work standalone and will require deployment to an Android device. It is fine if you are just planning to import something but not start Android functionality at all.
You can include common libraries. That is to say, package the Android code as a library or .jar file, and include the libraries in the build path of the Java application. This should work both ways. Android uses a lot of the same Objects and Principles as Java, so some things will work without a hitch. Beware of having to tweak it, though. Projects aren't structured the same way
Perhaps there are some limited cases where it might work, but I doubt it. The jar files that come with the SDK are stubs; they do not include much of the code that you see when browsing the source at android.git.kernel.org. (See this thread, for example.)
What in particular were you interested in using?
As I am very pissed off of using the emulator to develop any Java class, I thought of setting up a project in Eclipse and instead of the usual JRE I linked to the Android.jar (version 2.1) that usually the Android projects link to. I don't mean to use this to develop Layouts or other specific platform things, I was just trying to create a class that uses HttpClient. It miserably crashes like this.
Exception in thread "main"
java.lang.RuntimeException: Stub! at
org.apache.http.impl.client.AbstractHttpClient.(AbstractHttpClient.java:5)
at
org.apache.http.impl.client.DefaultHttpClient.(DefaultHttpClient.java:7)
at
AdsCatcher.(AdsCatcher.java:26)
at TestAll.main(TestAll.java:10)
Stub! I mean I'd like to develop libraries (and test them) so that when I go to the emulator I don't have to deal with them. Is there a good way to do this? This seems not to work for some reason.
This will not work, sorry. The android.jar file, as the error message indicates, contains only stubs of the Android API. This makes sense, since that API cannot work outside of Android -- the android.jar file is just there for compilation.
For class libraries you are working on that have no dependencies on Android, you are welcome to create a standard JRE Eclipse project that generates a JAR that you then use in your Android project.
In your case, you may be able to create a class library using the JRE that uses HttpClient. The latest version from Apache may differ slightly from the version in Android, though, so while probably you will be OK, there's a chance you will run into runtime errors due to changes in method signatures and such (VerifyError).