Caching jfieldID, jmethodID, and referencing data to improve performance

This recipe covers caching in Android JNI, which can improve the performance of our native code.

Getting ready

You should make sure you've read the following recipes before going through this recipe:

• Accessing Java static and instance fields in native code

• Calling static and instance methods from native code

How to do it…

The following steps detail how to build a sample Android application that demonstrates caching in JNI:

1. Create a project named Caching. Set the package name as cookbook.chapter2. Create an activity named CachingActivity. Under the project, create a folder named jni. Refer to the Loading native libraries and registering native methods recipe of this chapter for more detailed instructions.

2. Create a file named cachingtest.c under the jni folder, then implement the InitIDs, CachingFieldMethodIDDemo1, CachingFieldMethodIDDemo2, and CachingReferencesDemo methods.

3. Modify the CachingActivity.java file by adding code...