PhoneGap / JQuery Mobile dbShell questions - jquery-mobile

Question

I am trying to do a query everytime the user changes a page in a phonegap app. I am new to Phonegap/JQuery Mobile, but don't understand what is going on.
When I click a button, the pagebeforechange is getting called twice.
First time it works correctly. Next call, it does not run the dbshell.transaction, and no error is shown. So, if I click the overview page first, it works, but the other page does not. If I click the other page first, the overview page does not work. In both cases, re-visiting the same page does not re-do the query.
What's going on here? It must be something incorrect with the way I am calling dbshell?
//Listen for any attempts to call changePage().
$(document).bind( "pagebeforechange", function( e, data ) {
alert("pagebeforechange");
// We only want to handle changePage() calls where the caller is
// asking us to load a page by URL.
if ( typeof data.toPage === "string" ) {
// We are being asked to load a page by URL, but we only
// want to handle URLs that request the data for a specific
// category.
var u = $.mobile.path.parseUrl( data.toPage ),
reOverviewPage = /^#overviewPage/,
reViewByType = /^#viewByType/,
pageUrl=data.toPage;
var params = parseParams(pageUrl.substr(pageUrl.lastIndexOf("?") + 1));
if ( u.hash.search(reOverviewPage) !== -1 ) {
alert("overview");
dbShell.transaction(function(tx) {
alert("doing query");
tx.executeSql("select _id, description from area where _id=?",[params['id']],renderOverview,dbErrorHandler);
},dbErrorHandler);
} else if (u.hash.search(reViewByType) !== -1 ) {
alert("viewByType");
dbShell.transaction(function(tx) {
try
{
alert("!");
tx.executeSql("select trip.* from trip, trip_type, trip_type_lookup where trip_type.trip_id = trip._id and trip_type_lookup._id = trip_type.trip_type_lookup_id and lower(trip_type_lookup.type_name) = ?",[params['type']],dbErrorHandler, renderViewByType);
}
catch(e)
{
alert(e.message);
}
},dbErrorHandler);
}
}
});