无法在 Blazor 中移动 Div

Cannot Move Divs in Blazor

我有一个带有以下 DIV 标签的 Blazor 服务器应用程序

<div class=mainScreen id="outerBox" style="width:@(TotalWidth)px;height:@(TotalHeight)px;">
    foreach(Device thisDevice in MyDevices)
    {
      <div class=column id="@MainDiv" style="width:@(thisDevice.Width)px;height:@(thisDevice.Height)px;left:@thisDevice.XCoordinate;top:@thisDevice.YCoordinate">
        Main Content Here...
      </div>
    }
    </div>

我尝试使用此页面中的代码示例设置高度、宽度和 X/Y 坐标 - https://blazor.tips/blazor-how-to-ready-window-dimensions/ 但无论我将其放置在何处,它都没有用,只是抛出了一个未捕获的异常 Try ...块。

然后我转向更直接的 JS 调用:

 await Task.Run(async () =>
 {
  //Commenting out the OnInitializeAsync makes no difference but needs to be commented out when embedded
  //On the main component
  await this.OnInitializedAsync();
  string data = await JSRuntime.InvokeAsync<string>("getMyWindow", new object[] { });
  JObject offsets = (JObject)JsonConvert.DeserializeObject(data);
  TotalHeight = offsets.Value<int>("height");
  TotalHeight = offsets.Value<int>("width");
}

//In my JS file, the function looks as follows:
function getMyWindow() {
    var obj = {};
    obj.width = window.width;
    obj.height = window.height;
    return JSON.stringify(obj);
}

如果我直接在代码中进行此调用,则什么也不会发生 - 即使 OnInitializeAsync 已被注释掉。

var result = SetDimensions().Result;

如果我将此方法放在 OnAfterRendor 方法中:

protected override void OnAfterRender(bool firstRender)
{
    if (firstRender)
    {
        if (!SetTheDivs)
            SetTheDivs = SetDimensions().Result;

        StateHasChanged();
    }
}
 
protected override void OnInitialized()
{
   base.OnInitialized();
   this.OnAfterRender(true);
}

一切都挂起,直到我终止该项目。从来没有任何错误,但是当我在高度或宽度语句上放置断点时,代码永远不会 运行s。

我什至在异步版本中添加也无济于事:

protected override async Task OnAfterRenderAsync(bool firstRender)
{
    if (firstRender)
    {
        await SetDimensions();

        StateHasChanged();
    }
}

protected override async Task OnInitializedAsync()
{
    await this.OnAfterRenderAsync(true);
}

与所有内容挂起的结果相同。我完全不知道如何继续,我真的需要一些帮助!

为了清楚起见,是对 JS 的调用导致了挂起:

string data = await JSRuntime.InvokeAsync<string>("getMyWindow", new object[] { });

我添加了一些警报,但它们从来没有 运行:

function getMyWindow() {
    var obj = {};
    alert("hi");
    obj.width = screen.width;
    obj.height = screen.height;
    alert("ho");
    return JSON.stringify(obj);
}

感谢您的宝贵时间!

顺便说一句 - 我确实将双重等待更改为 string data = JSRuntime.InvokeAsync<string>("getMyWindow", new object[] { }).Result;

更新:我将 JS 调用完全移到了 await 之外,我得到了错误:

InvalidOperationException:JavaScript 此时无法发出互操作调用。这是因为组件是静态渲染的。启用预呈现后,JavaScript 互操作调用只能在 OnAfterRenderAsync 生命周期方法期间执行。

在这种情况下,我实际上是从 OnAfterRenderAsync 方法调用方法:

protected override async Task OnAfterRenderAsync(bool firstRender)
{
    await base.OnInitializedAsync();
    if (firstRender)
    {
        await SetDimensions();

        StateHasChanged();
    }
}

不确定您想要什么...复制下面的代码并运行它,然后告诉我们这是否是您想要的。

Index.razor

@page "/"

<div class=mainScreen id="outerBox" style="width:@($"{TotalWidth}px");height:@($"{TotalHeight}px"); background-color: green; top:60px; position:absolute">
    @foreach (Device device in devices)
    {
    <div class=column style="width:@($"{device.Width}px");height:@($"{device.Height}px");margin-left:@($"{device.Left}px");margin-top:@($"{device.Top}px"); background-color:aliceblue">
       @device.Name: Main Content Here...
    </div>
    }
</div>

@code {
    private int TotalWidth = 520;
    private int TotalHeight = 530;

    private IList<Device> devices = Enumerable.Range(1, 5).Select(i => new Device { Name = $"Name {i}", Width = 520, Height = 100, Left = 0, Top = 5 }).ToList();

    public class Device
    {
        public string Name { get; set; }
        public int Width { get; set; }
        public int Height { get; set; }
        public int Left { get; set; }
        public int Top { get; set; }
    }
}

注意:OnInitialized{Async} 对方法是基础的生命周期方法 class ComponentBase. 它们在创建 Razor 组件时由 Blazor 框架自动调用.它们只执行一次。您可以覆盖它们,并添加您的逻辑,但您永远不应该从您的代码中手动调用它们。

这个:

protected override async Task OnInitializedAsync()
{
    await this.OnAfterRenderAsync(true);
} 

这是错误的,绝不能这样做。您不应该调用 OnAfterRender{Async}. 应该调用 OnAfterRender{Async} 的是 Blazor 框架,而不是开发人员。你能试着理解你的代码在做什么吗...

