Android 调用Jni的全过程

1、下载ndk并解压即可

2、下载cygwin并安装。环境搭建:点击打开链接下载cygwin的作用主要是模拟linux环境。工程名是：MyFirstJniDemo

public class Main extends Activity {

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);
TextView textView=(TextView)this.findViewById(R.id.textview);
textView.setText(show()+"");
}

public native String show();

static{
System.loadLibrary("firstso");//创建动态库
}

}

3、项目编译后（一定要编译后：build-project）生成.h文件（.h文件可剪切到bin下）。

/* DO NOT EDIT THIS FILE - it is machine generated */
#include <jni.h>
/* Header for class com_example_myfirstjnidemo_Main */

#ifndef _Included_com_example_myfirstjnidemo_Main
#define _Included_com_example_myfirstjnidemo_Main
#ifdef __cplusplus
extern "C" {
#endif
/*
* Class:     com_example_myfirstjnidemo_Main
* Method:    show
* Signature: ()Ljava/lang/String;
*/
JNIEXPORT jstring JNICALL Java_com_example_myfirstjnidemo_Main_show
(JNIEnv *, jobject);

#ifdef __cplusplus
}
#endif
#endif

4、根据生成的.h文件编写firstso.c文件，如下

#include<string.h>
#include<jni.h>
jstring
JNICALL Java_com_example_myfirstjnidemo_Main_show
(JNIEnv* env,jobject thiz){
return (*env)->NewStringUTF(env,"你好");
}

注意：此文件的字节编码格式一定要是UTF-8，否则可能会出问题（主要是我遇到过）

5、编写Android.mk文件，我是将ndk下samples下hello-jni中Android.mk文件修改了一下。

主要是修改两个地方

LOCAL_MODULE : 组件

LOCAL_SRC_FILES ：文件，如果有多个，要用“，”隔开

# Copyright (C) 2009 The Android Open Source Project
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#      http://www.apache.org/licenses/LICENSE-2.0 #
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#
LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)

LOCAL_MODULE    := firstso
LOCAL_SRC_FILES := firstso.c

include $(BUILD_SHARED_LIBRARY)

6、在工程下创建jni文件，将Android.mk和firstso.c拷贝到jni中，然后再，将该项目拷贝到ndk中的samples目录下

然后作如下操作：



之后会生成.so文件。

7、将该项目导入eclipse既可以运行，例子很简单，只是显示一句”你好“，就不截图了。