为什么将 TextField 绑定到正在另一个线程上更新的 属性 最终导致应用程序抛出错误？
Why does binding a TextField to a property which is being updated on another thread end up with the application throwing errors?
我有一个 javafx 应用程序，其中有多个选项卡（计时器、秒表、时钟），每个选项卡都有一个单独的控制器，用户可以使用 start/stop 按钮添加和独立启动多个计时器。
我尝试将一个 TextField 绑定到另一个 class MyTimer 的 属性，它跟踪经过的时间，但它最终（在 运行 几秒钟后）开始抛出一个错误。 （如果你检查下面的代码，请注意只有当 "Thread.sleep" 设置为 10ms 时才会发生 - 当我将延迟增加到 100ms 时，它保持 运行 大约一分钟并且没有崩溃 - 我没有进一步测试，因为我想解决根本原因而不是增加延迟）。
让你有个快速的想法：
app image
MyTimer class:
public class MyTimer implements Startable {
...
private long startNanoTime, storedElapsedTime, totalTime;
private TimerStates state;
private StringProperty timerStringProperty = new SimpleStringProperty(DEFAULT_TIMER_STRING_VALUE);
public MyTimer() {
//constructor
}
public long getRemainingTime() {
//returns remaining time
}
public StringProperty timerStringPropertyProperty() {
return timerStringProperty;
}
@Override
public boolean start() {
if (this.state.isRunning() ) {
System.out.println("Already running.");
return false;
}
this.startNanoTime = System.nanoTime();
this.state = TimerStates.RUNNING;
Runnable startTimerRunnable = new Runnable() {
@Override
public void run() {
while(state.isRunning()) {
timerStringProperty.set(MyFormatter.longMillisecondsTimeToTimeString(getRemainingTime())); //The parameter passed is simply the remaining time formatted to a String
try {
Thread.sleep(10);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
};
Thread daemonTimer = new Thread(startTimerRunnable);
daemonTimer.setDaemon(true);
daemonTimer.start();
return true;
}
}
在尝试实现绑定时，我尝试将一个在应用程序启动时无需任何用户交互就存在的默认 TextProperty 绑定到 属性，表示从 MyTimer class 到控制器中的值：
public class TimerTabController {
...
@FXML
private Tab timerTab;
@FXML
private HBox defaultTimerHBox;
@FXML
private TextField defaultTimerTextField;
private Map<HBox, MyTimer> timers = new HashMap<>();
@FXML
protected void initialize() {
MyTimer defaultTimer = new MyTimer();
timers.put(defaultTimerHBox, defaultTimer);
defaultTimerTextField.textProperty().bind(defaultTimer.timerStringPropertyProperty());
}
}
启动它的 Main 方法是相当标准的，但无论如何我都会包括它：
public class Main extends Application {
@Override
public void start(Stage primaryStage) throws Exception{
Parent root = FXMLLoader.load(getClass().getResource("fxml/mainWindow.fxml"));
primaryStage.setTitle("Mortimer");
primaryStage.setScene(new Scene(root, 800, 700));
primaryStage.show();
}
public static void main(String[] args) {
launch(args);
}
}
最后，堆栈跟踪：
首先，有这个：
Exception in thread "Thread-3" java.lang.NullPointerException
at javafx.graphics/com.sun.javafx.text.PrismTextLayout.createLine(PrismTextLayout.java:893)
at javafx.graphics/com.sun.javafx.text.PrismTextLayout.layout(PrismTextLayout.java:1193)
at javafx.graphics/com.sun.javafx.text.PrismTextLayout.ensureLayout(PrismTextLayout.java:222)
at javafx.graphics/com.sun.javafx.text.PrismTextLayout.getBounds(PrismTextLayout.java:245)
at javafx.graphics/javafx.scene.text.Text.getLogicalBounds(Text.java:430)
at javafx.graphics/javafx.scene.text.Text.getYRendering(Text.java:1085)
at javafx.graphics/javafx.scene.text.Text.access00(Text.java:127)
at javafx.graphics/javafx.scene.text.Text$TextAttribute.computeValue(Text.java:1764)
at javafx.graphics/javafx.scene.text.Text$TextAttribute.computeValue(Text.java:1756)
at javafx.base/javafx.beans.binding.ObjectBinding.get(ObjectBinding.java:151)
at javafx.base/javafx.beans.binding.ObjectExpression.getValue(ObjectExpression.java:49)
at javafx.base/javafx.beans.property.ObjectPropertyBase.get(ObjectPropertyBase.java:133)
at javafx.controls/javafx.scene.control.skin.TextFieldSkin.lambda$new(TextFieldSkin.java:252)
