1
我有一個以基本階段開始的簡單程序。然後我選擇一個啓動對話框的菜單項。我在對話框上有一個按鈕，除了關閉當前舞臺外，什麼都不做。我期待對話會結束，焦點將回到初始階段。但是，當我點擊創建遊戲按鈕時，我得到一個空指針異常。我對Java相當陌生，可能錯過了一些明顯的東西。請幫忙。關閉JavaFX對話框時出現空指針異常
HWFX.JAVA
package Main;
import java.util.Date;
import javafx.application.Application;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.fxml.FXMLLoader;
import javafx.scene.Group;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.control.TableView;
import javafx.scene.control.TextField;
import javafx.scene.layout.GridPane;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;
public class HWFX extends Application {
public static void main(String[] args) {
// TODO Auto-generated method stub
launch(args);
}
@Override
public void start(Stage primaryStage) throws Exception {
// TODO Auto-generated method stub
FXMLLoader loader = new FXMLLoader(getClass().getResource("/fxml/Main.fxml"));
Parent root = loader.load();
MainController controller = (MainController) loader.getController();
controller.init(primaryStage);
Scene scene = new Scene(root,600,400);
scene.getStylesheets().add("/fxml/styles/mainfx.css");
primaryStage.setScene(scene);
primaryStage.setTitle("Hello World FX");
primaryStage.show();
}
MainController.java
package Main;
import java.io.File;
import java.io.IOException;
import java.net.URL;
import java.util.ResourceBundle;
import javafx.application.Platform;
import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.fxml.FXMLLoader;
import javafx.fxml.Initializable;
import javafx.scene.Parent;
import javafx.scene.control.Button;
import javafx.scene.control.TextField;
import javafx.stage.FileChooser;
import javafx.stage.Stage;
import javafx.stage.StageStyle;
import java.sql.*;
import javax.sql.*;
import oracle.jdbc.*;
import oracle.jdbc.pool.OracleDataSource;
public class MainController implements Initializable {
private Stage stage;
@FXML
javafx.scene.layout.AnchorPane AnchorPane;
@FXML
javafx.scene.layout.GridPane GridPane;
@FXML
javafx.scene.layout.GridPane GridPaneMain;
@FXML
Button TestButton1;
Button TestButton2;
Button TestButton3;
@FXML
javafx.scene.control.TextField PlayerName;
@Override
public void initialize(URL arg0, ResourceBundle arg1) {
// TODO Auto-generated method stub
}
public void doExit() {
Platform.exit();
}
public void openFile() {
FileChooser fileChooser = new FileChooser();
fileChooser.setTitle("Open text file");
fileChooser.setInitialDirectory(new File(System.getProperty("user.home")));
fileChooser.getExtensionFilters().addAll(
new FileChooser.ExtensionFilter("Text Files","*.txt"),
new FileChooser.ExtensionFilter("All Files","*.*")
);
File file = fileChooser.showOpenDialog(stage);
if (file != null){
System.out.println("Choosen File: " + file);
}
}
public void ButtonClicked() throws SQLException {
System.out.println("Click!");
final TextField F1 = new TextField();
F1.setPromptText("F1");
F1.setPrefColumnCount(10);
F1.getText();
// javafx.scene.layout.GridPane.setConstraints(F1,10,10);
GridPaneMain.add(F1, 0, 0);
OracleDataSource ods = new OracleDataSource();
// Set the user name, password, driver type and network protocol
ods.setUser("ppmcdev");
ods.setPassword("ppmc");
ods.setURL("jdbc:oracle:thin:@172.21.51.56:1521:INAVD");
ods.setDriverType("oci8");
ods.setNetworkProtocol("ipc");
ods.setTNSEntryName("INAVD");
// Retrieve a connection
Connection conn = ods.getConnection();
getUserName(conn);
// Close the connection
conn.close();
conn = null;
}
public void CreateGame(ActionEvent event) throws IOException {
System.out.println("Create Game Menu");
CreateGameDialogController CreateGameDialog = new CreateGameDialogController();
try {
CreateGameDialog.showCreateGameDialog(stage);
} catch (Exception e) {
e.printStackTrace();
}
}
public void init(Stage stage) {
// TODO Auto-generated method stub
this.stage = stage;
}
}
Main.fxml
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.input.*?>
<?import javafx.geometry.*?>
<?import javafx.scene.control.*?>
<?import javafx.scene.layout.*?>
<?import java.lang.*?>
<?import javafx.scene.image.*?>
<AnchorPane fx:id="AnchorPane" maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="400.0" prefWidth="600.0" xmlns="http://javafx.com/javafx/8" xmlns:fx="http://javafx.com/fxml/1" fx:controller="Main.MainController">
<children>
<BorderPane layoutX="-2.0" layoutY="-3.0" prefHeight="400.0" prefWidth="606.0" AnchorPane.bottomAnchor="0.0" AnchorPane.leftAnchor="0.0" AnchorPane.rightAnchor="0.0" AnchorPane.topAnchor="0.0">
<center>
