java - 带有 Activity 编辑器的 Vaadin 双击网格上的按钮会引发异常 ("java.lang.NullPointerException: Editor can' t edit null")

Question

我有一个带有 Activity 缓冲编辑器的 vaadin 网格。默认情况下，双击一行时会打开编辑器。一切正常，除非我双击按钮时出现异常:(异常未指向我的代码中的任何位置)

java.lang.NullPointerException: Editor can't edit null
at java.base/java.util.Objects.requireNonNull(Objects.java:246)
at com.vaadin.ui.components.grid.EditorImpl.doEdit(EditorImpl.java:216)
at com.vaadin.ui.components.grid.EditorImpl$1.bind(EditorImpl.java:151)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:564)
at com.vaadin.server.ServerRpcManager.applyInvocation(ServerRpcManager.java:155)
at com.vaadin.server.ServerRpcManager.applyInvocation(ServerRpcManager.java:116)
at com.vaadin.server.communication.ServerRpcHandler.handleInvocation(ServerRpcHandler.java:445)
at com.vaadin.server.communication.ServerRpcHandler.handleInvocations(ServerRpcHandler.java:410)
at com.vaadin.server.communication.ServerRpcHandler.handleRpc(ServerRpcHandler.java:274)
at com.vaadin.server.communication.PushHandler.lambda$new$1(PushHandler.java:145)
at com.vaadin.server.communication.PushHandler.callWithUi(PushHandler.java:235)
at com.vaadin.server.communication.PushHandler.onMessage(PushHandler.java:520)
at com.vaadin.server.communication.PushAtmosphereHandler.onMessage(PushAtmosphereHandler.java:87)
at com.vaadin.server.communication.PushAtmosphereHandler.onRequest(PushAtmosphereHandler.java:77)
at org.atmosphere.cpr.AsynchronousProcessor.action(AsynchronousProcessor.java:223)
at org.atmosphere.cpr.AsynchronousProcessor.suspended(AsynchronousProcessor.java:115)
at org.atmosphere.container.Servlet30CometSupport.service(Servlet30CometSupport.java:67)
at org.atmosphere.cpr.AtmosphereFramework.doCometSupport(AtmosphereFramework.java:2284)
at org.atmosphere.websocket.DefaultWebSocketProcessor.dispatch(DefaultWebSocketProcessor.java:593)
at org.atmosphere.websocket.DefaultWebSocketProcessor$3.run(DefaultWebSocketProcessor.java:345)
at org.atmosphere.util.VoidExecutorService.execute(VoidExecutorService.java:101)
at org.atmosphere.websocket.DefaultWebSocketProcessor.dispatch(DefaultWebSocketProcessor.java:340)
at org.atmosphere.websocket.DefaultWebSocketProcessor.invokeWebSocketProtocol(DefaultWebSocketProcessor.java:447)
at org.atmosphere.container.JSR356Endpoint$3.onMessage(JSR356Endpoint.java:272)
at org.atmosphere.container.JSR356Endpoint$3.onMessage(JSR356Endpoint.java:269)
at org.apache.tomcat.websocket.WsFrameBase.sendMessageText(WsFrameBase.java:395)
at org.apache.tomcat.websocket.server.WsFrameServer.sendMessageText(WsFrameServer.java:119)
at org.apache.tomcat.websocket.WsFrameBase.processDataText(WsFrameBase.java:495)
at org.apache.tomcat.websocket.WsFrameBase.processData(WsFrameBase.java:294)
at org.apache.tomcat.websocket.WsFrameBase.processInputBuffer(WsFrameBase.java:133)
at org.apache.tomcat.websocket.server.WsFrameServer.onDataAvailable(WsFrameServer.java:82)
at org.apache.tomcat.websocket.server.WsFrameServer.doOnDataAvailable(WsFrameServer.java:171)
at org.apache.tomcat.websocket.server.WsFrameServer.notifyDataAvailable(WsFrameServer.java:151)
at org.apache.tomcat.websocket.server.WsHttpUpgradeHandler.upgradeDispatch(WsHttpUpgradeHandler.java:148)
at org.apache.coyote.http11.upgrade.UpgradeProcessorInternal.dispatch(UpgradeProcessorInternal.java:54)
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:53)
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:868)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1459)
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1167)
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.base/java.lang.Thread.run(Thread.java:844)

