CODEWITHSUNDEEP
androidandroid-cursor
ambit
ambit

Reputation: 1119

Cursor movetofirst() & null pointer exception

I am using a Cursor to fetch some data stored in my SQLite database. The code works fine when my Cursor has some data from the database. But when the Cursor does not contain any data, I get a NullPointerException at cursor.movetofirst() method. I have used a similar code elsewhere but movetofirst() method does not give a NullPointerException elsewhere. I am trying this since a couple of days and I'm not able to figure out what is the problem. Kindly help.

    public class Country extends Activity {

        private DbAdapter mDb;
        private Cursor mCurSugCnt;
        String country=null;

        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.country);

            mDb=new DbAdapter(this);
            mDb.open();

            country= this.getIntent().getExtras().getString("country");
            fillSugCntData(country);

        }

    private void fillSugCntData(String cnt) {
        //I have tried multiple methods. The problem occurs when there is no data returned by any of the methods called
        //mCurSugCnt=mDb.fetchCatNotes("abc");
        mCurSugCnt=mDb.fetchCntNotes(cnt);

        //This is where I called the null pointer exception in case no data is returned by the cursor
        mCurSugCnt.moveToFirst();

    }


---------------------

public Cursor fetchCntNotes(String cnt){

        int id;
        Cursor appfinlist=null;
        Cursor temp=mDb.query(CNT_TABLE, new String[]{KEY_ROWID}, KEY_CNTNM + "=\"" + cnt + "\"", null, null , null, null);
        Cursor applist;

        if(temp.moveToFirst()){
            id=temp.getInt(temp.getColumnIndexOrThrow(DbAdapter.KEY_ROWID));

            applist=mDb.rawQuery("SELECT appcntid FROM appcntlist WHERE cntappid = "+id, null);
            if(applist.moveToFirst()){
                String[] cntin=new String[applist.getCount()];
                for(int i=0;i<applist.getCount();i++){
                    cntin[i]=""+applist.getInt(applist.getColumnIndexOrThrow(DbAdapter.KEY_APPCNTID));
                    Log.d("amit","countryname id cnt var: " + cntin[i]);
                    applist.moveToNext();   
                }

                String query = "SELECT * FROM applist"
                    + " WHERE _id IN (" + makePlaceholders(applist.getCount()) + ")";

                appfinlist = mDb.rawQuery(query, cntin);
                Log.d("amit","countryname id get count: " + appfinlist.getCount());
            }
        }    
            return appfinlist;
    }

    private String makePlaceholders(int count) {
        String toRet="?";

        for (int i=1;i<count;i++){
            toRet=toRet + ",?";
        }
        return toRet;
    }

Upvotes: 2

Views: 6208

Answers (3)

rrrrong
rrrrong

Reputation: 371

check your code

Cursor appfinlist=null; 
Cursor temp=mDb.query(CNT_TABLE, new String[]{KEY_ROWID}, KEY_CNTNM + "=\"" + cnt + "\"", null, null , null, null);

and if there is no record find, after your block of 

if(temp.moveToFirst()){
    ....
}

you return null "appfinlist" to mCurSugCnt

return appfinlist;

that is why you got Nullpointer exception, normally it won't return null object if you call query method to get cursor

Upvotes: 0

Paresh Mayani
Paresh Mayani

Reputation: 128428

If you are getting NullPointerException on mCurSugCnt.moveToFirst(); then you should put some kind of condition to check whether Cursor mCurSugCnt is Null or not before accessing it.

like:

private void fillSugCntData(String cnt) {
         mCurSugCnt = mDb.fetchCntNotes(cnt);
         if(mCurSugCnt != null && mCurSugCnt.getCount() > 0)
         {
            mCurSugCnt.moveToFirst();
         }
    }

Upvotes: 1

Niranj Patel
Niranj Patel

Reputation: 33248

Always check getCount before use it. 

if(mCurSugCnt!=null && mCurSugCnt.getCount()>0 )
{
 mCurSugCnt.moveToFirst();
}

Upvotes: 6

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