<TextArea prefHeight="200.0" prefWidth="200.0" BorderPane.alignment="CENTER" />
</center>
<top>
<MenuBar BorderPane.alignment="CENTER">
<menus>
<Menu text="_File">
<items>
<MenuItem onAction="#openFile" text="_Open">
<accelerator>
<KeyCodeCombination alt="UP" code="O" control="DOWN" meta="UP" shift="UP" shortcut="UP" />
</accelerator>
</MenuItem>
<MenuItem onAction="#doExit" text="E_xit">
<accelerator>
<KeyCodeCombination alt="UP" code="X" control="DOWN" meta="UP" shift="UP" shortcut="UP" />
</accelerator>
</MenuItem>
</items>
</Menu>
<Menu text="_Game">
<items>
<MenuItem onAction="#CreateGame" text="_Create">
<accelerator>
<KeyCodeCombination alt="DOWN" code="C" control="UP" meta="UP" shift="UP" shortcut="UP" />
</accelerator></MenuItem>
</items>
</Menu>
</menus>
</MenuBar>
</top>
<bottom>
<Button mnemonicParsing="false" onAction="#ButtonClicked" text="ClickMeButton" BorderPane.alignment="CENTER" />
</bottom>
</BorderPane>
<GridPane id="GridPane" fx:id="GridPane" layoutX="20.0" layoutY="70.0" prefHeight="68.0" prefWidth="594.0" AnchorPane.bottomAnchor="30.0" AnchorPane.leftAnchor="0.0" AnchorPane.rightAnchor="6.0">
<columnConstraints>
<ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
</columnConstraints>
<rowConstraints>
<RowConstraints fillHeight="false" minHeight="10.0" prefHeight="30.0" vgrow="SOMETIMES" />
</rowConstraints>
<padding>
<Insets top="40.0" />
</padding>
<children>
<Button id="TestButton1" alignment="TOP_LEFT" contentDisplay="BOTTOM" mnemonicParsing="false" prefHeight="22.0" prefWidth="94.0" text="Test Button 1" />
<Button id="TestButton2" contentDisplay="BOTTOM" mnemonicParsing="false" prefHeight="25.0" prefWidth="91.0" text="Test Button 2">
<GridPane.margin>
<Insets left="100.0" />
</GridPane.margin>
</Button>
<Button id="addPlayer" fx:id="addPlayer" alignment="BASELINE_RIGHT" mnemonicParsing="false" onAction="#addPlayer" text="Add Player">
<GridPane.margin>
<Insets left="300.0" />
</GridPane.margin>
</Button>
<TextField fx:id="PlayerName" prefHeight="25.0" prefWidth="152.0" promptText="Player Name">
<GridPane.margin>
<Insets left="400.0" />
</GridPane.margin>
</TextField>
</children>
</GridPane>
<GridPane id="GridPaneMain" fx:id="GridPaneMain" gridLinesVisible="true" layoutY="29.0" prefHeight="308.0" prefWidth="600.0">
<columnConstraints>
<ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
<ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
<ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
</columnConstraints>
<rowConstraints>
<RowConstraints minHeight="10.0" prefHeight="30.0" vgrow="SOMETIMES" />
<RowConstraints minHeight="10.0" prefHeight="30.0" vgrow="SOMETIMES" />
<RowConstraints minHeight="10.0" prefHeight="30.0" vgrow="SOMETIMES" />
</rowConstraints>
</GridPane>
</children>
</AnchorPane>
CreateGameDialogController.java
package Main;
import java.io.File;
import java.io.IOException;
import java.net.URL;
import java.util.ResourceBundle;
import javafx.application.Platform;
import javafx.stage.Modality;
import javafx.stage.Stage;
import javafx.event.ActionEvent;
import javafx.fxml.*;
import javafx.scene.layout.*;
import javafx.scene.*;
public class CreateGameDialogController implements Initializable {
@FXML
private javafx.scene.layout.AnchorPane AnchorPane;
@FXML
private javafx.scene.control.Slider NumberOfPlayers;
private Stage myParent;
private Stage CreateGameDialogStage;
public void showCreateGameDialog(Stage parentStage) {
this.myParent = parentStage;
try {
CreateGameDialogStage = new Stage();
AnchorPane page = (AnchorPane) FXMLLoader.load(CreateGameDialogController.class.getResource("/fxml/CreateGameDialog.fxml"));
Scene scene = new Scene(page);
CreateGameDialogStage.setScene(scene);
CreateGameDialogStage.setTitle("Create Game");
CreateGameDialogStage.initOwner(this.myParent);
CreateGameDialogStage.initModality(Modality.WINDOW_MODAL);
CreateGameDialogStage.show();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public void CreateGame(ActionEvent event) {
try {
System.out.println("Create Game");
CreateGameDialogStage.close();
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
@Override
public void initialize(URL location, ResourceBundle resources) {
// TODO Auto-generated method stub
}
}
CreateGameDialog.fxml
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.text.*?>
<?import javafx.scene.control.*?>
<?import java.lang.*?>
<?import javafx.scene.layout.*?>
<?import javafx.scene.layout.AnchorPane?>
