Question

我使用html5和javascript创建移动Web应用程序。我有两个javascript文件。 AttributesDatabase.js和AttributeView.js.From AttributeView.js我从AttributeDatabase.js中调用一个函数，即我执行一个select查询。现在查询结果应该转到AtttributeView.js.But Websql事务是异步调用那是什么呢没有返回正确的结果。有没有办法处理websql结果。请帮忙，如果有的话？

被修改

AttributeView.js

var AttributeDAOObj = new AttributeDAO();

AttributeDAOObj.GetAttributeList();
alert(AttributeDAOObj.GetAttributeList());  //This alert is coming as undefined.   

AttributeDAO.js
this.GetAttributeList = function () {
    var baseDAOObj = new BaseDAO();
    var query = "SELECT AttributeName FROM LOGS";
    //  this.Successcalbackfromsrc = this.myInstance.Successcalback;
    var parm = { 'query': query, 'Successcalback': this.myInstance.Successcalback };
    baseDAOObj.executeSql(parm);
}

//To Create database and execute sql queries.
function BaseDAO() {
this.myInstance = this;
//Creating database
this.GetMobileWebDB = function () {
    if (dbName == null) {
        var dbName = 'ABC';
    }
    var objMobileWebDB = window.openDatabase(dbName, "1.0", dbName, 5 * 1024 * 1024);
    return objMobileWebDB;
}

//Executing queries and getting result 
this.executeSql = function (query) {
    var objMobileWebDB = this.myInstance.GetMobileWebDB();
    objMobileWebDB.transaction(function (transaction) {
 //In this transaction i m returning the result.The result value is coming.
        transaction.executeSql(query, [], function (transaction, result) { return result; }, this.Errorclback);
    });
}

}

Answer 1

问题在于你成功回电（比如你的问题的评论，由DCoder说明）

 function (transaction, result) { return result; }

这是回到哪里？

所以这是如何做到的（或者至少是一种方式）

你可以这样做：

function (transaction,result){
   console.log("yes, I have some result, but this doesn't say anything, empty result gives also a result");
   // so check if there is a result:
    if (result != null && result.rows != null) {
       if (result.rows.length == 0) {
            // do something if there is no result
       }else{
            for ( var i = 0; i < result.rows.length; i++) {
                var row = result.rows.item(i);
                var id = result.rows.item(i).id; //supposing there is an id in your result
                console.log('Yeah! row id = '+id);
            }
        }
    }else{
       // do something if there is no result
    }
};

请注意，上面的代码可以更加紧凑，但这是如何更好地理解它。

另一种方法是把这个函数放在一个单独的代码片段中，这样你就可以保持sql语句更加紧凑和可读。就像你称之为错误回调一样，这可以在你的函数中（在它之前。）或一个完全独立的函数。

如何在html 5中处理websql的结果集？

1 个答案: