npe在尝试从文本字段获取文本时？

gpnt7bae  于 2021-07-09  发布在  Java
关注(0)|答案(1)|浏览(270)

因此，我的计划是从textfield获取文本，将其保存在“currentvalue”变量中，并使其在每次从按钮调用其中一个方法时都保存一个新值。这是我的控制器类：

package application;

import java.io.IOException;

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.Button;
import javafx.scene.control.TextField;
import javafx.stage.Stage;

public class Controller {
@FXML
Button buttonyes,buttonno;
private Stage stage;
private Scene scene;
private Parent root;

public void yes(ActionEvent event) throws IOException {
 root = FXMLLoader.load(getClass().getResource("Order.fxml"));
 stage = (Stage)((Node)event.getSource()).getScene().getWindow();
 scene = new Scene(root);
 stage.setScene(scene);
 stage.show();
}

 public void no(ActionEvent event) {
  System.exit(0);
 }

@FXML
Button buttonback;

public void back(ActionEvent event) throws IOException{
    root = FXMLLoader.load(getClass().getResource("Welcome.fxml"));
     stage = (Stage)((Node)event.getSource()).getScene().getWindow();
     scene = new Scene(root);
     stage.setScene(scene);
     stage.show();
}

@FXML
private TextField display = new TextField("0,00"); // I either get a NFE here 

double currentvalue = Double.parseDouble(display.getText()); //or a NPE here if I delete the new TextField line
double value1 = 3.00;
double value2 = 2.50;
double value3 = 2.00;
double value4 = 1.50;
double value5 = 1.00;

public void order3() {
    display.setText(String.valueOf(currentvalue+value1));
}

public void order25() {
    display.setText(String.valueOf(currentvalue+value2));
}

public void order2() {
    display.setText(String.valueOf(currentvalue+value3));
}

public void order15() {
    display.setText(String.valueOf(currentvalue+value4));
}
public void order1() {
    display.setText(String.valueOf(currentvalue+value5));
}

public void order(ActionEvent event) throws IOException{
    root = FXMLLoader.load(getClass().getResource("Bye.fxml"));
     stage = (Stage)((Node)event.getSource()).getScene().getWindow();
     scene = new Scene(root);
     stage.setScene(scene);
     stage.show();
}

}

所以基本上我想计算一个新的值，一旦按下按钮，它就会显示在文本字段中。我在网上找到了很多解决方案，但似乎都不管用，这就是为什么我要问这个问题。
这是nfe的错误

javafx.fxml.LoadException: 
/C:/Users/daydr/eclipse-workspace/Projektarbeit-Bestellen/Bestellservice/bin/application/Welcome.fxml:11

    at javafx.fxml/javafx.fxml.FXMLLoader.constructLoadException(FXMLLoader.java:2707)
    at javafx.fxml/javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2685)
    at javafx.fxml/javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2548)
    at javafx.fxml/javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3323)
    at javafx.fxml/javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3280)
    at javafx.fxml/javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3249)
    at javafx.fxml/javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3222)
    at javafx.fxml/javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3199)
    at javafx.fxml/javafx.fxml.FXMLLoader.load(FXMLLoader.java:3192)
    at application.Main.start(Main.java:14)
    at javafx.graphics/com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$9(LauncherImpl.java:846)
    at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runAndWait$12(PlatformImpl.java:474)
    at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runLater$10(PlatformImpl.java:447)
    at java.base/java.security.AccessController.doPrivileged(AccessController.java:391)
    at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runLater$11(PlatformImpl.java:446)
    at javafx.graphics/com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:96)
    at javafx.graphics/com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at javafx.graphics/com.sun.glass.ui.win.WinApplication.lambda$runLoop$3(WinApplication.java:174)
    at java.base/java.lang.Thread.run(Thread.java:832)
Caused by: java.lang.NumberFormatException: For input string: "0,00"
    at java.base/jdk.internal.math.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:2054)
    at java.base/jdk.internal.math.FloatingDecimal.parseDouble(FloatingDecimal.java:110)
    at java.base/java.lang.Double.parseDouble(Double.java:549)
    at application.Controller.<init>(Controller.java:52)
    at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:64)
    at java.base/jdk.internal.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.base/java.lang.reflect.Constructor.newInstanceWithCaller(Constructor.java:500)
    at java.base/java.lang.reflect.ReflectAccess.newInstance(ReflectAccess.java:128)
    at java.base/jdk.internal.reflect.ReflectionFactory.newInstance(ReflectionFactory.java:350)
    at java.base/java.lang.Class.newInstance(Class.java:645)
    at javafx.fxml/javafx.fxml.FXMLLoader$ValueElement.processAttribute(FXMLLoader.java:938)
    at javafx.fxml/javafx.fxml.FXMLLoader$InstanceDeclarationElement.processAttribute(FXMLLoader.java:982)
    at javafx.fxml/javafx.fxml.FXMLLoader$Element.processStartElement(FXMLLoader.java:229)
    at javafx.fxml/javafx.fxml.FXMLLoader$ValueElement.processStartElement(FXMLLoader.java:754)
    at javafx.fxml/javafx.fxml.FXMLLoader.processStartElement(FXMLLoader.java:2808)
    at javafx.fxml/javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2634)
    ... 17 more

