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jni使用基礎（九）之c調用java事例demo
1.Activity
package com.devchina.ndk4;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
public class DevchinaActivity extends Activity {
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
}
public void click(View view){
DevchinaProvider devchina = new DevchinaProvider();
devchina.cCallJava();
}
public void clickAdd(View view){
DevchinaProvider devchina = new DevchinaProvider();
devchina.cCallAdd();
}
public void clickStrng(View view){
DevchinaProvider devchina = new DevchinaProvider();
devchina.cCallString();
}
}
2.native
package com.devchina.ndk4;
public class DevchinaProvider {
static {
System.loadLibrary("devchina");
}
public native void cCallJava();
public native void cCallString();
public native int cCallAdd();
//1.調用java空方法
public void callJava(){
System.out.println("i come from java");
}
public int add(int x,int y){
System.out.println("devchina java res = "+(x+y));
return x+y;
}
public void printString(String s){
System.out.println("devchina java "+ s);
}
}
3.h文件
/* DO NOT EDIT THIS FILE - it is machine generated */
#include <jni.h>
/* Header for class com_devchina_ndk4_DevchinaProvider */
#ifndef _Included_com_devchina_ndk4_DevchinaProvider
#define _Included_com_devchina_ndk4_DevchinaProvider
#ifdef __cplusplus
extern "C" {
#endif
/*
* Class: com_devchina_ndk4_DevchinaProvider
* Method: cCallJava
* Signature: ()V
*/
JNIEXPORT void JNICALL Java_com_devchina_ndk4_DevchinaProvider_cCallJava
(JNIEnv *, jobject);
/*
* Class: com_devchina_ndk4_DevchinaProvider
* Method: cCallAdd
* Signature: ()I
*/
JNIEXPORT jint JNICALL Java_com_devchina_ndk4_DevchinaProvider_cCallAdd
(JNIEnv *, jobject);
/*
* Class: com_devchina_ndk4_DevchinaProvider
* Method: cCallString
* Signature: ()V
*/
JNIEXPORT void JNICALL Java_com_devchina_ndk4_DevchinaProvider_cCallString
(JNIEnv *, jobject);
#ifdef __cplusplus
}
#endif
#endif
4.c文件
#include<stdio.h>
#include<jni.h>
#include"com_devchina_ndk4_DevchinaProvider.h"
#include <android/log.h>
#define LOG_TAG "devchina"
#define LOGD(...) __android_log_print(ANDROID_LOG_DEBUG, LOG_TAG, __VA_ARGS__)
#define LOGI(...) __android_log_print(ANDROID_LOG_INFO, LOG_TAG, __VA_ARGS__)
JNIEXPORT void JNICALL Java_com_devchina_ndk4_DevchinaProvider_cCallJava
(JNIEnv * env, jobject obj){//ojb,誰調用了此Native方法，這個Obj就是誰
//new 出java對象
jclass clazz = (*env)->FindClass(env,"com/devchina/ndk4/DevchinaProvider");//注意：不能為“.”
if(clazz==0){//沒有找到類
LOGI("can't find devchina class");
}else{
LOGI("find dechina class");
}
//獲取類中的方法
jmethodID j_method = (*env)->GetMethodID(env,clazz,"callJava","()V");//最後一個參數是表示方法的簽名
if(j_method==0){
LOGI("can't get method");
}else{
LOGI("get method");
}
(*env)->CallVoidMethod(env,obj,j_method);//第二個參數表示調用的類對象
}
JNIEXPORT jint JNICALL Java_com_devchina_ndk4_DevchinaProvider_cCallAdd
(JNIEnv * env, jobject obj){
//1.new java obj
jclass clazz = (*env)->FindClass(env,"com/devchina/ndk4/DevchinaProvider");
//2.get method id
jmethodID mId = (*env)->GetMethodID(env,clazz,"add","(II)I");
//3.invoke method
jint res = (*env)->CallIntMethod(env,obj,mId,5,6);
LOGI("c log %d",res);
}
JNIEXPORT void JNICALL Java_com_devchina_ndk4_DevchinaProvider_cCallString
(JNIEnv * env, jobject obj){
jclass clazz = (*env)->FindClass(env,"com/devchina/ndk4/DevchinaProvider");
jmethodID mId = (*env)->GetMethodID(env,clazz,"printString","(Ljava/lang/String;)V");
(*env)->CallVoidMethod(env,obj,mId,(*env)->NewStringUTF(env," devchina from c "));
}
5.mk文件
LOCAL_PATH := $(call my-dir) include $(CLEAR_VARS) LOCAL_MODULE :=devchina LOCAL_SRC_FILES :=devchina.c LOCAL_LDLIBS += -llog include $(BUILD_SHARED_LIBRARY)
6.xml文件
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:andro
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="調用c代碼"
android:onClick="click" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="調用c代碼,加法"
android:onClick="clickAdd" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="調用c代碼,打印String"
android:onClick="clickStrng" />
</LinearLayout>
package com.devchina.ndk4;
public class DevchinaProvider {
static {
System.loadLibrary("devchina");
}
public native void cCallJava();
public native void cCallString();
public native int cCallAdd();
//1.調用java空方法
public void callJava(){
System.out.println("i come from java");
}
public int add(int x,int y){
System.out.println("devchina java res = "+(x+y));
return x+y;
}
public void printString(String s){
System.out.println("devchina java "+ s);
}
}
資源下載：https://download.csdn.net/detail/hudan2714/4328983
最後更新：2017-04-02 17:09:25