How To Get File In Assets From Android NDK

Issue

I’m trying to access an image file in the assets folder from the native side. Now I can successfully search through the assets folder and its subdirectories locating the particular file that I am looking for:

AAssetDir* assetDir  AAssetManager_openDir(asset_manager, "images");
const char* filename;
while ((filename  AAssetDir_getNextFileName(assetDir)) ! NULL)
{
   __android_log_print(ANDROID_LOG_DEBUG, "Debug", filename);
}

AAssetDir_close(assetDir);

I am also using OSG. I set the image as a texture to my shader with the following code:

texture->setImage(osgDB::readImageFile(fileNameWithPath));

But that file name must include the absolute path as well since it is not located in the same directory. However I found out that I cannot get the absolute path for the assets directory, being that it is compressed along with the APK.

Being that I can’t access the absolute path, what other way could I use to get the image? Also to note, I do want to keep the files in the asset folder as appose to the sd card.

Solution

You can read the image from an asset with AAssetManager_open & AAsset_read, but since asset lies in apk you can’t get a file path name for it – it is also compressed there. You can save the data to a file and read from that file later or you can directly process the chunk you got from your asset file if OSG allows.

From here:

AAssetDir* assetDir  AAssetManager_openDir(mgr, "");
const char* filename  (const char*)NULL;
while ((filename  AAssetDir_getNextFileName(assetDir)) ! NULL) {
    AAsset* asset  AAssetManager_open(mgr, filename, AASSET_MODE_STREAMING);
    char buf[BUFSIZ];
    int nb_read  0;
    FILE* out  fopen(filename, "w");
    while ((nb_read  AAsset_read(asset, buf, BUFSIZ)) > 0)
        fwrite(buf, nb_read, 1, out);
    fclose(out);
    AAsset_close(asset);
}
AAssetDir_close(assetDir);

Answered By – auselen

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