问题：

如何将从一个JavaFX选项卡添加到数据库中的内容反映到另一个JavaFX选项卡中？

巴洲

2023-03-14

我有一个简单的基于JavaFXML、scenebuilder和Derby数据库的双选项卡应用程序。有一个MainController类声明为：

package tabpane.view;

import javafx.fxml.FXML;
import javafx.scene.control.Button;
import javafx.scene.control.Tab;
import javafx.scene.control.TabPane;

public class MainController {
  @FXML public TabPane tabPane;
  @FXML public Tab inputTab;
  @FXML public Tab accountTab;
  @FXML private Button exitBtn;

  @FXML private void handleExitBtn() {
    System.exit(0);
  }
}

InputController类定义了第一个名为Input的选项卡。它编组一些基本数据，包括一个新帐户名称和一个复选框以指示帐户是否处于活动状态。收集输入后，它会通过DAO控制器类写入derby数据库中的表：

package tabpane.view;

import java.net.URL;
import java.sql.SQLException;
import java.util.ResourceBundle;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.scene.control.Button;
import javafx.scene.control.CheckBox;
import javafx.scene.control.TextField;
import tabpane.db.NdDao;
import tabpane.model.AccountObject;

public class InputController implements Initializable
{
  @FXML private TextField accName;
  @FXML private CheckBox isEnabled;
  @FXML private Button saveBtn;  

  @Override
  public void initialize(URL location, ResourceBundle resources) {}

  @FXML private void handleSaveBtn() throws SQLException {
    AccountObject obj = new AccountObject(accName.getText(), isEnabled.isSelected());
    NdDao.connect();
    NdDao.insertAccount(obj);
    NdDao.disconnect();
  }
}

以下是DAO控制器类中的代码：

package tabpane.db;

import tabpane.model.AccountObject;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.TreeMap;

public class NdDao 
{  
  private static final String strAccountInsert = "INSERT INTO ACCOUNTS " +
            "   (ACCNAME, ISENABLED) " + "VALUES (?, ?)";
  private static final String strAccountSelectAll = "SELECT * from ACCOUNTS ORDER BY ACCNAME ASC";

  private static PreparedStatement pstmtAccountInsert;
  private static PreparedStatement pstmtAccountSelectAll;

  private static Connection conn = null;

  public static void connect() throws SQLException {
    conn = DriverManager.getConnection("jdbc:derby:C:/Users/" + System.getenv("USERNAME") + "/AppData/Local/TabPaneEx/db" + ";create=true");
    prepareStatements();
  } 

  public static void disconnect() throws SQLException {
    if (conn != null) {
      conn.close();
      conn = null;
    }
  }

  private static void prepareStatements() throws SQLException{
    pstmtAccountInsert  = conn.prepareStatement(strAccountInsert);
    pstmtAccountSelectAll  = conn.prepareStatement(strAccountSelectAll);
  }

  public static void insertAccount(AccountObject obj) throws SQLException
  {  
    pstmtAccountInsert.clearParameters();        
    pstmtAccountInsert.setString(1, obj.getAccName());
    pstmtAccountInsert.setBoolean(2, obj.getIsEnabled());
    pstmtAccountInsert.executeUpdate();         
  }

  public static TreeMap<Integer, AccountObject> selectAccounts() throws SQLException        {
    TreeMap<Integer, AccountObject> map = new TreeMap<>();
    ResultSet results;
    AccountObject obj;
    results = pstmtAccountSelectAll.executeQuery();    
    while(results.next()) {
      obj = new AccountObject(
                results.getString(1),
                results.getBoolean(2)
      );
      map.put( (obj.hashCode() ), obj);       
    } 
    return map;
  }

}

DetailController类定义了第二个选项卡。在此类中，帐户名称组合框通过DAO从数据库初始化：

package tabpane.view;

import java.net.URL;
import java.sql.SQLException;
import java.util.Iterator;
import java.util.ResourceBundle;
import java.util.TreeMap;
import java.util.logging.Level;
import java.util.logging.Logger;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.scene.control.ComboBox;
import javafx.scene.layout.AnchorPane;
import tabpane.db.NdDao;
import tabpane.model.AccountObject;

public class DetailController implements Initializable
{
  @FXML public ComboBox<String> accNames;

