尝试将Label设置为SQLite DB列值时出现JavaFX NullPointerException

时间：2018-05-10 14:45:40

标签： java javafx nullpointerexception settext

我在使用label.setText(String)时遇到问题。我已为我尝试使用fx:id的标签设置了setText()，并将我的Controller与我的.fxml文件相关联。

我最初有这个问题尝试在加载场景时用我的SQLite数据库中的值填充标签，并决定通过Button(ActionEvent)加载场景时它是否有效，因为我不确定我的{{1}工作正常。

我可以将变量的值打印到控制台，但不是EventListener。我查看了其他已提交的问题，例如this one和this one also，但没有进一步转发。

感谢任何帮助！

Options.java 

label.setText()

OptionsController.java（我删除了很多此问题不需要的代码）

package PengVapour;

import Controllers.OptionsController;
import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.stage.Stage;
import javafx.stage.WindowEvent;

public class Options extends Application {
    public static void main(String[] args) {
        launch(args);
    }

    @Override
    public void start(Stage optionsStage) {
        try {
            FXMLLoader loader = new FXMLLoader(getClass().getResource("../FXML/Options.fxml"));
            Parent root = (Parent)loader.load();
            OptionsController opCont = (OptionsController)loader.getController();
            optionsStage.addEventHandler(WindowEvent.WINDOW_SHOWN, event -> opCont.handleSceneShownEvent());
            Scene scene = new Scene(root);
            scene.getStylesheets().add(getClass().getResource("../CSS/PengVapour.css").toExternalForm());
            optionsStage.setTitle("Peng Vapour - Application Options");
            optionsStage.setScene(scene);
            optionsStage.show();
            optionsStage.setResizable(false);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

OptionsDB.java（我删除了很多此问题不需要的代码）

package Controllers;

import Database.OptionsDB;
import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.scene.Node;
import javafx.scene.control.*;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;

import java.io.IOException;
import java.lang.reflect.InvocationTargetException;
import java.net.URL;
import java.sql.SQLException;
import java.util.ResourceBundle;

public class OptionsController implements Initializable {
    @FXML MenuItem fileExit;
    @FXML Button mainMenu;
    @FXML TextField concentrateThreshold;
    @FXML TextField vgThreshold;
    @FXML TextField pgThreshold;
    @FXML TextField nicotineThreshold;
    @FXML TextField cleanerThreshold;
    @FXML public static Label currentConcentrateThresholdLabel;
    @FXML public static Label currentVGThresholdLabel;
    @FXML public static Label currentPGThresholdLabel;
    @FXML public static Label currentNicotineThresholdLabel;
    @FXML public static Label currentCleanerThresholdLabel;
    @FXML CheckBox confirm;
    @FXML Button submit;
    @FXML Button testB;

    public static double concentrateUpdateValue;
    public static double vgUpdateValue;
    public static double pgUpdateValue;
    public static double nicotineUpdateValue;
    public static double cleanerUpdateValue;
    public boolean confirmed = false;

    @Override
    public void initialize(URL location, ResourceBundle resources) {}

    @FXML
    public void handleSceneShownEventTest(ActionEvent e) throws InvocationTargetException {
        OptionsDB.showCurrentThresholds();
    }

Options.fxml 

package Database;

import Controllers.OptionsController;

import java.lang.reflect.InvocationTargetException;
import java.sql.*;

public class OptionsDB {
    public static String concentrateCurrentThreshold;
    public static String vgCurrentThreshold;
    public static String pgCurrentThreshold;
    public static String nicotineCurrentThreshold;
    public static String cleanerCurrentThreshold;

    public static void main() {
        connect();
    }

    public static Connection connect() {
        String url = "jdbc:sqlite:C:\\Users\\PengStation420\\IdeaProjects\\PengVapour\\PVIM.sqlite";
        Connection conn = null;
        try {
            conn = DriverManager.getConnection(url);
        } catch (SQLException e) {
            System.out.println(e.getMessage());
        }
        return conn;
    }


    public static void showCurrentThresholds() throws InvocationTargetException {
        String sqlShowCurrentThresholds = "SELECT * FROM Options";

        try (Connection conn = connect();
             Statement stmt = conn.createStatement();
             ResultSet rs = stmt.executeQuery(sqlShowCurrentThresholds)){
            while (rs.next()) {
                concentrateCurrentThreshold = String.valueOf(rs.getDouble("ConcentrateThreshold"));
                vgCurrentThreshold = String.valueOf(rs.getDouble("VGThreshold"));
                pgCurrentThreshold = String.valueOf(rs.getDouble("PGThreshold"));
                nicotineCurrentThreshold = String.valueOf(rs.getDouble("NicotineThreshold"));
                cleanerCurrentThreshold = String.valueOf(rs.getDouble("CleanerThreshold"));

                System.out.println(concentrateCurrentThreshold);
                System.out.println(vgCurrentThreshold);
                System.out.println(pgCurrentThreshold);
                System.out.println(nicotineCurrentThreshold);
                System.out.println(cleanerCurrentThreshold);

