Android NDK封装非系统第3方so库

前言: 在项目过程中遇到一个需求, 要集成第3方公司提供的滤镜功能, 第3方提供了对外接口的.h头文件和实现so库, 项目需要整合第3方so库到自己的so库中

1: 新建android工程, 建立jni目录, 在jni目录新建ImageAlogrithm目录, 放入第3方公司提供的.h头文件,
在jni目录下放入第3方提供的实现so库文件libImageAlorgrithm.so

2 编写对应的Android.mk文件:

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)
LOCAL_MODULE := ImageAlogrithm
LOCAL_SRC_FILES := libImageAlogrithm.so
LOCAL_EXPORT_C_INCLUDES := $(LOCAL_PATH)/ImageAlogrithm
include $(PREBUILT_SHARED_LIBRARY) 

include $(CLEAR_VARS)
LOCAL_MODULE     := neosharePragueFilters
LOCAL_SRC_FILES  := neosharePragueFilters.c
LOCAL_SDK_VERSION := 9
LOCAL_SHARED_LIBRARIES := libImageAlogrithm
LOCAL_LDLIBS     := -llog -ljnigraphics

include $(BUILD_SHARED_LIBRARY)

3 编写实现的c文件，native方法和C/C++ 函数有两种对应方式，一种是静态注册，即 Java_包名_类名_方法名对应，另一种通过重写JNI_OnLoad函数实现动态注册。我们使用第2种方式。

#include <string.h>
#include <jni.h>
#include <NubiaEffectInterface.h>
#include <android/bitmap.h>

#define JNIREG_CLASS "cn/nubia/prague/PragueFilterNative"


void applyFilter(JNIEnv* env, jobject thiz, jobject bitmap, jint width,
		jint height, jint index) {

	char* destination = 0;
	AndroidBitmap_lockPixels(env, bitmap, (void**) &destination);

	int tot_len = height * width * 4;

	int i;
	unsigned char * dst = destination;
	unsigned char * pTemp = malloc(tot_len * sizeof(unsigned char));
	NubiaFunctionRGBA8888ToBGRA8888(pTemp, dst, width, height);

	char * effect;
	switch (index) {
	case 1:
		effect = "LOMO_effect";
		break;
	case 2:
		effect = "gray-scale";
		break;

	case 3:
		effect = "miniature";
		break;

	case 4:
		effect = "sketch";
		break;

	case 5:
		effect = "pragueThree";
		break;

	case 6:
		effect = "emboss_effect";
		break;
	default:
		break;
	}

	NubiaFunctionSpecialEffectBGRA8888InAndRGBA8888Out(effect, pTemp, dst,
			width, height);
	free(pTemp);

	AndroidBitmap_unlockPixels(env, bitmap);

}


/**
 * Table of methods associated with a single class.
 */
static JNINativeMethod gMethods[] = {
		{ "nativeApplyFilter", "(Landroid/graphics/Bitmap;III)V", (void *)applyFilter}, //绑定
};



/*
* Register several native methods for one class.
*/
static int registerNativeMethods(JNIEnv* env, const char* className,
        JNINativeMethod* gMethods, int numMethods)
{
    jclass clazz;
    clazz = (*env)->FindClass(env, className);
    if (clazz == NULL) {
        return JNI_FALSE;
    }
    if ((*env)->RegisterNatives(env, clazz, gMethods, numMethods) < 0) {
        return JNI_FALSE;
    }

    return JNI_TRUE;
}

/**
 * Register native methods for all classes we know about.
 */

static int registerNatives(JNIEnv* env) {

	if (!registerNativeMethods(env, JNIREG_CLASS, gMethods,
			sizeof(gMethods) / sizeof(gMethods[0])))
		return JNI_FALSE;

	return JNI_TRUE;
}

JNIEXPORT jint JNICALL JNI_OnLoad(JavaVM* vm, void* reserved) {
	JNIEnv* env = NULL;
	jint result = -1;

	if ((*vm)->GetEnv(vm, (void**) &env, JNI_VERSION_1_4) != JNI_OK) {
		return result;
	}

	if (!registerNatives(env)) { //register
		return result;
	}

	result = JNI_VERSION_1_4;

	return result;

}

其中applyFilter函数中调用的NubiaFunctionRGBA8888ToBGRA8888和 NubiaFunctionSpecialEffectBGRA8888InAndRGBA8888Out函数的由第3方提供so库实现，并定义在对外的头文件里。由此整个工作就大功告成

Android NDK封装非系统第3方so库

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