尝试了解虽然 Razor 组件定义为 C# classes,但它们是 类 的特例,需要框架进行特殊处理...

更新

Ken Tola,我相信以下代码可以满足您的需求。它读取 window 对象的宽度和高度,将其传递给 Index 组件,并重新定位您亲爱的 divs。请注意,在应用重新定位 div 之前,我检查了宽度和高度的值,并确定了 div 的尺寸。这当然是为了演示目的而完成的,您可以根据需要操作这些值...

Index.razor

@page "/"
    
@implements IDisposable
@inject IJSRuntime JSRuntime

    
<div class=mainScreen id="outerBox" style="width:@($" {TotalWidth}px");height:@($"{TotalHeight}px"); background-color: green; top:60px; position:absolute">
    @foreach (Device device in devices)
    {
        <div class=column style="width:@($" {device.Width}px");height:@($"{device.Height}px");margin-left:@($"{device.Left}px");margin-top:@($"{device.Top}px"); background-color:aliceblue">
            @device.Name: Main Content Here...
        </div>
    }
</div>

@code
{

    private DotNetObjectReference<BrowserService> objRef;
    private BrowserService BSS;

    private int TotalWidth; 
    private int TotalHeight; 

    private IList<Device> devices = Enumerable.Range(1, 5).Select(i => new Device { Name = $"Name {i}", Width = 520, Height = 100, Left = 0, Top = 5 }).ToList();

    public class Device
    {
        public string Name { get; set; }
        public int Width { get; set; }
        public int Height { get; set; }
        public int Left { get; set; }
        public int Top { get; set; }
    }
      
    protected override void OnInitialized()
    {
        BSS = new BrowserService();

        objRef = DotNetObjectReference.Create(BSS);

        BSS.Notify += OnNotify;
    }
    
    public void Dispose()
    {
        BSS.Notify -= OnNotify;

        objRef?.Dispose();
    }

    public async Task OnNotify()
    {
        // Note that the notifier only notify your component 
        // that data is ready, and that the dimensions are read
        // from a property. You can instead define event handler
        // that pass the data in the form of EventArgs... 
        TotalWidth = BSS.Dimension.Width >= 877 ? 520 : 550;
        TotalHeight = BSS.Dimension.Height >= 550 ? 800 : 1200;
    
        await InvokeAsync(() => StateHasChanged());
    }

    protected override async Task OnAfterRenderAsync(bool firstRender)
    {
        // This code is excuted only once, in order to initialize
        // the JavaScript objects
        if (firstRender)
        {
            await JSRuntime.InvokeAsync<object> 
                  ("myJsFunctions.getDimensions", objRef);
                
        }
    }

}

BrowserService.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.Json;
using System.Threading.Tasks;
using Microsoft.JSInterop;

 public class BrowserService
    {
        public event Func<Task> Notify;
#nullable enable
        public Dimension? Dimension { get; set; }
#nullable disable

        [JSInvokableAttribute("GetDimensions")]
        public async Task GetDimensions(string dimension)
        {
            JsonSerializerOptions options = new(JsonSerializerDefaults.Web)
            {
                WriteIndented = true
            };
            var _dimension = System.Text.Json.JsonSerializer.Deserialize(dimension, typeof(Dimension), options);
            Dimension = (Dimension)_dimension;

            if (Notify != null)
            {
                await Notify?.Invoke();
            }
        }
    }
    public class Dimension
    {
        public int Width { get; set; }
        public int Height { get; set; }

    }
}

Startup.ConfigureServices

services.AddScoped<BrowserService>();

_Host.cshtml

<script src="_framework/blazor.server.js"></script>

<script type="text/javascript">
    window.myJsFunctions = {

        getDimensions: function (dotnetHelper) {
            var dimension = {
                 width: window.innerWidth,
                 height: window.innerHeight
            };
            var json = JSON.stringify(dimension);

            return dotnetHelper.invokeMethodAsync('GetDimensions', json);
        }
    };
</script>

注意:考虑在 window 调整大小时处理 div 元素的重定位。它应该是响应式的,对吧?不确定您的情况是否可以使用媒体查询。无论如何,如您所见,我设计代码的方式考虑到您的 div 元素可能需要一次又一次地重新定位,因此它会不断(在调整大小时)通知您的 Index 组件变化的维度。我想这值得提出一个新问题......