java - 如何在JavaFX中显示表信息？

Question

以下代码应该显示库存所有零件可观察列表中的零件。我不确定这是否是库存类没有返回正确的对象，或者是否发生了其他事情，或者我在表的初始化中是否遗漏了某些内容。

编辑:我期望 MainViewController initializer 加载 PartId、PartName、 PartStock 和 PartPrice 通过 Inventory 类通过 observableList allParts 实现。 InHouse 类扩展了 Part 类

MainViewController

package ViewController;

import Model.InHouse;
import Model.Inventory;
import Model.Part;
import Model.Product;
import java.io.IOException;
import java.net.URL;
import java.util.HashSet;
import java.util.ResourceBundle;
import javafx.collections.ObservableList;
import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.fxml.FXMLLoader;
import javafx.fxml.Initializable;
import javafx.scene.Node;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.control.TableColumn;
import javafx.scene.control.TableView;
import javafx.scene.control.TextField;
import javafx.scene.control.cell.PropertyValueFactory;
import javafx.stage.Stage;

public class MainViewController implements Initializable {


    private static Inventory inventory;

    //Part FXIDs
    @FXML private TableView<Part> PartsTable;
    @FXML private TableColumn<Part, Integer> PartId;
    @FXML private TableColumn<Part, String> PartName;
    @FXML private TableColumn<Part, Integer> PartStock;
    @FXML private TableColumn<Part, Double> PartPrice;

    //sets up the table view and loads the parts from the inventory list
    public void initialize(URL url, ResourceBundle rb) {

        PartId.setCellValueFactory(new PropertyValueFactory<>("PartId"));
        PartName.setCellValueFactory(new PropertyValueFactory<>("PartName"));
        PartStock.setCellValueFactory(new PropertyValueFactory<>("PartStock"));
        PartPrice.setCellValueFactory(new PropertyValueFactory<>("PartPrice"));

        inventory.addPart(new InHouse(0, "name", 5.00, 1, 1, 5, 0));

        PartsTable.setItems(inventory.getAllParts());
    }

}

Inventory

package Model;

public class Inventory {

    public final static ObservableList<Part> allParts = FXCollections.observableArrayList();

    public void addPart(Part newPart){
        this.allParts.add(newPart);
    }

    public ObservableList<Part> getAllParts(){
        return this.allParts;
    }
}

adding parts class

public abstract class Part {

    private int id,
            stock,
            min,
            max;
    private String name;
    private double price;

    public Part(int id, String name, double price, int stock, int min, int max) {
        this.id = id;
        this.stock = stock;
        this.min = min;
        this.max = max;
        this.name = name;
        this.price = price;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public int getStock() {
        return stock;
    }

    public void setStock(int stock) {
        this.stock = stock;
    }

    public int getMin() {
        return min;
    }

    public void setMin(int min) {
        this.min = min;
    }

    public int getMax() {
        return max;
    }

    public void setMax(int max) {
        this.max = max;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public double getPrice() {
        return price;
    }

    public void setPrice(double price) {
        this.price = price;
    }


}

error output

Exception in Application start method
java.lang.reflect.InvocationTargetException
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at com.sun.javafx.application.LauncherImpl.launchApplicationWithArgs(LauncherImpl.java:389)
    at com.sun.javafx.application.LauncherImpl.launchApplication(LauncherImpl.java:328)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at sun.launcher.LauncherHelper$FXHelper.main(LauncherHelper.java:767)
Caused by: java.lang.RuntimeException: Exception in Application start method
    at com.sun.javafx.application.LauncherImpl.launchApplication1(LauncherImpl.java:917)
    at com.sun.javafx.application.LauncherImpl.lambda$launchApplication$1(LauncherImpl.java:182)
    at java.lang.Thread.run(Thread.java:748)
Caused by: javafx.fxml.LoadException: 
file:/home/Projects/2019.08.03_C482/InventorySystem/dist/run1962514670/InventorySystem.jar!/ViewController/MainView.fxml

    at javafx.fxml.FXMLLoader.constructLoadException(FXMLLoader.java:2601)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2579)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2441)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3214)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3175)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3148)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3124)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3104)
    at javafx.fxml.FXMLLoader.load(FXMLLoader.java:3097)
    at c482.C482.start(C482.java:23)
    at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$8(LauncherImpl.java:863)
    at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$7(PlatformImpl.java:326)
    at com.sun.javafx.application.PlatformImpl.lambda$null$5(PlatformImpl.java:295)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.application.PlatformImpl.lambda$runLater$6(PlatformImpl.java:294)
    at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
    at com.sun.glass.ui.gtk.GtkApplication._runLoop(Native Method)
    at com.sun.glass.ui.gtk.GtkApplication.lambda$null$10(GtkApplication.java:245)
    ... 1 more
Caused by: java.lang.NullPointerException
    at ViewController.MainViewController.initialize(MainViewController.java:142)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2548)
    ... 17 more
Exception running application c482.C482
Java Result: 1

Answer 1

请阅读类 PropertyValueFactory 的javadoc .
这行代码(来自 MainViewController 类)...