  @Override
  public void initialize(URL location, ResourceBundle resources) {
    try {
      getAccCBoxView();
    } catch (SQLException ex) {
      Logger.getLogger(DetailController.class.getName()).log(Level.SEVERE, null, ex);
    }
    accNames.getSelectionModel().select(0);
  }

  public void getAccCBoxView() throws SQLException
  {
    ObservableList<String> list = FXCollections.observableArrayList();
    NdDao.connect();//
    TreeMap<Integer, AccountObject> map = NdDao.selectAccounts() ;
    NdDao.disconnect();//
    AccountObject obj ;
    Iterator<AccountObject> li = map.values().iterator();
    while (li.hasNext()){
      obj = li.next();
      list.add(obj.getAccName());
    }
    accNames.setItems(list);
  } 
}

首先，数据库表“L Enqvist”中有一个条目。在“详细信息”选项卡组合框中，如下所示：[！[Fig 1][1][1]

图1。

然后，我通过输入选项卡输入一个新名称，然后按Save:[！[Fig 2][2]][2]

图2

ACCOUNTS表的转储显示添加已成功：

ACCNAME ISENABLED
L Enqvist   false
K Berg      false

如果我单击Account选项卡，我会在组合框中找到它：[！[Fig 3][3][3]Fig 3。

然而，组合框没有更新，我看到的只是图1中的视图。我真的不知道该如何进行，我非常希望能提供一些指导，也许是让它按预期工作所需的代码，或者一些特定的参考信息。到目前为止，我在互联网上的广泛搜索中没有发现任何东西，我想知道这种实现是否真的可行。

In first approach I get the following error dump:

Exception in thread "JavaFX Application Thread" java.lang.NullPointerException
    at tabpane.view.MainController.reloadAccounts(MainController.java:31)
    at tabpane.view.MainController.lambda$initialize$0(MainController.java:26)
    at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
    at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:49)
    at javafx.event.Event.fireEvent(Event.java:198)
    at javafx.scene.control.Tab$1.invalidated(Tab.java:209)
    at javafx.beans.property.BooleanPropertyBase.markInvalid(BooleanPropertyBase.java:109)
    at javafx.beans.property.BooleanPropertyBase.set(BooleanPropertyBase.java:144)
    at javafx.scene.control.Tab.setSelected(Tab.java:185)
    at javafx.scene.control.TabPane$TabPaneSelectionModel.select(TabPane.java:722)
    at javafx.scene.control.TabPane$TabPaneSelectionModel.select(TabPane.java:735)
    at javafx.scene.control.TabPane$TabPaneSelectionModel.select(TabPane.java:656)
    at com.sun.javafx.scene.control.behavior.TabPaneBehavior.selectTab(TabPaneBehavior.java:122)
    at com.sun.javafx.scene.control.skin.TabPaneSkin$TabHeaderSkin$5.handle(TabPaneSkin.java:1332)
    at com.sun.javafx.scene.control.skin.TabPaneSkin$TabHeaderSkin$5.handle(TabPaneSkin.java:1317)
    at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
    at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
    at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)
    at javafx.event.Event.fireEvent(Event.java:198)
    at javafx.scene.Scene$MouseHandler.process(Scene.java:3757)
    at javafx.scene.Scene$MouseHandler.access$1500(Scene.java:3485)
    at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1762)
    at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2494)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:394)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:295)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$353(GlassViewEventHandler.java:432)
    at com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:389)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:431)
    at com.sun.glass.ui.View.handleMouseEvent(View.java:555)
    at com.sun.glass.ui.View.notifyMouse(View.java:937)
    at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at com.sun.glass.ui.win.WinApplication.lambda$null$147(WinApplication.java:177)
    at java.lang.Thread.run(Thread.java:748)

我尝试了许多不同的方法，但都没有成功：

detailController = new FXMLLoader(getClass().getResource("DetailView.fxml")).getController();
detailController = new FXMLLoader(getClass().getResource("/DetailView.fxml")).getController();
detailController = new FXMLLoader(getClass().getResource("./DetailView.fxml")).getController();
detailController = new FXMLLoader(getClass().getResource("view/DetailView.fxml")).getController();
detailController = new FXMLLoader(getClass().getResource("/view/DetailView.fxml")).getController();
detailController = new FXMLLoader(getClass().getResource("src/view/DetailView.fxml")).getController();
detailController = new FXMLLoader(getClass().getResource("/src/view/DetailView.fxml")).getController();

我的项目继承权如上图所示：[！[Fig 4][4][4]

编辑3可能的解决方案

public class MainController实现可初始化的{@FXML public TabPane TabPane；@FXML public Tab inputTab；@FXML public Tab accountTab；@FXML public ComboBox accNames；

    private static String selectedAccount;

