page before database - phonegap

问题

I have a page that has to display information from a websql database. However the page loads with blanks, even though the information is in the database. I am guessing that the page gets populated before the database is open / active? Is there anything I can do so slow the page load or speed up the database load?

回答1:

I was struggling with the same issue. Below is the sample db service function code.

Reason this was happening because web-sql calls are asynchronous. For example, below getItemData is returning itemData before mapItemRow converts the resultset into required object type.

getItemData:function(){
            var itemData= [];
            _dbCon.transaction(function (tx) {
            var queryExp = 'SELECT description as Item, amount as Amount from inventory';
                tx.executeSql(queryExp, [],mapItemRow);
            }, dbConnectionFactory.errorDBSql, dbConnectionFactory.successDBSql);

            function mapItemRow(tx, results) {
                console.log('Calling mapItemRow....')
                var len = results.rows.length;
                for (i = 0; i < len; i++) {
                    itemData.push({ITEM: results.rows.item(i).description, Amount: results.rows.item(i).amount});
                }
                return itemData;
            };
        }

I am also using angularJs so to fix this problem i used $q and promise functionality. Let me know if you are interested to see the solution.

In your case you can use settimeout functionality:

var millisecondsToWait = 500;
setTimeout(function() {
    // call your db service
}, millisecondsToWait);

You can also implement solution like waitfor mentioned in following link: Wait until a condition is true?

You can also think of using some other db libraries which can handle these asynch calls like jaydata or breeze.

Hope this helps you.

来源：https://stackoverflow.com/questions/21402597/page-before-database-phonegap

标签

cordova

web-sql