从Vaadin 7中的枚举中创建一个OptionGroup（单选按钮）？

时间：2015-04-01 23:30:07

标签： enums vaadin vaadin7

我有一个带有getter的Java枚举，用于显示所需的显示文本。如何使用它来填充Vaadin 7中的OptionGroup？

2 个答案:

答案 0 :(得分：6)

以下是在Vaadin 7中执行此操作的三种方法：

  • 我建造的课程EnumBackedOptionGroup。 Vaadin 7中OptionGroup的子类。
  • 滚动你自己的短暂甜蜜的方式。
  • 以更灵活的方式自己动手。

OptionGroup

的子类

这是我写的OptionGroup的新子类的源代码。 

package com.basilbourque;

import com.vaadin.ui.OptionGroup;
import java.util.Arrays;
import java.util.Collection;
import java.util.function.Function;
import org.slf4j.LoggerFactory;

/**
 * A subclass of the Vaadin 7 OptionGroup (radio buttons or bunch of checkboxes) widget, taking as its set of options
 * the instances of an Enum.
 *
 * In canonical usage, pass the class of your Enum and a reference to the method to be called for obtaining a textual
 * label for display to the user.
 *
 * Alternatively, if your Enum overrides the `toString` method, you may pass only the class of the Enum without a
 * Function. This approach is not recommended per the class documentation which explains `toString` should only be used
 * for debugging message. Nevertheless, some people override `toString` to provide a user-readable label, so we support
 * this.
 *
 * Even if your Enum does not override `toString` you may choose to omit passing the Function argument. As a default,
 * the Enum’s built-in `toString` method will be called, returning the "name" of the Enum’s instance. This is handy for
 * quick-and-dirty prototyping. Again, neither I nor the class doc recommend this approach for serious work.
 *
 * If you want to display a subset of your enum’s instances rather than all, pass a Collection.
 *
 * This source code available under terms of ISC License.  https://en.wikipedia.org/wiki/ISC_license
 * 
 * Copyright (c) 2015, Basil Bourque
 * Permission to use, copy, modify, and/or distribute this software for any purpose with or without fee is hereby
 * granted, provided that the above copyright notice and this permission notice appear in all copies. THE SOFTWARE IS
 * PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT,
 * OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
 * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
 * SOFTWARE.
 *
 * @author Basil Bourque
 * @version 2015-08-27T21:00:00Z
 * @since 2015-08-27T21:00:00Z
 */
public class EnumBackedOptionGroup<T extends Enum> extends OptionGroup
{

    final org.slf4j.Logger logger = LoggerFactory.getLogger( this.getClass() );

    /**
     * Constructor. The usual constructor for automatically detecting all the instances of an enum for use as the
     * options in a Vaadin 7 OptionGroup. Pass a function to be called for providing each option’s displayed labeling.
     *
     * Example usage:
     *
     * myRadios = new EnumBackedOptionGroup<DogBreed>( "Choose breed:" , DogBreed.class , DogBreed :: getTitle );
     *
     * @param caption
     * @param enumClass
     * @param f
     */
    public EnumBackedOptionGroup ( final String caption , final Class<T> enumClass , final Function<T , String> f ) {
        super( caption );
        Function<T , String> func = f;
        // If passed a null for the Function, fallback to using 'toString'.
        if ( func == null ) {
            func = T -> T.toString();
        }
        this.buildAndAssignCaptions( enumClass , func );
    }

    /**
     * Constructor. Similar to usual constructor, but here you may additionally pass a Collection of the subset of Enum
     * instances.
     *
     * For use where business logic dictates that you give only some of the Enum values an options rather than all of
     * them. The omitted options are effectively hidden from the user.
     *
     * @param caption
     * @param enumClass
     * @param enumValues
     * @param f
     */
    public EnumBackedOptionGroup ( final String caption , final Class<T> enumClass , final Collection<T> enumValues , final Function<T , String> f ) {
        super( caption );
        Function<T , String> func = f;
        // If passed a null for the Function, fallback to using 'toString'.
        if ( func == null ) {
            func = T -> T.toString();
        }
        Collection<T> ev = enumValues;
        // Handle where calling method passed us a null or empty collection.
        if ( ( ev == null ) || ev.isEmpty() ) {
            this.buildAndAssignCaptions( enumClass , f ); // Fallback to assiging all the instances of enum as options in our OptionGroup.
        } else {
            this.addItems( enumValues );  // Add the passed subset of instances of the enum as items backing our OptionGroup.
            this.assignCaptions( enumValues , f );
        }
    }

