I'm going to calculate the average rating of books.
Here,Rating and Counter is initialized in Firebase. I am getting fatal error on this line of my code sum = Double.parseDouble(r); which is
java.lang.NullPointerException: Attempt to invoke virtual method 'double java.lang.Double.doubleValue()' on a null object reference
But I could not find out the reason. It accurately retrieves both the counter value and rating without the rating calculation portion.
Here's the code and the database snapshot.
public class GetReview {
private FirebaseUser user;
private Firebase mrootref;
private String path2="hhhh";
private String c;
private String r;
private Double sum;
// private String rate = " ";
private Double avg;
private Double counter;
private Double rate;
private double rounded;
GetReview()
{
user = FirebaseAuth.getInstance().getCurrentUser();
Log.d("path1", path2);
path2= myCategory.getPath();
Log.d("paths", path2);
};
public void setReview(String bookname, Double rating) {
rate= rating;
//sum = sum+rate;
Log.d("sum?", rating.toString());
path2 += "/"+bookname+"/";
mrootref = new Firebase(path2);
mrootref.addValueEventListener(new com.firebase.client.ValueEventListener() {
@Override
public void onDataChange(com.firebase.client.DataSnapshot dataSnapshot) {
for (com.firebase.client.DataSnapshot mshot : dataSnapshot.getChildren())
{
Log.d("emmaList ", mshot.toString());
//Map<String, String> mmap = mshot.getValue(Map.class);
// c = mshot.child("Counter:").getValue().toString();
//String review = mshot.getKey().toString();
//String emma = mshot.getKey().toString();
//Log.d(review, "I am the key");
if (mshot.getKey().toString().equals("Counter")) {
c =String.valueOf( mshot.getValue());
Log.d(c, "I am counter");
}
if (mshot.getKey().toString().equals("Rating")) {
r =String.valueOf( mshot.getValue());
Log.d(r, "I am rate");
}
//r = mmap.get("Rating");
counter = Double.parseDouble(c);
counter++;
sum = Double.parseDouble(r);
sum = sum + rate;
avg = sum / counter;
sum = avg;
Log.d(counter.toString(), "i am review");
//Log.d( avg.toString(),"i am avg");
BigDecimal bd = new BigDecimal(avg);
bd = bd.round(new MathContext(3));
rounded = bd.doubleValue();
//Map revBook = new HashMap();
mrootref.child("Counter").setValue(counter.toString());
mrootref.child("Rating").setValue(Double.toString(rounded));
}
}
@Override
public void onCancelled(FirebaseError firebaseError) {
//Toast.makeText(GetReview.this, "Error in data retrieval", Toast.LENGTH_SHORT).show();
}
});
}
}
