JavaApacheWicket：按下按钮后更新标签的值

1 月，3 周 Questions & Answers 5828

我已经开始学习ApacheWicket web框架，在完成一项任务时遇到了一些困难

如果你能从附件中看到，我去了http://www.wicket-library.com/wicket-examples-6.0.x/echo/

尝试此基本输入表单功能

我的问题是：最初我不想在标签字段中显示任何内容，但一旦单击设置消息按钮，我就想更新标签值。我该怎么做？谢谢

enter image description here

更新：

回音中的代码。java，如下所示。PropertyModel随附标签，用于更新值

/*
 * 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>

# 1 楼答案

试试这个：

add(new Label("msg", messageModel)) {
  @Override public boolean isVisible() {
    return !messageModel.getObject().equals(message);
  }
};

文本字段需要知道应该在何时呈现。请注意，如果希望通过Ajax使组件可见，则需要在Label上设置setOutputMarkupId(true)和setOutputMarkupPlaceholderTag(true)，例如submit组件是AjaxSubmitButton

当执行比String比较更复杂的任务时，应该从重写的onConfigure方法调用setVisible，如注释中所述^在渲染阶段，{}可能会被多次调用，以避免计算。如下所示：

add(new Label("msg", messageModel)) {
  @Override protected void onConfigure() {
    super.onConfigure();
    setVisible(!messageModel.getObject().equals(message));
  }
};

不过，千万别忘了调用super方法

为了提高代码的可读性，我个人更喜欢覆盖isVisible方法，以完成像String比较这样的简单任务。JIT编译器通常负责其余部分

共 (1) 个答案

# 1 楼答案
试试这个：
```
add(new Label("msg", messageModel)) {
  @Override public boolean isVisible() {
    return !messageModel.getObject().equals(message);
  }
};
```
文本字段需要知道应该在何时呈现。请注意，如果希望通过Ajax使组件可见，则需要在Label上设置setOutputMarkupId(true)和setOutputMarkupPlaceholderTag(true)，例如submit组件是AjaxSubmitButton

当执行比String比较更复杂的任务时，应该从重写的onConfigure方法调用setVisible，如注释中所述^在渲染阶段，{}可能会被多次调用，以避免计算。如下所示：
```
add(new Label("msg", messageModel)) {
  @Override protected void onConfigure() {
    super.onConfigure();
    setVisible(!messageModel.getObject().equals(message));
  }
};
```
不过，千万别忘了调用super方法

为了提高代码的可读性，我个人更喜欢覆盖isVisible方法，以完成像String比较这样的简单任务。JIT编译器通常负责其余部分

Python中文网

有 Java 编程相关的问题?

JavaApacheWicket：按下按钮后更新标签的值

共 (1) 个答案

# 1 楼答案