An error occured while executing doInBackground()

[dnish]

Hey,
I'm getting a lof of these errors in our Android project (using latest 0.10.8 version). Here is the raw log:

java.lang.RuntimeException An error occured while executing doInBackground() 
    AsyncTask.java:304 android.os.AsyncTask$3.done
    FutureTask.java:355 java.util.concurrent.FutureTask.finishCompletion
    FutureTask.java:222 java.util.concurrent.FutureTask.setException
    FutureTask.java:242 java.util.concurrent.FutureTask.run
    AsyncTask.java:231 android.os.AsyncTask$SerialExecutor$1.run
    ThreadPoolExecutor.java:1112 java.util.concurrent.ThreadPoolExecutor.runWorker
    ThreadPoolExecutor.java:587 java.util.concurrent.ThreadPoolExecutor$Worker.run
    Thread.java:818 java.lang.Thread.run


Caused by: java.lang.NullPointerException Attempt to get length of null array 
    RNFetchBlobFS.java:610 com.RNFetchBlob.RNFetchBlobFS$1.doInBackground
    RNFetchBlobFS.java:595 com.RNFetchBlob.RNFetchBlobFS$1.doInBackground
    AsyncTask.java:292 android.os.AsyncTask$2.call
    FutureTask.java:237 java.util.concurrent.FutureTask.run
    AsyncTask.java:231 android.os.AsyncTask$SerialExecutor$1.run
    ThreadPoolExecutor.java:1112 java.util.concurrent.ThreadPoolExecutor.runWorker
    ThreadPoolExecutor.java:587 java.util.concurrent.ThreadPoolExecutor$Worker.run
    Thread.java:818 java.lang.Thread.run

It seems that lstat causes this issue? Due to our logs, some people are on Android 5.1.1. Maybe we should check if String [] files = src.list(); is really an array. I'm also wondering why it could be null? Shouldn't it be an empty array?

[dnish]

Maybe this has something to do with this?

If this abstract pathname does not denote a directory, then this method returns null.

In our project, we're checking if the current selection is really a dir:

  RNFetchBlob.fs.isDir(folderChooserStore.currentFolder).then((isDir) => {

            if(isDir) {

                RNFetchBlob.fs.lstat(folderChooserStore.currentFolder).then((files) => {
                    folderChooserStore.folders = _.filter(files,(file) => (file && file.type === "directory")); // Need to check for null values
                }).catch(() => {});

            }
        });

In the native code we also have this:

  if(src.isDirectory()) {
                    String [] files = src.list();
                    for(String p : files) {
                        res.pushMap(statFile ( src.getPath() + "/" + p));
                    }
                }

So how could it be null? 😂

[lll000111]

Thanks for the report, I'll look into it.

[lll000111]

Please try my own 0.10.9 tree at https://github.com/lll000111/react-native-fetch-blob/tree/0.10.9

There now is an isDirectory check there for 0.10.9: https://github.com/lll000111/react-native-fetch-blob/blob/0.10.9/android/src/main/java/com/RNFetchBlob/RNFetchBlobFS.java#L734

0.10.9 should be more robust in a few places especially on Android, I added checks for previously ignored potential errors.

[dnish]

Hey,
it seems like that 0.10.8 already have this check (if I take a look into my package source):

     if(src.isDirectory()) {
                    String [] files = src.list();
                    for(String p : files) {
                        res.pushMap(statFile ( src.getPath() + "/" + p));
                    }
                }

But the funny part is that the isDirectory check seems not to guarantee that src.list(); returns a file array. Due to our Bugsnag logs this only happens on Android 5.x devices. Maybe we can add an additional check if files != null before we handle the for loop.

[lll000111]

Oh indeed - that isDirectory was already there. I thought I checked master and didn't see it but now I do... glasses won't help with such problems I fear.

Anyway, I added that check to my 0.10.9 repo (link in my previous comment above).