PartId.setCellValueFactory(new PropertyValueFactory<>("PartId"));

意味着您的类Part具有以下声明的方法...

public ObservableValue<Integer> PartIdProperty()

请注意，名称区分大小写。换句话说，partIdProperty 是不正确的。这同样适用于彼此的TableColumn。从您发布的代码来看，您的 Part 类中似乎缺少这些方法。

或者，您可以编写自己的接口(interface) Callback 实现。该接口(interface)中方法的声明可能看起来很吓人，但实现起来实际上并不困难。请记住，接口(interface)方法是由JavaFX基础设施调用的。使用作为 Part 类实例的参数调用您的方法，并且您的方法需要返回适当的 ObservableValue您从方法参数中提取的内容。

这是一个使用 Part 类显示零件表的小示例程序。请注意，它使用 method references Java 1.8 中添加的。另请注意，在下面的代码中，该方法 getValue() CellDataFeatures 类返回一个 Part 对象。

import javafx.application.Application;
import javafx.beans.property.SimpleDoubleProperty;
import javafx.beans.property.SimpleIntegerProperty;
import javafx.beans.property.SimpleStringProperty;
import javafx.beans.value.ObservableValue;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.scene.Scene;
import javafx.scene.control.TableColumn;
import javafx.scene.control.TableView;
import javafx.scene.control.TableColumn.CellDataFeatures;
import javafx.scene.layout.BorderPane;
import javafx.stage.Stage;

public class CellValueFactoryExample extends Application {
    private ObservableList<Part> items;

    @Override
    public void init() {
        items = FXCollections.observableArrayList();
        for (int i = 0; i < 10; i++) {
            Part part = new Part(i, String.valueOf(i), (double) i, i, i, i);
            items.add(part);
        }
    }

    @Override
    public void start(Stage primaryStage) throws Exception {
        primaryStage.setTitle("Inventory");
        TableView<Part> table = createTable();
        BorderPane root = new BorderPane();
        root.setCenter(table);
        Scene scene = new Scene(root);
        primaryStage.setScene(scene);
        primaryStage.show();
    }

    private TableView<Part> createTable() {
        TableView<Part> table = new TableView<Part>(items);

        TableColumn<Part, Number> idCol = new TableColumn<>("ID");
        idCol.setCellValueFactory(this::getIdColumnValue);

        TableColumn<Part, String> nameCol = new TableColumn<>("Name");
        nameCol.setCellValueFactory(this::getNameColumnValue);

        TableColumn<Part, Number> priceCol = new TableColumn<>("Price");
        priceCol.setCellValueFactory(this::getPriceColumnValue);

        TableColumn<Part, Number> stockCol = new TableColumn<>("Stock");
        stockCol.setCellValueFactory(this::getStockColumnValue);

        TableColumn<Part, Number> minCol = new TableColumn<>("Min");
        minCol.setCellValueFactory(this::getMinColumnValue);

        TableColumn<Part, Number> maxCol = new TableColumn<>("Max");
        maxCol.setCellValueFactory(this::getMaxColumnValue);

        table.getColumns().addAll(idCol, nameCol, priceCol, stockCol, minCol, maxCol);
        return table;
    }

    private ObservableValue<Number> getIdColumnValue(CellDataFeatures<Part, Number> param) {
        return new SimpleIntegerProperty(param.getValue().getId());
    }

    private ObservableValue<String> getNameColumnValue(CellDataFeatures<Part, String> param) {
        return new SimpleStringProperty(param.getValue().getName());
    }

    private ObservableValue<Number> getPriceColumnValue(CellDataFeatures<Part, Number> param) {
        return new SimpleDoubleProperty(param.getValue().getPrice());
    }

    private ObservableValue<Number> getStockColumnValue(CellDataFeatures<Part, Number> param) {
        return new SimpleIntegerProperty(param.getValue().getStock());
    }

    private ObservableValue<Number> getMinColumnValue(CellDataFeatures<Part, Number> param) {
        return new SimpleIntegerProperty(param.getValue().getMin());
    }

    private ObservableValue<Number> getMaxColumnValue(CellDataFeatures<Part, Number> param) {
        return new SimpleIntegerProperty(param.getValue().getMax());
    }

    public static void main(String[] args) {
        launch(args);
    }
}

这是正在运行的应用程序的屏幕截图。