在 fxml 中带有 Textfield 的 NullPointerException
NullPointerException with Textfield in fxml
我遇到了 NullPointerException 问题。
这是我的控制器：
public class Controller implements Initializable{
public Label lbTitle;
public Label lbAuthor;
public Label lbChapters;
public TextField tfTitle;
public TextField tfAuthor;
public TextArea taChapters;
public ListView<Book> listView;
private void OpenNewWindow(Book book1) throws Exception {
String selected = listView.getSelectionModel().getSelectedItem().toString();
FXMLLoader fxmlLoader = new FXMLLoader();
fxmlLoader.setLocation(getClass().getResource("/zli/BooksFX/NewWindow.fxml"));
Scene scene = new Scene(fxmlLoader.load(), 400, 400);
Stage stage = new Stage();
tfTitle.setText(book1.getTitle());
tfAuthor.setText(book1.getAuthor());
taChapters.setText(book1.toStringChapters());
stage.setTitle(selected);
stage.setScene(scene);
stage.show();
}
@Override
public void initialize(URL location, ResourceBundle resources) {
Chapter chapter1Book1 = new Chapter(1, 100, "First Chapter...");
Chapter chapter2Book1 = new Chapter(2, 400, "Second Chapter...");
ArrayList<Chapter> book1Chapters = new ArrayList<>();
book1Chapters.add(chapter1Book1);
book1Chapters.add(chapter2Book1);
Book book1 = new Book("IT: Not the one with the clown", "Stephen ITBerg", book1Chapters);
Chapter chapter1Book2 = new Chapter(1, 100, "First Chapter...");
Chapter chapter2Book2 = new Chapter(2, 400, "Second Chapter...");
ArrayList<Chapter> book2Chapters = new ArrayList<>();
book1Chapters.add(chapter1Book2);
book1Chapters.add(chapter2Book2);
Book book2 = new Book("Z Men", "Stan Lee", book2Chapters);
Chapter chapter1Book3 = new Chapter(1, 100, "First Chapter...");
Chapter chapter2Book3 = new Chapter(2, 400, "Second Chapter...");
ArrayList<Chapter> book3Chapters = new ArrayList<>();
book1Chapters.add(chapter1Book3);
book1Chapters.add(chapter2Book3);
Book book3 = new Book("Captain AlivePool", "Undead Zombie", book3Chapters);
ObservableList<Book> items = FXCollections.observableArrayList (book1, book2, book3);
listView.setItems(items);
listView.setOnMouseClicked(e -> {
try {
OpenNewWindow(book1);
} catch (Exception e1) {
e1.printStackTrace();
}
});
}
}
这是我的 .fxml：
<Pane prefHeight="400.0" prefWidth="400.0" style="-fx-background-color: #1ba77f;" xmlns="http://javafx.com/javafx/8.0.121" xmlns:fx="http://javafx.com/fxml/1" fx:controller="zli.BooksFX.Controller">
<ListView fx:id="listView" disable="true" opacity="0.0" prefHeight="400.0" prefWidth="400.0" />
<Label fx:id="lbTitle" layoutX="8.0" layoutY="20.0" prefHeight="27.0" prefWidth="57.0" text="Title: " />
<Label fx:id="lbAuthor" layoutX="8.0" layoutY="90.0" text="Author: " />
<TextField text="ert" fx:id="tfTitle" editable="false" layoutX="72.0" layoutY="14.0" prefHeight="39.0" prefWidth="316.0" />
<TextField text="sdf" fx:id="tfAuthor" editable="false" layoutX="72.0" layoutY="84.0" prefHeight="39.0" prefWidth="316.0" />
<Label fx:id="lbChapters" layoutX="8.0" layoutY="160.0" text="Chapters: " />
<TextArea text="sdfs" fx:id="taChapters" editable="false" layoutX="7.0" layoutY="187.0" prefHeight="200.0" prefWidth="383.0" />
</Pane>
这是错误信息：
java.lang.NullPointerException
at zli.BooksFX.Controller.OpenNewWindow(Controller.java:37)
at zli.BooksFX.Controller.lambda$initialize[=12=](Controller.java:73)
at javafx.base/com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86)
at javafx.base/com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
at javafx.base/com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
at javafx.base/com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at javafx.base/com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
at javafx.base/com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)
at javafx.base/javafx.event.Event.fireEvent(Event.java:198)
at javafx.graphics/javafx.scene.Scene$ClickGenerator.postProcess(Scene.java:3589)
at javafx.graphics/javafx.scene.Scene$ClickGenerator.access00(Scene.java:3517)
at javafx.graphics/javafx.scene.Scene$MouseHandler.process(Scene.java:3885)
at javafx.graphics/javafx.scene.Scene$MouseHandler.access00(Scene.java:3604)
at javafx.graphics/javafx.scene.Scene.processMouseEvent(Scene.java:1874)
