lingochamp/FileDownloader · error · IllegalArgumentException

can't create the block complete message for id

Error message

can't create the block complete message for id[%d], status[%d]

What it means

FileDownloader throws this IllegalArgumentException from the BlockCompleteMessageImpl constructor when the snapshot passed in is not in the 'completed' status. A block-complete message can only be built from a completed snapshot, since it wraps the completed snapshot to later transmit it; the constructor fails fast on any other status (pending, progress, error, warn, etc.).

Solutions

1. Check the snapshot status with snapshot.getStatus() and only construct BlockCompleteMessageImpl when it equals FileDownloadStatus.completed
2. Log snapshot.getStatus() and getId() at the call site to find where the wrong snapshot is being passed
3. Ensure the completed snapshot is delivered before the block-complete flow is triggered (do not pre-construct with a progress snapshot)
4. Update the library: newer versions of FileDownloader handle block-complete conversion internally without exposing this path

Example fix

// before
BlockCompleteMessage msg = new BlockCompleteMessage.BlockCompleteMessageImpl(anySnapshot);
// after
if (anySnapshot.getStatus() == FileDownloadStatus.completed) {
    BlockCompleteMessage msg = new BlockCompleteMessage.BlockCompleteMessageImpl(anySnapshot);
}

if (snapshot != null && snapshot.getStatus() != FileDownloadStatus.completed) {
    throw new IllegalStateException("BlockCompleteMessage requires a completed snapshot, got status=" + snapshot.getStatus());
}

boolean isCompletedSnapshot(MessageSnapshot s) {
    return s != null && s.getStatus() == FileDownloadStatus.completed;
}

try {
    BlockCompleteMessage msg = new BlockCompleteMessage.BlockCompleteMessageImpl(snapshot);
} catch (IllegalArgumentException e) {
    Log.e(TAG, "Cannot build block complete message: " + e.getMessage());
}

When it happens

Trigger: Calling new BlockCompleteMessage.BlockCompleteMessageImpl(snapshot) with a snapshot whose getStatus() != FileDownloadStatus.completed — e.g. wrapping a progress or error snapshot instead of the completed one.

Common situations: Custom code or patched library code that intercepts download lifecycle messages and manually constructs a block-complete message from the wrong snapshot; internal callers receiving a snapshot of an unexpected status from a custom MessageStation/Service layer.

Understand the failure class

Background: "Must be a positive integer", "Invalid value", "Unsupported": the invalid-argument-value error family, when a library rejects the value you pass — this error's family across 35 libraries.

Related errors

• fetched length[ ] != content length[ ], range[ , ) offset[…
• listener must not be null!
• event must not be null!
• getThrowable
• getRetryingTimes

AI-assisted analysis of lingochamp/FileDownloader@6237a8cac1 (2026-09-08). Data as JSON: /api/errors/bb07391180b2d599. Report an issue: GitHub.

Appendix: source

Thrown at library/src/main/java/com/liulishuo/filedownloader/message/BlockCompleteMessage.java:39

/**
 * The interface of block complete message.
 *
 * @see SmallMessageSnapshot
 * @see LargeMessageSnapshot
 */

public interface BlockCompleteMessage {

    MessageSnapshot transmitToCompleted();

    class BlockCompleteMessageImpl extends MessageSnapshot implements BlockCompleteMessage {
        private final MessageSnapshot mCompletedSnapshot;

        public BlockCompleteMessageImpl(MessageSnapshot snapshot) {
            super(snapshot.getId());
            if (snapshot.getStatus() != FileDownloadStatus.completed) {
                throw new IllegalArgumentException(FileDownloadUtils.formatString(
                        "can't create the block complete message for id[%d], status[%d]",
                        snapshot.getId(), snapshot.getStatus()));
            }
            this.mCompletedSnapshot = snapshot;
        }

        @Override
        public MessageSnapshot transmitToCompleted() {
            return this.mCompletedSnapshot;
        }

        @Override
        public byte getStatus() {
            return FileDownloadStatus.blockComplete;
        }
    }

}

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