FXML 一直告诉我有一个空字符串

大卫·博伊斯顿

我有一个更复杂的程序，但在多次查看代码后，我认为我已经能够确定问题所在，我希望能得到一些帮助来检查此代码。
这是其他代码的一个非常基本的版本，但它复制了错误，所以我希望如果我可以在这个简化版本中修复它，我可以在更大的版本中修复它。

import java.net.URL;
import java.time.LocalDateTime;
import java.util.ArrayList;
import java.util.List;
import java.util.ResourceBundle;
import java.util.stream.DoubleStream;
import java.util.stream.Stream;
import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.scene.control.Label;
import javafx.scene.control.TextArea;
import javafx.scene.control.TextField;




    public class FXMLDocumentController implements Initializable {

        //SPECIAL CLASSES NEEDED
        public class TemperatureReading {
            private final double[] values;
            private final LocalDateTime timeStamp;

            public TemperatureReading(LocalDateTime timeStamp, double... values) {
                this.timeStamp = timeStamp;
                this.values = new double[values.length];
                System.arraycopy(values, 0, this.values, 0, values.length);
            }

            public TemperatureReading(double... values){
                this(LocalDateTime.now(), values);
            }

            public double getValue(int channel) {
                return values[channel];
            }

            public int getNumberOfChannels() {
                return values.length;
            }

            public LocalDateTime getTimestamp(){
                return timeStamp;
            }

            public boolean noneExceed(double max) {
                return DoubleStream.of(values).allMatch(v -> v <= max);
            }
        }
        //ANOTHER SPECIAL CLASS TO PARSE THE DATA
        public class TemperatureParser {
            public TemperatureReading parse (String text) {
                System.out.println("String received: " + text);
                if (text != null && text.length() > 0) //CHECK THAT THE STRING RECEIVED IS NOT EMPTY AND NOT NULL
                {
                return new TemperatureReading(Stream.of(text.split("\\s")).mapToDouble(Double::parseDouble).toArray());
                }
                else
                {
                System.out.println("Null reading");
                return null;
                }
            }
        }
        //SIMPLE GUI FXML COMPONENTS
        @FXML
        private Label label;
        @FXML
        private TextArea displayLog;
        @FXML
        private TextField input; //INPUT IS USUALLY NUMBERS EX 24.458  24.435  24.355  24.433  24.511  24.554  24.507  24.515  24.413




        @FXML
        private void handleButtonAction(ActionEvent event) {
            System.out.println("You clicked me!");
            System.out.println(readings.size());
            displayLog.setText("Getting ready to print! Beep Boop!");

                    for (int t = 0; t < readings.size(); t++)
            {
                displayLog.setText("Time: " + readings.get(t).getTimestamp() + " CH1: " + readings.get(t).getValue(0) + " CH2: " + readings.get(t).getValue(1) + " CH3: " + readings.get(t).getValue(2) + " CH4: " + readings.get(t).getValue(3) + " CH5: " + readings.get(t).getValue(4) + " CH6: " + readings.get(t).getValue(5) + " CH7: " + readings.get(t).getValue(6) + " CH8: " + readings.get(t).getValue(7) + " CH9: " + readings.get(t).getValue(8));
            }
        }
        public List<TemperatureReading> readings = new ArrayList<>();
        @FXML
        private void doPass(ActionEvent event)
        {
            TemperatureReading reading;
            TemperatureParser parser = new TemperatureParser();

            reading = parser.parse(input.getText());
            displayLog.appendText("Value Parsed " + input.getText());
            readings.add(reading);
            displayLog.appendText("Value Passed!");
            input.clear();
        }
        @Override
        public void initialize(URL url, ResourceBundle rb) {
            // TODO
        }    

    }

我在那里添加了一条评论，所以你得到了一个例子，但在 TextField 中，我放置了以下字符串（复制粘贴）：
24.458 24.435 24.355 24.433 24.511 24.554 24.507 24.515 24.413 2 \ s 从每个数字之间理解 TemperatureReading 列表中的元素我应该得到一些类似的东西：

Time: 2017-04-20T15:28:19.118 CH1: 24.024 CH2: 23.961 CH3: 23.889 CH4: 24.163 CH5: 24.085 CH6: 24.107 CH7: 24.017 CH8: 24.042 CH9: 24.473

