Question

So I’m working on a game for android and I’m currently stuck at the ‘load savegame’ button in the main menu.
This button calls methods that read data from the database and write it into a resource class from which on this data will be accessed.

The problem is: I want to disable the load button if there are no rows in the tables, which means that no savegame exists.

To do this I used the following method:

public boolean checkForTables(){
    boolean hasTables;
    String[] column = new String[1];
    column[0] = "Position";
    Cursor cursor;
    cursor = db.query("itemtable", column, null, null, null, null, null);
    if(cursor.isNull(0) == true){
        hasTables=false;
    }else{
        hasTables=true;
    }
    return hasTables;

As you can see it starts a query on one of the database tables and checks if the 0-column, which is the only one that should be in this cursor, is null. ATM I can’t check logcat results on this call because I seem to have some problems with it, but it seems that the query throws an exception because the table is empty.

Any idea to check the tables for rows?

____________________EDIT______________

NOTE: I checked the database and it sure is empty

Okay I used a rawQuery on the table but the approach with count-statement produced an error, so I’m using

public boolean checkForTables(){
        boolean hasTables;

        Cursor cursor = db.rawQuery("SELECT * FROM playertable", null);

        if(cursor.getCount() == 0){
            hasTables=false;
        if(cursor.getCount() > 0){
            hasTables=true;
        }

        cursor.close();
        return hasTables;
    }

I’m using this method to decide whether or not to disable the loadGame-button which looks like this:

loadGame = (ImageButton) findViewById(R.id.loadButton);
    loadGame.setEnabled(databaseAccess.checkForTables());
    loadGame.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View v) {
            databaseAccess.loadPlayer();
            databaseAccess.loadItems();
            databaseAccess.dropTables();

        }
    });

So if checkForTables gets a rowcount of != 0 it will return true and therefore enable the Button, or disable it if rowcount = 0

Amusingly, although the tables are empty, checkForTables() returns true because getCount() seems to return a != 0 value – I just don’t get it.

Answer 1

Perform a query such as select count(*) from itemtable. This query will yield you a single integer result, containing the number of rows in that table.

For example:

Cursor cursor = db.rawQuery("SELECT count(*) FROM itemtable");
if (cursor.getInt(0) > 0) ... // there are rows in the table

————————————————————————————-

Please note that the following edit was attempted by @PareshDudhat but was rejected by reviewers. I have not kept up with Android since this answer was posted, but a very brief bit of research suggests the edit (at least the change to how rawQuery() is called, I didn’t inspect the moveToFirst() but @k2col’s comment suggests it is required now as well) has merit.

Cursor cursor = db.rawQuery("SELECT count(*) FROM itemtable",null);
cursor.moveToFirst();
if (cursor.getInt(0) > 0) ... // there are rows in the table