我正在从Dropbox上传和下载文件。当我上传文件时，它会正确上传。当我下载文件并打开它时，该文件是零字节。有人能告诉我为什么会这样吗？
下载代码：
try {
File localFile = new File(localFilePath);
File fileSelected = new File(dropboxPath);
if (!localFile.exists()) {
localFile.createNewFile();
} else {
//copy(fileSelected, localFile);
//mApi.copy("/Test/test.png", "/sdcard/testfile.png");
BufferedInputStream br = null;
BufferedOutputStream bw = null;
DropboxInputStream fd;
try {
fd = mApi.getFileStream(fileSelected.getPath(), null);
br = new BufferedInputStream(fd);
bw = new BufferedOutputStream(new FileOutputStream(localFile));
byte[] buffer = new byte[4096];
int read;
while (true) {
read = br.read(buffer);
if (read <= 0) {
break;
}
bw.write(buffer, 0, read);
}
} catch (DropboxException e) {
e.printStackTrace();
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
if (bw != null) {
try {
bw.close();
if (br != null) {
br.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
}/*
else {
showToast("File already exists");
}*/
}
catch (IOException e) {
showToast("Exception");
e.printStackTrace();
}
catch (Exception e) {
showToast("Exception");
e.printStackTrace();
}
答案 0 :(得分：0)
/*
* Copyright (c) 2010-11 Dropbox, Inc.
*
* Permission is hereby granted, free of charge, to any person
* obtaining a copy of this software and associated documentation
* files (the "Software"), to deal in the Software without
* restriction, including without limitation the rights to use,
* copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following
* conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
* OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
* HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
* WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
* OTHER DEALINGS IN THE SOFTWARE.
*/
package codelynks.easydropbox;
import android.app.ProgressDialog;
import android.content.Context;
import android.content.DialogInterface;
import android.content.DialogInterface.OnClickListener;
import android.graphics.drawable.Drawable;
import android.os.AsyncTask;
import android.widget.Toast;
import com.dropbox.client2.DropboxAPI;
import com.dropbox.client2.DropboxAPI.Entry;
import com.dropbox.client2.ProgressListener;
import com.dropbox.client2.exception.DropboxException;
import com.dropbox.client2.exception.DropboxIOException;
import com.dropbox.client2.exception.DropboxParseException;
import com.dropbox.client2.exception.DropboxPartialFileException;
import com.dropbox.client2.exception.DropboxServerException;
import com.dropbox.client2.exception.DropboxUnlinkedException;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
/**
* Here we show getting metadata for a directory and downloading a file in a
* background thread, trying to show typical exception handling and flow of
* control for an app that downloads a file from Dropbox.
*/
public class Download extends AsyncTask<Void, Long, Boolean> {
private Context mContext;
private final ProgressDialog mDialog;
private DropboxAPI<?> mApi;
private String mPath;
private Drawable mDrawable;
private FileOutputStream mFos;
private boolean mCanceled;
private Long mFileLen;
private String mErrorMsg;
private String mDownloadpath;
// Note that, since we use a single file name here for simplicity, you
// won't be able to use this code for two simultaneous downloads.
private final static String IMAGE_FILE_NAME = "dbroulette.png";
public Download(Context context, DropboxAPI<?> api,
String dropboxPath, String downloadpath) {
// We set the context this way so we don't accidentally leak activities
mContext = context.getApplicationContext();
mApi = api;
mPath = dropboxPath;
mDownloadpath = downloadpath;
mDialog = new ProgressDialog(context);
mDialog.setMax(100);
mDialog.setMessage("Downloading File");
mDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
mDialog.setProgress(0);
mDialog.setButton(ProgressDialog.BUTTON_POSITIVE, "Cancel", new OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
mCanceled = true;
mErrorMsg = "Canceled";
// This will cancel the getThumbnail operation by closing
// its stream
if (mFos != null) {
try {
mFos.close();
} catch (IOException e) {
}
}
}
});
mDialog.show();
mDialog.setCanceledOnTouchOutside(false);
}
@Override
protected Boolean doInBackground(Void... params) {
try {
if (mCanceled) {
return false;
}
// Get the metadata for a directory
Entry dirent = mApi.metadata(mPath, 1000, null, true, null);
if (dirent.isDir) {
// It's not a directory, or there's nothing in it
mErrorMsg = "Directory Can't be download";
return false;
}
if (mCanceled) {
return false;
}
try {
mFos = new FileOutputStream(mDownloadpath);
} catch (FileNotFoundException e) {
mErrorMsg = "Couldn't create a local file to store the image";
return false;
}
mApi.getFile(mPath, null, mFos, new ProgressListener() {
@Override
public long progressInterval() {
return 500;
}
@Override
public void onProgress(long arg0, long arg1) {
mFileLen = arg1;//Total File Length
publishProgress(arg0);//Downloaded File Length
}
});
if (mCanceled) {
return false;
}
// We must have a legitimate picture
return true;
} catch (DropboxUnlinkedException e) {
// The AuthSession wasn't properly authenticated or user unlinked.
} catch (DropboxPartialFileException e) {
// We canceled the operation
mErrorMsg = "Download canceled";
} catch (DropboxServerException e) {
// Server-side exception. These are examples of what could happen,
// but we don't do anything special with them here.
if (e.error == DropboxServerException._304_NOT_MODIFIED) {
// won't happen since we don't pass in revision with metadata
} else if (e.error == DropboxServerException._401_UNAUTHORIZED) {
// Unauthorized, so we should unlink them. You may want to
// automatically log the user out in this case.
} else if (e.error == DropboxServerException._403_FORBIDDEN) {
// Not allowed to access this
} else if (e.error == DropboxServerException._404_NOT_FOUND) {
// path not found (or if it was the thumbnail, can't be
// thumbnailed)
} else if (e.error == DropboxServerException._406_NOT_ACCEPTABLE) {
// too many entries to return
} else if (e.error == DropboxServerException._415_UNSUPPORTED_MEDIA) {
// can't be thumbnailed
} else if (e.error == DropboxServerException._507_INSUFFICIENT_STORAGE) {
// user is over quota
} else {
// Something else
}
// This gets the Dropbox error, translated into the user's language
mErrorMsg = e.body.userError;
if (mErrorMsg == null) {
mErrorMsg = e.body.error;
}
} catch (DropboxIOException e) {
// Happens all the time, probably want to retry automatically.
mErrorMsg = "Network error. Try again.";
} catch (DropboxParseException e) {
// Probably due to Dropbox server restarting, should retry
mErrorMsg = "Dropbox error. Try again.";
} catch (DropboxException e) {
// Unknown error
mErrorMsg = "Unknown error. Try again.";
}
return false;
}
@Override
protected void onProgressUpdate(Long... progress) {
int percent = (int) (100.0 * (double) progress[0] / mFileLen + 0.5);
mDialog.setProgress(percent);
}
@Override
protected void onPostExecute(Boolean result) {
mDialog.dismiss();
if (result) {
showToast("Downloading Finished");
// Set the image now that we have it
//mView.setImageDrawable(mDrawable);
} else {
// Couldn't download it, so show an error
showToast(mErrorMsg);
}
}
private void showToast(String msg) {
Toast error = Toast.makeText(mContext, msg, Toast.LENGTH_LONG);
error.show();
}
}
调用背景线程，如下所示
Download download = new Download(context, mApi, drop_box_file_path, sdcard_path_to_store);
download.execute();
其中，mApi是DropboxAPI的参考