<AnchorPane id="AnchorPane" prefHeight="427.0" prefWidth="602.0" xmlns="http://javafx.com/javafx/8" xmlns:fx="http://javafx.com/fxml/1" fx:controller="Main.CreateGameDialogController">
<children>
<BorderPane prefHeight="200.0" prefWidth="200.0" AnchorPane.bottomAnchor="0.0" AnchorPane.leftAnchor="0.0" AnchorPane.rightAnchor="0.0" AnchorPane.topAnchor="0.0">
<left>
<Pane prefHeight="427.0" prefWidth="257.0" BorderPane.alignment="CENTER">
<children>
<Slider id="NumberOfPlayers" fx:id="NumberOfPlayers" blockIncrement="1.0" layoutX="14.0" layoutY="42.0" majorTickUnit="1.0" max="8.0" min="3.0" minorTickCount="0" orientation="VERTICAL" prefHeight="310.0" prefWidth="14.0" showTickLabels="true" showTickMarks="true" snapToTicks="true" value="1.0" />
<Label alignment="CENTER" contentDisplay="CENTER" prefHeight="29.0" prefWidth="257.0" text="Select the Players" textAlignment="CENTER">
<font>
<Font name="System Bold" size="14.0" />
</font>
</Label>
<Button id="CreateGameButton" layoutX="79.0" layoutY="388.0" mnemonicParsing="false" onAction="#CreateGame" prefHeight="25.0" prefWidth="102.0" text="Create Game" />
</children>
</Pane>
</left>
<right>
<ScrollPane prefHeight="427.0" prefWidth="360.0" BorderPane.alignment="CENTER" />
</right>
</BorderPane>
</children>
</AnchorPane>
當我點擊創建遊戲按鈕，我得到：
Create Game
java.lang.NullPointerException
at Main.CreateGameDialogController.CreateGame(CreateGameDialogController.java:47)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at sun.reflect.misc.Trampoline.invoke(Unknown Source)
at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at sun.reflect.misc.MethodUtil.invoke(Unknown Source)
at javafx.fxml.FXMLLoader$MethodHandler.invoke(Unknown Source)
at javafx.fxml.FXMLLoader$ControllerMethodEventHandler.handle(Unknown Source)
at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(Unknown Source)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(Unknown Source)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(Unknown Source)
at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(Unknown Source)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Source)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Source)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Source)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Source)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Source)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Source)
at com.sun.javafx.event.EventUtil.fireEventImpl(Unknown Source)
at com.sun.javafx.event.EventUtil.fireEvent(Unknown Source)
at javafx.event.Event.fireEvent(Unknown Source)
at javafx.scene.Node.fireEvent(Unknown Source)
at javafx.scene.control.Button.fire(Unknown Source)
at com.sun.javafx.scene.control.behavior.ButtonBehavior.mouseReleased(Unknown Source)
at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(Unknown Source)
at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(Unknown Source)
at com.sun.javafx.event.CompositeEventHandler$NormalEventHandlerRecord.handleBubblingEvent(Unknown Source)
at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(Unknown Source)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(Unknown Source)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(Unknown Source)
at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(Unknown Source)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Source)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Source)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Source)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Source)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Source)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Source)
at com.sun.javafx.event.EventUtil.fireEventImpl(Unknown Source)
at com.sun.javafx.event.EventUtil.fireEvent(Unknown Source)
at javafx.event.Event.fireEvent(Unknown Source)
at javafx.scene.Scene$MouseHandler.process(Unknown Source)
at javafx.scene.Scene$MouseHandler.access$1500(Unknown Source)
at javafx.scene.Scene.impl_processMouseEvent(Unknown Source)
at javafx.scene.Scene$ScenePeerListener.mouseEvent(Unknown Source)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(Unknown Source)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(Unknown Source)
at com.sun.glass.ui.View.handleMouseEvent(Unknown Source)
at com.sun.glass.ui.View.notifyMouse(Unknown Source)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.lambda$null$141(Unknown Source)
at com.sun.glass.ui.win.WinApplication$$Lambda$38/2075313.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)