at javafx.base/com.sun.javafx.binding.ExpressionHelper$SingleInvalidation.fireValueChangedEvent(ExpressionHelper.java:136)
at javafx.base/com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(ExpressionHelper.java:80)
at javafx.base/javafx.beans.property.ObjectPropertyBase.fireValueChangedEvent(ObjectPropertyBase.java:106)
at javafx.base/javafx.beans.property.ObjectPropertyBase.markInvalid(ObjectPropertyBase.java:113)
at javafx.base/javafx.beans.property.ObjectPropertyBase.access[=14=]0(ObjectPropertyBase.java:52)
at javafx.base/javafx.beans.property.ObjectPropertyBase$Listener.invalidated(ObjectPropertyBase.java:234)
at javafx.base/com.sun.javafx.binding.ExpressionHelper$SingleInvalidation.fireValueChangedEvent(ExpressionHelper.java:136)
at javafx.base/com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(ExpressionHelper.java:80)
at javafx.base/javafx.beans.binding.ObjectBinding.invalidate(ObjectBinding.java:170)
at javafx.graphics/javafx.scene.text.Text.doGeomChanged(Text.java:842)
at javafx.graphics/javafx.scene.text.Text.access0(Text.java:127)
at javafx.graphics/javafx.scene.text.Text.doGeomChanged(Text.java:158)
at javafx.graphics/com.sun.javafx.scene.shape.TextHelper.geomChangedImpl(TextHelper.java:106)
at javafx.graphics/com.sun.javafx.scene.NodeHelper.geomChanged(NodeHelper.java:137)
at javafx.graphics/javafx.scene.text.Text.needsTextLayout(Text.java:266)
at javafx.graphics/javafx.scene.text.Text.needsFullTextLayout(Text.java:261)
at javafx.graphics/javafx.scene.text.Text.access0(Text.java:127)
at javafx.graphics/javafx.scene.text.Text.invalidated(Text.java:461)
at javafx.base/javafx.beans.property.StringPropertyBase.markInvalid(StringPropertyBase.java:110)
at javafx.base/javafx.beans.property.StringPropertyBase.access[=14=]0(StringPropertyBase.java:50)
at javafx.base/javafx.beans.property.StringPropertyBase$Listener.invalidated(StringPropertyBase.java:231)
at javafx.base/com.sun.javafx.binding.ExpressionHelper$SingleInvalidation.fireValueChangedEvent(ExpressionHelper.java:136)
at javafx.base/com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(ExpressionHelper.java:80)
at javafx.base/javafx.beans.binding.StringBinding.invalidate(StringBinding.java:169)
at javafx.base/com.sun.javafx.binding.BindingHelperObserver.invalidated(BindingHelperObserver.java:52)
at javafx.base/com.sun.javafx.binding.ExpressionHelper$Generic.fireValueChangedEvent(ExpressionHelper.java:348)
at javafx.base/com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(ExpressionHelper.java:80)
at javafx.controls/javafx.scene.control.TextInputControl$TextProperty.fireValueChangedEvent(TextInputControl.java:1430)
at javafx.controls/javafx.scene.control.TextInputControl$TextProperty.markInvalid(TextInputControl.java:1434)
at javafx.controls/javafx.scene.control.TextInputControl$TextProperty.controlContentHasChanged(TextInputControl.java:1373)
at javafx.controls/javafx.scene.control.TextInputControl$TextProperty.access00(TextInputControl.java:1341)
at javafx.controls/javafx.scene.control.TextInputControl.lambda$new[=14=](TextInputControl.java:144)
at javafx.base/com.sun.javafx.binding.ExpressionHelper$SingleInvalidation.fireValueChangedEvent(ExpressionHelper.java:136)
at javafx.base/com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(ExpressionHelper.java:80)
at javafx.controls/javafx.scene.control.TextField$TextFieldContent.insert(TextField.java:87)
at javafx.controls/javafx.scene.control.TextInputControl.replaceText(TextInputControl.java:1244)
at javafx.controls/javafx.scene.control.TextInputControl.filterAndSet(TextInputControl.java:1211)
