android 源码下的JNI编译

本文仅作为记录之用

案例: BitmapBlur 图片虚化库.

编译JAVA

package com.a.b.c;import android.content.Context;import android.graphics.Bitmap;import android.os.Build.VERSION;import android.renderscript.Allocation;import android.renderscript.Element;import android.renderscript.RenderScript;import android.renderscript.ScriptIntrinsicBlur;public class BitmapBlur {static{System.loadLibrary("BitmapBlur");}/** * blur src bitmap * @param src * @param cxt * @param radius 0 <= radius <= 25 * @return */public static Bitmap getBlurBitmap(Bitmap src, Context cxt, int radius){return getBlurBitmap(src, cxt, radius, false);}/** * blur src bitmap by JNI * @param src * @param radius * @return */public static Bitmap getBlurBitmapJNI(Bitmap src, int radius){return getBlurBitmap(src, null, radius, true);}/** * blur src, if SDK > 16, use SDK, else use JNI; * @param src * @param cxt * @param radius radius 0 <= radius <= 25 * @param forceJNI * @return */public static Bitmap getBlurBitmap(Bitmap src, Context cxt, int radius, boolean forceJNI){if (VERSION.SDK_INT > 16 && !forceJNI) {            Bitmap bitmap = src.copy(src.getConfig(), true);            final RenderScript rs = RenderScript.create(cxt);            final Allocation input = Allocation.createFromBitmap(rs, src, Allocation.MipmapControl.MIPMAP_NONE,                    Allocation.USAGE_SCRIPT);            final Allocation output = Allocation.createTyped(rs, input.getType());            final ScriptIntrinsicBlur script = ScriptIntrinsicBlur.create(rs, Element.U8_4(rs));            script.setRadius(radius /* e.g. 3.f */);            script.setInput(input);            script.forEach(output);            output.copyTo(bitmap);            return bitmap;        }else{        blur(src, radius);        }return src;}public native static void blurArray(int[] bm, int w, int h, int radius);public native static void blur(Bitmap bm, int radius);}

拷贝BitmapBlur.class到JNI目录下:

mkdir -p com/a/b/c/

cp xxx/BitmapBlur.class com/a/b/c/

生成JNI 头文件

javah -classpath . -d jni com.a.b.c.BitmapBlur

生成jni/com_a_b_c_BitmapBlur.h

/* DO NOT EDIT THIS FILE - it is machine generated */#include <jni.h>/* Header for class com_a_b_c_BitmapBlur */#ifndef _Included_com_a_b_c_BitmapBlur#define _Included_com_a_b_c_BitmapBlur#ifdef __cplusplusextern "C" {#endif/* * Class:     com_a_b_c_BitmapBlur * Method:    blurArray * Signature: ([IIII)V */JNIEXPORT void JNICALL Java_com_a_b_c_BitmapBlur_blurArray  (JNIEnv *, jclass, jintArray, jint, jint, jint);/* * Class:     com_a_b_c_BitmapBlur * Method:    blur * Signature: (Landroid/graphics/Bitmap;I)V */JNIEXPORT void JNICALL Java_a_b_c_BitmapBlur_blur  (JNIEnv *, jclass, jobject, jint);#ifdef __cplusplus}#endif#endif

编写CPP文件com_a_b_c_BitmapBlur.cpp

/* DO NOT EDIT THIS FILE - it is machine generated */#include <com_a_b_c_BitmapBlur.h>#include <android/bitmap.h>#include <android/log.h>#include <blur.c>#include <stdio.h>JNIEXPORT void JNICALL Java_a_b_c_BitmapBlur_blurArray  (JNIEnv *env, jclass thiz, jintArray arrIn, jint w, jint h, jint r){jint *pix;pix = env->GetIntArrayElements(arrIn, 0);if (pix == NULL)return;//Startpix = blurIntArray(pix, w, h, r);//End//int size = w * h;//jintArray result = env->NewIntArray(size);//env->SetIntArrayRegion(result, 0, size, pix);env->ReleaseIntArrayElements(arrIn, pix, 0);//return result;}JNIEXPORT void JNICALL Java_a_b_c_BitmapBlur_blur  (JNIEnv *env, jclass thiz, jobject bitmapIn, jint r){/***************************************/AndroidBitmapInfo infoIn;void* pixelsIn;int ret;// Get image infoif ((ret = AndroidBitmap_getInfo(env, bitmapIn, &infoIn)) < 0)return;// Check imageif (infoIn.format != ANDROID_BITMAP_FORMAT_RGBA_8888)return;// Lock all imagesif ((ret = AndroidBitmap_lockPixels(env, bitmapIn, &pixelsIn)) < 0) {//AndroidBitmap_lockPixels failed!}//height widthint h = infoIn.height;int w = infoIn.width;//StartpixelsIn = blurIntArray((int*)pixelsIn, w, h, r);//End// Unlocks everythingAndroidBitmap_unlockPixels(env, bitmapIn);/**********************************/}

