ubuntu android 调用动态链接库-优快云博客

以下开发是在ubuntu12.04进行。

准备开发环境：

1.这里我直接用的android官方提供的IDE。

http://developer.android.com/sdk/index.html

2.android sdk.

环境变量设置：

export ANDROID_HOME=$HOME/download/adt-bundle-linux-x86-20130729/sdk

export ANDROID_NDK_HOME=$HOME/download/android-ndk-r9

export JAVA_HOME=$HOME/jdk1.7.0_25

export PATH=$JAVA_HOME/bin:$JAVA_HOME/jre/bin:$ANDROID_HOME/platform-tools:$ANDROID_HOME/tools:$ANDROID_NDK_HOME:$PATH

export CLASSPATH=$CLASSPATH:.:$JAVA_HOME/lib:$JAVA_HOME/jre/lib

3.ndk,http://developer.android.com/tools/sdk/ndk/index.html

如图：

创建一个android项目。

layout-->main.xml内容很简单，就一个文本框，展示结果使用：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivity" >

    <TextView
        android:id="@+id/txtView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="124dp"/>

</RelativeLayout>

现在建立一个类，这个类主要是调用底层c函数的类：

package org.chenjun.jni;

public class JniUtil {

	public native static int getSum(int a,int b);
	
	static{
		System.loadLibrary("jniUtil");//libjniUtil.so
	}
	
}

只有一个方法，getSum,传递2个数值进行求和操作。通过javah编译出头文件出来。文件内容：

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

#ifndef _Included_org_chenjun_jni_JniUtil
#define _Included_org_chenjun_jni_JniUtil
#ifdef __cplusplus
extern "C" {
#endif
/*
 * Class:     org_chenjun_jni_JniUtil
 * Method:    getSum
 * Signature: (II)I
 */
JNIEXPORT jint JNICALL Java_org_chenjun_jni_JniUtil_getSum
  (JNIEnv *, jclass, jint, jint);

#ifdef __cplusplus
}
#endif
#endif

在android工程下建立jni目录。将该头文件放到jni目录中。jni目录中创建c文件jniUtil.c：

#include <string.h>
#include <jni.h>
#include "org_chenjun_jni_JniUtil.h"

JNIEXPORT jint JNICALL Java_org_chenjun_jni_JniUtil_getSum
  (JNIEnv *env, jclass clazz, jint a, jint b){
	return a + b;
}

jni目录中创建android.mk文件，文件的含义在ndk的doc中有介绍：

# 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    := jniUtil
LOCAL_SRC_FILES := jniUtil.c

include $(BUILD_SHARED_LIBRARY)

目录结构如下图：

使用终端进入到android项目的根目录下面，执行ndk-build命令就会生成我们要的动态链接库：

在MainActivity中我们调用动态链接库给我们的方法进行计算并展示在文本框中：

package org.chenjun.android.jni;

import org.chenjun.jni.JniUtil;

import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.widget.TextView;

public class MainActivity extends Activity {
	
	private TextView txtView;
	
	
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);
		txtView = (TextView) findViewById(R.id.txtView);
		int c = JniUtil.getSum(2, 6);
		txtView.setText("2+6=" + c);
	}

	@Override
	public boolean onCreateOptionsMenu(Menu menu) {
		getMenuInflater().inflate(R.menu.main, menu);
		return true;
	}

}

运行后的结果如图：