我试图在我的控制器类中获取gridPane的所有成员（它们是按钮），但是我遇到了异常，您可以在下面看到它：
Exception in Application start methodjava.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:497)
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:497)
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$152(LauncherImpl.java:182)
at com.sun.javafx.application.LauncherImpl$$Lambda$51/1263764.run(Unknown Source)
at java.lang.Thread.run(Thread.java:745)
Caused by: javafx.fxml.LoadException:
file:/C:/Users/Family/Documents/NetBeansProjects/FarsiCallender/dist/run1583526066/FarsiCallender.jar!/farsicallender/FXMLDocument.fxml
at javafx.fxml.FXMLLoader.constructLoadException(FXMLLoader.java:2605)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2583)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2445)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3218)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3179)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3152)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3128)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3108)
at javafx.fxml.FXMLLoader.load(FXMLLoader.java:3101)
at farsicallender.FarsiCallender.start(FarsiCallender.java:29)
at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$159(LauncherImpl.java:863)
at com.sun.javafx.application.LauncherImpl$$Lambda$54/4239053.run(Unknown Source)
at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$172(PlatformImpl.java:326)
at com.sun.javafx.application.PlatformImpl$$Lambda$47/20085625.run(Unknown Source)
at com.sun.javafx.application.PlatformImpl.lambda$null$170(PlatformImpl.java:295)
at com.sun.javafx.application.PlatformImpl$$Lambda$49/3796086.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.application.PlatformImpl.lambda$runLater$171(PlatformImpl.java:294)
at com.sun.javafx.application.PlatformImpl$$Lambda$48/2900468.run(Unknown Source)
at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.lambda$null$145(WinApplication.java:101)
at com.sun.glass.ui.win.WinApplication$$Lambda$37/17230114.run(Unknown Source)
... 1 more
Caused by: java.lang.NullPointerException
at farsicallender.FXMLDocumentController.setDays(FXMLDocumentController.java:249)
at farsicallender.FXMLDocumentController.initialize(FXMLDocumentController.java:181)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2552)
... 22 more
Exception running application farsicallender.FarsiCallender
Java Result: 1
此异常来自我的代码的这一部分，在检查我的代码之前，您必须知道我有gridPane（6 * 7），这是我的代码：
for (int i = 0; i < 6; i++) {
for (int j = 0; j < 7; j++) {
for (Node node : grid.getChildren()) {
if (grid.getRowIndex(node) == i && grid.getColumnIndex(node) == j) {
Button b = (Button)node;
b.setText(ar[i][j]+"");
System.out.println("z:" + i+" "+j);
break;
}
}
}
}
249行是：
if (grid.getRowIndex(node) == i && grid.getColumnIndex(node) == j) {
最佳答案
顺便说一句，您不应从非静态上下文中调用静态方法。您的IDE应对此发出警告。但是你应该使用
GridPane.getRowIndex(node)
不
grid.getRowIndex(node)
等等
方法
GridPane.getRowIndex(Node)和GridPane.getColumnIndex(node)返回包装器Integer对象，而不是原始的int。因此，当您使用==按身份进行比较时，您将隐式使用拆箱。换句话说，您的代码相当于if (GridPane.getRowIndex(node).intValue() == i
&& GridPane.getColumnIndex(node).intValue() == j) { ... }
如果在网格窗格中添加了任何未指定行索引和列索引的节点，则
GridPane.getRowIndex(...)或GridPane.getColumnIndex(...)将返回null，因此您将隐式尝试在null引用上调用intValue()，从而导致null指针异常。请注意，如果调用了grid.setGridLinesVisible(true);，则会导致GridPane添加未设置行索引或列索引的节点。因此，此方法的快速解决方案是执行空检查：
Integer rowIndex = GridPane.getRowIndex(node);
Integer columnIndex = GridPane.getColumnIndex(node);
if (rowIndex != null && rowIndex.intValue() == i
&& columnIndex != null && columnIndex.intValue() == j) {
// ...
}
我可能更喜欢组织代码，以便将按钮保存在数组中，这样就可以在没有所有迭代的情况下访问它们，但是我想这只是样式问题。
关于java - 获取按钮在gridPane中并使用javaFx更改其文本，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/35629820/