blur.c

/* DO NOT EDIT THIS FILE - it is machine generated */#include <jni.h>#include <math.h>#include <android/bitmap.h>#include <android/log.h>#include <stdio.h>/* Header for class com_a_b_c_BitmapBlur */#include<malloc.h>#define ABS(a) ((a)<(0)?(-a):(a))#define MAX(a,b) ((a)>(b)?(a):(b))#define MIN(a,b) ((a)<(b)?(a):(b))/* * Class:     com_a_b_c_BitmapBlur * Method:    blur * Signature: (Landroid/graphics/Bitmap;)V */static int* blurIntArray(int* pix, int w, int h, int radius) {    int wm = w - 1;    int hm = h - 1;    int wh = w * h;    int div = radius + radius + 1;    int *r = (int *)malloc(wh * sizeof(int));    int *g = (int *)malloc(wh * sizeof(int));    int *b = (int *)malloc(wh * sizeof(int));    int rsum, gsum, bsum, x, y, i, p, yp, yi, yw;    int *vmin = (int *)malloc(MAX(w,h) * sizeof(int));    int divsum = (div + 1) >> 1;    divsum *= divsum;    int *dv = (int *)malloc(256 * divsum * sizeof(int));    for (i = 0; i < 256 * divsum; i++) {        dv[i] = (i / divsum);    }    yw = yi = 0;    int(*stack)[3] = (int(*)[3])malloc(div * 3 * sizeof(int));    int stackpointer;    int stackstart;    int *sir;    int rbs;    int r1 = radius + 1;    int routsum, goutsum, boutsum;    int rinsum, ginsum, binsum;    for (y = 0; y < h; y++) {        rinsum = ginsum = binsum = routsum = goutsum = boutsum = rsum = gsum = bsum = 0;        for (i = -radius; i <= radius; i++) {            p = pix[yi + (MIN(wm, MAX(i, 0)))];            sir = stack[i + radius];            sir[0] = (p & 0xff0000) >> 16;            sir[1] = (p & 0x00ff00) >> 8;            sir[2] = (p & 0x0000ff);            rbs = r1 - ABS(i);            rsum += sir[0] * rbs;            gsum += sir[1] * rbs;            bsum += sir[2] * rbs;            if (i > 0) {                rinsum += sir[0];                ginsum += sir[1];                binsum += sir[2];            }            else {                routsum += sir[0];                goutsum += sir[1];                boutsum += sir[2];            }        }        stackpointer = radius;        for (x = 0; x < w; x++) {            r[yi] = dv[rsum];            g[yi] = dv[gsum];            b[yi] = dv[bsum];            rsum -= routsum;            gsum -= goutsum;            bsum -= boutsum;            stackstart = stackpointer - radius + div;            sir = stack[stackstart % div];            routsum -= sir[0];            goutsum -= sir[1];            boutsum -= sir[2];            if (y == 0) {                vmin[x] = MIN(x + radius + 1, wm);            }            p = pix[yw + vmin[x]];            sir[0] = (p & 0xff0000) >> 16;            sir[1] = (p & 0x00ff00) >> 8;            sir[2] = (p & 0x0000ff);            rinsum += sir[0];            ginsum += sir[1];            binsum += sir[2];            rsum += rinsum;            gsum += ginsum;            bsum += binsum;            stackpointer = (stackpointer + 1) % div;            sir = stack[(stackpointer) % div];            routsum += sir[0];            goutsum += sir[1];            boutsum += sir[2];            rinsum -= sir[0];            ginsum -= sir[1];            binsum -= sir[2];            yi++;        }        yw += w;    }    for (x = 0; x < w; x++) {        rinsum = ginsum = binsum = routsum = goutsum = boutsum = rsum = gsum = bsum = 0;        yp = -radius * w;        for (i = -radius; i <= radius; i++) {            yi = MAX(0, yp) + x;            sir = stack[i + radius];            sir[0] = r[yi];            sir[1] = g[yi];            sir[2] = b[yi];            rbs = r1 - ABS(i);            rsum += r[yi] * rbs;            gsum += g[yi] * rbs;            bsum += b[yi] * rbs;            if (i > 0) {                rinsum += sir[0];                ginsum += sir[1];                binsum += sir[2];            }            else {                routsum += sir[0];                goutsum += sir[1];                boutsum += sir[2];            }            if (i < hm) {                yp += w;            }        }        yi = x;        stackpointer = radius;        for (y = 0; y < h; y++) {            // Preserve alpha channel: ( 0xff000000 & pix[yi] )            pix[yi] = (0xff000000 & pix[yi]) | (dv[rsum] << 16) | (dv[gsum] << 8) | dv[bsum];            rsum -= routsum;            gsum -= goutsum;            bsum -= boutsum;            stackstart = stackpointer - radius + div;            sir = stack[stackstart % div];            routsum -= sir[0];            goutsum -= sir[1];            boutsum -= sir[2];            if (x == 0) {                vmin[y] = MIN(y + r1, hm) * w;            }            p = x + vmin[y];            sir[0] = r[p];            sir[1] = g[p];            sir[2] = b[p];            rinsum += sir[0];            ginsum += sir[1];            binsum += sir[2];            rsum += rinsum;            gsum += ginsum;            bsum += binsum;            stackpointer = (stackpointer + 1) % div;            sir = stack[stackpointer];            routsum += sir[0];            goutsum += sir[1];            boutsum += sir[2];            rinsum -= sir[0];            ginsum -= sir[1];            binsum -= sir[2];            yi += w;        }    }    free(r);    free(g);    free(b);    free(vmin);    free(dv);    free(stack);    return(pix);}

