Android JNI入门第五篇——基本数据类型使用

前面讲到了java和native数据类型，这里就开始做一下使用：

       第一步：新建工程

       第二部：书写 java方法：

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);
}

 

           第三部：调用javac、javah命令生成h文件。

           第四部：补充native方法，如下：

#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;
  }

       第五步：制作mk文件

 

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)

LOCAL_MODULE    := com_nedu_jni_jnidemo5-jni
LOCAL_SRC_FILES :=NativeMethod.c

include $(BUILD_SHARED_LIBRARY)

 

      第六步：调用native方法

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("返回boolean："+method.getBoolean(true)+"\n"+
            "返回byte："+method.getByte((byte) 0)+"\n"+
            "返回char："+method.getChar('c')+"\n"+
            "返回short："+method.getShort((short) 1)+"\n"+
            "返回int："+method.getInt(1)+"\n"+
            "返回long："+method.getLong(9)+"\n"+
            "返回float："+method.getFloat((float) 1.0)+"\n"+
            "返回double："+method.getDouble(2.0)+"\n");
   }

 

运行截图：

总结：JNI中传过来的java基本类型可以直接使用。

/**
* @author 张兴业
* 邮箱：xy-zhang#163.com
* android开发进阶群：278401545
*
*/