因此，我对此并不陌生，并且我的应用程序一直崩溃。我在这里找到了这段代码，无法使其一生使用。我想做的只是下载选定的文件，当我不在作业文件夹的子目录中时，它可以工作。我从MySQL数据库下载作业文件夹名称，并且工作正常。每个工作都有用于照片，文档，杂项等的子文件夹。说我有工作4131 ..，而在4131内部有以下文件。
4131 / cdgjkg.png
4131 /其他
4131 /照片
在photots内部还有另一个png。 （4131 / Photos / dioghg.png）。问题是，如果我在base 4131方法中下载png wthin，它将起作用。没有错误。如果我进入Photots目录并尝试下载该文件，则会收到大量异步错误。下面是代码。如果您需要更多信息，请告诉我。
new LoadAllJobs().execute();
ListView lv = getListView();
lv.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
String file = ((TextView)view).getText().toString();
String current_dir = dir + "/" + file;
if(file.contains(".")){
//download the file or view it
try {
Log.d("Downloading ", file);
new FTPDownload().execute(file); // <-----This is where I start the task to enter the FTPDownload, never to be seen again :(
Log.d("Success ", current_dir);
}
catch (Exception e) {
e.printStackTrace();
}
这是我在其中检索清单并仅在文件中包含“。”的情况下下载文件的地方。 （在服务器上，文件夹名称中不允许使用'。'字符，因此这是一个快速作弊的功能）。
FTPDownload类
class FTPDownload extends AsyncTask<String, Integer, String> {
//public FTPClient client;
@Override
protected String doInBackground(String... filename) {
try {
System.out.println("Filename->: " + filename[0]);
GetFileFTP("/" + filename[0], Environment.getExternalStorageDirectory() + "/Download/", filename[0]);
}
finally
{
//e.printStackTrace();
Log.v("DONE: ", "All done!");
}
System.out.println("I HATE YOU."); // <----- NEVER REACHES THIS LINE WHEN TRYING TO DOWNLOAD IN A SUBFOLDER
return null;
}
public void GetFileFTP(String srcFileSpec, String destpath, String destname) {
FTPClient client = new FTPClient();
Log.v("pathSpec: ", destpath);
try {
client.connect("xxxxxx");
client.login("xxxxxx", "xxxxxx");
client.enterLocalPassiveMode();
client.setFileType(org.apache.commons.net.ftp.FTP.BINARY_FILE_TYPE);
InputStream input = client.retrieveFileStream(srcFileSpec);
if(input != null) Log.v("GetFileFTP: ", "INPUT STREAM OPENED SUCCESSFULLY!");
Log.v("File InputStream: ", srcFileSpec);
File output_file = new File(destpath + destname);
Log.v("OUTPUTFILE: ", destpath + destname);
inputstreamcopy(input, output_file);
/*try {
//Log.e("Closing connection: ", client.toString());
client.logout();
client.disconnect();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}*/
}
catch (IOException e) {
Log.e("FTP", "Error Getting File");
e.printStackTrace();
}
}
public static void inputstreamcopy(InputStream source, File destination){
try {
org.apache.commons.io.FileUtils.copyInputStreamToFile(source, destination);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
控制台输出
04-08 15:10:05.010: D/Downloading(29309): login.php
04-08 15:10:05.010: D/Success(29309): 4131/Miscellaneous/login.php
04-08 15:10:05.010: I/System.out(29309): Filename->: login.php
04-08 15:10:05.020: V/pathSpec:(29309): /storage/emulated/0/Download/
04-08 15:10:06.010: V/File InputStream:(29309): /login.php
04-08 15:10:06.020: V/OUTPUTFILE:(29309): /storage/emulated/0/Download/login.php
04-08 15:10:06.030: V/DONE:(29309): All done!
04-08 15:10:06.030: W/dalvikvm(29309): threadid=11: thread exiting with uncaught exception (group=0x418f5930)
04-08 15:10:06.040: E/AndroidRuntime(29309): FATAL EXCEPTION: AsyncTask #1
04-08 15:10:06.040: E/AndroidRuntime(29309): java.lang.RuntimeException: An error occured while executing doInBackground()
04-08 15:10:06.040: E/AndroidRuntime(29309): at android.os.AsyncTask$3.done(AsyncTask.java:299)
04-08 15:10:06.040: E/AndroidRuntime(29309): at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:352)
04-08 15:10:06.040: E/AndroidRuntime(29309): at java.util.concurrent.FutureTask.setException(FutureTask.java:219)
04-08 15:10:06.040: E/AndroidRuntime(29309): at java.util.concurrent.FutureTask.run(FutureTask.java:239)
04-08 15:10:06.040: E/AndroidRuntime(29309): at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230)
04-08 15:10:06.040: E/AndroidRuntime(29309): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1080)
04-08 15:10:06.040: E/AndroidRuntime(29309): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:573)
04-08 15:10:06.040: E/AndroidRuntime(29309): at java.lang.Thread.run(Thread.java:856)
04-08 15:10:06.040: E/AndroidRuntime(29309): Caused by: java.lang.NullPointerException
04-08 15:10:06.040: E/AndroidRuntime(29309): at org.apache.commons.io.IOUtils.copyLarge(IOUtils.java:1792)
04-08 15:10:06.040: E/AndroidRuntime(29309): at org.apache.commons.io.IOUtils.copyLarge(IOUtils.java:1769)
04-08 15:10:06.040: E/AndroidRuntime(29309): at org.apache.commons.io.IOUtils.copy(IOUtils.java:1744)
04-08 15:10:06.040: E/AndroidRuntime(29309): at org.apache.commons.io.FileUtils.copyInputStreamToFile(FileUtils.java:1512)
04-08 15:10:06.040: E/AndroidRuntime(29309): at com.example.tdsi.FTPDownload.inputstreamcopy(FTPDownload.java:70)
04-08 15:10:06.040: E/AndroidRuntime(29309): at com.example.tdsi.FTPDownload.GetFileFTP(FTPDownload.java:51)
04-08 15:10:06.040: E/AndroidRuntime(29309): at com.example.tdsi.FTPDownload.doInBackground(FTPDownload.java:21)
04-08 15:10:06.040: E/AndroidRuntime(29309): at com.example.tdsi.FTPDownload.doInBackground(FTPDownload.java:1)
04-08 15:10:06.040: E/AndroidRuntime(29309): at android.os.AsyncTask$2.call(AsyncTask.java:287)
04-08 15:10:06.040: E/AndroidRuntime(29309): at java.util.concurrent.FutureTask.run(FutureTask.java:234)
04-08 15:10:06.040: E/AndroidRuntime(29309): ... 4 more
最佳答案
这是您的罪魁祸首：
04-08 15:10:06.040: E/AndroidRuntime(29309): Caused by: java.lang.NullPointerException
[...]
org.apache.commons.io.FileUtils.copyInputStreamToFile(FileUtils.java:1512)
您将
null传递给inputstreamcopy()，这将导致NPE。