编写Android.mk文件

LOCAL_PATH := $(call my-dir)include $(CLEAR_VARS)LOCAL_MODULE    := libBitmapBlurLOCAL_SRC_FILES := com_a_b_c_BitmapBlur.cppLOCAL_SHARED_LIBRARIES := \        libandroid_runtime \        libcutils \        libjnigraphicsinclude $(BUILD_SHARED_LIBRARY)

普通的JNI编译到此结束.

接下来只需要通过mm / mmm命令编译即可生成相应lib库.

以下补充一些遇到的问题:

1. 引用让部lib库.

    在编译当前的lib时, 需要依赖到libExt1.so, libExt2.so, 我们把两个lib库放在编译目录的lib/目录下, 同时, 新建lib/Android.mk文件, 内容如下:

LOCAL_PATH := $(call my-dir)include $(CLEAR_VARS)LOCAL_MODULE := libExt1.soLOCAL_MODULE_TAGS := optionalLOCAL_MODULE_CLASS := SHARED_LIBRARIESLOCAL_MODULE_STEM := $(LOCAL_MODULE)LOCAL_SRC_FILES := $(LOCAL_MODULE)LOCAL_MODULE_SUFFIX := include $(BUILD_PREBUILT)include $(CLEAR_VARS)LOCAL_MODULE := libExt2.soLOCAL_MODULE_TAGS := optionalLOCAL_MODULE_CLASS := SHARED_LIBRARIESLOCAL_MODULE_STEM := $(LOCAL_MODULE)LOCAL_SRC_FILES := $(LOCAL_MODULE)LOCAL_MODULE_SUFFIX := include $(BUILD_PREBUILT)

在需要编译的模块的Android.mk中, 添加如下:

LOCAL_SHARED_LIBRARIES := libExt1 libExt2

在这之前曾错误的使用了: include $(call all-subdir-makefiles), 导致编译出现很多问题:

最常见的make: *** No rule to make target 'packages/jni/BTP_S80/lib/com_example_testscanprn_Printer.cpp', needed by 'out/target/product/XXX/obj/SHARED_LIBRARIES/libScanPrnWrap_intermediates/com_example_testscanprn_Printer.o'.  Stop.

2. 源码文件,

LOCAL_SRC_FILES := com_a_b_c_BitmapBlur.cpp

使用错误的文件名, 也同样可以编译通过, 并生成so库, 但so库在JAVA调用时, 会提示

java.lang.UnsatisfiedLinkError: No implementation found for 后面紧跟的是函数名.

3. 关于javah.

javah -classpath . -d jni a.b.c.Printer 这里需注意classpath后面的参数

如, 刚开始是把native函数写在Activity中, 后面发现, 会出现找不到android.app.Activity类的错误

网上也有对应的解决方案, 但没时间去细细研究, 建议, 把native函数放在单的类中定义, 这样用javah生成.h文件时会少走些弯路.