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我尝试使用 android-ndk。面临这样的问题：需要分配缓冲区供jni部分使用，然后释放。我在这里找到了这样的实现： jni 部分的函数：

    jobject Java_com_domain_applicationname_FFMpegWrapper_allocNative(JNIEnv* env, jobject thiz, jlong size)
{
void* buffer = malloc(size);
jobject directBuffer = (*env)->NewDirectByteBuffer(env, buffer, size);
jobject globalRef = (*env)->NewGlobalRef(env, directBuffer);
return globalRef;
}
void Java_com_domain_applicationname_FFMpegWrapper_freeNative(JNIEnv* env, jobject thiz, jobject globalRef)
{
void *buffer = (*env)->GetDirectBufferAddress(env, globalRef);
free(buffer);
(*env)->DeleteGlobalRef(env, globalRef);
}

在 Java 部分，我这样做：

   public class FFMpegWrapper {
.........
/** allocate buffer*/
public static native ByteBuffer allocNative(long bufferSize);

/** free buffer*/
public static native void freeNative(ByteBuffer buffer);
}

在 MainActivity 中创建：

 long bufferSize = 1024;
    ByteBuffer my_buffer = FFMpegWrapper.allocNative(bufferSize);
    FFMpegWrapper.logFileInfo("/storage/sdcard0/movies/126_3_17.avi");//this function I won't describe it business doesn't treat but it works it is visible from logs below
    //to here everything works well
    FFMpegWrapper.freeNative(my_buffer);//and here we receive a departure from the program and even the window of an exception isn't shown simply is closed activity.