                OptionsController.currentConcentrateThresholdLabel.setText(concentrateCurrentThreshold);
                OptionsController.currentVGThresholdLabel.setText(vgCurrentThreshold);
                OptionsController.currentPGThresholdLabel.setText(pgCurrentThreshold);
                OptionsController.currentNicotineThresholdLabel.setText(nicotineCurrentThreshold);
                OptionsController.currentCleanerThresholdLabel.setText(cleanerCurrentThreshold);
            }
            System.out.println();
        } catch (SQLException e) {
            System.out.println(e.getMessage());
        }
    }
}

NullPointerException在OptionsDB.java中的<?xml version="1.0" encoding="UTF-8"?> <?import javafx.scene.control.Button?> <?import javafx.scene.control.CheckBox?> <?import javafx.scene.control.Label?> <?import javafx.scene.control.Menu?> <?import javafx.scene.control.MenuBar?> <?import javafx.scene.control.MenuItem?> <?import javafx.scene.control.TextField?> <?import javafx.scene.layout.AnchorPane?> <?import javafx.scene.layout.VBox?> <VBox fx:id="vBox" alignment="CENTER" minHeight="450" minWidth="600" prefHeight="450.0" prefWidth="600.0" stylesheets="@../CSS/PengVapour.css" xmlns="http://javafx.com/javafx/8.0.121" xmlns:fx="http://javafx.com/fxml/1" fx:controller="Controllers.OptionsController"> <children> <MenuBar> <menus> <Menu mnemonicParsing="false" text="File"> <items> <MenuItem fx:id="fileExit" mnemonicParsing="false" onAction="#menuBarFileExit" text="Exit" /> </items> </Menu> </menus> </MenuBar> <Label fx:id="head" alignment="CENTER" prefHeight="58.0" prefWidth="600.0" stylesheets="@../CSS/PengVapour.css" text="Options" textAlignment="CENTER" /> <AnchorPane prefHeight="368.0" prefWidth="407.0"> <children> <Button fx:id="testB" layoutX="250.0" layoutY="320.0" mnemonicParsing="false" onAction="#handleSceneShownEventTest" text="Test" /> <Label layoutX="99.0" layoutY="29.0" text="Set Running Low Thresholds:" /> <Label layoutX="78.0" layoutY="75.0" text="Concentrates:" /> <TextField fx:id="concentrateThreshold" layoutX="173.0" layoutY="71.0" prefHeight="29.0" prefWidth="100.0" /> <Label layoutX="146.0" layoutY="107.0" text="VG:" /> <TextField fx:id="vgThreshold" layoutX="173.0" layoutY="103.0" prefHeight="29.0" prefWidth="100.0" /> <Label layoutX="146.0" layoutY="139.0" text="PG:" /> <TextField fx:id="pgThreshold" layoutX="173.0" layoutY="135.0" prefHeight="29.0" prefWidth="100.0" /> <Label layoutX="110.0" layoutY="172.0" text="Nicotine:" /> <TextField fx:id="nicotineThreshold" layoutX="173.0" layoutY="168.0" prefHeight="29.0" prefWidth="100.0" /> <Label layoutX="51.0" layoutY="206.0" text="Isopropyl Alcohol:" /> <TextField fx:id="cleanerThreshold" layoutX="173.0" layoutY="202.0" prefHeight="29.0" prefWidth="100.0" /> <Button fx:id="mainMenu" layoutX="490.0" layoutY="319.0" mnemonicParsing="false" onAction="#mainMenuButton" text="Main Menu" /> <Button fx:id="submit" layoutX="344.0" layoutY="266.0" mnemonicParsing="false" onAction="#submitButton" text="Submit" visible="false" /> <CheckBox fx:id="confirm" layoutX="174.0" layoutY="271.0" mnemonicParsing="false" onAction="#confirmChanges" text="Confirm Change(s)" /> <Label layoutX="281.0" layoutY="75.0" text="ml" /> <Label layoutX="281.0" layoutY="107.0" text="ml" /> <Label layoutX="281.0" layoutY="139.0" text="ml" /> <Label layoutX="281.0" layoutY="172.0" text="ml" /> <Label layoutX="281.0" layoutY="206.0" text="ml" /> <Label layoutX="388.0" layoutY="29.0" text="Current Thresholds:" /> <Label layoutX="517.0" layoutY="74.0" text="ml" /> <Label layoutX="517.0" layoutY="106.0" text="ml" /> <Label layoutX="517.0" layoutY="138.0" text="ml" /> <Label layoutX="517.0" layoutY="171.0" text="ml" /> <Label layoutX="517.0" layoutY="205.0" text="ml" /> <Label fx:id="currentConcentrateThresholdLabel" layoutX="444.0" layoutY="74.0" text="??" /> <Label fx:id="currentVGThresholdLabel" layoutX="444.0" layoutY="106.0" text="??" /> <Label fx:id="currentPGThresholdLabel" layoutX="444.0" layoutY="138.0" text="??" /> <Label fx:id="currentNicotineThresholdLabel" layoutX="444.0" layoutY="171.0" text="??" /> <Label fx:id="currentCleanerThresholdLabel" layoutX="444.0" layoutY="205.0" text="??" /> </children> </AnchorPane> </children> </VBox> 方法的OptionsController.currentConcentrateThresholdLabel.setText(concentrateCurrentThreshold);处抛出。

我认为我错过了一些愚蠢的东西。

0 个答案:

没有答案
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