这就是我将 Button 添加到网格的方式:

// Adding the column
    grid.addComponentColumn(this::buildAddButton);

这是返回每一行按钮的方法:

// Building the button
private Button buildAddButton(ProductTemplate p) {
    Button button = new Button("add");
    // Configurate the button
    ...
    return button;
}

不幸的是，我对这个问题的发现很少......
由于 vaadin 按钮不会停止点击事件传播，我试过这个:

通过从布局中删除单击监听器，将按钮添加到布局以“阻止”单击事件。

// Adding the column 
    grid.addComponentColumn(this::buildAddLayout);

构建一个布局而不仅仅是一个按钮:

// Building the layout with the button
private VerticalLayout buildAddLayout(ProductTemplate p) {
    Button button = new Button("add");

    // Configurate the button
    ...

    VerticalLayout layout = new VerticalLayout();
    layout.addComponent(button);
    layout.getListeners(Event.class).clear();

    return layout;
}

单击时禁用按钮，直到它的任务是
完成(禁止双击按钮)。

// Building the button
private Button buildAddButton(ProductTemplate p) {
    Button button = new Button("add");
    // Configurate the button
        ...
    button.addClickListener(e -> {
        button.setEnabled(false);
        buttonClicked(p);
        button.setEnabled(true);
    });        
    return button;
}

两者都没有让我能够摆脱异常。在启用编辑器的网格上双击按钮时，有什么建议，如何防止这种类型的异常？

编辑:编辑器正在尝试编辑按钮的值，这显然是不可能的。我想阻止编辑这样做。 (“can't edit null”表示 vaadin 无法从按钮中创建有效的 bean)

编辑 2:我之前在第一次编辑中做出的假设似乎是错误的。我的按钮点击正在刷新网格，我无法阻止编辑器尝试编辑一行，即使所有项目都被删除并重新加载。

这里有一个类和一个pom，可以用来重现异常(快速点击按钮时出现异常):

MyUI.java

package com.example.sample;

import java.util.ArrayList;
import java.util.List;

import javax.servlet.annotation.WebServlet;

import com.vaadin.annotations.Theme;
import com.vaadin.annotations.VaadinServletConfiguration;
import com.vaadin.server.VaadinRequest;
import com.vaadin.server.VaadinServlet;
import com.vaadin.ui.Button;
import com.vaadin.ui.Grid;
import com.vaadin.ui.Notification;
import com.vaadin.ui.TextField;
import com.vaadin.ui.UI;
import com.vaadin.ui.VerticalLayout;

@Theme("mytheme")
public class MyUI extends UI {
    List<Product> items = new ArrayList<Product>();
    Grid<Product> grid;

    @Override
    protected void init(VaadinRequest vaadinRequest) {
        items.add(new Product("test", "test test"));

        final VerticalLayout layout = new VerticalLayout();

        grid = new Grid<Product>();
        layout.addComponent(grid);

        grid.getEditor().setBuffered(true);
        grid.getEditor().setEnabled(true);

        grid.removeAllColumns();

        grid.addComponentColumn(this::buildAddButton);

        TextField nameField = new TextField();
        TextField descriptionField = new TextField();

        grid.addColumn(Product::getName).setCaption("Name").setEditorComponent(nameField, Product::setName)
                .setExpandRatio(1);
        grid.addColumn(Product::getDescription).setCaption("Description")
                .setEditorComponent(descriptionField, Product::setDescription).setExpandRatio(1);

        grid.getEditor().addSaveListener(event -> {

            Notification.show((event.getBean() + "saved"));
        });

        grid.setItems(items);
        setContent(layout);
    }

    private Button buildAddButton(Product p) {

        Button button = new Button();

        button.addClickListener(event -> addButtonClicked(p));

        return button;
    }

    private void addButtonClicked(Product p) {
        refreshGrid();
    }

    private void refreshGrid() {
        grid.setItems(items);
    }

    @WebServlet(urlPatterns = "/*", name = "MyUIServlet", asyncSupported = true)
    @VaadinServletConfiguration(ui = MyUI.class, productionMode = false)
    public static class MyUIServlet extends VaadinServlet {
    }

    public class Product {
        String name;
        String description;

        public Product(String name, String description) {
            super();
            this.name = name;
            this.description = description;
        }

        public Product() {
            super();

