CODEWITHSUNDEEP
androidandroid-cursor
Raddino
Raddino

Reputation: 185

Method invocation may produce java NullpointerException

I have a code:

public String getNameUpdateEvent(long id) {
    Cursor mCursor =
            db.rawQuery("select name from events WHERE _id=" + id + ";", null);
    if (mCursor != null) {
        mCursor.moveToFirst();
    }
    String updateNameEvent;
    updateNameEvent = mCursor.getString(mCursor.getColumnIndex("name"));
    return updateNameEvent;
}

and I´m getting a warning 

    Warning:(173, 45) Method invocation 'mCursor.getColumnIndex("name")' may produce 'java.lang.NullPointerException'

How i can fix it pls?

Upvotes: 15

Views: 50297

Answers (2)

Orest Savchak
Orest Savchak

Reputation: 4569

Your cursor can not be null, it will always have any value. But cursor can be empty, so you should firstly go to first row in cursor with method moveToFirst(), and if it returns true - it means, that cursor has at least one row, so you can do with it all you want, if it returns false - it means, that there is nothing for your query, so you have not any rows to get data from. Your code should look like this:

public String getNameUpdateEvent(long id) {
    Cursor mCursor =
        db.rawQuery("select name from events WHERE _id=" + id + ";", null);

    String updateNameEvent = null;
    if (mCursor != null && mCursor.moveToFirst()) {
        updateNameEvent = mCursor.getString(mCursor.getColumnIndex("name"));
    }
    return updateNameEvent;
}

Upvotes: 23

kamoor
kamoor

Reputation: 2939

Solution 1: Since you are hard coding SQL, why not hard code the index

 updateNameEvent = mCursor.getString(0);

Solution 2:

try{
    updateNameEvent = mCursor.getString(mCursor.getColumnIndexOrThrow("name"));
}catch(IllegalArgumentException ie){
    updateNameEvent = 0; 
}

getColumnIndexOrThrow method will throw IllegalArgumentException if column don't exists.

Solution 1 is faster and simple.

Upvotes: 0

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