Blazor中日益增长的TextArea [英] Growing TextArea in Blazor

问题描述

我需要一个随着行数增加而增加的文本区域.删除行后，TextArea应该会再次缩小.最好是最大高度.

I need a text area that grows as the number of lines increases. As soon as lines are deleted, the TextArea should shrink again. In the best case with a maximum height.

它如何与Javascript一起工作我已经在这里阅读了: > textarea-to-resize-based-on-content-length

How it works with Javascript I could already read here: textarea-to-resize-based-on-content-length

但是不幸的是，据我所知，在Blazor中，TextArea没有可用的"scrollHeight".

But in Blazor I have unfortunately, as far as I know, no "scrollHeight" available for the TextArea.

(我的问题与 Blazor框架有关，使用C#(+ HTML/CSS)而不是WPF/WinForms等桌面UI的浏览器前端开发.

(My problem relates to the Blazor framework, which allows browser frontend development using C# (+HTML/CSS) and not a desktop UI like WPF/WinForms.)

推荐答案

只要您知道文本中有多少行，就可以像这样使用TextView上的行"属性

As long as you know how many lines are in your text, you can just use the "rows" attribute on the TextView, like this

<textarea rows="@Rows"
          @bind-value="MyText"
          @bind-value:event="oninput" />

在代码中，您可以确定Rows的值

And in your code, you can determine the value for Rows

请注意，我使用Math.Max(Rows，2)至少保留两行.

Note, I use Math.Max(Rows,2) to keep a minimum of two rows.

private void CalculateSize(string value)
{
  Rows = Math.Max(value.Split('\n').Length, value.Split('\r').Length);
  Rows = Math.Max(Rows, 2);
}

我从处理"MyText"更改的代码中调用CalculateSize-这样的自定义设置器或A.N.Other方法

I call CalculateSize from code that handles changes to "MyText" - either a custom setter like this or A.N.Other method

string _myText;
protected string MyText
{
  get => _myText;
  set
  {
    _myText = value; 
    CalculateSize(value);
  }
}

通过设计方法的CSS或在CalculateSize方法中添加另一个约束，可以轻松设置最大高度.

The maximum height can easily be set either through CSS for a design approach or by adding another constraint to the CalculateSize method.

private void CalculateSize(string value)
{
  Rows = Math.Max(value.Split('\n').Length, value.Split('\r').Length);
  Rows = Math.Max(Rows, MIN_ROWS);
  Rows = Math.Min(Rows, MAX_ROWS);
}

---

选项2

如果您想要简单并且不介意使用内联JS(如果您这样做，那么该是时候打开JSInterop了.)

---

Option 2

If you want simplicity and don't mind a bit of inline JS (if you do, then it's time to crack open the JSInterop....)

<textarea 
      rows="2" 
      placeholder="Sample text."
      style="resize:both;"
      oninput="this.style.height = 'auto'; this.style.height = (this.scrollHeight) + 'px';">
</textarea>

---

选项3

如果您确实想使用JSInterop，则可以执行类似的操作或将您的代码放在JS文件中并将其包含在页面中.

---

Option 3

If you did want to use JSInterop, you could do something like this or place your code in a JS file and include it in the page.

<textarea id="MyTextArea"
      rows="2" 
      placeholder="Sample text."
      @oninput="Resize"></textarea>

<label>This area is @(MyHeight)px</label>
@code
{
[Inject] IJSRuntime JSRuntime { get; set; }
double MyHeight=0;
async Task Resize()
{
    var result = await JSRuntime.InvokeAsync<object>("eval",@"(function() {
            MyTextArea.style.height='auto';
            MyTextArea.style.height=(MyTextArea.scrollHeight)+'px';
            return MyTextArea.scrollHeight;
        })()");
    Double.TryParse(result.ToString(), out MyHeight);
}
}

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