    @Override
    public void initialize(URL location, ResourceBundle resources) { 
      try {
        accNames.setVisible(false);
        loadAccounts();
      } catch (SQLException ex) {
        Logger.getLogger(MainController.class.getName()).log(Level.SEVERE, null, ex);
      }

      accountTab.setOnSelectionChanged(event -> {
        try {
          loadAccounts();
          accNames.setVisible(true);
        } catch (SQLException ex) {
          Logger.getLogger(MainController.class.getName()).log(Level.SEVERE, null, ex);
        }
      });

      inputTab.setOnSelectionChanged(event -> { 
        accNames.setVisible(false);         
      });

      accNames.getSelectionModel().select(0);
    }

    @FXML private void handleAccNamesCBox () {
      try {
        selectedAccount = accNames.getSelectionModel().getSelectedItem().toString();
      } catch (NullPointerException e) {}
    }

    public static String setSelectedAccount() {
      return selectedAccount;
    }


    public void loadAccounts() throws SQLException
    {
      ObservableList<String> list = FXCollections.observableArrayList();
      NdDao.connect();//
      TreeMap<Integer, AccountObject> map = NdDao.selectAccounts() ;
      NdDao.disconnect();//
      AccountObject obj ;
      Iterator<AccountObject> li = map.values().iterator();
      while (li.hasNext()){
        obj = li.next();
        list.add(obj.getAccName());
      }
      accNames.setItems(list);
    } 

    @FXML private void handleExitBtn() {
        System.exit(0);
    }
}

input controller和inputPane保持不变，大部分处理逻辑从detailPane中剥离：

public class DetailController implements Initializable{

  @FXML private AnchorPane detailPane;

  @Override
  public void initialize(URL location, ResourceBundle resources) {}

}

仍然需要一个解决方案来从MainController中检索所选的值，并在DetailController中对其进行处理，但至少组合框更新现在正在按预期工作。在以某种方式加载选项卡时，我花了几天的时间试图解决持久的空指针异常，现在我确信没有其他解决方案，JavaFX上通过对象属性的自动更新功能并没有按照我最初希望的方式工作。当更新同一视图中的对象时，这很好，但当一个人试图从一个视图（如一个选项卡）更新对象，并在另一个视图（即不同的选项卡）中获得更新结果时，它会崩溃。

共有1个答案

狄峰

2023-03-14

解决方案似乎是从主控制器访问相关选项卡的控制器视图，方法是在主控制器中嵌入对选项卡控制器的引用，然后通过嵌入式选项卡GUI上的控制器执行您需要的任何操作。所以主控制器现在看起来像这样：

package tabpane.view;

import java.net.URL;
import java.sql.SQLException;
import java.util.ResourceBundle;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.scene.control.Button;
import javafx.scene.control.Tab;
import javafx.scene.control.TabPane;

public class MainController implements Initializable{
  @FXML private TabPane tabPane;
  // Inject input tab content.
  @FXML private Tab inputTab;
  // Inject input tab controller
  @FXML private InputController includedInputViewController;
  // Inject account detail tab.
  @FXML private Tab detailTab;
  // Inject account detail tab controller
  @FXML private DetailController includedDetailViewController;
  @FXML private Button exitBtn;

  @Override
  public void initialize(URL location, ResourceBundle resources) {     
    detailTab.setOnSelectionChanged(event -> {
      reloadAccounts();
    });
  }

  private void reloadAccounts() {
    try {
      includedDetailViewController.getAccCBoxView();
    } catch (SQLException ex) {
        ex.printStackTrace();
    }
    includedDetailViewController.accNames.getSelectionModel().select(0);
  }

  @FXML private void handleExitBtn() {
    System.exit(0);
  }
}

从主控制器到fxml视图的参考映射可以在主fxml中的fx:include语句中看到。需要注意的是，fxml中嵌入的视图id必须在主控制器中附加Controller。这是这种嵌入式视图的fxml命名约定。

<?xml version="1.0" encoding="UTF-8"?>

<?import javafx.scene.control.Button?>
<?import javafx.scene.control.Tab?>
<?import javafx.scene.control.TabPane?>
<?import javafx.scene.layout.AnchorPane?>

