Notes on loading a JAR library in Android

On Android, loading a JAR can be accomplished as follows:

String sdPath = Environment.getExternalStorageDirectory() + "/";
String fullPath = sdPath + "nativebridge.jar"; // produced by dx tool
File f = new File(fullPath);
final String libPath = fullPath;
final File tmpDir = getDir("dex", 0);

f = new File(libPath);

final DexClassLoader classloader = new DexClassLoader(libPath,
 tmpDir.getAbsolutePath(), null, this.getClass() .getClassLoader());
               
final Class classToLoad = (Class) classloader.loadClass("cx.ath.journeyman.MyBroadcastReceiver");

where the following is true:

• cx.ath.journeyman is the package name and MyBroadcastReceiver is the class name
• nativebridge.jar is located on /sdcard/ and contains a classes.dex file
• nativebridge.jar is produced like so:
  • "c:\Program Files\android-sdk-windows\build-tools\17.0.0\dx.bat" --dex --output="c:\temp\nativebridge.jar" D:\Development\Android\bin\nativebridge.jar
  • Android\bin\nativebridge.jar is the Java archive produced by the Eclipse compiler, and
  • c:\temp\nativebridge.jar is the output produced by the Android dx tool.

The above allows an Android application to load any class.

• JNI in Android (and a foreword of why JNI sucks)
• JNI- FindClass returns null
• JNI Tips
• How to bundle a native library and a JNI library inside a JAR?
• Mixing Android External JAR and JNI gone wild
• How to load a Java class dynamically on android/dalvik?
• The missing bridge between Java and native C++

Alternatively, use the LoadAPK magic function in the Android2DelphiImport tool.