javascript - Lightswitch HTML 自定义控件仅显示一次

Question

我有一个带有一个自定义控件的 LS 项目，我在其中使用 Chartjs 渲染图表。第一次加载页面时一切正常，但如果我移动到另一个页面然后返回，自定义控件将不再呈现(代码被调用但没有任何显示)。每次想看都得按F5!

我该如何解决这个问题？

更新: 我注意到，如果我设置了一个全局变量，当我回到屏幕时，该变量不会被重新初始化。另一个包含 jquery-week 日历的页面也有同样的问题。当我离开屏幕并稍后返回时，我会加载“屏幕”的另一个实例，还是只获取旧的实例，所有内容都已加载？

这里是代码

/// <reference path="~/GeneratedArtifacts/viewModel.js" />

function updateGraphs(chart, query, inizio, fine) {
    var last = 0;
    for (var i = inizio; i <= fine; i.addDays(1)) {
        query(i).execute().then(function (res) {
            try {
                if (chart.datasets[0].points.length > 25)
                    chart.removeData();
                var date = new Date(inizio.valueOf()).addDays(last++);
                var str = format_2digit(date.getDate()) + "/" + format_2digit(date.getMonth() + 1) + "/" + date.getFullYear();
                chart.addData([res.results.length], last % 5 == 0 ? str : "");
            }
            catch (e) { alert(e); }
        });
    }
}

myapp.Home.created = function (screen) {
    var now = new Date();
    var month = now.getMonth();
    var year = now.getFullYear();

    screen.GraficoInizio = new Date(year, month, 1);
    screen.GraficoFine = new Date(year, month + 1, 0);
};

myapp.Home.GraficoFine_postRender = function (element, contentItem) {
    contentItem.dataBind("screen.GraficoInizio", function (value) {
        var month = contentItem.screen.GraficoInizio.getMonth();
        var year = contentItem.screen.GraficoInizio.getFullYear();
        contentItem.value = new Date(year, month + 1, 0);
    });
};

myapp.Home.GraficoClienti_render = function (element, contentItem) {
    // creo il grafico

    $(element).append("<canvas id='chartClienti' width='500px' height='300px' />");
    var ctx = $('#chartClienti').get(0).getContext("2d");
    var chart = new Chart(ctx);

    var data = {
        labels: [],
        datasets: [
            {
                label: [],
                fillColor: "rgba(220,220,220,0.2)",
                strokeColor: "rgba(220,220,220,1)",
                pointColor: "rgba(220,220,220,1)",
                pointStrokeColor: "#fff",
                pointHighlightFill: "#fff",
                pointHighlightStroke: "rgba(220,220,220,1)",
                data: []
            }
        ]
    };

    chart = chart.Line(data, { animationSteps: 15 });
    contentItem.dataBind("screen.GraficoInizio", function (value) {
        updateGraphs(chart, myapp.activeDataWorkspace.ApplicationData.AbbonamentiAttivi,contentItem.screen.GraficoInizio, contentItem.screen.GraficoFine);
    });
    contentItem.dataBind("screen.GraficoFine", function (value) {
        updateGraphs(chart, myapp.activeDataWorkspace.ApplicationData.AbbonamentiAttivi, contentItem.screen.GraficoInizio, contentItem.screen.GraficoFine);
    });
};

myapp.Home.StampaQRCode_execute = function (screen) {
    var popup = window.open("../QRCode.aspx");
    popup.focus();
};

Answer 1

当您导航到另一个页面时，Lightswitch 不会从页面中删除(隐藏)html 元素。 -> 这就是“后退按钮”的工作原理，它显示/设置“旧页面”可见。

当您导航回页面源代码中的页面时，您将能够找到多个“chartClienti”元素。

一种可能的解决方案是删除该元素(如果它已存在):

myapp.Home.GraficoClienti_render = 函数(元素，contentItem){ //creo il grafico

var existedChart = $('#chartClienti');
//element exists if it's length is more than 0
if (existedChart.length > 0) { 
    existedChart.remove();
}

$(element).append("<canvas id='chartClienti' width='500px' height='300px' />");
var ctx = $('#chartClienti').get(0).getContext("2d");
var chart = new Chart(ctx);

var data = {
    labels: [],
    datasets: [
        {
            label: [],
            fillColor: "rgba(220,220,220,0.2)",
            strokeColor: "rgba(220,220,220,1)",
            pointColor: "rgba(220,220,220,1)",
            pointStrokeColor: "#fff",
            pointHighlightFill: "#fff",
            pointHighlightStroke: "rgba(220,220,220,1)",
            data: []
        }
    ]
};

chart = chart.Line(data, { animationSteps: 15 });
contentItem.dataBind("screen.GraficoInizio", function (value) {
    updateGraphs(chart, myapp.activeDataWorkspace.ApplicationData.AbbonamentiAttivi,contentItem.screen.GraficoInizio, contentItem.screen.GraficoFine);
});
contentItem.dataBind("screen.GraficoFine", function (value) {
    updateGraphs(chart, myapp.activeDataWorkspace.ApplicationData.AbbonamentiAttivi, contentItem.screen.GraficoInizio, contentItem.screen.GraficoFine);
});

};

更好的解决方案如下: A) 获取具有该 id 的所有元素并更新最新的。 B) 每次呈现控件时都提供唯一的 id(自动递增 1:chartClienti0、chartClienti1、...chartClientiN)