library/src/main/java/com/liulishuo/filedownloader/FileDownloader.java
public int replaceListener(int id, FileDownloadListener listener) {
        final BaseDownloadTask.IRunningTask task = FileDownloadList.getImpl().get(id);
        if (task == null) {
            return 0;
        }

        task.getOrigin().setListener(listener);
        return task.getOrigin().getId();
    }
public int replaceListener(int id, FileDownloadListener listener) {
        final BaseDownloadTask.IRunningTask task = FileDownloadList.getImpl().get(id);
        if (task == null) {
            return 0;
        }

        task.getOrigin().setListener(listener);
        return task.getOrigin().getId();
    }
Find the running task by {@code id}, and replace its listener width the new one
{@code listener}.

@return The target task's DownloadId, if not exist target task, and replace failed, will be 0
@see #replaceListener(String, FileDownloadListener)
@see #replaceListener(String, String, FileDownloadListener)