<AnchorPane id="AnchorPane" prefHeight="400.0" prefWidth="600.0" xmlns="http://javafx.com/javafx/8.0.171" xmlns:fx="http://javafx.com/fxml/1" fx:controller="tabpane.view.MainController">
 <children>
      <TabPane fx:id="tabPane" prefHeight="345.0" prefWidth="600.0" style="-fx-background-color: blue;" tabClosingPolicy="UNAVAILABLE">
        <tabs>
          <Tab fx:id="inputTab" closable="false" text="Input">
            <content> 
               <fx:include fx:id="includedInputView" source="InputView.fxml" />
            </content>
          </Tab>
          <Tab fx:id="detailTab" closable="false" text="Detail">
            <content> 
               <fx:include fx:id="includedDetailView" source="DetailView.fxml" />
            </content>
          </Tab>
        </tabs>
      </TabPane>
      <Button fx:id="exitBtn" layoutX="529.0" layoutY="345.0" mnemonicParsing="false" onAction="#handleExitBtn" text="Exit" />
   </children>

</AnchorPane>

在该应用程序中，当用户从MainController视图中单击Account选项卡时，组合框的更新视图始终会执行。因此，如果用户通过“输入”选项卡更新数据库，然后单击“帐户”选项卡，则数据库的更新视图始终显示在“帐户”选项卡组合框中。细节控制器现在看起来像这样：

package tabpane.view;

import java.net.URL;
import java.sql.SQLException;
import java.util.Iterator;
import java.util.ResourceBundle;
import java.util.TreeMap;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.scene.control.ComboBox;
import tabpane.db.NdDao;
import tabpane.model.AccountObject;

public class DetailController implements Initializable 
{
  @FXML protected ComboBox<String> accNames;

  @Override
  public void initialize(URL location, ResourceBundle resources) {
    try {
      getAccCBoxView();
    } catch (SQLException ex) {}
    accNames.getSelectionModel().select(0);
  }

  public void getAccCBoxView() throws SQLException
  {
    ObservableList<String> list = FXCollections.observableArrayList();
    NdDao.connect();//
    TreeMap<Integer, AccountObject> map = NdDao.selectAccounts() ;
    NdDao.disconnect();//
    AccountObject obj ;
    Iterator<AccountObject> li = map.values().iterator();
    while (li.hasNext()){
      obj = li.next();
      list.add(obj.getAccName());
    }
    accNames.setItems(list);
  } 
}

对于记录，输入视图和控制器看起来与之前基本相同：

package tabpane.view;

import java.net.URL;
import java.sql.SQLException;
import java.util.ResourceBundle;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.scene.control.CheckBox;
import javafx.scene.control.TextField;
import tabpane.db.NdDao;
import tabpane.model.AccountObject;

public class InputController implements Initializable   {
  @FXML private TextField accName;
  @FXML private CheckBox isEnabled; 

  @Override
  public void initialize(URL location, ResourceBundle resources) {}

  @FXML private void handleSaveBtn() throws SQLException {
    AccountObject obj = new AccountObject(accName.getText(), isEnabled.isSelected());
    NdDao.connect();
    NdDao.insertAccount(obj);
    NdDao.disconnect(); 
  }
}

输入视图：

<?xml version="1.0" encoding="UTF-8"?>

<?import javafx.scene.control.Button?>
<?import javafx.scene.control.CheckBox?>
<?import javafx.scene.control.Label?>
<?import javafx.scene.control.TextField?>
<?import javafx.scene.layout.AnchorPane?>

<AnchorPane id="AnchorPane" prefHeight="400.0" prefWidth="600.0" xmlns="http://javafx.com/javafx/8.0.171" xmlns:fx="http://javafx.com/fxml/1" fx:controller="tabpane.view.InputController">
   <children>
      <Label ellipsisString="" graphicTextGap="0.0" layoutX="134.0" layoutY="92.0" text="Account holder:" textFill="MAGENTA" />
      <CheckBox fx:id="isEnabled" ellipsisString="" graphicTextGap="0.0" layoutX="247.0" layoutY="137.0" mnemonicParsing="false" prefHeight="21.0" prefWidth="132.0" text="Enable" textFill="MAGENTA" />
      <TextField fx:id="accName" layoutX="247.0" layoutY="87.0" prefHeight="31.0" prefWidth="245.0" />
      <Button fx:id="saveBtn" layoutX="239.0" layoutY="200.0" mnemonicParsing="false" onAction="#handleSaveBtn" style="-fx-background-color: green;" text="Save" textFill="#eeecec" />
   </children>
</AnchorPane>

如果一开始觉得有点困惑，那么我在上面的一条评论中提到的FXML组合文档尤其有用。

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共有1个答案

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