Question

使用DownloadManager时我遇到了一个非常奇怪的问题。

我将一些.zip文件下载到/ mnt / sdcard / Download。

调用BroadcastReceiver.onReceive（），并检查下载的文件是否存在返回true。

然而，过了一会儿文件消失了。

虽然我不删除它。设置了权限WRITE_EXTERNAL_STORAGE 。

任何想法可能导致此问题或如何修复它？？

编辑：这是代码：

public class DownloadUtil {
private DownloadTask task = null;
private long downloadQueueId;
private DownloadManager downloadManager;
private DownloadCallback callback = null;


public DownloadUtil(DownloadCallback callback) {
    this.callback = callback;
}

public interface DownloadCallback {
    public void onDownloadComplete(String filename);
}

/** 
 * Call this to download a file.
 */
public void downloadFile(String address, String destName) {
    if (task != null) {
        return;
    }

    task = new DownloadTask(address, destName);
    task.execute((Void) null);
}

/**
 * Represents an asynchronous login/registration task used to download.
 */
public class DownloadTask extends AsyncTask<Void, Void, Boolean> {
    String address;
    String destName;

    public DownloadTask(String address, String destName) {
        this.address = address;
        this.destName = destName;
    }
    @Override
    protected Boolean doInBackground(Void... params) {
        boolean retVal = true;

        try {
            download(address, destName);
        } catch (Exception e1) {
            retVal = false;
            e1.printStackTrace();
            Log.e("DownloadUtil.java", "Exception downloading: ", e1);
        } 

        return retVal;
    }

    @Override
    protected void onPostExecute(final Boolean success) {
        task = null;

        if (success) {
            // finish();
        } else {

        }
    }

    @Override
    protected void onCancelled() {
        task = null;
    }
}


/**
 * Performs the actual download.
 */
private boolean download(String address, String destName) throws ClientProtocolException, IOException {
    boolean retVal = false;

    BroadcastReceiver onDownloadComplete = new BroadcastReceiver() {
        public void onReceive(Context ctxt, Intent intent) {
            String action = intent.getAction();
            if (DownloadManager.ACTION_DOWNLOAD_COMPLETE.equals(action)) {
                Query query = new Query();
                query.setFilterById(downloadQueueId);
                Cursor c = downloadManager.query(query);
                if (c.moveToFirst()) {
                    int columnIndex = c.getColumnIndex(DownloadManager.COLUMN_STATUS);
                    if (DownloadManager.STATUS_SUCCESSFUL == c.getInt(columnIndex)) {
                        String uriString = c.getString(c.getColumnIndex(DownloadManager.COLUMN_LOCAL_URI));
                        Log.i("DownloadUtil.java", "File downloaded to: "+uriString);

                        uriString = uriString.substring(7);
                        File f = new File(uriString);
                        Log.i("DownloadUtil.java", "File: "+uriString+" exits: "+f.exists());
                        callback.onDownloadComplete(uriString);
                    }
                }
                TabLayoutActivity.context.unregisterReceiver(this);
            }
        }
    };

    DownloadManager.Request request = new DownloadManager.Request(Uri.parse(address));
    request.setDescription("Download Request");
    request.setTitle("Download");
    request.setDestinationInExternalPublicDir(Environment.DIRECTORY_DOWNLOADS, destName);

    downloadManager = (DownloadManager) TabLayoutActivity.context.getSystemService(Context.DOWNLOAD_SERVICE);
    TabLayoutActivity.context.registerReceiver(onDownloadComplete, new IntentFilter(DownloadManager.ACTION_DOWNLOAD_COMPLETE));
    downloadQueueId = downloadManager.enqueue(request);

    return retVal;
}

}

编辑2：此行为是否可能是由远程服务器引起的？我刚刚注意到，如果我从我的一台服务器下载完全相同的文件，代码运行良好。仅当从客户服务器下载文件时，它似乎才会引起问题。

Answer 1

检查此问题：

Issue 18462: Android DownloadManager Downloads Same File Twice, Fails on Others (Error 1008, ERROR_CANNOT_RESUME)

Answer 2

是的，这与@Artjom列出的问题有关。 DownloadManager中有一个错误，它有时会（通常是？）触发已完成下载的另一个下载请求。 ACTION_DOWNLOAD_COMPLETE也是广播，但由于后续下载失败，它会删除下载条目并另外删除本地文件。

我通过检查存在（+大小）并将文件移动到另一个位置来解决此问题。

DownloadManager：刚下载的文件自行消失

2 个答案: