您试图在控制器的构造函数中设置树视图的根项。
当FXMLLoader
负载FXML文件,它将解析FXML文件,并指出任何fx:id
属性。它将实例化控制器(通过调用其no- arg构造函数),然后它将@FXML
使用具有匹配fx:id
属性的相应对象初始化任何带注释的字段。完成后,它将调用控制器的initialize()
方法(如果有的话)。
因此,构造函数是在noteTree
初始化之前执行的FXMLLoader
(当然,这是可能发生的唯一顺序)。因此,当您致电
noteTree.setRoot(rootItem);
@H_403_23@
noteTree
还是null
。解决方法只是将构造函数中的代码移至
initialize
方法:public class NoteKeeperController implements Initializable{ NoteBook noteBook; TreeItem<String> rootItem; public BorderPane root; @FXML private TreeView<String> noteTree; @FXML private ScrollPane sp; @FXML private Button newNoteButton; @Override public void initialize(URL location, ResourceBundle resources){ rootItem = new TreeItem<String> ("FirstNote"); rootItem.setExpanded(true); noteTree.setRoot(rootItem); noteBook= new NoteBook(); } // ... }
@H_403_23@解决方法
我的FXML注入有问题。据我所知,我已经设置了程序,但似乎缺少了一些东西。我的代码如下:
主要:
package application; import javafx.application.Application; import javafx.stage.Stage; import javafx.scene.Scene; import javafx.scene.layout.BorderPane; import javafx.fxml.FXML; import javafx.fxml.FXMLLoader; public class Main extends Application { @Override public void start(Stage primaryStage) { try { FXMLLoader loader = new FXMLLoader(getClass().getResource("NoteKeeper.fxml")); BorderPane root = (BorderPane)loader.load(); Scene scene = new Scene(root,root.getHeight(),root.getWidth()); scene.getStylesheets().add(getClass().getResource("application.css").toExternalForm()); primaryStage.setScene(scene); primaryStage.show(); } catch(Exception e) { e.printStackTrace(); } } public static void main(String[] args) { launch(args); } }
控制器:
package application; import java.net.URL; import java.util.ResourceBundle; import javafx.fxml.FXML; import javafx.fxml.Initializable; import javafx.scene.control.Button; import javafx.scene.control.ScrollPane; import javafx.scene.control.TreeItem; import javafx.scene.control.TreeView; import javafx.scene.layout.BorderPane; public class NoteKeeperController implements Initializable{ NoteBook noteBook; TreeItem<String> rootItem; public BorderPane root; @FXML private TreeView<String> noteTree; @FXML private ScrollPane sp; @FXML private Button newNoteButton; public NoteKeeperController(){ rootItem = new TreeItem<String> ("FirstNote"); rootItem.setExpanded(true); noteTree.setRoot(rootItem); noteBook= new NoteBook(); } @FXML private void closeProgram(){ System.exit(0); } @FXML private void addNewNote(){ Note note = noteBook.newNote("test","Problem"); TreeItem<String> newItem= new TreeItem<>(note.getNoteName()); rootItem.getChildren().add(newItem); } public BorderPane getRoot() { return root; } public void setRoot(BorderPane root) { this.root = root; } @Override public void initialize(URL location,ResourceBundle resources) { // TODO Auto-generated method stub } }
FXML文件:
<BorderPane fx:id="root" prefHeight="719.0" prefWidth="893.0" xmlns:fx="http://javafx.com/fxml/1" xmlns="http://javafx.com/javafx/8" fx:controller="application.NoteKeeperController"> <center> <BorderPane prefHeight="641.0" prefWidth="872.0" BorderPane.alignment="CENTER"> <center> <TabPane prefHeight="200.0" prefWidth="200.0" tabClosingPolicy="UNAVAILABLE" BorderPane.alignment="CENTER"> <tabs> <Tab text="Untitled Tab 1"> <content> <AnchorPane minHeight="0.0" minWidth="0.0" prefHeight="180.0" prefWidth="200.0" /> </content> </Tab> <Tab text="Untitled Tab 2"> <content> <AnchorPane minHeight="0.0" minWidth="0.0" prefHeight="180.0" prefWidth="200.0" /> </content> </Tab> </tabs> </TabPane> </center> <left> <ScrollPane fx:id="sp" prefHeight="200.0" prefWidth="200.0" BorderPane.alignment="CENTER"> <content> <AnchorPane minHeight="0.0" minWidth="0.0" prefHeight="650.0" prefWidth="200.0"> <children> <TreeView fx:id="noteTree" prefHeight="650.0" prefWidth="200.0" AnchorPane.bottomAnchor="0.0" AnchorPane.leftAnchor="0.0" AnchorPane.rightAnchor="0.0" AnchorPane.topAnchor="0.0" /> </children>
Scenebuilder
识别我正在注入 noteTree,sp和newNoteButton的字段
。但是,当我尝试将项目加载到树形视图时,我得到了NPE。我确认使用if语句表明我的3个字段是null
。堆栈跟踪如下:Caused by: java.lang.NullPointerException at application.NoteKeeperController.<init>(NoteKeeperController.java:31)
事实证明我
@FXML closeProgram()
和我的@FXML addNewNote()
功能都可以通过。谁能指出我缺少/做错了什么?