还有npe的那个

javafx.fxml.LoadException: 
/C:/Users/daydr/eclipse-workspace/Projektarbeit-Bestellen/Bestellservice/bin/application/Welcome.fxml:11

    at javafx.fxml/javafx.fxml.FXMLLoader.constructLoadException(FXMLLoader.java:2707)
    at javafx.fxml/javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2685)
    at javafx.fxml/javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2548)
    at javafx.fxml/javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3323)
    at javafx.fxml/javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3280)
    at javafx.fxml/javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3249)
    at javafx.fxml/javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3222)
    at javafx.fxml/javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3199)
    at javafx.fxml/javafx.fxml.FXMLLoader.load(FXMLLoader.java:3192)
    at application.Main.start(Main.java:14)
    at javafx.graphics/com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$9(LauncherImpl.java:846)
    at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runAndWait$12(PlatformImpl.java:474)
    at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runLater$10(PlatformImpl.java:447)
    at java.base/java.security.AccessController.doPrivileged(AccessController.java:391)
    at javafx.graphics/com.sun.javafx.application.PlatformImpl.lambda$runLater$11(PlatformImpl.java:446)
    at javafx.graphics/com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:96)
    at javafx.graphics/com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at javafx.graphics/com.sun.glass.ui.win.WinApplication.lambda$runLoop$3(WinApplication.java:174)
    at java.base/java.lang.Thread.run(Thread.java:832)
Caused by: java.lang.NullPointerException: Cannot invoke "javafx.scene.control.TextField.getText()" because "this.display" is null
    at application.Controller.<init>(Controller.java:52)
    at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:64)
    at java.base/jdk.internal.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.base/java.lang.reflect.Constructor.newInstanceWithCaller(Constructor.java:500)
    at java.base/java.lang.reflect.ReflectAccess.newInstance(ReflectAccess.java:128)
    at java.base/jdk.internal.reflect.ReflectionFactory.newInstance(ReflectionFactory.java:350)
    at java.base/java.lang.Class.newInstance(Class.java:645)
    at javafx.fxml/javafx.fxml.FXMLLoader$ValueElement.processAttribute(FXMLLoader.java:938)
    at javafx.fxml/javafx.fxml.FXMLLoader$InstanceDeclarationElement.processAttribute(FXMLLoader.java:982)
    at javafx.fxml/javafx.fxml.FXMLLoader$Element.processStartElement(FXMLLoader.java:229)
    at javafx.fxml/javafx.fxml.FXMLLoader$ValueElement.processStartElement(FXMLLoader.java:754)
    at javafx.fxml/javafx.fxml.FXMLLoader.processStartElement(FXMLLoader.java:2808)
    at javafx.fxml/javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2634)
    ... 17 more
Javajavafxscenebuilder

1条答案

按热度按时间
vktxenjb

vktxenjb1#

由于您没有包含fxml，我们只能假设textfield“display”在fxml文件中。这意味着它将通过fxml加载程序创建。不分配 display 到一个新的文本域。
您可以在initialize方法中访问display。

@Override
public void initialize(){
    currentValue = Double.parseDouble(display.getText());
}

您的语言环境有问题，因此可以使用本地化的解析来计算文本。

currentValue = NumberFormat.getInstance().parse(display.getText()).doubleValue();

这将使用默认的语言环境，可能更多的语言环境可能不使用逗号。
最后，您可能需要考虑绑定。因为你用的是javafx。

DoubleProperty currentValueProperty = new DoubleProperty();
public void initialize(){
    display.textProperty().bindBidirectional​( currentValueProperty, NumberFormat.getInstance() )
}
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