android - ThumbnailUtils.createVideoThumbnail 对于现有 mp4 视频返回 null

Question

我有一个视频，我需要获取其缩略图。我使用 ThumbnailUtils 类来实现此目的，但它返回 null 而不是预期的 Bitmap。当我调试应用程序时，我看到 createVideoThumbnail 方法 MediaMetadataRetriever.setDataSource 调用并抛出 IllegalArgumentException。在 setDataSource 中我看到了这段代码:

public void setDataSource(String path) throws IllegalArgumentException {
    if (path == null) {
        throw new IllegalArgumentException();
    }

    try (FileInputStream is = new FileInputStream(path)) {
        FileDescriptor fd = is.getFD();
        setDataSource(fd, 0, 0x7ffffffffffffffL);
    } catch (FileNotFoundException fileEx) {
        throw new IllegalArgumentException(); // and I've found out that method throws IllegalArgimentException inside this catch block
    } catch (IOException ioEx) {
        throw new IllegalArgumentException();
    }
}

我认为这意味着给定文件的文件不存在。但我在文件系统中看到它并且运行良好。也许还有其他原因？

Answer 1

问题是您将什么传递给该方法以及从什么中获取它？

下面是我这样做的方法，这对我有用，所以它也应该对你有用。

File videoFile = new File(selectedVideoPath);

Bitmap bitmap = ThumbnailUtils.createVideoThumbnail(videoFile.getAbsolutePath(), MediaStore.Video.Thumbnails.FULL_SCREEN_KIND);

要获取selectedVideoPath，您应该使用https://github.com/iPaulPro/aFileChooser/blob/master/aFileChooser/src/com/ipaulpro/afilechooser/utils/FileUtils.java#L257 getPath(Context context, Uri uri) 方法。最初它看起来像:

public static String getPath(final Context context, final Uri uri) {

    if (DEBUG)
        Log.d(TAG + " File -",
                "Authority: " + uri.getAuthority() +
                        ", Fragment: " + uri.getFragment() +
                        ", Port: " + uri.getPort() +
                        ", Query: " + uri.getQuery() +
                        ", Scheme: " + uri.getScheme() +
                        ", Host: " + uri.getHost() +
                        ", Segments: " + uri.getPathSegments().toString()
                );

    final boolean isKitKat = Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT;

    // DocumentProvider
    if (isKitKat && DocumentsContract.isDocumentUri(context, uri)) {
        // LocalStorageProvider
        if (isLocalStorageDocument(uri)) {
            // The path is the id
            return DocumentsContract.getDocumentId(uri);
        }
        // ExternalStorageProvider
        else if (isExternalStorageDocument(uri)) {
            final String docId = DocumentsContract.getDocumentId(uri);
            final String[] split = docId.split(":");
            final String type = split[0];

            if ("primary".equalsIgnoreCase(type)) {
                return Environment.getExternalStorageDirectory() + "/" + split[1];
            }

            // TODO handle non-primary volumes
        }
        // DownloadsProvider
        else if (isDownloadsDocument(uri)) {

            final String id = DocumentsContract.getDocumentId(uri);
            final Uri contentUri = ContentUris.withAppendedId(
                    Uri.parse("content://downloads/public_downloads"), Long.valueOf(id));

            return getDataColumn(context, contentUri, null, null);
        }
        // MediaProvider
        else if (isMediaDocument(uri)) {
            final String docId = DocumentsContract.getDocumentId(uri);
            final String[] split = docId.split(":");
            final String type = split[0];

            Uri contentUri = null;
            if ("image".equals(type)) {
                contentUri = MediaStore.Images.Media.EXTERNAL_CONTENT_URI;
            } else if ("video".equals(type)) {
                contentUri = MediaStore.Video.Media.EXTERNAL_CONTENT_URI;
            } else if ("audio".equals(type)) {
                contentUri = MediaStore.Audio.Media.EXTERNAL_CONTENT_URI;
            }

            final String selection = "_id=?";
            final String[] selectionArgs = new String[] {
                    split[1]
            };

            return getDataColumn(context, contentUri, selection, selectionArgs);
        }
    }
    // MediaStore (and general)
    else if ("content".equalsIgnoreCase(uri.getScheme())) {

        // Return the remote address
        if (isGooglePhotosUri(uri))
            return uri.getLastPathSegment();

        return getDataColumn(context, uri, null, null);
    }
    // File
    else if ("file".equalsIgnoreCase(uri.getScheme())) {
        return uri.getPath();
    }

    return null;
}

此外，您还可以通过调用 videoFile.exists() 添加检查 videoFile 是否存在的功能。

此外，如果您尝试从外部存储中读取数据，您可以检查 Manifest 文件中是否包含 READ_EXTERNAL_STORAGE 权限，如果您正在保存文件并尝试获取其缩略图，则还应该需要WRITE_EXTERNAL_STORAGE权限。