at javafx.graphics/javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2613)
at javafx.graphics/com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:397)
at javafx.graphics/com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:295)
at java.base/java.security.AccessController.doPrivileged(Native Method)
at javafx.graphics/com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent(GlassViewEventHandler.java:434)
at javafx.graphics/com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:389)
at javafx.graphics/com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:433)
at javafx.graphics/com.sun.glass.ui.View.handleMouseEvent(View.java:556)
at javafx.graphics/com.sun.glass.ui.View.notifyMouse(View.java:942)
at javafx.graphics/com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at javafx.graphics/com.sun.glass.ui.win.WinApplication.lambda$runLoop(WinApplication.java:175)
at java.base/java.lang.Thread.run(Thread.java:844)
现在，当我想将我的 TextFields 和 TextAreas（tfTitle、tfAuthor、taChapters）的文本设置为分配的值时，它在 Controller 的第 37 行给我一个 "java.lang.NullPointerException"，就是这个:
tfTitle.setText(book1.getTitle());
供您参考："Book" 是章节的存储 Class。
因为有人要求，我的另一个.fxml:
<GridPane xmlns:fx="http://javafx.com/fxml/1" xmlns="http://javafx.com/javafx/2.2"
fx:controller="zli.BooksFX.Controller">
<ListView fx:id="listView" prefWidth="400" />
</GridPane>
可能是您还没有初始化 Texfield。
在 tfTitle 声明上使用 @FXML 注释
@FXML
public TextField tfTitle;
其他领域也是如此。
您使用classController作为两个不同fxml-files的控制器。
第一个只声明 listView 而不是 tfTitle、tfAuthor 和 taChapters 因此你在 tfTitle.setText(book1.getTitle());
处得到一个 NullPointerException
当您在 OpenNewWindow 中加载第二个 fxml-file 时，您还会创建一个新的 Controller 对象。
现在您可以使用 fxmlLoader.setController(this); 重用第一个控制器并从 NewWindow.fxml 中删除 fx:controller="zli.BooksFX.Controller"（不要这样做，因为您会 运行进入类似这样的问题).
或者为每个控制器创建两个独立的控制器fxml-file并在控制器之间传递书籍。
对于第二个控制器，您需要类似的东西：
public void setBook(Book book) {
tfTitle.setText(book.getTitle());
tfAuthor.setText(book.getAuthor());
taChapters.setText(book.toStringChapters());
}
并在fxmlLoader.load()
之后传书((BookDetailController)fxmlLoader.getController()).setBook(book1);
我遇到了 NullPointerException 问题。
这是我的控制器：
public class Controller implements Initializable{
public Label lbTitle;
public Label lbAuthor;
public Label lbChapters;
public TextField tfTitle;
public TextField tfAuthor;
public TextArea taChapters;
public ListView<Book> listView;
private void OpenNewWindow(Book book1) throws Exception {
String selected = listView.getSelectionModel().getSelectedItem().toString();
FXMLLoader fxmlLoader = new FXMLLoader();
fxmlLoader.setLocation(getClass().getResource("/zli/BooksFX/NewWindow.fxml"));
Scene scene = new Scene(fxmlLoader.load(), 400, 400);
Stage stage = new Stage();
tfTitle.setText(book1.getTitle());
tfAuthor.setText(book1.getAuthor());
taChapters.setText(book1.toStringChapters());
stage.setTitle(selected);
stage.setScene(scene);
stage.show();
}
@Override
public void initialize(URL location, ResourceBundle resources) {
Chapter chapter1Book1 = new Chapter(1, 100, "First Chapter...");
Chapter chapter2Book1 = new Chapter(2, 400, "Second Chapter...");
ArrayList<Chapter> book1Chapters = new ArrayList<>();
book1Chapters.add(chapter1Book1);
book1Chapters.add(chapter2Book1);
Book book1 = new Book("IT: Not the one with the clown", "Stephen ITBerg", book1Chapters);
Chapter chapter1Book2 = new Chapter(1, 100, "First Chapter...");
Chapter chapter2Book2 = new Chapter(2, 400, "Second Chapter...");
ArrayList<Chapter> book2Chapters = new ArrayList<>();
book1Chapters.add(chapter1Book2);
book1Chapters.add(chapter2Book2);
Book book2 = new Book("Z Men", "Stan Lee", book2Chapters);
Chapter chapter1Book3 = new Chapter(1, 100, "First Chapter...");
Chapter chapter2Book3 = new Chapter(2, 400, "Second Chapter...");
ArrayList<Chapter> book3Chapters = new ArrayList<>();
book1Chapters.add(chapter1Book3);
book1Chapters.add(chapter2Book3);
Book book3 = new Book("Captain AlivePool", "Undead Zombie", book3Chapters);
ObservableList<Book> items = FXCollections.observableArrayList (book1, book2, book3);
listView.setItems(items);
listView.setOnMouseClicked(e -> {
try {