public class NoteKeeperController implements Initializable{ NoteBook noteBook; TreeItem<String> rootItem; public BorderPane root; @FXML private TreeView<String> noteTree; @FXML private ScrollPane sp; @FXML private Button newNoteButton; @Override public void initialize(URL location, ResourceBundle resources){ rootItem = new TreeItem<String> ("FirstNote"); rootItem.setExpanded(true); noteTree.setRoot(rootItem); noteBook= new NoteBook(); } // ... }
@H_403_23@解决方法
我的FXML注入有问题。据我所知,我已经设置了程序,但似乎缺少了一些东西。我的代码如下:
主要:
package application; import javafx.application.Application; import javafx.stage.Stage; import javafx.scene.Scene; import javafx.scene.layout.BorderPane; import javafx.fxml.FXML; import javafx.fxml.FXMLLoader; public class Main extends Application { @Override public void start(Stage primaryStage) { try { FXMLLoader loader = new FXMLLoader(getClass().getResource("NoteKeeper.fxml")); BorderPane root = (BorderPane)loader.load(); Scene scene = new Scene(root,root.getHeight(),root.getWidth()); scene.getStylesheets().add(getClass().getResource("application.css").toExternalForm()); primaryStage.setScene(scene); primaryStage.show(); } catch(Exception e) { e.printStackTrace(); } } public static void main(String[] args) { launch(args); } }
控制器:
package application; import java.net.URL; import java.util.ResourceBundle; import javafx.fxml.FXML; import javafx.fxml.Initializable; import javafx.scene.control.Button; import javafx.scene.control.ScrollPane; import javafx.scene.control.TreeItem; import javafx.scene.control.TreeView; import javafx.scene.layout.BorderPane; public class NoteKeeperController implements Initializable{ NoteBook noteBook; TreeItem<String> rootItem; public BorderPane root; @FXML private TreeView<String> noteTree; @FXML private ScrollPane sp; @FXML private Button newNoteButton; public NoteKeeperController(){ rootItem = new TreeItem<String> ("FirstNote"); rootItem.setExpanded(true); noteTree.setRoot(rootItem); noteBook= new NoteBook(); } @FXML private void closeProgram(){ System.exit(0); } @FXML private void addNewNote(){ Note note = noteBook.newNote("test","Problem"); TreeItem<String> newItem= new TreeItem<>(note.getNoteName()); rootItem.getChildren().add(newItem); } public BorderPane getRoot() { return root; } public void setRoot(BorderPane root) { this.root = root; } @Override public void initialize(URL location,ResourceBundle resources) { // TODO Auto-generated method stub } }
FXML文件:
<BorderPane fx:id="root" prefHeight="719.0" prefWidth="893.0" xmlns:fx="http://javafx.com/fxml/1" xmlns="http://javafx.com/javafx/8" fx:controller="application.NoteKeeperController"> <center> <BorderPane prefHeight="641.0" prefWidth="872.0" BorderPane.alignment="CENTER"> <center> <TabPane prefHeight="200.0" prefWidth="200.0" tabClosingPolicy="UNAVAILABLE" BorderPane.alignment="CENTER"> <tabs> <Tab text="Untitled Tab 1"> <content> <AnchorPane minHeight="0.0" minWidth="0.0" prefHeight="180.0" prefWidth="200.0" /> </content> </Tab> <Tab text="Untitled Tab 2"> <content> <AnchorPane minHeight="0.0" minWidth="0.0" prefHeight="180.0" prefWidth="200.0" /> </content> </Tab> </tabs> </TabPane> </center> <left> <ScrollPane fx:id="sp" prefHeight="200.0" prefWidth="200.0" BorderPane.alignment="CENTER"> <content> <AnchorPane minHeight="0.0" minWidth="0.0" prefHeight="650.0" prefWidth="200.0"> <children> <TreeView fx:id="noteTree" prefHeight="650.0" prefWidth="200.0" AnchorPane.bottomAnchor="0.0" AnchorPane.leftAnchor="0.0" AnchorPane.rightAnchor="0.0" AnchorPane.topAnchor="0.0" /> </children>
Scenebuilder
识别我正在注入 noteTree,sp和newNoteButton的字段
。但是,当我尝试将项目加载到树形视图时,我得到了NPE。我确认使用if语句表明我的3个字段是null
。堆栈跟踪如下:Caused by: java.lang.NullPointerException at application.NoteKeeperController.<init>(NoteKeeperController.java:31)
事实证明我
@FXML closeProgram()
和我的@FXML addNewNote()
功能都可以通过。谁能指出我缺少/做错了什么?