    /**
     * Constructor. Similar to the usual constructor, but omits the method for providing on-screen labeling. Instead
     * uses the 'toString' method defined either explicitly in the Enum subclass or implicitly calls to the Enum class’
     * own 'toString'.
     *
     * Not recommended, as the Enum documentation strongly suggests the 'toString' method on an Enum be used only for
     * debugging. Nevertheless this is handy for quick-and-dirty prototyping.
     *
     * @param caption
     * @param enumClass
     */
    public EnumBackedOptionGroup ( final String caption , final Class<T> enumClass ) {
        super( caption );
        // User passed no Function to call for getting the title. So fallback to using 'toString'.
        this.buildAndAssignCaptions( enumClass , T -> T.toString() );
    }

    // Helper method. (sub-routine)
    // Extracts all the instances of the enum, and uses them as options in our OptionGroup.
    // Also assigns each option a labeling using String returned by passed method to be called for each instance of enum.
    private void buildAndAssignCaptions ( final Class<T> enumClass , final Function<T , String> f ) {
        if ( enumClass.isEnum() ) {  // This check may be unnecessary with Generics code "<T extends Enum>" at top of this class.
            Collection<T> enumValues = Arrays.asList( enumClass.getEnumConstants() );
            this.addItems( enumValues );  // Add all the instances of the enum as items backing our OptionGroup.
            this.assignCaptions( enumValues , f );
        } else {
            // Else the passed class is not an enum.
            // This case should not be possible because of the Generics marked on this class "<T extends Enum>".
            logger.error( "Passed a class that is not a subclass of Enum. Message # f2098672-ab47-47fe-b720-fd411411052e." );
            throw new IllegalArgumentException( "Passed a class that is not a subclass of Enum." );
        }
    }

    // Helper method. (sub-routine)
    // Assigns each option a labeling using String returned by passed method to be called for each instance of enum
    private void assignCaptions ( Collection<T> enumValues , final Function<T , String> f ) {
        for ( T option : enumValues ) {
            // For each option in our OptionGroup, determine and set its title, the label displayed for the user next to each radio button or checkbox.
            // To determine the label (the second argument), we invoke the passed method which must return a String. Using Lambda syntax.
            this.setItemCaption( option , f.apply( option ) );
        }
    }

}

我希望你能使用像这样的枚举DogBreed。请注意此枚举如何具有构造函数，在该构造函数中，我们将文本传递给用户作为演示文稿的标签。我们添加了一个方法getTitle来检索此标题文本。

package com.example;

/**
 * Bogus example Enum.
 */
public enum DogBreed {

    AUSSIE("Australian Shepherd") ,
    BORDER_COLLIE("Border Collie"),
    BLACK_LAB("Labrador, Black"),
    MUTT("Mixed Breed");

    private String title = null;

    DogBreed ( final String titleArg) {
        this.title = titleArg;
    }

    public String getTitle() {
        return this.title;
    }

}

screen shot of radio buttons showing dog breeds using presentation labeling

感谢this Answer WillShackleford在我的问题Lambda syntax to pass and invoke a method reference上Lambda syntax，我只能完成该课程。

要使用此EnumBackedGroupOption类，请传递其类和该标题呈现方法的方法引用。这需要Java 8中的新toString。但是还没有必要掌握你对Lambda的理解，只需遵循你在这里看到的模式。

OptionGroup optionGroup = new EnumBackedOptionGroup<DogBreed>( "Choose Breed:" , DogBreed.class , DogBreed :: getTitle );

对于快速和脏的原型设计，您可以定义一个没有这种构造函数和getter的简单枚举。在这种情况下，只传递你的标题和枚举类。 EnumBackedOptionGroup类回退到使用内置的Enum方法。我和this Question类文档都没有推荐这条路线用于认真工作，其中toString应仅用于调试。

package com.example;

/**
 * Bogus example Enum.
 */
public enum SaySo {

    YES, NO, MAYBE;
}

OptionGroup optionGroup = new EnumBackedOptionGroup<SaySo>( "Says you:" , SaySo.class );

有时您可能不想在OptionGroup中使用所有枚举的实例值。如果是，请使用EnumMap中解释的隐式方法values提取这些实例的集合。删除不需要的。请注意我们如何从ArrayList的输出中实例化新的Arrays.asList以允许此修改。然后将该集合传递给EnumBackedOptionGroup的另一个构造函数。

您可以将null作为最后一个参数传递，以使用toString作为演示文稿标签。

您可以使用EnumSet或toString代替.values，但我没有相关经验。

Collection<T> enumValues = new ArrayList( Arrays.asList( SaySo.values() ) );
enumValues.remove( SaySo.MAYBE );
OptionGroup optionGroup = new EnumBackedOptionGroup<SaySo>( "Says you:" , SaySo.class , null );

