java Javafx将文本字段中当前的值保存到外部txt文件
我正在为学校创建一个省钱项目,目标是你想存多少钱,计算你一周挣多少钱,并根据你花多少钱和存多少钱来编辑你的目标。我目前正试图在一个文本字段中实现这个目标,以便在程序关闭时保存到一个txt文件中。然而,无论我如何尝试修复它,我都会得到一个NullPointerException或textfield的值另存为“null”
下面是main(我试图将目标变量保存在stop()
方法中)
package sample;
import javafx.application.Application;
import javafx.application.Platform;
import javafx.fxml.FXML;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.control.TextField;
import javafx.stage.Stage;
import java.io.*;
public class Main extends Application {
@FXML
public TextField finalGoal;
@Override
public void start(Stage primaryStage)throws Exception {
File f = new File("Goal.txt");
boolean bool = false;
if (f.exists() )
{
Parent root = FXMLLoader.load(getClass().getResource("MainPage.fxml"));
primaryStage.setTitle("Money Saver Program");
primaryStage.setScene(new Scene(root, 600, 400));
primaryStage.show();
}
else
{
bool = f.createNewFile();
Parent root = FXMLLoader.load(getClass().getResource("OpeningPage.fxml"));
primaryStage.setTitle("Money Saver Program");
primaryStage.setScene(new Scene(root, 638, 400));
primaryStage.show();
}
primaryStage.setOnCloseRequest(e -> closeProgram());
}
public static void main(String[] args) throws Exception {
launch(args);
}
public void closeProgram(){
Platform.exit();
}
@Override
public void stop()throws Exception{
PrintWriter write = new PrintWriter("Goal.txt");
String end;
end = finalGoal.getAccessibleText();
write.write(end);
write.close();
}
}
这是文本字段所在的fxml的控制器
package sample;
import javafx.application.Platform;
import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.fxml.FXMLLoader;
import javafx.scene.Node;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.control.TextField;
import javafx.stage.Stage;
import java.io.*;
import java.io.FileReader;
import javax.annotation.PostConstruct;
public class MainPageController {
@FXML
public TextField finalGoal;
@FXML
private Stage myStage;
//Method that reads the current goal saved in an external textfile.
@PostConstruct
public void initialize() throws Exception{
//Initialize Reader
FileReader reader = new FileReader("Goal.txt");
BufferedReader br = new BufferedReader(reader);
//Store goal in the textField
finalGoal.setText(br.readLine());
//Close Reader
reader.close();
}
//Method that handles close request and handles the current scene and controller
@PostConstruct
public void start(Stage stage1)throws Exception{
myStage = stage1;
FXMLLoader loader = new FXMLLoader(getClass().getResource("MainPage.fxml"));
Parent root = loader.load();
loader.getController();
loader.load();
loader.getController();
stage1.getScene().getWindow();
myStage.setOnCloseRequest(e -> onEnd());
}
public void openPage1(ActionEvent event) throws Exception {
FXMLLoader fxmlLoader = new FXMLLoader(getClass().getResource("MandatoryCostCollector.fxml"));
Parent root = fxmlLoader.load();
Stage stage = new Stage();
stage.setScene(new Scene(root));
stage.setTitle("Money Saver Program");
stage.show();
((Node) event.getSource()).getScene().getWindow().hide();
}
public void openPage2(ActionEvent event) throws Exception {
FXMLLoader fxmlLoader = new FXMLLoader(getClass().getResource("PayDataCollector.fxml"));
Parent root = fxmlLoader.load();
Stage stage = new Stage();
stage.setScene(new Scene(root));
stage.setTitle("Money Saver Program");
stage.show();
((Node) event.getSource()).getScene().getWindow().hide();
}
public void resetGoal(ActionEvent event) throws Exception {
finalGoal.setText("");
}
public void onEnd(){
Platform.exit();
}
}
这是fxml文件
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.text.*?>
<?import javafx.scene.control.*?>
<?import java.lang.*?>
<?import javafx.scene.layout.*?>
<BorderPane fx:id="BorderPane" 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="sample.MainPageController">
<top>
