Edit for clarification: Why this does not appear to be a normal null reference is the fact that I have already used this code in another form and have had no issue there. I could manually delete the file from my device and the file will just be replaced later. This should be handled by my try/catch statement where if the file does not exist it will initialize a new object for me.
Furthermore when I get the error in android studio upon running it, the error points directly at the FileInputStream fis = openFileInput(FILENAME);
Another thing to note is that when I add an item to the object that I am trying to pass into gson I have no issues. The object is created and I have no issue whatsoever adding items to it.
Furthermore as context, I have these two functions in an object class that manages my data for me. I create a single one of these objects as a DataManager and use these functions to save/load (among others) an object that contains all of my data within itself.
When I was putting the class together I had to add that the object class extends Activity
Because I was getting the fileoutput and fileinput as red functions beforehand. However this seems very sketchy to me (and perhaps explains exactly why I am seeing this error...?)
Original before edit: In my Android Studio application I've been trying my best to utilize gson and at present I am attempting to save a single object containing multiple attributes using gson.
However I just successfully managed to use this same gson code to put an ArrayList into a file. I could delete that file myself and everything would work just fine. However I am now trying to place an entire object in.
The error is: "java.lang.NullPointerException: Attempt to invoke virtual method 'java.io.FileOutputStream android.content.Context.openFileOutput(java.lang.String, int)' on a null object reference"
The code looks like the following:
public void loadFromFile() {
try {
FileInputStream fis = openFileInput(FILENAME);
BufferedReader in = new BufferedReader(new InputStreamReader(fis));
Gson gson = new Gson();
// https://google-gson.googlecode.com/svn/trunk/gson/docs/javadocs/com/google/gson/Gson.html, 2015-09-23
Type objectType = new TypeToken<StatisticsRecordObject>() {}.getType();
recordObject = gson.fromJson(in, objectType);
} catch (FileNotFoundException e) {
recordObject = new StatisticsRecordObject();
}
}
public void saveInFile() {
try {
FileOutputStream fos = openFileOutput(FILENAME, 0);
BufferedWriter out = new BufferedWriter(new OutputStreamWriter(fos));
Gson gson = new Gson();
gson.toJson(recordObject, out);
out.flush(); //same as fflush as before. Buffer must go. FLUSH AFTER WRITING.
fos.close();
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
recordObject = new StatisticsRecordObject();
} catch (IOException e) {
// TODO Auto-generated catch block
throw new RuntimeException(e);
}
}