滚动你自己的

想象一下这个CRITTER_FILTER枚举嵌套在SomeClass。

public enum CRITTER_FILTER
{

    CANINE ( "Dogs" ), // Pass the text to be displayed to user as the radio button’s Caption (label).
    FELINE ( "Cats" ),
    COCKATIEL ( "Cockatiel birds" );

    private String title;

    CRITTER_FILTER ( String t )
    {
        this.title = t;
    }

    // Add this method for the more flexible approach.
    // JavaBeans "getter" for use in BeanItemContainer.
    public String getTitle ()
    {
        return this.title;
    }

    // Add this method for the short simple approach.
    @Override
    public String toString ()
    {
        return this.title;
    }

}

添加构造函数使我们能够将所需的显示文本传递给每个枚举实例，然后将该文本存储在私有成员String变量中。

简单简单方法

如果在确定显示文本时没有花哨的工作，只需覆盖documentation方法即可返回存储的显示文字。

我不推荐这种方法。仅当您要在调试工作中创建一个特殊值以供程序员显示时，name才会建议覆盖toString。但是，我确实尝试过这种方法，但确实有效。

  

public String toString（）

     

...可以覆盖此方法，但通常不需要或不需要。当存在更“程序员友好”的字符串形式时，枚举类型应覆盖此方法。

this.filterRadios = new OptionGroup( "Filter:" , Arrays.asList( SomeClass.CRITTER_FILTER.values() ) );  // Convert plain array of the enum instances (the values) into a `Collection` object by calling utility method `Arrays.asList`.
this.filterRadios.setMultiSelect( false ); // Radio buttons are single-select.

toString方法的完整示例

Person类，带有嵌套枚举。

package com.example.vaadinradiobuttons;

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

/**
 *
 * @author Basil Bourque
 */
public class Person {

    // Members
    String name;
    Person.VITAL_STATUS vitalStatus;

    public enum VITAL_STATUS {

        LIVING( "Alive and Kicking" ),
        DECEASED( "Dead" ),
        UNKNOWN( "DUNNO" );

        private String captionText;

        VITAL_STATUS ( String t ) {
            this.captionText = t;
        }

        @Override
        public String toString () {
            return this.captionText;
        }

    }

    // Constructor
    public Person ( String nameArg , VITAL_STATUS vitalStatusArg ) {
        this.name = nameArg;
        this.vitalStatus = vitalStatusArg;
    }

}

使用嵌套枚举填充选项组的一个小小的Vaadin 7.4.3应用程序。查看评论// Core of example.以查看重要的行。

package com.example.vaadinradiobuttons;

import javax.servlet.annotation.WebServlet;

import com.vaadin.annotations.Theme;
import com.vaadin.annotations.VaadinServletConfiguration;
import com.vaadin.annotations.Widgetset;
import com.vaadin.data.Property;
import com.vaadin.server.VaadinRequest;
import com.vaadin.server.VaadinServlet;
import com.vaadin.ui.OptionGroup;
import com.vaadin.ui.UI;
import com.vaadin.ui.VerticalLayout;
import java.util.Arrays;
import java.util.Collection;

/**
 *
 */
@Theme ( "mytheme" )
@Widgetset ( "com.example.vaadinradiobuttons.MyAppWidgetset" )
public class MyUI extends UI {

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

        // Core of example.
        Collection<Person.VITAL_STATUS> v = Arrays.asList( Person.VITAL_STATUS.values() );
        OptionGroup radios = new OptionGroup( "Vital Status :" , v );
        radios.setImmediate( true );
        radios.addValueChangeListener( ( Property.ValueChangeEvent event ) -> {
            Person.VITAL_STATUS vitalStatus = ( Person.VITAL_STATUS ) event.getProperty().getValue();
            System.out.println( "User selected a vital status name: " + vitalStatus.name() + ", labeled: " + vitalStatus.toString() );
        } );
        layout.addComponent( radios );

    }

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

更灵活的方法

请注意我们在上面的枚举中添加了getTitle方法。您可以使用所需的任何方法名称，getName或{{3}}除外，它已被定义为Java中枚举的一部分。

创建一个BeanItemContainer，填充我们枚举的实例，并告诉Vaadin提供显示文本的“属性”的名称（用于反射性地找到匹配的getter方法）。

除了更灵活之外，考虑到医生关于覆盖toString的警告，这种方法可能更为明智。 

BeanItemContainer<SomeClass.CRITTER_FILTER> radiosBic = new BeanItemContainer<SomeClass.CRITTER_FILTER>( SomeClass.CRITTER_FILTER.class );
radiosBic.addAll( Arrays.asList( SomeClass.CRITTER_FILTER.values() ) );  // Convert array of values to a `Collection` object.
this.filterRadios = new OptionGroup( "Critter Filter:" , radiosBic );
this.filterRadios.setMultiSelect( false ); // Radio buttons are single-select.
this.filterRadios.setItemCaptionMode( AbstractSelect.ItemCaptionMode.PROPERTY );  
this.filterRadios.setItemCaptionPropertyId( "title" );  // Matches the getter method defined as part of the enum.