at javafx.controls/javafx.scene.control.TextInputControl.access0(TextInputControl.java:80)
at javafx.controls/javafx.scene.control.TextInputControl$TextProperty.doSet(TextInputControl.java:1451)
at javafx.controls/javafx.scene.control.TextInputControl$TextProperty.access00(TextInputControl.java:1341)
at javafx.controls/javafx.scene.control.TextInputControl$TextProperty$Listener.invalidated(TextInputControl.java:1474)
at javafx.base/com.sun.javafx.binding.ExpressionHelper$SingleInvalidation.fireValueChangedEvent(ExpressionHelper.java:136)
at javafx.base/com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(ExpressionHelper.java:80)
at javafx.base/javafx.beans.property.StringPropertyBase.fireValueChangedEvent(StringPropertyBase.java:104)
at javafx.base/javafx.beans.property.StringPropertyBase.markInvalid(StringPropertyBase.java:111)
at javafx.base/javafx.beans.property.StringPropertyBase.set(StringPropertyBase.java:145)
at javafx.base/javafx.beans.property.StringPropertyBase.set(StringPropertyBase.java:50)
at MorTimer/sample.MyTimer.run(MyTimer.java:106)
at java.base/java.lang.Thread.run(Thread.java:834)
然后下面的错误不断重复：
Exception in thread "JavaFX Application Thread" java.lang.NullPointerException
at javafx.graphics/com.sun.javafx.text.PrismTextLayout.getRuns(PrismTextLayout.java:235)
at javafx.graphics/javafx.scene.text.Text.getRuns(Text.java:389)
at javafx.graphics/javafx.scene.text.Text.updatePGText(Text.java:1460)
at javafx.graphics/javafx.scene.text.Text.doUpdatePeer(Text.java:1490)
at javafx.graphics/javafx.scene.text.Text.access0(Text.java:127)
at javafx.graphics/javafx.scene.text.Text.doUpdatePeer(Text.java:137)
at javafx.graphics/com.sun.javafx.scene.shape.TextHelper.updatePeerImpl(TextHelper.java:75)
at javafx.graphics/com.sun.javafx.scene.NodeHelper.updatePeer(NodeHelper.java:102)
at javafx.graphics/javafx.scene.Node.syncPeer(Node.java:710)
at javafx.graphics/javafx.scene.Scene$ScenePulseListener.synchronizeSceneNodes(Scene.java:2366)
at javafx.graphics/javafx.scene.Scene$ScenePulseListener.pulse(Scene.java:2512)
at javafx.graphics/com.sun.javafx.tk.Toolkit.lambda$runPulse(Toolkit.java:412)
at java.base/java.security.AccessController.doPrivileged(Native Method)
at javafx.graphics/com.sun.javafx.tk.Toolkit.runPulse(Toolkit.java:411)
at javafx.graphics/com.sun.javafx.tk.Toolkit.firePulse(Toolkit.java:438)
at javafx.graphics/com.sun.javafx.tk.quantum.QuantumToolkit.pulse(QuantumToolkit.java:519)
at javafx.graphics/com.sun.javafx.tk.quantum.QuantumToolkit.pulse(QuantumToolkit.java:499)
at javafx.graphics/com.sun.javafx.tk.quantum.QuantumToolkit.pulseFromQueue(QuantumToolkit.java:492)
at javafx.graphics/com.sun.javafx.tk.quantum.QuantumToolkit.lambda$runToolkit(QuantumToolkit.java:320)
at javafx.graphics/com.sun.glass.ui.InvokeLaterDispatcher$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$runLoop(WinApplication.java:174)
at java.base/java.lang.Thread.run(Thread.java:834)
Exception in thread "JavaFX Application Thread" java.lang.NullPointerException
at javafx.graphics/javafx.scene.Scene$ScenePulseListener.synchronizeSceneNodes(Scene.java:2365)
at javafx.graphics/javafx.scene.Scene$ScenePulseListener.pulse(Scene.java:2512)
at javafx.graphics/com.sun.javafx.tk.Toolkit.lambda$runPulse(Toolkit.java:412)
at java.base/java.security.AccessController.doPrivileged(Native Method)
at javafx.graphics/com.sun.javafx.tk.Toolkit.runPulse(Toolkit.java:411)
at javafx.graphics/com.sun.javafx.tk.Toolkit.firePulse(Toolkit.java:438)
at javafx.graphics/com.sun.javafx.tk.quantum.QuantumToolkit.pulse(QuantumToolkit.java:519)
