在运行时JavaFx上设置TextField提示文本

埃德蒙

在运行时运行案例0时,我不断收到java.lang.NullPointerException。该问题似乎与为我的TextField设置提示文本有关。但是,当我切换选项卡时问题不会再出现。GUI是在Scene Builder中构建的。如何将TextField初始化为非null值。

public class BackEndController implements Initializable{

@FXML
private TabPane tabPane;
@FXML
private Tab bookingTab;
@FXML
private Tab waitListTab;
@FXML
private Tab excursionsTab;
@FXML
private TextField searchEntry;

@Override
public void initialize(URL location, ResourceBundle resources) {
    searchEntry.setPromptText("");

}

@FXML
public void switchTabs() {

    int selectedTab = tabPane.getSelectionModel().getSelectedIndex();
    switch (selectedTab){
        case 0:
            searchEntry.setPromptText("Enter booking ID");
            break;
        case 1:
            searchEntry.setPromptText("Enter event name");
            break;
        case 2:
            searchEntry.setPromptText("Enter list ID");
            break;
    }

}

这是确切的错误代码

    Exception in thread "JavaFX Application Thread" java.lang.RuntimeException: java.lang.reflect.InvocationTargetException
    at javafx.fxml/javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1787)
    at javafx.fxml/javafx.fxml.FXMLLoader$ControllerMethodEventHandler.handle(FXMLLoader.java:1670)
    at javafx.base/com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86)
    at javafx.base/com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
    at javafx.base/com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
    at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
    at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at javafx.base/com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
    at javafx.base/com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)
    at javafx.base/javafx.event.Event.fireEvent(Event.java:198)
    at javafx.controls/javafx.scene.control.Tab$1.invalidated(Tab.java:215)
    at javafx.base/javafx.beans.property.BooleanPropertyBase.markInvalid(BooleanPropertyBase.java:110)
    at javafx.base/javafx.beans.property.BooleanPropertyBase.set(BooleanPropertyBase.java:145)
    at javafx.controls/javafx.scene.control.Tab.setSelected(Tab.java:189)
    at javafx.controls/javafx.scene.control.TabPane$TabPaneSelectionModel.select(TabPane.java:738)
    at javafx.controls/javafx.scene.control.TabPane$TabPaneSelectionModel.select(TabPane.java:751)
    at javafx.controls/javafx.scene.control.TabPane$TabPaneSelectionModel.findNearestAvailableTab(TabPane.java:810)
    at javafx.controls/javafx.scene.control.TabPane$TabPaneSelectionModel.lambda$new$0(TabPane.java:707)
    at javafx.base/com.sun.javafx.collections.ListListenerHelper$Generic.fireValueChangedEvent(ListListenerHelper.java:329)
    at javafx.base/com.sun.javafx.collections.ListListenerHelper.fireValueChangedEvent(ListListenerHelper.java:73)
    at javafx.base/javafx.collections.ObservableListBase.fireChange(ObservableListBase.java:233)
    at javafx.base/javafx.collections.ListChangeBuilder.commit(ListChangeBuilder.java:482)
    at javafx.base/javafx.collections.ListChangeBuilder.endChange(ListChangeBuilder.java:541)
    at javafx.base/javafx.collections.ObservableListBase.endChange(ObservableListBase.java:205)
    at javafx.base/javafx.collections.ModifiableObservableListBase.add(ModifiableObservableListBase.java:155)
    at java.base/java.util.AbstractList.add(AbstractList.java:111)
    at javafx.fxml/javafx.fxml.FXMLLoader$Element.add(FXMLLoader.java:175)
    at javafx.fxml/javafx.fxml.FXMLLoader$PropertyElement.add(FXMLLoader.java:1415)
    at javafx.fxml/javafx.fxml.FXMLLoader$ValueElement.processEndElement(FXMLLoader.java:796)
    at javafx.fxml/javafx.fxml.FXMLLoader.processEndElement(FXMLLoader.java:2838)
    at javafx.fxml/javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2557)
    at javafx.fxml/javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2466)
    at javafx.fxml/javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3253)
    at javafx.fxml/javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3210)
    at javafx.fxml/javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3179)
    at javafx.fxml/javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3152)
    at javafx.fxml/javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3129)
    at javafx.fxml/javafx.fxml.FXMLLoader.load(FXMLLoader.java:3122)
    at com.main.backend.BackEnd.start(BackEnd.java:18)
    at javafx.graphics/com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$9(LauncherImpl.java:919)
    at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runAndWait$11(PlatformImpl.java:449)
    at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runLater$9(PlatformImpl.java:418)
    at java.base/java.security.AccessController.doPrivileged(Native Method)
    at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runLater$10(PlatformImpl.java:417)
    at javafx.graphics/com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:96)
    at javafx.graphics/com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at javafx.graphics/com.sun.glass.ui.win.WinApplication.lambda$runLoop$3(WinApplication.java:175)
    at java.base/java.lang.Thread.run(Thread.java:844)
Caused by: java.lang.reflect.InvocationTargetException
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:564)
    at com.sun.javafx.reflect.Trampoline.invoke(MethodUtil.java:76)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:564)
    at javafx.base/com.sun.javafx.reflect.MethodUtil.invoke(MethodUtil.java:275)
    at javafx.fxml/com.sun.javafx.fxml.MethodHelper.invoke(MethodHelper.java:83)
    at javafx.fxml/javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1784)
    ... 47 more
Caused by: java.lang.NullPointerException
    at com.main.backend.BackEndController.switchTabs(BackEndController.java:58)
    ... 59 more