OpenNewWindow(book1);
} catch (Exception e1) {
e1.printStackTrace();
}
});
}
}
这是我的 .fxml：
<Pane prefHeight="400.0" prefWidth="400.0" style="-fx-background-color: #1ba77f;" xmlns="http://javafx.com/javafx/8.0.121" xmlns:fx="http://javafx.com/fxml/1" fx:controller="zli.BooksFX.Controller">
<ListView fx:id="listView" disable="true" opacity="0.0" prefHeight="400.0" prefWidth="400.0" />
<Label fx:id="lbTitle" layoutX="8.0" layoutY="20.0" prefHeight="27.0" prefWidth="57.0" text="Title: " />
<Label fx:id="lbAuthor" layoutX="8.0" layoutY="90.0" text="Author: " />
<TextField text="ert" fx:id="tfTitle" editable="false" layoutX="72.0" layoutY="14.0" prefHeight="39.0" prefWidth="316.0" />
<TextField text="sdf" fx:id="tfAuthor" editable="false" layoutX="72.0" layoutY="84.0" prefHeight="39.0" prefWidth="316.0" />
<Label fx:id="lbChapters" layoutX="8.0" layoutY="160.0" text="Chapters: " />
<TextArea text="sdfs" fx:id="taChapters" editable="false" layoutX="7.0" layoutY="187.0" prefHeight="200.0" prefWidth="383.0" />
</Pane>
这是错误信息：
java.lang.NullPointerException
at zli.BooksFX.Controller.OpenNewWindow(Controller.java:37)
at zli.BooksFX.Controller.lambda$initialize[=12=](Controller.java:73)
at javafx.base/com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86)
at javafx.base/com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
at javafx.base/com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
at javafx.base/com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at javafx.base/com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
at javafx.base/com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)
at javafx.base/javafx.event.Event.fireEvent(Event.java:198)
at javafx.graphics/javafx.scene.Scene$ClickGenerator.postProcess(Scene.java:3589)
at javafx.graphics/javafx.scene.Scene$ClickGenerator.access00(Scene.java:3517)
at javafx.graphics/javafx.scene.Scene$MouseHandler.process(Scene.java:3885)
at javafx.graphics/javafx.scene.Scene$MouseHandler.access00(Scene.java:3604)
at javafx.graphics/javafx.scene.Scene.processMouseEvent(Scene.java:1874)
at javafx.graphics/javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2613)
at javafx.graphics/com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:397)
at javafx.graphics/com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:295)
at java.base/java.security.AccessController.doPrivileged(Native Method)
at javafx.graphics/com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent(GlassViewEventHandler.java:434)
at javafx.graphics/com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:389)
at javafx.graphics/com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:433)
at javafx.graphics/com.sun.glass.ui.View.handleMouseEvent(View.java:556)
at javafx.graphics/com.sun.glass.ui.View.notifyMouse(View.java:942)
at javafx.graphics/com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at javafx.graphics/com.sun.glass.ui.win.WinApplication.lambda$runLoop(WinApplication.java:175)
at java.base/java.lang.Thread.run(Thread.java:844)
现在，当我想将我的 TextFields 和 TextAreas（tfTitle、tfAuthor、taChapters）的文本设置为分配的值时，它在 Controller 的第 37 行给我一个 "java.lang.NullPointerException"，就是这个:
tfTitle.setText(book1.getTitle());
供您参考："Book" 是章节的存储 Class。
因为有人要求，我的另一个.fxml:
<GridPane xmlns:fx="http://javafx.com/fxml/1" xmlns="http://javafx.com/javafx/2.2"
fx:controller="zli.BooksFX.Controller">
<ListView fx:id="listView" prefWidth="400" />
</GridPane>
可能是您还没有初始化 Texfield。
在 tfTitle 声明上使用 @FXML 注释
@FXML
public TextField tfTitle;
其他领域也是如此。
您使用classController作为两个不同fxml-files的控制器。
第一个只声明 listView 而不是 tfTitle、tfAuthor 和 taChapters 因此你在 tfTitle.setText(book1.getTitle());
当您在 OpenNewWindow 中加载第二个 fxml-file 时，您还会创建一个新的 Controller 对象。
现在您可以使用 fxmlLoader.setController(this); 重用第一个控制器并从 NewWindow.fxml 中删除 fx:controller="zli.BooksFX.Controller"（不要这样做，因为您会 运行进入类似这样的问题).
或者为每个控制器创建两个独立的控制器fxml-file并在控制器之间传递书籍。
对于第二个控制器，您需要类似的东西：
public void setBook(Book book) {
tfTitle.setText(book.getTitle());
tfAuthor.setText(book.getAuthor());
taChapters.setText(book.toStringChapters());
}
并在fxmlLoader.load()
((BookDetailController)fxmlLoader.getController()).setBook(book1);