[英]Apache Wicket : Update value of the Label after the Button has been pressed
我已經開始學習Apache Wicket Web框架,並且在執行任務時遇到了一些困難。
如果您可以從所附的圖片中看到,我去了http://www.wicket-library.com/wicket-examples-6.0.x/echo/ ,
試用此基本輸入表單功能。
我的問題是:我最初不想在“標簽”字段中顯示任何內容,但是一旦單擊“設置消息”按鈕后,我想更新“標簽”值。 我怎么做 ? 謝謝
更新 :
下面顯示了echo.java中的代碼。 一個PropertyModel隨Label一起附加,以更新值。
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.wicket.examples.echo;
import org.apache.wicket.examples.WicketExamplePage;
import org.apache.wicket.markup.html.basic.Label;
import org.apache.wicket.markup.html.form.Form;
import org.apache.wicket.markup.html.form.TextField;
import org.apache.wicket.model.PropertyModel;
/**
* The simplest form application possible. Just prints any user input to a label.
*
* @author Eelco Hillenius
*/
public class Echo extends WicketExamplePage
{
private String message = "[type your message to the world here]";
/**
* Constructor.
*/
public Echo()
{
// This model references the page's message property and is
// shared by the label and form component
PropertyModel<String> messageModel = new PropertyModel<String>(this, "message");
// The label displays the currently set message
add(new Label("msg", messageModel));
// Add a form to change the message. We don't need to do anything
// else with this form as the shared model is automatically updated
// on form submits
Form<?> form = new Form("form");
form.add(new TextField<String>("msgInput", messageModel));
add(form);
}
/**
* @return the message
*/
public String getMessage()
{
return message;
}
/**
* @param message
* the message to set
*/
public void setMessage(String message)
{
this.message = message;
}
}
html文件如下所示:
<?xml version="1.0" encoding="UTF-8"?>
<html xmlns="http://www.w3.org/1999/xhtml" xmlns:wicket="http://wicket.apache.org">
<head>
<title>Wicket Examples - echo</title>
<link rel="stylesheet" type="text/css" href="style.css"/>
</head>
<body>
<span wicket:id="mainNavigation"/>
<form wicket:id="form">
<input type="text" wicket:id="msgInput" value="" size="50" />
<input type="submit" value="set message" />
</form>
<span wicket:id="msg" id="msg">Message goes here</span>
</body>
</html>
嘗試這個:
add(new Label("msg", messageModel)) {
@Override public boolean isVisible() {
return !messageModel.getObject().equals(message);
}
};
文本字段需要知道何時應呈現。 請注意,如果要通過Ajax使組件可見,則需要在Label
上設置setOutputMarkupId(true)
和setOutputMarkupPlaceholderTag(true)
,例如, submit
組件例如是AjaxSubmitButton
。
當執行比String
比較更復雜的任務時,您應該從重寫的onConfigure
方法調用setVisible
,如注釋中所述。 在渲染階段可能多次調用isVisible
,以便避免計算。 如下所示:
add(new Label("msg", messageModel)) {
@Override protected void onConfigure() {
super.onConfigure();
setVisible(!messageModel.getObject().equals(message));
}
};
但是,永遠不要忘記調用super
方法。
為了提高代碼的可讀性,我個人更喜歡覆蓋isVisible
方法來完成諸如所需的String
比較之類的簡單任務。 JIT編譯器通常會處理其余的工作。
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