at javafx.graphics/com.sun.javafx.tk.quantum.QuantumToolkit.pulse(QuantumToolkit.java:499)
at javafx.graphics/com.sun.javafx.tk.quantum.QuantumToolkit.pulseFromQueue(QuantumToolkit.java:492)
at javafx.graphics/com.sun.javafx.tk.quantum.QuantumToolkit.lambda$runToolkit(QuantumToolkit.java:320)
at javafx.graphics/com.sun.glass.ui.InvokeLaterDispatcher$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(WinApplication.java:174)
at java.base/java.lang.Thread.run(Thread.java:834)
当我在 MyTimer.start() 函数中使用 Platform.runLater() 时，它确实起作用了，就像这样：
Runnable startTimerRunnable = new Runnable() {
@Override
public void run() {
while(state.isRunning()) {
Platform.runLater(new Runnable() {
@Override
public void run() {
timerStringProperty.set(MyFormatter.longMillisecondsTimeToTimeString(getRemainingTime()));
}
});
try {
Thread.sleep(10);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
};
Thread daemonTimer = new Thread(startTimerRunnable);
daemonTimer.setDaemon(true);
daemonTimer.start();
但是这样用Platform.runLater好像不对，还是可以的？我知道 GUI 不应该在 FX 线程之外更新，但我认为绑定属性可以解决这个问题——更新绑定到 GUI 元素的 属性 不需要在 FX 线程中进行，作为绑定的一部分，GUI 更新确实会在 FX 线程上得到正确处理...
最终，我的解决方案似乎工作得相当好，是不使用绑定，而是定期更新控制器本身的字段（以下方法在选项卡本身的 "onSelectionChanged" 上调用）- 但是我想知道如何使绑定工作，因为绑定似乎是更好的做法。
不管怎样，下面是同样有效的代码：
public void startTimeFieldUpdates() {
Runnable timeTracker = new Runnable() {
@Override
public void run() {
while(timerTab.isSelected()) {
Platform.runLater(new Runnable() {
@Override
public void run() {
for (HBox hBox : timers.keySet()) {
if (hBox.getChildren().get(1) instanceof TextField) {
TextField currentField = (TextField) hBox.getChildren().get(1);
currentField.setText(MyFormatter.longMillisecondsTimeToTimeString(
timers.get(hBox).getRemainingTime())
);
}
}
}
});
try {
Thread.sleep(10);
} catch (InterruptedException ex) {
ex.printStackTrace();
}
}
}
};
Thread daemonStopwatch = new Thread(timeTracker);
daemonStopwatch.setDaemon(true);
daemonStopwatch.start();
}
那么我的问题是，解决这个问题的正确方法是什么？
正如我的问题的评论中所发布的那样，答案确实是 属性 绑定使用的侦听器最终 运行 在 属性 本身更新的同一线程上 -因此，为避免出现问题，需要在 Java FX 应用程序线程上更新绑定属性（或者应该寻求其他解决方案，就像我的情况一样）。
对我有用的解决方案 - 正如我的问题的评论中提到的，我查看了 AnimationTimer 是什么，它似乎正是我正在寻找的并且完美地工作。
如果对某人有帮助，这是我的实现：
import ...
public class TimerTabController {
public static final int TIMER_HBOX_TEXTFIELD_INDEX = 1;
public static final int TIMER_HBOX_STARTSTOP_BUTTON_INDEX = 2;
@FXML
private Tab timerTab;
@FXML
private HBox defaultTimerHBox;
@FXML
private TextField defaultTimerTextField;
private Map<HBox, MyTimer> timers = new HashMap<>();
private AnimationTimer timerTabAnimationTimer = new AnimationTimer() {
@Override
public void handle(long l) {
//the GUI updates go here
for (HBox hBox : timers.keySet()) {
if (hBox.getChildren().get(TIMER_HBOX_TEXTFIELD_INDEX) instanceof TextField) {
TextField currentField = (TextField) hBox.getChildren().get(TIMER_HBOX_TEXTFIELD_INDEX);
currentField.setText(MyFormatter.longMillisecondsTimeToTimeString(
timers.get(hBox).getRemainingTime())
);
}
}
}
};
@FXML
protected void initialize() {
timers.put(defaultTimerHBox, new MyTimer());
}
@FXML
void handleSelectionChanged() { //triggered by changing tab selection
if (timerTab.isSelected()) {
timerTabAnimationTimer.start();
} else {
timerTabAnimationTimer.stop();
}
}
//some more code
}
我有一个 javafx 应用程序，其中有多个选项卡（计时器、秒表、时钟），每个选项卡都有一个单独的控制器，用户可以使用 start/stop 按钮添加和独立启动多个计时器。
我尝试将一个 TextField 绑定到另一个 class MyTimer 的 属性，它跟踪经过的时间，但它最终（在 运行 几秒钟后）开始抛出一个错误。 （如果你检查下面的代码，请注意只有当 "Thread.sleep" 设置为 10ms 时才会发生 - 当我将延迟增加到 100ms 时，它保持 运行 大约一分钟并且没有崩溃 - 我没有进一步测试，因为我想解决根本原因而不是增加延迟）。
让你有个快速的想法： app image
MyTimer class:
public class MyTimer implements Startable {
...
