DocumentsProvider.java 文件源码

private final AssetFileDescriptor openTypedAssetFileImpl(
        Uri uri, String mimeTypeFilter, Bundle opts, CancellationSignal signal)
        throws FileNotFoundException {
    enforceTree(uri);
    final String documentId = getDocumentId(uri);
    if (opts != null && opts.containsKey(ContentResolver.EXTRA_SIZE)) {
        final Point sizeHint = opts.getParcelable(ContentResolver.EXTRA_SIZE);
        return openDocumentThumbnail(documentId, sizeHint, signal);
    }
    if ("*/*".equals(mimeTypeFilter)) {
         // If they can take anything, the untyped open call is good enough.
         return openAssetFile(uri, "r");
    }
    final String baseType = getType(uri);
    if (baseType != null && ClipDescription.compareMimeTypes(baseType, mimeTypeFilter)) {
        // Use old untyped open call if this provider has a type for this
        // URI and it matches the request.
        return openAssetFile(uri, "r");
    }
    // For any other yet unhandled case, let the provider subclass handle it.
    return openTypedDocument(documentId, mimeTypeFilter, opts, signal);
}