有效。我希望它能在Vaadin 6和7中发挥作用。

BeanItemContainer方法的完整示例

让我们调整上面显示的示例Person和Vaadin app。

在Person类中，将toString方法替换为JavaBeans Property getter，getCaptionText。此方法的名称可以是任何内容，只要它与下面Vaadin应用程序中的setItemCaptionPropertyId调用相匹配。

package com.example.vaadinradiobuttons;

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

/**
 *
 * @author Basil Bourque
 */
public class Person {

    // Members
    String name;
    Person.VITAL_STATUS vitalStatus;

    public enum VITAL_STATUS {

        LIVING( "Alive and Kicking" ),
        DECEASED( "Dead" ),
        UNKNOWN( "DUNNO" );

        private String captionText;
        static public String CAPTION_TEXT_PROPERTY_NAME = "captionText";  //

        VITAL_STATUS ( String t ) {
            this.captionText = t;
        }

        // JavaBeans Property getter.
        public String getCaptionText () {
            return this.captionText;
        }

    }

    // Constructor
    public Person ( String nameArg , VITAL_STATUS vitalStatusArg ) {
        this.name = nameArg;
        this.vitalStatus = vitalStatusArg;
    }

}

Vaadin应用已更改为使用BeanItemContainer。通过调用setItemCaptionPropertyId，您可以指定该容器中的哪些属性应用作要显示的文本。

package com.example.vaadinradiobuttons;

import javax.servlet.annotation.WebServlet;

import com.vaadin.annotations.Theme;
import com.vaadin.annotations.VaadinServletConfiguration;
import com.vaadin.annotations.Widgetset;
import com.vaadin.data.Property;
import com.vaadin.data.util.BeanItemContainer;
import com.vaadin.server.VaadinRequest;
import com.vaadin.server.VaadinServlet;
import com.vaadin.ui.OptionGroup;
import com.vaadin.ui.UI;
import com.vaadin.ui.VerticalLayout;
import java.util.Arrays;
import java.util.Collection;

/**
 *
 */
@Theme ( "mytheme" )
@Widgetset ( "com.example.vaadinradiobuttons.MyAppWidgetset" )
public class MyUI extends UI {

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

        // Core of example.
        Collection<Person.VITAL_STATUS> v = Arrays.asList( Person.VITAL_STATUS.values() );
        BeanItemContainer<Person.VITAL_STATUS> bic = new BeanItemContainer<>( Person.VITAL_STATUS.class , v );
        OptionGroup radios = new OptionGroup( "Vital Status :" , bic );
        radios.setItemCaptionPropertyId(Person.VITAL_STATUS.CAPTION_TEXT_PROPERTY_NAME );  // …or… ( "captionText" );
        radios.setImmediate( true );
        radios.addValueChangeListener( ( Property.ValueChangeEvent event ) -> {
            Person.VITAL_STATUS vitalStatus = ( Person.VITAL_STATUS ) event.getProperty().getValue();
            System.out.println( "User selected a vital status name: " + vitalStatus.name() + ", labeled: " + vitalStatus.toString() );
        } );
        layout.addComponent( radios );

    }

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

答案 1 :(得分：3)

Viritin

Viritin，Vaadin的add-on，有一个非常方便的字段EnumSelect。它可以从已编辑的属性中自动检测可用属性。您还可以在UI上传递显示为标题的策略。

基本用法

    EnumSelect<AddressType> select = new EnumSelect<AddressType>()
            .withSelectType(OptionGroup.class);
    select.setStyleName(ValoTheme.OPTIONGROUP_HORIZONTAL);

    // The Enum type is detected when the edited property is bound to select
    // This typically happens via basic bean binding, but here done manually.
    ObjectProperty objectProperty = new ObjectProperty(AddressType.Home);
    select.setPropertyDataSource(objectProperty);

    // Alternatively, if not using databinding at all, you could just use 
    // basic TypedSelect, or the method from it
    // select.setOptions(AddressType.values());

请注意，当前版本的输入有限。我刚刚解决了这个问题，显示的类型api将在下一个版本中发布。

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