package application;
import javafx.application.Application;
import javafx.stage.Stage;
import javafx.scene.Scene;
import javafx.scene.layout.BorderPane;
import javafx.fxml.FXML;
import javafx.fxml.FXMLLoader;
public class Main extends Application {
@Override
public void start(Stage primaryStage) {
try {
FXMLLoader loader = new FXMLLoader(getClass().getResource("NoteKeeper.fxml"));
BorderPane root = (BorderPane)loader.load();
Scene scene = new Scene(root,root.getHeight(),root.getWidth());
scene.getStylesheets().add(getClass().getResource("application.css").toExternalForm());
primaryStage.setScene(scene);
primaryStage.show();
} catch(Exception e) {
e.printStackTrace();
}
}
public static void main(String[] args) {
launch(args);
}
}
package application;
import java.net.URL;
import java.util.ResourceBundle;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.scene.control.Button;
import javafx.scene.control.ScrollPane;
import javafx.scene.control.TreeItem;
import javafx.scene.control.TreeView;
import javafx.scene.layout.BorderPane;
public class NoteKeeperController implements Initializable{
NoteBook noteBook;
TreeItem<String> rootItem;
public BorderPane root;
@FXML private TreeView<String> noteTree;
@FXML private ScrollPane sp;
@FXML private Button newNoteButton;
public NoteKeeperController(){
rootItem = new TreeItem<String> ("FirstNote");
rootItem.setExpanded(true);
noteTree.setRoot(rootItem);
noteBook= new NoteBook();
}
@FXML
private void closeProgram(){
System.exit(0);
}
@FXML
private void addNewNote(){
Note note = noteBook.newNote("test","Problem");
TreeItem<String> newItem= new TreeItem<>(note.getNoteName());
rootItem.getChildren().add(newItem);
}
public BorderPane getRoot() {
return root;
}
public void setRoot(BorderPane root) {
this.root = root;
}
@Override
public void initialize(URL location,ResourceBundle resources) {
// TODO Auto-generated method stub
}
}
<BorderPane fx:id="root" prefHeight="719.0" prefWidth="893.0" xmlns:fx="http://javafx.com/fxml/1" xmlns="http://javafx.com/javafx/8" fx:controller="application.NoteKeeperController">
<center>
<BorderPane prefHeight="641.0" prefWidth="872.0" BorderPane.alignment="CENTER">
<center>
<TabPane prefHeight="200.0" prefWidth="200.0" tabClosingPolicy="UNAVAILABLE" BorderPane.alignment="CENTER">
<tabs>
<Tab text="Untitled Tab 1">
<content>
<AnchorPane minHeight="0.0" minWidth="0.0" prefHeight="180.0" prefWidth="200.0" />
</content>
</Tab>
<Tab text="Untitled Tab 2">
<content>
<AnchorPane minHeight="0.0" minWidth="0.0" prefHeight="180.0" prefWidth="200.0" />
</content>
</Tab>
</tabs>
</TabPane>
</center>
<left>
<ScrollPane fx:id="sp" prefHeight="200.0" prefWidth="200.0" BorderPane.alignment="CENTER">
<content>
<AnchorPane minHeight="0.0" minWidth="0.0" prefHeight="650.0" prefWidth="200.0">
<children>
<TreeView fx:id="noteTree" prefHeight="650.0" prefWidth="200.0" AnchorPane.bottomAnchor="0.0" AnchorPane.leftAnchor="0.0" AnchorPane.rightAnchor="0.0" AnchorPane.topAnchor="0.0" />
</children>
Caused by: java.lang.NullPointerException
at application.NoteKeeperController.<init>(NoteKeeperController.java:31)
noteTree
还是null
。
解决方法只是将构造函数中的代码移至initialize
方法:
我的FXML注入有问题。据我所知,我已经设置了程序,但似乎缺少了一些东西。我的代码如下:
主要:
控制器:
FXML文件:
Scenebuilder
识别我正在注入 noteTree,sp和newNoteButton的字段
。但是,当我尝试将项目加载到树形视图时,我得到了NPE。我确认使用if语句表明我的3个字段是null
。堆栈跟踪如下:
事实证明我@FXML closeProgram()
和我的@FXML addNewNote()
功能都可以通过。
谁能指出我缺少/做错了什么?
