ContextWrapper.getFilesDir（）中出现NullPointerException的原因

Question

I have my app published in Google Play and I have received a Crash report from one user. Unfortunately, due to anonymity reasons, I do not have the contact details of the reporter and therefore I cannot get any more details on the crash. I only have available the exception details from the report. Below is the function where I the exception is thrown. The exception is thrown at the following line:

File dbDir = new File(this.getFilesDir().getPath()+"/database");

I am trying to find out why a NullPointerException can be thrown at the above line.

Any suggestions are welcome.

The full function is below:

private void ensureDBAvailable() throws IOException{
            // The NullPointerException was thrown in the line below
    File dbDir = new File(this.getFilesDir().getPath()+"/database");
    if (!(dbDir.mkdirs() || dbDir.isDirectory()))
    {
        //This should never happen, in this case the caller should stop the service
        throw(new IOException("Cannot create database directory"));
    }

    File dbFile = new File(dbDir, MainService.DB_FILENAME);

    if(!dbFile.exists())
    {
        InputStream dbFromApk = null; 
        OutputStream dbout = null;

        try
        {
            dbFromApk = this.getAssets().open(DB_FILENAME, AssetManager.ACCESS_STREAMING);

            //the database file does not exist, let's get it from the APK. 
            dbout = new FileOutputStream(dbFile);

            byte[] buffer = new byte[1024];
            int bytesRead = 0;

            while((bytesRead = dbFromApk.read(buffer))> 0)
            {
                dbout.write(buffer, 0, bytesRead);
            }
        }
        finally
        {
            dbFromApk.close();
            dbout.close();
        }
    }
}

Answer 1

getFilesDir sometimes returns null. It's bug . So you mush check if getFilesDir returned null or not.