        }

        public String getName() {
            return name;
        }

        public void setName(String name) {
            this.name = name;
        }

        public String getDescription() {
            return description;
        }

        public void setDescription(String description) {
            this.description = description;
        }

        @Override
        public String toString() {
            return name + " " + description;
        }

    }
}

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.example</groupId>
    <artifactId>sample</artifactId>
    <packaging>war</packaging>
    <version>1.0-SNAPSHOT</version>
    <name>sample</name>

    <prerequisites>
        <maven>3</maven>
    </prerequisites>

    <properties>
        <vaadin.version>8.3.1</vaadin.version>
        <vaadin.plugin.version>8.3.1</vaadin.plugin.version>
        <jetty.plugin.version>9.3.9.v20160517</jetty.plugin.version>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>
        <!-- If there are no local customizations, this can also be "fetch" or "cdn" -->
        <vaadin.widgetset.mode>local</vaadin.widgetset.mode>
    </properties>

    <repositories>
        <repository>
            <id>vaadin-addons</id>
            <url>http://maven.vaadin.com/vaadin-addons</url>
        </repository>
    </repositories>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>com.vaadin</groupId>
                <artifactId>vaadin-bom</artifactId>
                <version>${vaadin.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <dependencies>
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>javax.servlet-api</artifactId>
            <version>3.0.1</version>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>com.vaadin</groupId>
            <artifactId>vaadin-server</artifactId>
        </dependency>
        <dependency>
            <groupId>com.vaadin</groupId>
            <artifactId>vaadin-push</artifactId>
        </dependency>
        <dependency>
            <groupId>com.vaadin</groupId>
            <artifactId>vaadin-client-compiled</artifactId>
        </dependency>
        <dependency>
            <groupId>com.vaadin</groupId>
            <artifactId>vaadin-themes</artifactId>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-war-plugin</artifactId>
                <version>3.0.0</version>
                <configuration>
                    <failOnMissingWebXml>false</failOnMissingWebXml>
                    <!-- Exclude an unnecessary file generated by the GWT compiler. -->
                    <packagingExcludes>WEB-INF/classes/VAADIN/widgetsets/WEB-INF/**</packagingExcludes>
                </configuration>
            </plugin>
            <plugin>
                <groupId>com.vaadin</groupId>
                <artifactId>vaadin-maven-plugin</artifactId>
                <version>${vaadin.plugin.version}</version>
                <executions>
                    <execution>
                        <goals>
                            <goal>update-theme</goal>
                            <goal>update-widgetset</goal>
                            <goal>compile</goal>
                            <!-- Comment out compile-theme goal to use on-the-fly theme compilation -->
                            <goal>compile-theme</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-clean-plugin</artifactId>
                <version>3.0.0</version>
                <!-- Clean up also any pre-compiled themes -->
                <configuration>
                    <filesets>
                        <fileset>
                            <directory>src/main/webapp/VAADIN/themes</directory>
                            <includes>
                                <include>**/styles.css</include>
                                <include>**/styles.scss.cache</include>
                            </includes>
                        </fileset>
                    </filesets>
                </configuration>
            </plugin>

            <!-- The Jetty plugin allows us to easily test the development build by
                running jetty:run on the command line. -->
            <plugin>
                <groupId>org.eclipse.jetty</groupId>
                <artifactId>jetty-maven-plugin</artifactId>
                <version>${jetty.plugin.version}</version>
                <configuration>
                    <scanIntervalSeconds>2</scanIntervalSeconds>
                </configuration>
            </plugin>
        </plugins>
    </build>

    <profiles>
        <profile>
            <!-- Vaadin pre-release repositories -->
            <id>vaadin-prerelease</id>
            <activation>
                <activeByDefault>false</activeByDefault>
            </activation>

