Question

我正在尝试编写简单的Vaadin表单。我希望在用户点击Button后将TextField中的文本写入Label。

我有这段代码：

package com.example;

import javax.servlet.annotation.WebServlet;

import com.vaadin.annotations.VaadinServletConfiguration;
import com.vaadin.server.VaadinRequest;
import com.vaadin.server.VaadinServlet;
import com.vaadin.ui.Button;
import com.vaadin.ui.Button.ClickEvent;
import com.vaadin.ui.Label;
import com.vaadin.ui.TextField;
import com.vaadin.ui.UI;
import com.vaadin.ui.VerticalLayout;

public class TestForm extends UI {

    @WebServlet(value = "/TestForm", asyncSupported = true)
    @VaadinServletConfiguration(productionMode = false, ui = TestForm.class)
    public static class Servlet extends VaadinServlet {
    }

    private TextField tf;
    private Label lbl;
    private Button btn;

    @Override
    protected void init(VaadinRequest request) {
        final VerticalLayout layout = new VerticalLayout();
        layout.setMargin(true);
        setContent(layout);

        tf = new TextField("Enter text");
        lbl = new Label();
        btn = new Button("Click");    

        btn.addClickListener(new Button.ClickListener() {
            public void buttonClick(ClickEvent event) {
                lbl.setCaption(tf.getValue());
            }
        });

        layout.addComponent(tf);
        layout.addComponent(btn);
        layout.addComponent(lbl);       

    }
}

但是点击Button doensn后发生标签，但网页浏览器显示错误：

通讯问题记下任何未保存的数据，然后单击此处继续。（SyntaxError）stack：eval @ [native code] Jda BR Zc Xc line：340：意外的令牌＆＃39;＆lt;＆＃39; - 原始JSON文本：html＆gt;

我做得不好？

Answer 1

修改问题是你的web.xml中有两个servlet映射。我评论了其中一个：

<强>的web.xml

<?xml version="1.0" encoding="UTF-8"?> <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:web="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="vaadinpokus" version="3.0"> <display-name>vaadintest</display-name> <description>...</description> <context-param> <description>Vaadin production mode</description> <param-name>productionMode</param-name> <param-value>false</param-value> </context-param> <servlet> <servlet-name>myservlet</servlet-name> <servlet-class>com.vaadin.server.VaadinServlet</servlet-class> <init-param> <param-name>UI</param-name> <param-value>com.example.MyVaadinUI</param-value> </init-param> <async-supported>true</async-supported> </servlet> <servlet-mapping> <servlet-name>myservlet</servlet-name> <url-pattern>/*</url-pattern> </servlet-mapping>  </web-app>

现在它应该工作了。感谢您分享您的代码。这种方式调试应用程序更容易。

Answer 2

您应该尝试 lbl.setValue 而不是 lbl.setCaption 。

btn.addClickListener(new Button.ClickListener() {
     public void buttonClick(ClickEvent event) {
         lbl.setValue(tf.getValue());
     }
 });

Vaadin：点击Button后，将文本从TextField设置为Label

2 个答案: