javascript - mysql lite 数据库 Cordova

Question

我的 cordova 项目中的 mysql lite 数据库有问题。我尝试在我的 htc one x+ 上使用 android 版本 4.2.2 进行测试，但没有任何效果。JavaScript 警报和数据库代码都无法在手机和模拟器上运行。奇怪的是后退按钮的代码可以工作，但此代码中的警报却不能。也许你能找到原因？代码来了。

        <script type="text/javascript" charset="utf-8">
        function onBackButton() {
            console.log("Test");
            alert("Back Button works!");
            window.location = "bearbeiten.html";
        }
        function onLoad() {
            alert("onLoad method works!");
            document.addEventListener("deviceready", onDeviceReadyBb, false);
        }
        function onDeviceReadyBb(){
            document.addEventListener("backbutton", onBackButton, false);
        }
        function saveTopic(){
            //Load the device API libraries 
            document.addEventListener("deviceready", onDeviceReady, false);
        }// Device APIs are now available
        function onDeviceReady() {
            //Create database object
            var db = window.openDatabase("Database", "1.0", "EasyLearning", 200000);
            db.transaction(populateDB, errorCB, successCB);
        }
        //Create database table "topics"
        function populateDB(tx){
            var text = document.getElementById("t1").value;
            alert(text+" is saved in database!");
            var abfrage = tx.executeSql('SELECT COUNT(*) FROM themen WHERE thema ='+text+');
            if(abfrage == 1)
            {
                alert("topic is alredy existing!");
            }
            else{
                alert("New topic will be saved...")
                tx.executeSql('CREATE TABLE IF NOT EXISTS themen (themennr INTEGER AUTO_INCREMENT, thema VARCHAR(10000)');
                tx.executeSql('INSERT INTO themen(thema) VALUES ('+text+')');
            }
        }
        //Shows error if the query is wrong
        function errorCB(tx, err) {
            alert("Error processing SQL: "+err);
        }
        //Shows successful message if it works
        function successCB() {
            alert("Thema erfolgreich gespeichert!");
        }
        </script>

Answer 1

首先，您使用的不是 SQLite，而是 WebSQL。

您的代码存在一些问题，我更改了它的结构，并按照 cordova 文档推荐的最佳实践方式进行了处理，我希望您的问题能够通过查看它得到解决:

    var app = {
            initialize: function() {
            this.bindEvents();
        },
        bindEvents: function(){

            document.addEventListener('deviceready', this.onDeviceReady, false);
            document.addEventListener('backbutton', this.onBackButton, false);

        },
        onBackButton: function(){
            console.log("Test");
            alert("Back Button works!");
            window.location = "bearbeiten.html";
        },
        onDeviceReady: function() {
            var db = window.openDatabase("Database", "1.0", "EasyLearning", 200000);
            db.transaction(populateDB, errorCB, successCB);

        },
        populateDB: function(tx){
           var text = document.getElementById("t1").value;
           alert(text+" is saved in database!");
           var abfrage = tx.executeSql('SELECT COUNT(*) FROM themen WHERE thema ='+text+');
           if(abfrage == 1)
           {
               alert("topic is alredy existing!");
           }
           else{
               alert("New topic will be saved...")
               tx.executeSql('CREATE TABLE IF NOT EXISTS themen (themennr INTEGER AUTO_INCREMENT, thema VARCHAR(10000)');
               tx.executeSql('INSERT INTO themen(thema) VALUES ('+text+')');
           }
        },
        errorCB: function(tx, err) {
            alert("Error processing SQL: "+err);
        },
        //Shows successful message if it works
        successCB: function() {
            alert("Thema erfolgreich gespeichert!");
        }
    }
    app.initialize();

请注意，我没有更改函数的主体，我只是按照函数执行的方式编写它们。在移动设备上测试之前，不要忘记使用浏览器控制台来调试代码。