private long startNanoTime, storedElapsedTime, totalTime;
private TimerStates state;
private StringProperty timerStringProperty = new SimpleStringProperty(DEFAULT_TIMER_STRING_VALUE);
public MyTimer() {
//constructor
}
public long getRemainingTime() {
//returns remaining time
}
public StringProperty timerStringPropertyProperty() {
return timerStringProperty;
}
@Override
public boolean start() {
if (this.state.isRunning() ) {
System.out.println("Already running.");
return false;
}
this.startNanoTime = System.nanoTime();
this.state = TimerStates.RUNNING;
Runnable startTimerRunnable = new Runnable() {
@Override
public void run() {
while(state.isRunning()) {
timerStringProperty.set(MyFormatter.longMillisecondsTimeToTimeString(getRemainingTime())); //The parameter passed is simply the remaining time formatted to a String
try {
Thread.sleep(10);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
};
Thread daemonTimer = new Thread(startTimerRunnable);
daemonTimer.setDaemon(true);
daemonTimer.start();
return true;
}
}
在尝试实现绑定时，我尝试将一个在应用程序启动时无需任何用户交互就存在的默认 TextProperty 绑定到 属性，表示从 MyTimer class 到控制器中的值：
public class TimerTabController {
...
@FXML
private Tab timerTab;
@FXML
private HBox defaultTimerHBox;
@FXML
private TextField defaultTimerTextField;
private Map<HBox, MyTimer> timers = new HashMap<>();
@FXML
protected void initialize() {
MyTimer defaultTimer = new MyTimer();
timers.put(defaultTimerHBox, defaultTimer);
defaultTimerTextField.textProperty().bind(defaultTimer.timerStringPropertyProperty());
}
}
启动它的 Main 方法是相当标准的，但无论如何我都会包括它：
public class Main extends Application {
@Override
public void start(Stage primaryStage) throws Exception{
Parent root = FXMLLoader.load(getClass().getResource("fxml/mainWindow.fxml"));
primaryStage.setTitle("Mortimer");
primaryStage.setScene(new Scene(root, 800, 700));
primaryStage.show();
}
public static void main(String[] args) {
launch(args);
}
}
最后，堆栈跟踪： 首先，有这个：
Exception in thread "Thread-3" java.lang.NullPointerException
at javafx.graphics/com.sun.javafx.text.PrismTextLayout.createLine(PrismTextLayout.java:893)
at javafx.graphics/com.sun.javafx.text.PrismTextLayout.layout(PrismTextLayout.java:1193)
at javafx.graphics/com.sun.javafx.text.PrismTextLayout.ensureLayout(PrismTextLayout.java:222)
at javafx.graphics/com.sun.javafx.text.PrismTextLayout.getBounds(PrismTextLayout.java:245)
at javafx.graphics/javafx.scene.text.Text.getLogicalBounds(Text.java:430)
at javafx.graphics/javafx.scene.text.Text.getYRendering(Text.java:1085)
at javafx.graphics/javafx.scene.text.Text.access00(Text.java:127)
at javafx.graphics/javafx.scene.text.Text$TextAttribute.computeValue(Text.java:1764)
at javafx.graphics/javafx.scene.text.Text$TextAttribute.computeValue(Text.java:1756)
at javafx.base/javafx.beans.binding.ObjectBinding.get(ObjectBinding.java:151)
at javafx.base/javafx.beans.binding.ObjectExpression.getValue(ObjectExpression.java:49)
at javafx.base/javafx.beans.property.ObjectPropertyBase.get(ObjectPropertyBase.java:133)
at javafx.controls/javafx.scene.control.skin.TextFieldSkin.lambda$new(TextFieldSkin.java:252)
at javafx.base/com.sun.javafx.binding.ExpressionHelper$SingleInvalidation.fireValueChangedEvent(ExpressionHelper.java:136)
at javafx.base/com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(ExpressionHelper.java:80)