我的FXML文件

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

<?import com.jfoenix.controls.JFXButton?>
<?import com.jfoenix.controls.JFXListView?>
<?import com.jfoenix.controls.JFXTabPane?>
<?import com.jfoenix.controls.JFXTextField?>
<?import javafx.scene.control.Label?>
<?import javafx.scene.control.Separator?>
<?import javafx.scene.control.Tab?>
<?import javafx.scene.layout.AnchorPane?>
<?import javafx.scene.text.Font?>

<AnchorPane maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="810.0" prefWidth="1250.0" style="-fx-background-color: #FFFFFF;" xmlns="http://javafx.com/javafx/9.0.1" xmlns:fx="http://javafx.com/fxml/1" fx:controller="com.main.backend.BackEndController">
   <children>
      <JFXTabPane fx:id="tabPane" layoutY="67.0" prefHeight="743.0" prefWidth="1250.0" stylesheets="@dark-theme.css">
         <tabs>
            <Tab fx:id="bookingTab" onSelectionChanged="#switchTabs" text="Bookings">
              <content>
                <AnchorPane minHeight="0.0" minWidth="0.0" prefHeight="180.0" prefWidth="200.0" style="-fx-background-color: #F7F7F9;" />
              </content>
            </Tab>
            <Tab fx:id="excursionsTab" onSelectionChanged="#switchTabs" text="Excursions">
              <content>
                <AnchorPane minHeight="0.0" minWidth="0.0" prefHeight="180.0" prefWidth="200.0" style="-fx-background-color: #F7F7F9;">
                     <children>
                        <AnchorPane layoutX="736.0" layoutY="16.0" prefHeight="672.0" prefWidth="501.0" style="-fx-background-color: #FFFFFF; -fx-border-color: #D4D6D8;">
                           <children>
                              <JFXTextField alignment="CENTER" layoutX="17.0" layoutY="85.0" prefHeight="33.0" prefWidth="135.0" promptText="Port ID" styleClass="main-text" stylesheets="@dark-theme.css">
                                 <font>
                                    <Font name="System Bold" size="15.0" />
                                 </font>
                              </JFXTextField>
                              <Label alignment="CENTER" layoutX="12.0" layoutY="33.0" prefHeight="33.0" prefWidth="478.0" text="Label" textFill="#9f9f9f">
                                 <font>
                                    <Font name="System Bold" size="15.0" />
                                 </font>
                              </Label>
                              <JFXButton layoutX="265.0" layoutY="178.0" prefHeight="33.0" prefWidth="174.0" style="-fx-background-color: #FA597A; -fx-border-color: #FA597A; -fx-border-radius: 30; -fx-background-radius: 30;" text="Delete Event" textFill="WHITE">
                                 <font>
                                    <Font name="System Bold" size="15.0" />
                                 </font>
                              </JFXButton>
                              <JFXButton layoutX="17.0" layoutY="178.0" prefHeight="33.0" prefWidth="185.0" style="-fx-background-color: #FFFFFF; -fx-border-color: #214099; -fx-border-radius: 30; -fx-background-radius: 30;" text="Update Event" textFill="#214099">
                                 <font>
                                    <Font name="System Bold" size="15.0" />
                                 </font>
                              </JFXButton>
                              <Separator layoutX="21.0" layoutY="272.0" prefHeight="13.0" prefWidth="460.0" />
                              <JFXTextField alignment="CENTER" layoutX="17.0" layoutY="321.0" prefHeight="33.0" prefWidth="468.0" promptText="Event Name" styleClass="main-text" stylesheets="@dark-theme.css">
                                 <font>
                                    <Font name="System Bold" size="15.0" />
                                 </font>
                              </JFXTextField>
                              <JFXTextField alignment="CENTER" layoutX="19.0" layoutY="396.0" prefHeight="33.0" prefWidth="135.0" promptText="Port ID" styleClass="main-text" stylesheets="@dark-theme.css">
                                 <font>
                                    <Font name="System Bold" size="15.0" />
                                 </font>
                              </JFXTextField>
                              <JFXButton layoutX="173.0" layoutY="470.0" prefHeight="33.0" prefWidth="185.0" style="-fx-background-color: #FFFFFF; -fx-border-color: #15d31e; -fx-border-radius: 30; -fx-background-radius: 30;" text="Add Event" textFill="#15d31e">
                                 <font>
                                    <Font name="System Bold" size="15.0" />
                                 </font>
                              </JFXButton>
                           </children>
                        </AnchorPane>
                        <JFXListView fx:id="excursionsList" layoutX="16.0" layoutY="16.0" prefHeight="672.0" prefWidth="711.0" styleClass="list-cell" stylesheets="@dark-theme.css" />
                     </children>
                  </AnchorPane>
              </content>
            </Tab>
            <Tab fx:id="waitListTab" onSelectionChanged="#switchTabs" text="Waiting List">
               <content>
                  <AnchorPane minHeight="0.0" minWidth="0.0" prefHeight="180.0" prefWidth="200.0" style="-fx-background-color: #F7F7F9;" />
               </content>
            </Tab>
         </tabs>
      </JFXTabPane>
      <JFXButton layoutX="609.0" layoutY="18.0" prefHeight="32.0" prefWidth="110.0" style="-fx-background-color: #214099; -fx-border-color: #214099; -fx-border-radius: 30; -fx-background-radius: 30;" text="Search" textFill="WHITE">
         <font>
            <Font name="System Bold" size="15.0" />
         </font>
      </JFXButton>
      <JFXButton layoutX="740.0" layoutY="18.0" prefHeight="32.0" prefWidth="99.0" style="-fx-background-color: #FFFFFF; -fx-border-color: #214099; -fx-border-radius: 30; -fx-background-radius: 30;" text="Reset" textFill="#214099">
         <font>
            <Font name="System Bold" size="15.0" />
         </font>
      </JFXButton>
      <JFXButton layoutX="1113.0" layoutY="18.0" prefHeight="32.0" prefWidth="116.0" style="-fx-background-color: #FA597A; -fx-border-color: #FA597A; -fx-border-radius: 30; -fx-background-radius: 30;" text="Sign Out" textFill="WHITE">
         <font>
            <Font name="System Bold" size="15.0" />
         </font>
      </JFXButton>
      <JFXTextField fx:id="searchEntry" layoutX="104.0" layoutY="20.0" prefHeight="32.0" prefWidth="449.0" promptText="Enter booking ID" styleClass="search-textfield" stylesheets="@dark-theme.css">
         <font>
            <Font name="System Bold" size="15.0" />
         </font>
      </JFXTextField>
   </children>
</AnchorPane>