noteTree
还是null
。
解决方法只是将构造函数中的代码移至initialize
方法:
public class NoteKeeperController implements Initializable{ NoteBook noteBook; TreeItem<String> rootItem; public BorderPane root; @FXML private TreeView<String> noteTree; @FXML private ScrollPane sp; @FXML private Button newNoteButton; @Override public void initialize(URL location, ResourceBundle resources){ rootItem = new TreeItem<String> ("FirstNote"); rootItem.setExpanded(true); noteTree.setRoot(rootItem); noteBook= new NoteBook(); } // ... }
@H_403_23@解决方法
我的FXML注入有问题。据我所知,我已经设置了程序,但似乎缺少了一些东西。我的代码如下:
主要:
package application; import javafx.application.Application; import javafx.stage.Stage; import javafx.scene.Scene; import javafx.scene.layout.BorderPane; import javafx.fxml.FXML; import javafx.fxml.FXMLLoader; public class Main extends Application { @Override public void start(Stage primaryStage) { try { FXMLLoader loader = new FXMLLoader(getClass().getResource("NoteKeeper.fxml")); BorderPane root = (BorderPane)loader.load(); Scene scene = new Scene(root,root.getHeight(),root.getWidth()); scene.getStylesheets().add(getClass().getResource("application.css").toExternalForm()); primaryStage.setScene(scene); primaryStage.show(); } catch(Exception e) { e.printStackTrace(); } } public static void main(String[] args) { launch(args); } }
控制器:
package application; import java.net.URL; import java.util.ResourceBundle; import javafx.fxml.FXML; import javafx.fxml.Initializable; import javafx.scene.control.Button; import javafx.scene.control.ScrollPane; import javafx.scene.control.TreeItem; import javafx.scene.control.TreeView; import javafx.scene.layout.BorderPane; public class NoteKeeperController implements Initializable{ NoteBook noteBook; TreeItem<String> rootItem; public BorderPane root; @FXML private TreeView<String> noteTree; @FXML private ScrollPane sp; @FXML private Button newNoteButton; public NoteKeeperController(){ rootItem = new TreeItem<String> ("FirstNote"); rootItem.setExpanded(true); noteTree.setRoot(rootItem); noteBook= new NoteBook(); } @FXML private void closeProgram(){ System.exit(0); } @FXML private void addNewNote(){ Note note = noteBook.newNote("test","Problem"); TreeItem<String> newItem= new TreeItem<>(note.getNoteName()); rootItem.getChildren().add(newItem); } public BorderPane getRoot() { return root; } public void setRoot(BorderPane root) { this.root = root; } @Override public void initialize(URL location,ResourceBundle resources) { // TODO Auto-generated method stub } }
FXML文件:
<BorderPane fx:id="root" prefHeight="719.0" prefWidth="893.0" xmlns:fx="http://javafx.com/fxml/1" xmlns="http://javafx.com/javafx/8" fx:controller="application.NoteKeeperController"> <center> <BorderPane prefHeight="641.0" prefWidth="872.0" BorderPane.alignment="CENTER"> <center> <TabPane prefHeight="200.0" prefWidth="200.0" tabClosingPolicy="UNAVAILABLE" BorderPane.alignment="CENTER"> <tabs> <Tab text="Untitled Tab 1"> <content> <AnchorPane minHeight="0.0" minWidth="0.0" prefHeight="180.0" prefWidth="200.0" /> </content> </Tab> <Tab text="Untitled Tab 2"> <content> <AnchorPane minHeight="0.0" minWidth="0.0" prefHeight="180.0" prefWidth="200.0" /> </content> </Tab> </tabs> </TabPane> </center> <left> <ScrollPane fx:id="sp" prefHeight="200.0" prefWidth="200.0" BorderPane.alignment="CENTER"> <content> <AnchorPane minHeight="0.0" minWidth="0.0" prefHeight="650.0" prefWidth="200.0"> <children> <TreeView fx:id="noteTree" prefHeight="650.0" prefWidth="200.0" AnchorPane.bottomAnchor="0.0" AnchorPane.leftAnchor="0.0" AnchorPane.rightAnchor="0.0" AnchorPane.topAnchor="0.0" /> </children>
Scenebuilder
识别我正在注入 noteTree,sp和newNoteButton的字段
。但是,当我尝试将项目加载到树形视图时,我得到了NPE。我确认使用if语句表明我的3个字段是null
。堆栈跟踪如下:Caused by: java.lang.NullPointerException at application.NoteKeeperController.<init>(NoteKeeperController.java:31)
事实证明我
@FXML closeProgram()
和我的@FXML addNewNote()
功能都可以通过。谁能指出我缺少/做错了什么?
