android - 从 GetStringUTFChars JNI 得不到结果

Question

我的 android 应用程序的 android NDK。我被困在起跑线上，它没有进一步编译。以下是我的代码。它不会在 "str = (*env)->GetStringUTFChars(env, filename, NULL);" 之后编译。请检查我的java和c代码

java代码:

public class MyffmpegActivity extends Activity {

private static native int logFileInfo(String filename);

static
{
    Log.i("HEHA", "HOHA");
    System.loadLibrary("mylib");
}

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_myffmpeg);
    String path=Environment.getExternalStorageDirectory().getPath();
    path=path+"/test.mp4";
    Log.i("Name Returned is ", ":"+path);
int x=logFileInfo(path);


}

C代码

jint Java_com_example_myffmpegtest_MyffmpegActivity_logFileInfo(JNIEnv * env, jobject  this, jstring filename)
{

av_register_all();
   AVFormatContext *pFormatCtx;
   const jbyte *str;

  str = (*env)->GetStringUTFChars(env, filename, NULL);
 if(av_open_input_file(&pFormatCtx, str, NULL, 0, NULL)!=0)
 {
    LOGE("Can't open file '%s'\n", str);
    return 1;
}
else
{

    LOGI("File was opened\n");
    LOGI("File '%s', Codec %s",
        pFormatCtx->filename,
        pFormatCtx->iformat->name
    );
}
return 0;}

Answer 1

正确的语法是:

const char *str;
str = (*env)->GetStringUTFChars(env, filename, NULL);

此外，您似乎正在尝试开发我已经为其创建了解决方案的东西。查看FFmpegMediaMetadataRetriever .