flutter_downloader這個插件在用的時候，Android模擬器上面會出現下面這個報錯，進度一直是0
Backoff delay duration less than minimum value

• 看了很多issue，發現一個issue戳中要害

https://github.com/fluttercommunity/flutter_downloader/issues/105
模擬器上面的WiFi或者信號中有個x號，因為無法訪問到google，則判斷網絡無法連接，導致無法下載，實際上是可以連接網絡的。

// 源碼在flutter_downloader/android/src/main/java/vn/hunghd/flutterdownloader/FlutterDownloaderPlugin.java 143行、
...
private WorkRequest buildRequest(String url, String savedDir, String filename, String headers, boolean showNotification, boolean openFileFromNotification, boolean isResume, boolean requiresStorageNotLow) {
        WorkRequest request = new OneTimeWorkRequest.Builder(DownloadWorker.class)
                .setConstraints(new Constraints.Builder()
                        .setRequiresStorageNotLow(requiresStorageNotLow)
                        .setRequiredNetworkType(NetworkType.CONNECTED) // 這里
                        .build())
                .addTag(TAG)
                .setBackoffCriteria(BackoffPolicy.EXPONENTIAL, 5, TimeUnit.SECONDS)
                .setInputData(new Data.Builder()
                        .putString(DownloadWorker.ARG_URL, url)
                        .putString(DownloadWorker.ARG_SAVED_DIR, savedDir)
                        .putString(DownloadWorker.ARG_FILE_NAME, filename)
                        .putString(DownloadWorker.ARG_HEADERS, headers)
                        .putBoolean(DownloadWorker.ARG_SHOW_NOTIFICATION, showNotification)
                        .putBoolean(DownloadWorker.ARG_OPEN_FILE_FROM_NOTIFICATION, openFileFromNotification)
                        .putBoolean(DownloadWorker.ARG_IS_RESUME, isResume)
                        .build()
                )
                .build();
        return request;
...

• 解決方案

1. Android 10的去除WiFi叉號/感嘆號方法

2.issue里面大佬的方案