package application;
import javafx.application.Application;
import javafx.stage.Stage;
import javafx.scene.Scene;
import javafx.scene.layout.BorderPane;
import javafx.fxml.FXML;
import javafx.fxml.FXMLLoader;
public class Main extends Application {
@Override
public void start(Stage primaryStage) {
try {
FXMLLoader loader = new FXMLLoader(getClass().getResource("NoteKeeper.fxml"));
BorderPane root = (BorderPane)loader.load();
Scene scene = new Scene(root,root.getHeight(),root.getWidth());
scene.getStylesheets().add(getClass().getResource("application.css").toExternalForm());
primaryStage.setScene(scene);
primaryStage.show();
} catch(Exception e) {
e.printStackTrace();
}
}
public static void main(String[] args) {
launch(args);
}
}
package application;
import java.net.URL;
import java.util.ResourceBundle;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.scene.control.Button;
import javafx.scene.control.ScrollPane;
import javafx.scene.control.TreeItem;
import javafx.scene.control.TreeView;
import javafx.scene.layout.BorderPane;
public class NoteKeeperController implements Initializable{
NoteBook noteBook;
TreeItem<String> rootItem;
public BorderPane root;
@FXML private TreeView<String> noteTree;
@FXML private ScrollPane sp;
@FXML private Button newNoteButton;
public NoteKeeperController(){
rootItem = new TreeItem<String> ("FirstNote");
rootItem.setExpanded(true);
noteTree.setRoot(rootItem);
noteBook= new NoteBook();
}
@FXML
private void closeProgram(){
System.exit(0);
}
@FXML
private void addNewNote(){
Note note = noteBook.newNote("test","Problem");
TreeItem<String> newItem= new TreeItem<>(note.getNoteName());
rootItem.getChildren().add(newItem);
}
public BorderPane getRoot() {
return root;
}
public void setRoot(BorderPane root) {
this.root = root;
}
@Override
public void initialize(URL location,ResourceBundle resources) {
// TODO Auto-generated method stub
}
}
<BorderPane fx:id="root" prefHeight="719.0" prefWidth="893.0" xmlns:fx="http://javafx.com/fxml/1" xmlns="http://javafx.com/javafx/8" fx:controller="application.NoteKeeperController">
<center>
<BorderPane prefHeight="641.0" prefWidth="872.0" BorderPane.alignment="CENTER">
<center>
<TabPane prefHeight="200.0" prefWidth="200.0" tabClosingPolicy="UNAVAILABLE" BorderPane.alignment="CENTER">
<tabs>
<Tab text="Untitled Tab 1">
<content>
<AnchorPane minHeight="0.0" minWidth="0.0" prefHeight="180.0" prefWidth="200.0" />
</content>
</Tab>
<Tab text="Untitled Tab 2">
<content>
<AnchorPane minHeight="0.0" minWidth="0.0" prefHeight="180.0" prefWidth="200.0" />
</content>
</Tab>
</tabs>
</TabPane>
</center>
<left>
<ScrollPane fx:id="sp" prefHeight="200.0" prefWidth="200.0" BorderPane.alignment="CENTER">
<content>
<AnchorPane minHeight="0.0" minWidth="0.0" prefHeight="650.0" prefWidth="200.0">
<children>
<TreeView fx:id="noteTree" prefHeight="650.0" prefWidth="200.0" AnchorPane.bottomAnchor="0.0" AnchorPane.leftAnchor="0.0" AnchorPane.rightAnchor="0.0" AnchorPane.topAnchor="0.0" />
</children>
Caused by: java.lang.NullPointerException
at application.NoteKeeperController.<init>(NoteKeeperController.java:31)
我的FXML注入有问题。据我所知,我已经设置了程序,但似乎缺少了一些东西。我的代码如下:
主要:
控制器:
FXML文件:
Scenebuilder
识别我正在注入 noteTree,sp和newNoteButton的字段
。但是,当我尝试将项目加载到树形视图时,我得到了NPE。我确认使用if语句表明我的3个字段是null
。堆栈跟踪如下:
事实证明我@FXML closeProgram()
和我的@FXML addNewNote()
功能都可以通过。
谁能指出我缺少/做错了什么?