修改Android(安卓)4.2.2的原生Camera引出的java.lang.UnsatisfiedLinkError: Native method not found,及解决方法
修改Android 4.2.2的原生Camera应用,做一些定制,将Camera的包名从之前的 package com.android.* 修改成了com.zhao3546.*。
调整后,应用可以正常运行,但是Camera自带的特效编辑等功能,无法正常使用。一点图片编辑的图标,就出现了下面的异常:
09-12 18:52:48.131: E/AndroidRuntime(6071): java.lang.UnsatisfiedLinkError: Native method not found: com.zhao3546.gallery3d.filtershow.filters.ImageFilterFx.nativeApplyFilter:(Landroid/graphics/Bitmap;IILandroid/graphics/Bitmap;II)V09-12 18:52:48.131: E/AndroidRuntime(6071): at com.zhao3546.gallery3d.filtershow.filters.ImageFilterFx.nativeApplyFilter(Native Method)09-12 18:52:48.131: E/AndroidRuntime(6071): at com.zhao3546.gallery3d.filtershow.filters.ImageFilterFx.apply(ImageFilterFx.java:58)09-12 18:52:48.131: E/AndroidRuntime(6071): at com.zhao3546.gallery3d.filtershow.presets.ImagePreset.apply(ImagePreset.java:291)09-12 18:52:48.131: E/AndroidRuntime(6071): at com.zhao3546.gallery3d.filtershow.cache.DirectPresetCache.compute(DirectPresetCache.java:156)09-12 18:52:48.131: E/AndroidRuntime(6071): at com.zhao3546.gallery3d.filtershow.cache.DelayedPresetCache.handleMessage(DelayedPresetCache.java:50)
原来,ImageFilterFx.nativeApplyFilter() 的这个方法是通过JNI实现的,想想也是,不使用JNI的话,使用Java实现图片编辑的特效,效率要低不少。
关于JNI的介绍,个人觉得写得最好的是《Android框架揭秘》这本书的 “第四章 JNI和NDK”,从示例出发,再将原理娓娓道来,很深入浅出。
言归正传,看看怎么解决吧。
如下是根据 nativeApplyFilter 关键字搜索,找到的结果如下,只保留一小部分:
---- nativeApplyFilter Matches (55 in 30 files) ----Bw.c (jni\filters):void JNIFUNCF(ImageFilterBW, nativeApplyFilter, jobject bitmap, jint width, jint height)Bw.c (jni\filters):void JNIFUNCF(ImageFilterBWRed, nativeApplyFilter, jobject bitmap, jint width, jint height)Bw.c (jni\filters):void JNIFUNCF(ImageFilterBWGreen, nativeApplyFilter, jobject bitmap, jint width, jint height)Bw.c (jni\filters):void JNIFUNCF(ImageFilterBWBlue, nativeApplyFilter, jobject bitmap, jint width, jint height)Bwfilter.c (jni\filters):void JNIFUNCF(ImageFilterBwFilter, nativeApplyFilter, jobject bitmap, jint width, jint height, jint rw, jint gw, jint bw)Contrast.c (jni\filters):void JNIFUNCF(ImageFilterContrast, nativeApplyFilter, jobject bitmap, jint width, jint height, jfloat bright)Exposure.c (jni\filters):void JNIFUNCF(ImageFilterExposure, nativeApplyFilter, jobject bitmap, jint width, jint height, jfloat bright)Fx.c (jni\filters):void JNIFUNCF(ImageFilterFx, nativeApplyFilter, jobject bitmap, jint width, jint height, jobject lutbitmap,jint lutwidth, jint lutheight )Geometry.c (jni\filters):void JNIFUNCF(ImageFilterGeometry, nativeApplyFilterFlip, jobject src, jint srcWidth, jint srcHeight, jobject dst, jint dstWidth, jint dstHeight, jint flip) {Geometry.c (jni\filters):void JNIFUNCF(ImageFilterGeometry, nativeApplyFilterRotate, jobject src, jint srcWidth, jint srcHeight, jobject dst, jint dstWidth, jint dstHeight, jint rotate) {Geometry.c (jni\filters):void JNIFUNCF(ImageFilterGeometry, nativeApplyFilterCrop, jobject src, jint srcWidth, jint srcHeight, jobject dst, jint dstWidth, jint dstHeight, jint offsetWidth, jint offsetHeight) {Geometry.c (jni\filters):void JNIFUNCF(ImageFilterGeometry, nativeApplyFilterStraighten, jobject src, jint srcWidth, jint srcHeight, jobject dst, jint dstWidth, jint dstHeight, jfloat straightenAngle) {Hue.c (jni\filters):void JNIFUNCF(ImageFilterHue, nativeApplyFilter, jobject bitmap, jint width, jint height, jfloatArray matrix)ImageFilterBW.java (src\com\android\gallery3d\filtershow\filters): native protected void nativeApplyFilter(Bitmap bitmap, int w, int h);ImageFilterBW.java (src\com\android\gallery3d\filtershow\filters): nativeApplyFilter(bitmap, w, h);
Native方法的实现,肯定是在C或CPP中,直接看第一个结果吧:
void JNIFUNCF(ImageFilterBW, nativeApplyFilter, jobject bitmap, jint width, jint height){ ...}
JNIFUNCF这个函数名有点怪啊,怎么全是大写,C或C++中,全大写一般是都常量或宏,啥情况?
看看是怎么定义的,再根据JNIFUNCF搜索下,在filters.h中有定义:
#define JNIFUNCF(cls, name, vars...) Java_com_android_gallery3d_filtershow_filters_ ## cls ## _ ## name(JNIEnv* env, jobject obj, vars)
原来是个宏,这个宏是啥意思如果你不明白,需要了解一些C的基础,
此处将 “Java_com_android_gallery3d_filtershow_filters_” 和 cls 对应的实际值和 name 对应的实际值,拼接成一个字符串作为实际的方法名。
之前我们修改了Java的包名,但是 Java_com_android_gallery3d_filtershow_filters_ 这个没有修改,所以导致最终生成的方法与修改后Java实现的Native方法的符号匹配不上了,将 Java_com_android_gallery3d_filtershow_filters_ 修改成 Java_com_zhao3546_gallery3d_filtershow_filters_ ,再放到源码编译环境上重新生成相应的so,再重新生成APK测试,ok,问题解决。
了解JNI机制,才是解决此类问题的KEY。
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