at javafx.base/javafx.beans.property.ObjectPropertyBase.fireValueChangedEvent(ObjectPropertyBase.java:106)
at javafx.base/javafx.beans.property.ObjectPropertyBase.markInvalid(ObjectPropertyBase.java:113)
at javafx.base/javafx.beans.property.ObjectPropertyBase.access[=14=]0(ObjectPropertyBase.java:52)
at javafx.base/javafx.beans.property.ObjectPropertyBase$Listener.invalidated(ObjectPropertyBase.java:234)
at javafx.base/com.sun.javafx.binding.ExpressionHelper$SingleInvalidation.fireValueChangedEvent(ExpressionHelper.java:136)
at javafx.base/com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(ExpressionHelper.java:80)
at javafx.base/javafx.beans.binding.ObjectBinding.invalidate(ObjectBinding.java:170)
at javafx.graphics/javafx.scene.text.Text.doGeomChanged(Text.java:842)
at javafx.graphics/javafx.scene.text.Text.access0(Text.java:127)
at javafx.graphics/javafx.scene.text.Text.doGeomChanged(Text.java:158)
at javafx.graphics/com.sun.javafx.scene.shape.TextHelper.geomChangedImpl(TextHelper.java:106)
at javafx.graphics/com.sun.javafx.scene.NodeHelper.geomChanged(NodeHelper.java:137)
at javafx.graphics/javafx.scene.text.Text.needsTextLayout(Text.java:266)
at javafx.graphics/javafx.scene.text.Text.needsFullTextLayout(Text.java:261)
at javafx.graphics/javafx.scene.text.Text.access0(Text.java:127)
at javafx.graphics/javafx.scene.text.Text.invalidated(Text.java:461)
at javafx.base/javafx.beans.property.StringPropertyBase.markInvalid(StringPropertyBase.java:110)
at javafx.base/javafx.beans.property.StringPropertyBase.access[=14=]0(StringPropertyBase.java:50)
at javafx.base/javafx.beans.property.StringPropertyBase$Listener.invalidated(StringPropertyBase.java:231)
at javafx.base/com.sun.javafx.binding.ExpressionHelper$SingleInvalidation.fireValueChangedEvent(ExpressionHelper.java:136)
at javafx.base/com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(ExpressionHelper.java:80)
at javafx.base/javafx.beans.binding.StringBinding.invalidate(StringBinding.java:169)
at javafx.base/com.sun.javafx.binding.BindingHelperObserver.invalidated(BindingHelperObserver.java:52)
at javafx.base/com.sun.javafx.binding.ExpressionHelper$Generic.fireValueChangedEvent(ExpressionHelper.java:348)
at javafx.base/com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(ExpressionHelper.java:80)
at javafx.controls/javafx.scene.control.TextInputControl$TextProperty.fireValueChangedEvent(TextInputControl.java:1430)
at javafx.controls/javafx.scene.control.TextInputControl$TextProperty.markInvalid(TextInputControl.java:1434)
at javafx.controls/javafx.scene.control.TextInputControl$TextProperty.controlContentHasChanged(TextInputControl.java:1373)
at javafx.controls/javafx.scene.control.TextInputControl$TextProperty.access00(TextInputControl.java:1341)
at javafx.controls/javafx.scene.control.TextInputControl.lambda$new[=14=](TextInputControl.java:144)
at javafx.base/com.sun.javafx.binding.ExpressionHelper$SingleInvalidation.fireValueChangedEvent(ExpressionHelper.java:136)
at javafx.base/com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(ExpressionHelper.java:80)
at javafx.controls/javafx.scene.control.TextField$TextFieldContent.insert(TextField.java:87)
at javafx.controls/javafx.scene.control.TextInputControl.replaceText(TextInputControl.java:1244)
at javafx.controls/javafx.scene.control.TextInputControl.filterAndSet(TextInputControl.java:1211)
