在新的Vaadin 7.4 版本中，新的Grid小部件作为古老小部件的替代品首次亮相Table。
显示 Grid 后，我稍后想用新数据替换整个数据集。我不想更新各个行，而是简单地替换它们。
我碰巧使用BeanItemContainerJavaBeans 风格的 getter 方法来简单地只读显示某些对象。
问问题
11616 次
2 回答
6
我考虑了两种方法：
- 更换 bean 项目的两步过程。
- （1）首先用方法删除所有
BeanItem对象Container::removeAllItems。 - (2) 然后用方法添加替换
BeanItem对象BeanItemContainer::addAll。
- （1）首先用方法删除所有
- 替换整个
BeanItemContainer.- 调用并传递一个用新数据构造
Grid::setContainerDataSource的新实例。BeanItemContainer
- 调用并传递一个用新数据构造
下面是显示这两种方法的示例应用程序 (Vaadin 7.4.2)。出现一对相同的 Grid 小部件。每个都有一个按钮，可以使用任何一种方法更新数据。
结果
第一种方法（删除项目和添加项目）有效。新数据立即出现。
第二种方法（替换容器而不是项目）似乎应该有效，在缺乏文档中没有任何相反的建议。但什么也没有发生。没有出现异常或错误，但没有出现新数据。我为此问题在 Vaadin trac 上打开了Ticket #17268 。
也许还有其他更好的方法。请张贴或评论任何替代品。
示例应用
下面显示了三个类。您应该能够复制粘贴到新的 Vaadin 7.4.x 应用程序中。
- 一个类是在每个新的 Vaadin 应用程序中创建的常用“MyUI”。
- 另一个是简单的 JavaBeans 风格的类，“Astronomer”，为我们的 Grid 中的行提供数据。该 Astronomer 类包含一个方便的静态方法，用于生成实例列表。每个新的天文学家都会获得随机数量的人气投票，以显示新的数据值。
- 该示例的主要部分是在“AstronomersLayout”类中，它创建了一对带有分配按钮的网格。
我使用 Java 8 Lambda 语法和新的 java.time 类。因此，您可能需要更改项目的设置以使用 Java 8。在 NetBeans 8 中，这意味着Project > Properties > Sources > Source/Binary Format (popup menu) > 1.8.
MyUI.java
启动您的 Vaadin 应用程序。
package com.example.vaadingridexample;
import javax.servlet.annotation.WebServlet;
import com.vaadin.annotations.Theme;
import com.vaadin.annotations.VaadinServletConfiguration;
import com.vaadin.annotations.Widgetset;
import com.vaadin.server.VaadinRequest;
import com.vaadin.server.VaadinServlet;
import com.vaadin.ui.UI;
/**
* Example app in Vaadin 7.4.2 experimenting with two ways to replace data in a
* displayed Grid.
*
* @author Basil Bourque
*/
@Theme ( "mytheme" )
@Widgetset ( "com.example.vaadingridexample.MyAppWidgetset" )
public class MyUI extends UI
{
@Override
protected void init ( VaadinRequest vaadinRequest )
{
this.setContent( new AstronomersLayout() );
}
@WebServlet ( urlPatterns = "/*" , name = "MyUIServlet" , asyncSupported = true )
@VaadinServletConfiguration ( ui = MyUI.class , productionMode = false )
public static class MyUIServlet extends VaadinServlet
{
}
}
天文学家布局.java
示例的主要部分。
package com.example.vaadingridexample;
import com.vaadin.data.util.BeanItemContainer;
import com.vaadin.shared.ui.grid.HeightMode;
import com.vaadin.ui.Button;
import com.vaadin.ui.Button.ClickEvent;
import com.vaadin.ui.Grid;
import com.vaadin.ui.VerticalLayout;
import java.time.ZoneOffset;
import java.time.ZonedDateTime;
import java.time.format.DateTimeFormatter;
import java.util.List;
/**
* Layout displays a pair of Grids, each with a Button to replace its contents
* with fresh data in either of two ways: (a) Replace all the items within the
* Container, or (b) Replace container itself.
