Android NDK初步涉獵

標籤：android

大致分是這幾步：

（1）建立Android工程：

                                                                                                          

HelloJni.java代碼

package com.panpass.main;public class HelloJni {static{System.loadLibrary("demo-jni");}public void sayHello(){}public native String jniSay();}

MainActivity.java代碼

package com.panpass.main;import android.app.Activity;import android.os.Bundle;import android.widget.TextView;import com.example.demo.R;public class MainActivity extends Activity {private TextView mTextView;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.main_activity);mTextView = (TextView) findViewById(R.id.text_view);HelloJni demojin = new HelloJni();mTextView.setText(demojin.jniSay());}}

（2）產生標頭檔。

在cmd中進入相應的目錄下：

例如我的工程在這裡：

最終是進入到這裡：

也就是開啟cmd後輸入命令：

cd  C:\android\workone\Demo\bin\classes

接著輸入：javah  -jni com.panpass.main.HelloJni

就會產生.h檔案。

（3）建立jni檔案。

                                                                  

demo-jni.c就是c層函數的具體實現。如下：

/* * 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. * */#include <string.h>#include <jni.h>/* This is a trivial JNI example where we use a native method * to return a new VM String. See the corresponding Java source * file located at: * *   apps/samples/hello-jni/project/src/com/example/hellojni/HelloJni.java */jstringJava_com_panpass_main_HelloJni_jniSay( JNIEnv* env,                                                  jobject thiz){    return (*env)->NewStringUTF(env, "hello jni");}

其中的

Java_com_panpass_main_HelloJni_jniSay( JNIEnv* env,                                                  jobject thiz)

就是從產生的.h檔案中來的。看產生的.h檔案：

/* DO NOT EDIT THIS FILE - it is machine generated */#include <jni.h>/* Header for class com_panpass_main_HelloJni */#ifndef _Included_com_panpass_main_HelloJni#define _Included_com_panpass_main_HelloJni#ifdef __cplusplusextern "C" {#endif/* * Class:     com_panpass_main_HelloJni * Method:    haveReturnFromJni * Signature: (Ljava/lang/String;)Ljava/lang/String; */JNIEXPORT jstring JNICALL Java_com_panpass_main_HelloJni_haveReturnFromJni  (JNIEnv *, jobject, jstring);/* * Class:     com_panpass_main_HelloJni * Method:    jniSay * Signature: ()Ljava/lang/String; */JNIEXPORT jstring JNICALL Java_com_panpass_main_HelloJni_jniSay  (JNIEnv *, jobject);#ifdef __cplusplus}#endif#endif

Android.mk代碼如下：

# 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    := demo-jniLOCAL_SRC_FILES := demo-jni.cinclude $(BUILD_SHARED_LIBRARY)

具體意思可以baidu。

（4）下載ndk使用ndk產生.so庫。

ndk下載去百度。

配置ndk環境變數：

其中NDK：

在cmd中進入工程根目錄：

接著執行：

ndk-build

重新整理工程你就會發現：

多了libs和obj

最後運行，OK。

                                                                                                             

Android NDK初步涉獵