MECOP: Android phone memory management and performance optimization

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1. What is JNI

JNI, starting with Java1.1, the Java Native Interface (JNI) standard becomes part of the Java platform, which allows Java code to interact with code written in other languages. JNI was initially designed for local compiled languages, especially C and C + +, but it does not prevent you from using other languages, as long as the calling convention is supported. Using Java to interact with locally compiled code often loses platform portability. However, in some cases it is acceptable and even necessary. For example, use some old libraries to interact with the hardware, the operating system, or to improve the performance of the program. The JNI standard ensures that the local code can work in any Java Virtual machine environment at least.

2. What is the NDK

The Android NDK was added in front of the SDK with the word "native", the native development Kit, which Google called the "NDK".

As is known to all, Android programs run in Dalvik virtual machines, and the NDK allows users to execute part of the program using native code languages like C + +.

The NDK includes:

The tools and build files required to generate the native code base from C + +.

Embed a consistent native library into the application package files that you can deploy on your Android device (application packages files, the. apk file).

Support for all future Android platforms with some column native system header files and libraries

Why use the NDK?

Broadly speaking, it is mainly divided into the following situations:

1. Protection of the code, because the Java layer Code of the APK is easy to decompile, and the C + + library is difficult to reverse the sink.

2. Call the third-party C/S library in the NDK, because most of the open source libraries are written in C/s code.

3. Easy to transplant, the library written in C + + can be reused on other embedded platforms.

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MECOP: Android phone memory management and performance optimization