at javafx.controls/javafx.scene.control.TextInputControl.access0(TextInputControl.java:80)
at javafx.controls/javafx.scene.control.TextInputControl$TextProperty.doSet(TextInputControl.java:1451)
at javafx.controls/javafx.scene.control.TextInputControl$TextProperty.access00(TextInputControl.java:1341)
at javafx.controls/javafx.scene.control.TextInputControl$TextProperty$Listener.invalidated(TextInputControl.java:1474)
at javafx.base/com.sun.javafx.binding.ExpressionHelper$SingleInvalidation.fireValueChangedEvent(ExpressionHelper.java:136)
at javafx.base/com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(ExpressionHelper.java:80)
at javafx.base/javafx.beans.property.StringPropertyBase.fireValueChangedEvent(StringPropertyBase.java:104)
at javafx.base/javafx.beans.property.StringPropertyBase.markInvalid(StringPropertyBase.java:111)
at javafx.base/javafx.beans.property.StringPropertyBase.set(StringPropertyBase.java:145)
at javafx.base/javafx.beans.property.StringPropertyBase.set(StringPropertyBase.java:50)
at MorTimer/sample.MyTimer.run(MyTimer.java:106)
at java.base/java.lang.Thread.run(Thread.java:834)
然后下面的错误不断重复：
Exception in thread "JavaFX Application Thread" java.lang.NullPointerException
at javafx.graphics/com.sun.javafx.text.PrismTextLayout.getRuns(PrismTextLayout.java:235)
at javafx.graphics/javafx.scene.text.Text.getRuns(Text.java:389)
at javafx.graphics/javafx.scene.text.Text.updatePGText(Text.java:1460)
at javafx.graphics/javafx.scene.text.Text.doUpdatePeer(Text.java:1490)
at javafx.graphics/javafx.scene.text.Text.access0(Text.java:127)
at javafx.graphics/javafx.scene.text.Text.doUpdatePeer(Text.java:137)
at javafx.graphics/com.sun.javafx.scene.shape.TextHelper.updatePeerImpl(TextHelper.java:75)
at javafx.graphics/com.sun.javafx.scene.NodeHelper.updatePeer(NodeHelper.java:102)
at javafx.graphics/javafx.scene.Node.syncPeer(Node.java:710)
at javafx.graphics/javafx.scene.Scene$ScenePulseListener.synchronizeSceneNodes(Scene.java:2366)
at javafx.graphics/javafx.scene.Scene$ScenePulseListener.pulse(Scene.java:2512)
at javafx.graphics/com.sun.javafx.tk.Toolkit.lambda$runPulse(Toolkit.java:412)
at java.base/java.security.AccessController.doPrivileged(Native Method)
at javafx.graphics/com.sun.javafx.tk.Toolkit.runPulse(Toolkit.java:411)
at javafx.graphics/com.sun.javafx.tk.Toolkit.firePulse(Toolkit.java:438)
at javafx.graphics/com.sun.javafx.tk.quantum.QuantumToolkit.pulse(QuantumToolkit.java:519)
at javafx.graphics/com.sun.javafx.tk.quantum.QuantumToolkit.pulse(QuantumToolkit.java:499)
at javafx.graphics/com.sun.javafx.tk.quantum.QuantumToolkit.pulseFromQueue(QuantumToolkit.java:492)
at javafx.graphics/com.sun.javafx.tk.quantum.QuantumToolkit.lambda$runToolkit(QuantumToolkit.java:320)
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(WinApplication.java:174)
at java.base/java.lang.Thread.run(Thread.java:834)
Exception in thread "JavaFX Application Thread" java.lang.NullPointerException
at javafx.graphics/javafx.scene.Scene$ScenePulseListener.synchronizeSceneNodes(Scene.java:2365)
at javafx.graphics/javafx.scene.Scene$ScenePulseListener.pulse(Scene.java:2512)
at javafx.graphics/com.sun.javafx.tk.Toolkit.lambda$runPulse(Toolkit.java:412)
at java.base/java.security.AccessController.doPrivileged(Native Method)
at javafx.graphics/com.sun.javafx.tk.Toolkit.runPulse(Toolkit.java:411)
