WinJS.UI.Repeater 项的事件处理程序绑定到对象方法

Question

我目前正在尝试将 <select> 的 onchange 事件绑定到内部的事件处理程序，该事件处理程序是一个对象方法（JavaScript class 用 TypeScript 编写) 这样：

HTML:

<div id="readerTemplate" data-win-control="WinJS.Binding.Template">
  <div>
    <select class="win-dropdown" 
            data-win-control="WinJS.UI.Repeater" 
            data-win-options="{data: versions}" 
            data-win-bind="value: version; onchange: versionChangeHandler">
      <option data-win-bind="value: fileName; textContent: versionName">
      </option>
    </select>
    <div class="win-type-title" data-win-bind="textContent: version"></div>
  </div>
</div>

JS/TypeScript:

loadTabsUI(pivot: WinJS.UI.Pivot) {
  for (let tab of this.tabs) {
    var tabDiv = document.createElement("div");
    var pivotItemDiv = document.createElement("div");
    var pivotItem = new WinJS.UI.PivotItem(pivotItemDiv);
    pivotItemDiv.setAttribute('data-win-bind', 'winControl.header: title');
    var rptrDiv = document.createElement("div");
    var rptr = new WinJS.UI.Repeater(rptrDiv, { "data": tab.readers, "template": document.getElementById("readerTemplate").winControl });
    pivotItem.contentElement.appendChild(rptrDiv);

    pivot.items.push(pivotItem);

    WinJS.Binding.processAll(pivotItemDiv, tab);
  }
}

进行绑定的行：
var rptr = new WinJS.UI.Repeater(rptrDiv, { "data": tab.readers, "template": document.getElementById("readerTemplate").winControl });

Reader class 方法：

class Reader {
  ...
  ...
  versionChangeHandler(evt: UIEvent): void {
    // goal is to execute the following line:
    this.setVersionAsync((evt.target as any).value);
  }
  ...
  ...
}

当 <select> 的选择发生变化时，versionChangeHandler 会被调用。但是，问题是我无法在函数内部访问正确的 this，这使我无法在正确的对象实例上访问运行 setVersionAsync，也就是那个对象实例被 WinJS.UI.Repeater（在早先的 JS 绑定中）用于 populate/bind readerTemplate.

对解决这个问题有什么想法吗？（我在 Reader class 的构造函数中调用此 WinJS.Utilities.markSupportedForProcessing(this.versionChangeHandler);，否则我会遇到绑定异常。）

谢谢！

Answer 1

However, the issue is that I'm not able to access the correct this inside the function.

因为语境变了。您可以使用以下代码解决此问题：

class Reader {
   public handlerProxy: any;

   constructor() {
     this.handlerProxy = (evt: UIEvent) => { this.versionChangeHandler(evt, this); }
   }
   ...
   ...
   versionChangeHandler(evt: UIEvent,that): void {
     // goal is to execute the following line:
     that.setVersionAsync((evt.target as any).value);
   }
  ...
  ...
}

然后在您的 HTML 中将 versionChangeHandler 更改为 handlerProxy:

<div id="readerTemplate" data-win-control="WinJS.Binding.Template">
<div>
<select class="win-dropdown" 
        data-win-control="WinJS.UI.Repeater" 
        data-win-options="{data: versions}" 
        <!--here change versionChangeHandler to handlerProxy.-->
        data-win-bind="value: version; onchange: handlerProxy">
  <option data-win-bind="value: fileName; textContent: versionName">
  </option>
</select>
<div class="win-type-title" data-win-bind="textContent: version"></div>

WinJS.UI.Repeater 项的事件处理程序绑定到对象方法

Event Handler Binding of WinJS.UI.Repeater item to Object method

javascript

windows

winjs

windows-store-apps

uwp