*
* @author Basil Bourque
*/
@SuppressWarnings ( "serial" )
public class AstronomersLayout extends VerticalLayout
{
// -----| Member vars |--------------------------
Grid grid_ReplaceItems;
String gridCaption_ReplaceItems = "Astronomers - Replacing Items";
Button button_ReplaceItems;
Grid grid_ReplaceContainer;
String gridCaption_ReplaceContainer = "Astronomers - Replacing Container";
Button button_ReplaceContainer;
// -----| Constructor |--------------------------
public AstronomersLayout ()
{
this.prepareWidgets();
this.composeLayout();
}
// -----| Helper Methods |--------------------------
private void prepareWidgets ()
{
// Show updating a Grid by replacing the bean items within a container.
// Grid
List<Astronomer> listA = Astronomer.makeList();
BeanItemContainer<Astronomer> containerA = new BeanItemContainer<>( Astronomer.class , listA );
this.grid_ReplaceItems = new Grid( this.gridCaption_ReplaceItems , containerA );
//this.grid_ReplaceItems.setColumnOrder( "votes" , "givenName" , "surName" , "birthYear" );
this.grid_ReplaceItems.setColumnOrder( Astronomer.FIELD.VOTES.getName() , Astronomer.FIELD.GIVENNAME.getName() , Astronomer.FIELD.SURNAME.getName() , Astronomer.FIELD.BIRTHYEAR.getName() ); // Enum is a safer way of doing this: this.grid_ReplaceItems.setColumnOrder( "votes" , "givenName" , "surName" , "birthYear" );
this.grid_ReplaceItems.setHeightMode( HeightMode.ROW ); // Show all rows of data for this grid.
this.updateCaptionAndSize( this.grid_ReplaceItems , this.gridCaption_ReplaceItems );
// Button
this.button_ReplaceItems = new Button( "Replace Items" );
this.button_ReplaceItems.addClickListener( ( ClickEvent event ) -> {
@SuppressWarnings ( "unchecked" )
BeanItemContainer<Astronomer> bic = ( BeanItemContainer<Astronomer> ) this.grid_ReplaceItems.getContainerDataSource(); // Access existing container. Cast as need be.
bic.removeAllItems(); // Remove existing items.
bic.addAll( Astronomer.makeList() ); // Add fresh bean items to existing container.
this.updateCaptionAndSize( this.grid_ReplaceItems , this.gridCaption_ReplaceItems );
} );
// Show updating a Grid by replacing the container rather than its contents.
// Grid
List<Astronomer> listB = Astronomer.makeList();
BeanItemContainer<Astronomer> containerB = new BeanItemContainer<>( Astronomer.class , listB );
this.grid_ReplaceContainer = new Grid( this.gridCaption_ReplaceContainer , containerB );
this.grid_ReplaceContainer.setColumnOrder( Astronomer.FIELD.VOTES.getName() , Astronomer.FIELD.GIVENNAME.getName() , Astronomer.FIELD.SURNAME.getName() , Astronomer.FIELD.BIRTHYEAR.getName() );
this.grid_ReplaceContainer.setHeightMode( HeightMode.ROW ); // Show all rows of data for this grid.
this.updateCaptionAndSize( this.grid_ReplaceContainer , this.gridCaption_ReplaceContainer );
// Button
this.button_ReplaceContainer = new Button( "Replace Container" );
this.button_ReplaceContainer.addClickListener( ( ClickEvent event ) -> {
@SuppressWarnings ( "unchecked" )
BeanItemContainer<Astronomer> bic = new BeanItemContainer<>( Astronomer.class , listB ); // Create replacement container.
this.grid_ReplaceContainer.setContainerDataSource( bic );
this.updateCaptionAndSize( this.grid_ReplaceContainer , this.gridCaption_ReplaceContainer );
} );
}
private void updateCaptionAndSize ( final Grid grid , final String caption )
{
// Caption
grid.setCaption( caption + " ( updated " + this.now() + " )" ); // Update caption of Grid to indicate fresh data.