日志猫：

01-14 17:53:06.924: I/com.domain.tag(22249): initialize_passed
01-14 17:53:06.964: I/com.domain.tag(22249): openened
01-14 17:53:06.964: I/ttag(22249): 3270391527096277528
01-14 17:53:06.984: I/com.domain.tag(22249): File was opened
01-14 17:53:06.984: I/com.domain.tag(22249): File '/storage/sdcard0/Movies/126_3_17.avi', Codec avi
01-14 17:53:06.984: W/dalvikvm(22249): JNI WARNING: DeleteGlobalRef on non-global 0x4780001d (type=1)
01-14 17:53:06.984: I/dalvikvm(22249): "main" prio=5 tid=1 NATIVE
01-14 17:53:06.984: I/dalvikvm(22249): | group="main" sCount=0 dsCount=0 obj=0x41065568 self=0x40ebe9a0
01-14 17:53:06.984: I/dalvikvm(22249): | sysTid=22249 nice=0 sched=0/0 cgrp=apps handle=1074450224
01-14 17:53:06.984: I/dalvikvm(22249): | schedstat=( 74908625 168640538 138 ) utm=4 stm=2 core=0
01-14 17:53:06.999: I/dalvikvm(22249): #00 pc 00001260 /system/lib/libcorkscrew.so (unwind_backtrace_thread+27)
01-14 17:53:06.999: I/dalvikvm(22249): #01 pc 0005f904 /system/lib/libdvm.so (dvmDumpNativeStack(DebugOutputTarget const*, int)+35)
01-14 17:53:06.999: I/dalvikvm(22249): #02 pc 000537ac /system/lib/libdvm.so (dvmDumpThreadEx(DebugOutputTarget const*, Thread*, bool)+303)
01-14 17:53:06.999: I/dalvikvm(22249): #03 pc 00053846 /system/lib/libdvm.so (dvmDumpThread(Thread*, bool)+25)
01-14 17:53:06.999: I/dalvikvm(22249): #04 pc 00038e02 /system/lib/libdvm.so
01-14 17:53:06.999: I/dalvikvm(22249): #05 pc 000414da /system/lib/libdvm.so
01-14 17:53:06.999: I/dalvikvm(22249): #06 pc 0002f728 /data/data/ru.dzakhov.ffmpeg.test/lib/libmylib.so (Java_ru_dzakhov_ffmpeg_test_FFMpegWrapper_freeNative+25)
01-14 17:53:06.999: I/dalvikvm(22249): #07 pc 0001de70 /system/lib/libdvm.so (dvmPlatformInvoke+112)
01-14 17:53:06.999: I/dalvikvm(22249): #08 pc 0004d0c2 /system/lib/libdvm.so (dvmCallJNIMethod(unsigned int const*, JValue*, Method const*, Thread*)+393)
01-14 17:53:06.999: I/dalvikvm(22249): #09 pc 0004f1dc /system/lib/libdvm.so (dvmResolveNativeMethod(unsigned int const*, JValue*, Method const*, Thread*)+171)
01-14 17:53:06.999: I/dalvikvm(22249): #10 pc 000272a0 /system/lib/libdvm.so
01-14 17:53:06.999: I/dalvikvm(22249): #11 pc 0002bba8 /system/lib/libdvm.so (dvmInterpret(Thread*, Method const*, JValue*)+180)
01-14 17:53:06.999: I/dalvikvm(22249): #12 pc 0005faf6 /system/lib/libdvm.so (dvmInvokeMethod(Object*, Method const*, ArrayObject*, ArrayObject*, ClassObject*, bool)+373)
01-14 17:53:06.999: I/dalvikvm(22249): #13 pc 0006709c /system/lib/libdvm.so
01-14 17:53:06.999: I/dalvikvm(22249): #14 pc 000272a0 /system/lib/libdvm.so
01-14 17:53:06.999: I/dalvikvm(22249): #15 pc 0002bba8 /system/lib/libdvm.so (dvmInterpret(Thread*, Method const*, JValue*)+180)
01-14 17:53:06.999: I/dalvikvm(22249): #16 pc 0005f830 /system/lib/libdvm.so (dvmCallMethodV(Thread*, Method const*, Object*, bool, JValue*, std::__va_list)+271)
01-14 17:53:06.999: I/dalvikvm(22249): #17 pc 000496b2 /system/lib/libdvm.so
01-14 17:53:06.999: I/dalvikvm(22249): #18 pc 0004c44e /system/lib/libandroid_runtime.so
01-14 17:53:06.999: I/dalvikvm(22249): #19 pc 0004d556 /system/lib/libandroid_runtime.so (android::AndroidRuntime::start(char const*, char const*)+389)
01-14 17:53:07.004: I/dalvikvm(22249): #20 pc 00000dce /system/bin/app_process
01-14 17:53:07.004: I/dalvikvm(22249): #21 pc 00017120 /system/lib/libc.so (__libc_init+35)
01-14 17:53:07.004: I/dalvikvm(22249): at ru.dzakhov.ffmpeg.test.FFMpegWrapper.freeNative(Native Method)
01-14 17:53:07.004: I/dalvikvm(22249): at ru.dzakhov.ffmpeg.test.MainActivity.onCreate(MainActivity.java:39)
01-14 17:53:07.004: I/dalvikvm(22249): at android.app.Activity.performCreate(Activity.java:5184)
01-14 17:53:07.004: I/dalvikvm(22249): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1083)
01-14 17:53:07.004: I/dalvikvm(22249): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2064)
01-14 17:53:07.004: I/dalvikvm(22249): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2125)
01-14 17:53:07.004: I/dalvikvm(22249): at android.app.ActivityThread.access$600(ActivityThread.java:140)
01-14 17:53:07.004: I/dalvikvm(22249): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1227)
01-14 17:53:07.004: I/dalvikvm(22249): at android.os.Handler.dispatchMessage(Handler.java:99)
01-14 17:53:07.004: I/dalvikvm(22249): at android.os.Looper.loop(Looper.java:137)
01-14 17:53:07.004: I/dalvikvm(22249): at android.app.ActivityThread.main(ActivityThread.java:4898)
01-14 17:53:07.004: I/dalvikvm(22249): at java.lang.reflect.Method.invokeNative(Native Method)
01-14 17:53:07.004: I/dalvikvm(22249): at java.lang.reflect.Method.invoke(Method.java:511)
01-14 17:53:07.004: I/dalvikvm(22249): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1006)
01-14 17:53:07.004: I/dalvikvm(22249): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:773)
01-14 17:53:07.004: I/dalvikvm(22249): at dalvik.system.NativeStart.main(Native Method)
01-14 17:53:07.004: E/dalvikvm(22249): VM aborting
01-14 17:53:07.004: A/libc(22249): Fatal signal 11 (SIGSEGV) at 0xdeadd00d (code=1), thread 22249 (hov.ffmpeg.test)

我做错了什么？

4

1 回答 1

0

关于 JNI：http ://docs.oracle.com/javase/6/docs/technotes/guides/jni/spec/design.html#wp16785

  1. Objects are passed to native methods as local references. 这意味着您必须将全局引用存储在本机端，如果您将全局引用传递回 java，它将被包装为本地对象。因此，当您稍后尝试释放它时，此本地对象将传递给您的代码。
  2. 当您从本地创建全局引用时 - 如果您不再需要它，则免费本地引用。

因此，您可以为分配的全局对象（或分配的缓冲区）维护某种映射，并返回对 NewDirectByteBuffer 返回的作业对象的本地引用。

于 2013-01-15T17:35:39.850 回答