            <repositories>
                <repository>
                    <id>vaadin-prereleases</id>
                    <url>http://maven.vaadin.com/vaadin-prereleases</url>
                </repository>
                <repository>
                    <id>vaadin-snapshots</id>
                    <url>https://oss.sonatype.org/content/repositories/vaadin-snapshots/</url>
                    <releases>
                        <enabled>false</enabled>
                    </releases>
                    <snapshots>
                        <enabled>true</enabled>
                    </snapshots>
                </repository>
            </repositories>
            <pluginRepositories>
                <pluginRepository>
                    <id>vaadin-prereleases</id>
                    <url>http://maven.vaadin.com/vaadin-prereleases</url>
                </pluginRepository>
                <pluginRepository>
                    <id>vaadin-snapshots</id>
                    <url>https://oss.sonatype.org/content/repositories/vaadin-snapshots/</url>
                    <releases>
                        <enabled>false</enabled>
                    </releases>
                    <snapshots>
                        <enabled>true</enabled>
                    </snapshots>
                </pluginRepository>
            </pluginRepositories>
        </profile>
    </profiles>

</project>

Answer 1

免责声明 : 由于缺少 setHandleWidgetEvents，此解决方案不适用于 8.3 之前的版本方法。否则，虽然复杂，但此解决方案可能适用于某些人:

从按钮 ( addClickListener ) 中删除单击事件处理。无法在那里获得有关双击的信息，但是

有一种方法可以使用 addItemClickListener和它的 clickedItem.getMouseEventDetails().isDoubleClick() , 但是 再次

使用 grid.getEditor().setEnabled(true); 启用网格后双击检查总是返回 false ,所以

您需要默认禁用编辑器 grid.getEditor().setEnabled(false);(这里有一个很好的相关答案 Couldn't capture double click event using vaadin 7)

并且，一旦发生双击事件(并打开一行)，重新启用它
grid.getEditor().setEnabled(true);
grid.getEditor().editRow(item.getRowIndex());

如果，否则，单击按钮列一次，执行您的 addButtonClicked然后行动

为了从 Grid 列的组件接收事件，当单击按钮时，列应该能够处理事件。这是使用 grid.addComponentColumn(this::buildAddButton).setHandleWidgetEvents(true).setId("buttonClick"); 实现的

来自 init 的完整修改代码方法。所有其他保持不变(另外，请记住从按钮中删除 addClickListener):

        items.add(new Product("test", "test test"));

        grid = new Grid<Product>();

        grid.getEditor().setBuffered(true);
        grid.getEditor().setEnabled(false);

        grid.removeAllColumns();

        // Important! Propagate events from components to Grid
        grid.addComponentColumn(this::buildAddButton).setHandleWidgetEvents(true).setId("buttonClick");

        TextField nameField = new TextField();
        TextField descriptionField = new TextField();

        grid.addColumn(Product::getName).setCaption("Name").setEditorComponent(nameField, Product::setName)
                .setExpandRatio(1);
        grid.addColumn(Product::getDescription).setCaption("Description")
                .setEditorComponent(descriptionField, Product::setDescription).setExpandRatio(1);

        //Once close editor--> Disable it
        grid.getEditor().addSaveListener(event -> {
            grid.getEditor().setEnabled(false);

        });
        grid.getEditor().addCancelListener(e->{
            grid.getEditor().setEnabled(false);
        });
        //THIS IS WHERE ALL THE LOGIC IS HAPPENING
        grid.addItemClickListener(item->{
            //If the button column is clicked
           if("buttonClick".equals(item.getColumn().getId())){
               //Regual click--> update content; also fired twice before editor is opened
               if(!item.getMouseEventDetails().isDoubleClick()){
                  addButtonClicked(item.getItem());
               }
               //If Double click is detected, just opened editor. The data is already updated
               else{
                   grid.getEditor().setEnabled(true);
                   grid.getEditor().editRow(item.getRowIndex());
               }
            }
           //In all the other cases, when double click is detected--> open editor
           else if(item.getMouseEventDetails().isDoubleClick()){
               grid.getEditor().setEnabled(true);
               grid.getEditor().editRow(item.getRowIndex());
           }
        });

        grid.setItems(items);
        addComponent(grid);