at javafx.graphics/com.sun.javafx.tk.Toolkit.firePulse(Toolkit.java:438)
at javafx.graphics/com.sun.javafx.tk.quantum.QuantumToolkit.pulse(QuantumToolkit.java:519)
at javafx.graphics/com.sun.javafx.tk.quantum.QuantumToolkit.pulse(QuantumToolkit.java:499)
at javafx.graphics/com.sun.javafx.tk.quantum.QuantumToolkit.pulseFromQueue(QuantumToolkit.java:492)
at javafx.graphics/com.sun.javafx.tk.quantum.QuantumToolkit.lambda$runToolkit(QuantumToolkit.java:320)
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(WinApplication.java:174)
at java.base/java.lang.Thread.run(Thread.java:834)
当我在 MyTimer.start() 函数中使用 Platform.runLater() 时，它确实起作用了，就像这样：
Runnable startTimerRunnable = new Runnable() {
@Override
public void run() {
while(state.isRunning()) {
Platform.runLater(new Runnable() {
@Override
public void run() {
timerStringProperty.set(MyFormatter.longMillisecondsTimeToTimeString(getRemainingTime()));
}
});
try {
Thread.sleep(10);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
};
Thread daemonTimer = new Thread(startTimerRunnable);
daemonTimer.setDaemon(true);
daemonTimer.start();
但是这样用Platform.runLater好像不对，还是可以的？我知道 GUI 不应该在 FX 线程之外更新，但我认为绑定属性可以解决这个问题——更新绑定到 GUI 元素的 属性 不需要在 FX 线程中进行，作为绑定的一部分，GUI 更新确实会在 FX 线程上得到正确处理...
最终，我的解决方案似乎工作得相当好，是不使用绑定，而是定期更新控制器本身的字段（以下方法在选项卡本身的 "onSelectionChanged" 上调用）- 但是我想知道如何使绑定工作，因为绑定似乎是更好的做法。 不管怎样，下面是同样有效的代码：
public void startTimeFieldUpdates() {
Runnable timeTracker = new Runnable() {
@Override
public void run() {
while(timerTab.isSelected()) {
Platform.runLater(new Runnable() {
@Override
public void run() {
for (HBox hBox : timers.keySet()) {
if (hBox.getChildren().get(1) instanceof TextField) {
TextField currentField = (TextField) hBox.getChildren().get(1);
currentField.setText(MyFormatter.longMillisecondsTimeToTimeString(
timers.get(hBox).getRemainingTime())
);
}
}
}
});
try {
Thread.sleep(10);
} catch (InterruptedException ex) {
ex.printStackTrace();
}
}
}
};
Thread daemonStopwatch = new Thread(timeTracker);
daemonStopwatch.setDaemon(true);
daemonStopwatch.start();
}
那么我的问题是，解决这个问题的正确方法是什么？
正如我的问题的评论中所发布的那样，答案确实是 属性 绑定使用的侦听器最终 运行 在 属性 本身更新的同一线程上 -因此，为避免出现问题，需要在 Java FX 应用程序线程上更新绑定属性（或者应该寻求其他解决方案，就像我的情况一样）。
对我有用的解决方案 - 正如我的问题的评论中提到的，我查看了 AnimationTimer 是什么，它似乎正是我正在寻找的并且完美地工作。
如果对某人有帮助，这是我的实现：
import ...
public class TimerTabController {
public static final int TIMER_HBOX_TEXTFIELD_INDEX = 1;
public static final int TIMER_HBOX_STARTSTOP_BUTTON_INDEX = 2;
@FXML
private Tab timerTab;
@FXML
private HBox defaultTimerHBox;
@FXML
private TextField defaultTimerTextField;
private Map<HBox, MyTimer> timers = new HashMap<>();
private AnimationTimer timerTabAnimationTimer = new AnimationTimer() {
@Override
public void handle(long l) {
//the GUI updates go here
for (HBox hBox : timers.keySet()) {
if (hBox.getChildren().get(TIMER_HBOX_TEXTFIELD_INDEX) instanceof TextField) {
TextField currentField = (TextField) hBox.getChildren().get(TIMER_HBOX_TEXTFIELD_INDEX);
currentField.setText(MyFormatter.longMillisecondsTimeToTimeString(
timers.get(hBox).getRemainingTime())
);
}
}
}
};
@FXML
protected void initialize() {
timers.put(defaultTimerHBox, new MyTimer());
}
@FXML
void handleSelectionChanged() { //triggered by changing tab selection
if (timerTab.isSelected()) {
timerTabAnimationTimer.start();
} else {
timerTabAnimationTimer.stop();
}
}
//some more code
}