Android JNI entry 5-Basic Data Type usage

The Java and native data types are mentioned earlier. Here we will start to use them:

Step 1: Create a project

Part 2: Writing Java methods:

public class NativeMethod {static {        System.loadLibrary("com_nedu_jni_jnidemo5-jni");    }    public native boolean getBoolean(boolean b);public native byte getByte(byte b);public native char getChar(char c);public native short getShort(short s);public native int getInt(int i);public native long getLong(long l);public native float getFloat(float f);public native double getDouble(double d);}

 

Part 3: Call the javac and javah commands to generate an H file.

Part 4: add the native method as follows:

#include<stdio.h>  #include <stdlib.h>  #include "com_nedu_jni_jnidemo5_NativeMethod.h"  /* * Class:     com_nedu_jni_jnidemo5_NativeMethod * Method:    getBoolean * Signature: (Z)Z */JNIEXPORT jboolean JNICALL Java_com_nedu_jni_jnidemo5_NativeMethod_getBoolean  (JNIEnv *e, jobject thiz, jboolean b){        return b;  }/* * Class:     com_nedu_jni_jnidemo5_NativeMethod * Method:    getByte * Signature: (B)B */JNIEXPORT jbyte JNICALL Java_com_nedu_jni_jnidemo5_NativeMethod_getByte  (JNIEnv *e, jobject thiz, jbyte by){     return by;  }/* * Class:     com_nedu_jni_jnidemo5_NativeMethod * Method:    getChar * Signature: (C)C */JNIEXPORT jchar JNICALL Java_com_nedu_jni_jnidemo5_NativeMethod_getChar  (JNIEnv *e, jobject thiz, jchar c){   return c;     }/* * Class:     com_nedu_jni_jnidemo5_NativeMethod * Method:    getShort * Signature: (S)S */JNIEXPORT jshort JNICALL Java_com_nedu_jni_jnidemo5_NativeMethod_getShort  (JNIEnv *e, jobject thiz, jshort s){     return s;  }/* * Class:     com_nedu_jni_jnidemo5_NativeMethod * Method:    getInt * Signature: (I)I */JNIEXPORT jint JNICALL Java_com_nedu_jni_jnidemo5_NativeMethod_getInt  (JNIEnv *e, jobject thiz, jint i){        return i;  }/* * Class:     com_nedu_jni_jnidemo5_NativeMethod * Method:    getLong * Signature: (J)J */JNIEXPORT jlong JNICALL Java_com_nedu_jni_jnidemo5_NativeMethod_getLong  (JNIEnv *e, jobject thiz, jlong l){           return l;  }/* * Class:     com_nedu_jni_jnidemo5_NativeMethod * Method:    getFloat * Signature: (F)F */JNIEXPORT jfloat JNICALL Java_com_nedu_jni_jnidemo5_NativeMethod_getFloat  (JNIEnv *e, jobject thiz, jfloat f){        return f;  }/* * Class:     com_nedu_jni_jnidemo5_NativeMethod * Method:    getDouble * Signature: (D)D */JNIEXPORT jdouble JNICALL Java_com_nedu_jni_jnidemo5_NativeMethod_getDouble  (JNIEnv *e, jobject thiz, jdouble d){          return d;  }

Step 5: Create an MK File

LOCAL_PATH := $(call my-dir)include $(CLEAR_VARS)LOCAL_MODULE    := com_nedu_jni_jnidemo5-jniLOCAL_SRC_FILES :=NativeMethod.cinclude $(BUILD_SHARED_LIBRARY)

 

Step 6: Call the NATIVE METHOD

Public void oncreate (bundle savedinstancestate) {super. oncreate (savedinstancestate); setcontentview (R. layout. main); textview text = (textview) findviewbyid (R. id. text); nativemethod method = new nativemethod (); text. settext ("Return Boolean:" + method. getboolean (true) + "\ n" + "returns byte:" + method. getbyte (byte) 0) + "\ n" + "returns CHAR:" + method. getchar ('C') + "\ n" + "Return short:" + method. getshort (short) 1) + "\ n" + "Return INT:" + method. getint (1) + "\ n" + "returned long:" + method. getlong (9) + "\ n" + "returns float:" + method. getfloat (float) 1.0) + "\ n" + "returns double:" + method. getdouble (2.0) + "\ n ");}

 

Run:

Summary: The Basic Java types passed in JNI can be directly used.

/**
* @ Author Zhang xingye
* Email: xy-Zhang # 163.com
* Android Development Group: 278401545
*
*/