1 Platform Library Example 2 ~~~~~~~~~~~~~~~~~~~~~~~~ 3 4 5 This directory contains a full example of writing your own Android platform 6 shared library, without changing the Android framework. It also shows how to 7 write JNI code for incorporating native code into the library, and a client 8 application that uses the library. 9 10 This example is ONLY for people working with the open source platform to 11 create a system image that will be delivered on a device which will include 12 a custom library as shown here. It can not be used to create a third party 13 shared library, which is not currently supported in Android. 14 15 To declare your library to the framework, you must place a file with a .xml 16 extension in the /system/etc/permissions directory with the following contents: 17 18 <?xml version="1.0" encoding="utf-8"?> 19 <permissions> 20 <library name="com.example.android.platform_library" 21 file="/system/framework/com.example.android.platform_library.jar"/> 22 </permissions> 23 24 There are three major parts of this example, supplying three distinct 25 build targets and corresponding build outputs: 26 27 28 com.example.android.platform_library 29 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 30 31 The top-level Android.mk defines the rules to build the shared library itself, 32 whose target is "com.example.android.platform_library". The code for this 33 library lives under java/. 34 35 Note that the product for this library is a raw .jar file, NOT a .apk, which 36 means there is no manifest or resources associated with the library. 37 Unfortunately this means that if you need any resources for the library, such 38 as drawables or layout files, you will need to add these to the core framework 39 resources under frameworks/base/res. Please make sure when doing this that 40 you do not make any of these resources public, they should not become part of 41 the Android API. In the future we will allow shared libraries to have their 42 own resources. 43 44 Other than that, the library is very straight-forward, and you can write 45 basically whatever code you want. You can also put code in other Java 46 namespaces -- the namespace given in the <library> tag above is just the 47 public unique name by which clients will link to your library, but once this 48 link happens all of the Java namespaces in that library will be available 49 to the client. 50 51 52 libplatform_library_jni 53 ~~~~~~~~~~~~~~~~~~~~~~~ 54 55 This is an optional example of how to write JNI code associated with a 56 shared library. This code lives under jni/. The jni/Android.mk file defines 57 the rules for building the final .so in which the code lives. This example 58 provides everything needed to hook up the native code with the Java library 59 and call through to it, plus a very simple JNI call. 60 61 62 PlatformLibraryClient 63 ~~~~~~~~~~~~~~~~~~~~~ 64 65 This shows an example of how you can write client applications for your new 66 shared library. This code lives under client/. Note that the example is 67 simply a regular Android .apk, like all of the other .apks created by the 68 build system. The only two special things needed to use your library are: 69 70 - A LOCAL_JAVA_LIBRARIES line in the Android.mk to have the build system link 71 against your shared library. 72 73 - A <uses-library> line in the AndroidManifest.xml to have the runtime load 74 your library into the application. 75