<VBox prefHeight="65.0" prefWidth="600.0" BorderPane.alignment="CENTER">
<children>
<TextField alignment="CENTER" editable="false" prefHeight="68.0" prefWidth="600.0" text="Welcome to the Money Saving Program">
<font>
<Font name="Arial Rounded MT Bold" size="26.0" />
</font>
</TextField>
</children>
</VBox>
</top>
<left>
<VBox prefHeight="335.0" prefWidth="159.0" BorderPane.alignment="CENTER">
<children>
<Button fx:id="openPage1" mnemonicParsing="false" onAction="#openPage1" prefHeight="88.0" prefWidth="167.0" text="1. Open Mandatory Cost Collector" wrapText="true">
<font>
<Font name="Arial" size="18.0" />
</font>
</Button>
<Button fx:id="openPage2" mnemonicParsing="false" onAction="#openPage2" prefHeight="60.0" prefWidth="173.0" text="2. Open Pay Data Collector" wrapText="true">
<font>
<Font name="Arial" size="18.0" />
</font>
</Button>
</children>
</VBox>
</left>
<right>
<VBox prefHeight="335.0" prefWidth="166.0" BorderPane.alignment="CENTER">
<children>
<TextField fx:id="finalGoal" promptText="\$">
<font>
<Font name="Arial" size="40.0" />
</font>
</TextField>
<Button fx:id="resetGoal" contentDisplay="RIGHT" mnemonicParsing="false" onAction="#resetGoal" prefHeight="33.0" prefWidth="173.0" text="Reset Goal" wrapText="true">
<font>
<Font name="Arial" size="18.0" />
</font>
</Button>
</children>
</VBox>
</right>
<bottom>
<HBox prefHeight="100.0" prefWidth="200.0" BorderPane.alignment="CENTER">
<children>
<Button fx:id="generateNewGoal" mnemonicParsing="false" prefHeight="63.0" prefWidth="161.0" text="3. Generate your new goal" translateY="36.0" wrapText="true">
<font>
<Font name="Arial" size="18.0" />
</font>
</Button>
<TextField alignment="CENTER" editable="false" prefHeight="75.0" prefWidth="221.0" text="Money saved this week" translateX="38.0" translateY="23.0">
<font>
<Font name="Arial" size="18.0" />
</font>
</TextField>
<TextField fx:id="moneySaved" editable="false" prefHeight="75.0" prefWidth="180.0" promptText="\$" translateX="38.0" translateY="23.0">
<font>
<Font name="Arial" size="40.0" />
</font>
</TextField>
</children>
</HBox>
</bottom>
<center>
<VBox prefHeight="200.0" prefWidth="100.0" BorderPane.alignment="CENTER">
<children>
<TextField editable="false" maxHeight="-Infinity" maxWidth="-Infinity" prefHeight="68.0" prefWidth="167.0" text="Your current goal" translateX="108.0">
<font>
<Font name="Arial" size="18.0" />
</font>
</TextField>
</children>
</VBox>
</center>
</BorderPane>
最后是我犯的错误
Exception in Application stop method
Exception in thread "main" java.lang.RuntimeException: Exception in Application stop method
at com.sun.javafx.application.LauncherImpl.launchApplication1(LauncherImpl.java:922)
at com.sun.javafx.application.LauncherImpl.lambda$launchApplication$155(LauncherImpl.java:182)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.NullPointerException
at sample.Main.stop(Main.java:59)
at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$163(LauncherImpl.java:882)
at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$175(PlatformImpl.java:326)
at com.sun.javafx.application.PlatformImpl.lambda$null$173(PlatformImpl.java:295)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.application.PlatformImpl.lambda$runLater$174(PlatformImpl.java:294)
at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.lambda$null$148(WinApplication.java:191)
问题似乎主要在于代码end = finalGoal.getAccessibleText();
。我也尝试过end = finalGoal.getText();
但是它返回NullPointer
,我也尝试过
end = String.valueOf(finalgoal.getText);
返回值为“null”
# 1 楼答案
您需要从
MainPageController
类中获取对finalGoal
变量的引用,而不是在Main
类中定义具有相同名称的变量# 2 楼答案
FXMLLoader
将finalGoal
{Main
类的任何信息,也没有在那里注入Node
因此,在调用
stop
时,默认值仍然被分配给fieldGoal
字段解决方案
FXMLLoader.getController
加载fxml文件后访问控制器。可以在控制器类中使用getter来访问值(fieldGoal
)。或者您还可以使用控制器工厂注册监听器以关闭,并删除一些代码重复(即加载FXML)
这允许您将关闭处理程序放置在数据所在的位置:
另见Passing Parameters JavaFX FXML