Cursor while loop returning every value but the last

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旧巷少年郎
旧巷少年郎 2021-01-12 16:59

I am using a while loop to iterate through a cursor and then outputing the longitude and latitude values of every point within the database.

For some reason it is n

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  • 2021-01-12 17:28

    You just executed the query. Can't you just get rid of the moveToFirst()?

    public void loadTrack() {
    SQLiteDatabase db1 = waypoints.getWritableDatabase();
    Cursor trackCursor = db1.query(TABLE_NAME, FROM, "trackidfk=1", null, null, null,ORDER_BY); 
    
        while (trackCursor.moveToNext()) {
            Double lat = trackCursor.getDouble(2);
            Double lon = trackCursor.getDouble(1);
            //overlay.addGeoPoint( new GeoPoint( (int)(lat*1E6),  (int)(lon*1E6)));
            System.out.println(lon);
            System.out.println(lat);
        }
    }
    
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  • 2021-01-12 17:32
    Cursor c=null;
    c=......;
    try {
        if (c!=null) {
            for (c.moveToFirst(); !c.isAfterLast(); c.moveToNext()) {
    
            }
    
        }
    } finally {
        if (c!=null) {
            c.close();
        }
    }
    
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  • 2021-01-12 17:50

    Your skipping the first value actually, not the last.

    trackCursor.moveToFirst();
    while (trackCursor.moveToNext()) {
    

    The first time into the while loop you are pointing at the 2nd row.

    I would convert your while loop to a do-while loop

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  • 2021-01-12 17:54

    moveToNext() has two features. It returns a boolean signifying that there is a next, but at the same time it goes ahead and moves the cursor.

    public void loadTrack() {
    SQLiteDatabase db1 = waypoints.getWritableDatabase();
    Cursor trackCursor = db1.query(TABLE_NAME, FROM, "trackidfk=1", null, null, null,ORDER_BY); 
    
        trackCursor.moveToFirst();
        do {
            Double lat = trackCursor.getDouble(2);
            Double lon = trackCursor.getDouble(1);
            //overlay.addGeoPoint( new GeoPoint( (int)(lat*1E6),  (int)(lon*1E6)));
            System.out.println(lon);
            System.out.println(lat);
        } while (trackCursor.moveToNext());
    }
    
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