// Show all rows.
double h = grid.getContainerDataSource().size() > 0 ? grid.getContainerDataSource().size() : 3; // Cannot set height to zero rows. So if no data, set height to some arbitrary number of (empty) rows.
grid.setHeightByRows( h );
}
private void composeLayout ()
{
// Initialize this layout.
this.setMargin( true );
this.setSpacing( true );
// Content
this.addComponent( this.button_ReplaceItems );
this.addComponent( this.grid_ReplaceItems );
this.addComponent( this.button_ReplaceContainer );
this.addComponent( this.grid_ReplaceContainer );
}
// Helper method.
private String now ()
{
// Get current time in UTC. Truncate fractional seconds. Append a 'Z' to indicate UTC time zone.
return ZonedDateTime.now( ZoneOffset.UTC ).format( DateTimeFormatter.ISO_LOCAL_TIME ).substring( 0 , 8 ).concat( "Z" );
}
}
天文学家.java
数据，即 bean 项，存储在 BeanItemContainer 中以在 Grid 中显示。
嵌套枚举提供了一种更安全的方式来引用其他类中的字段名称，AstronomersLayout以调用setColumnOrder.
package com.example.vaadingridexample;
import java.util.ArrayList;
import java.util.List;
/**
* Provides the beans to appear as rows in a BeanItemContainer backing a Grid.
*
* Note the static convenience method for generating a List of instances.
*
* @author Basil Bourque
*/
public class Astronomer
{
public enum FIELD
{
SURNAME( "surname" ),
GIVENNAME( "givenName" ),
BIRTHYEAR( "birthYear" ),
VOTES( "votes" );
private String name;
private FIELD ( String s )
{
this.name = s;
}
public String getName ()
{
return this.name;
}
}
// Members
private String surname;
private String givenName;
private Integer birthYear;
private Integer votes;
public Astronomer ( final String givenName , final String surName , final Integer birthYear )
{
this.surname = surName;
this.givenName = givenName;
this.birthYear = birthYear;
this.votes = this.random();
}
public static List<Astronomer> makeList ()
{
List<Astronomer> list = new ArrayList<>( 7 );
list.add( new Astronomer( "Hypatia" , "of Alexandria" , -370 ) );
list.add( new Astronomer( "Nicolaus" , "Copernicus" , 1473 ) );
list.add( new Astronomer( "Tycho" , "Brahe" , 1546 ) );
list.add( new Astronomer( "Giordano" , "Bruno" , 1548 ) );
list.add( new Astronomer( "Galileo" , "Galilei" , 1564 ) );
list.add( new Astronomer( "Johannes" , "Kepler" , 1571 ) );
list.add( new Astronomer( "Isaac" , "Newton" , 1643 ) );
list.add( new Astronomer( "Caroline" , "Herschel" , 1750 ) );
return list;
}
// ----| Helper Methods |----------------------------------
private Integer random ()
{
return ( int ) ( java.lang.Math.random() * 100 );
}
// ----| Bean Getters |----------------------------------
public String getSurname ()
{
return this.surname;
}
public String getGivenName ()
{
return this.givenName;
}
public Integer getBirthYear ()
{
return this.birthYear;
}
public Integer getVotes ()
{
return this.votes;
}
// ----| Object Superclass |----------------------------------
@Override
public String toString ()
{
return "Astronomer{ " + "surName=" + surname + " | givenName=" + givenName + " | birthYear=" + birthYear + " | votes=" + votes + " }";
}
}
于 2015-03-23T06:53:33.520 回答
1
您可以通过 clickListener 简单地获取已从按钮中删除的记录.getSelectedRow()。在此之后，您可以使用 . 从网格中删除您的项目.removeItem()。
IE：
Grid yourGrid = new Grid();
yourGrid.setContainerDataSource(yourData);
Button removeItem = new Button("Remove item");
removeItem.addClickListener(l -> {
Item selectedItem = (Item) yourGrid.getSelectedRow();
yourGrid.getContainerDataSource().removeItem(selectedItem);
});
再见！
于 2016-11-23T11:59:49.973 回答