但是我不断收到此错误：

String received: 24.458  24.435  24.355  24.433  24.511  24.554  24.507  24.515  24.413
Exception in thread "JavaFX Application Thread" java.lang.RuntimeException: java.lang.reflect.InvocationTargetException
    at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1774)
    at javafx.fxml.FXMLLoader$ControllerMethodEventHandler.handle(FXMLLoader.java:1657)
    at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
    at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
    at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:49)
    at javafx.event.Event.fireEvent(Event.java:198)
    at javafx.scene.Node.fireEvent(Node.java:8413)
    at javafx.scene.control.Button.fire(Button.java:185)
    at com.sun.javafx.scene.control.behavior.ButtonBehavior.mouseReleased(ButtonBehavior.java:182)
    at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:96)
    at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:89)
    at com.sun.javafx.event.CompositeEventHandler$NormalEventHandlerRecord.handleBubblingEvent(CompositeEventHandler.java:218)
    at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:80)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
    at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
    at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)
    at javafx.event.Event.fireEvent(Event.java:198)
    at javafx.scene.Scene$MouseHandler.process(Scene.java:3757)
    at javafx.scene.Scene$MouseHandler.access$1500(Scene.java:3485)
    at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1762)
    at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2494)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:381)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:295)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$354(GlassViewEventHandler.java:417)
    at com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:389)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:416)
    at com.sun.glass.ui.View.handleMouseEvent(View.java:555)
    at com.sun.glass.ui.View.notifyMouse(View.java:937)
    at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at com.sun.glass.ui.win.WinApplication.lambda$null$148(WinApplication.java:191)
    at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.reflect.InvocationTargetException
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at sun.reflect.misc.Trampoline.invoke(MethodUtil.java:71)
    at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at sun.reflect.misc.MethodUtil.invoke(MethodUtil.java:275)
    at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1769)
    ... 48 more
Caused by: java.lang.NumberFormatException: empty String
    at sun.misc.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:1842)
    at sun.misc.FloatingDecimal.parseDouble(FloatingDecimal.java:110)
    at java.lang.Double.parseDouble(Double.java:538)
    at java.util.stream.ReferencePipeline$6$1.accept(ReferencePipeline.java:244)
    at java.util.Spliterators$ArraySpliterator.forEachRemaining(Spliterators.java:948)
    at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:481)
    at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:471)
    at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:545)
    at java.util.stream.AbstractPipeline.evaluateToArrayNode(AbstractPipeline.java:260)
    at java.util.stream.DoublePipeline.toArray(DoublePipeline.java:506)
    at trytheclass.FXMLDocumentController$TemperatureParser.parse(FXMLDocumentController.java:67)
    at trytheclass.FXMLDocumentController.doPass(FXMLDocumentController.java:105)
    ... 58 more

它说“由空字符串引起”但是您也可以看到解析器不应该在我实际发送之前使用空字符串（if 语句）运行，并在我将其输出到日志文件中并在我输入时显示完整字符串.

卢克伍德沃德

此问题的原因与 JavaFX 和 FXML 无关。

事实上，让我们暂时不考虑流。你觉得下面的印刷品怎么样？

String text = "24.458  24.435  24.355  24.433  24.511  24.554  24.507  24.515  24.413";
System.out.println(Arrays.toString(text.split("\\s")));

实际输出是这样的：

[24.458, , 24.435, , 24.355, , 24.433, , 24.511, , 24.554, , 24.507, , 24.515, , 24.413]

问题是您在一个空格上拆分，但您的数字之间有两个空格。因此，每对空格之间是一个空字符串，这就是您在返回数组中的每个其他索引处得到的结果。

解决方法很简单：通过+在任意数量的空格而不是一个空格上添加拆分来调整正则表达式：

String text = "24.458  24.435  24.355  24.433  24.511  24.554  24.507  24.515  24.413";
System.out.println(Arrays.toString(text.split("\\s+")));

这给了我输出

[24.458, 24.435, 24.355, 24.433, 24.511, 24.554, 24.507, 24.515, 24.413]

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编辑于 2021-06-4

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