FXML文件确实附加了正确的控制器

詹姆斯·D

解析FXML时,FXMLLoader会创建TabPane,并创建Tab并将它们添加到中TabPane添加第一个选项卡后,该选项卡将变为选中selected状态,因此其状态将更改并onSelectionChanged调用处理程序。由于TabPane出现在FXML文件中的searchEntry文本字段之前,因此发生在searchEntry初始化之前,因此您的switchTabs()方法将引发空指针异常。

您可以简单地向处理程序方法添加一个空检查:

@FXML
public void switchTabs() {

    if (searchEntry == null) {
        return ;
    }

    int selectedTab = tabPane.getSelectionModel().getSelectedIndex();
    switch (selectedTab){
        case 0:
            searchEntry.setPromptText("Enter booking ID");
            break;
        case 1:
            searchEntry.setPromptText("Enter event name");
            break;
        case 2:
            searchEntry.setPromptText("Enter list ID");
            break;
    }

}

添加此代码只是为了处理仅在加载期间发生的特殊情况,这有点难看。我宁愿只在initalize()方法中注册一个处理程序onSelectionChanged从FXML文件的选项卡中删除所有处理程序,然后将以下内容添加到控制器的initialize()方法中:

@Override
public void initialize(URL location, ResourceBundle resources) {
    tabPane.getSelectionModel().selectedIndexProperty().addListener(
        (obs, oldIndex, newIndex) -> switchTabs());

    // initialize prompt text for initially-selected tab:
    switchTabs();
    // searchEntry.setPromptText("");

}

本文收集自互联网,转载请注明来源。

如有侵权,请联系 [email protected] 删除。

编辑于
0

我来说两句

0 条评论
登录 后参与评论

相关文章