我正在尝试加载 FXML 文件并将其显示为应用程序窗口,但出现异常。 FXML 文件由 FXML Scene Builder 创建。
sup.java文件:
package sup;
import java.io.IOException;
import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
public class Sup extends Application {
@Override
public void start(Stage primaryStage) throws IOException {
Parent root = FXMLLoader.load(getClass().getResource("sample.fxml"));
primaryStage.setTitle("Sup");
Scene scene = new Scene(root, 300, 250);
primaryStage.setScene(scene);
primaryStage.show();
}
public static void main(String[] args) {
launch(args);
}
}
sample.fxml 文件:
<?import javafx.geometry.Insets?>
<?import javafx.scene.layout.GridPane?>
<?import javafx.scene.control.Button?>
<?import javafx.scene.control.Label?>
<?import javafx.scene.text.Text?>
<?import javafx.scene.control.TextField?>
<GridPane fx:controller="sup.Controller"
xmlns:fx="http://javafx.com/fxml" alignment="center" hgap="10" vgap="5">
<Text text="Sup"
GridPane.rowIndex="0"
GridPane.columnSpan="2"
GridPane.halignment="CENTER"/>
<Label text="First Name:"
GridPane.rowIndex="1"
GridPane.columnIndex="0"/>
<TextField
GridPane.columnIndex="1"
GridPane.rowIndex="1"/>
<Button text="Say Sup!"
GridPane.rowIndex="2"
GridPane.columnIndex="1"
GridPane.halignment="RIGHT"/>
</GridPane>
结构截图:
错误信息:
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$155(LauncherImpl.java:182)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.NullPointerException: Location is required.
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3207)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3175)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3148)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3124)
at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3104)
at javafx.fxml.FXMLLoader.load(FXMLLoader.java:3097)
at sup.Sup.start(Sup.java:34)
at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$162(LauncherImpl.java:863)
at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$175(PlatformImpl.java:326)
at com.sun.javafx.application.PlatformImpl.lambda$null$173(PlatformImpl.java:295)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.application.PlatformImpl.lambda$runLater$174(PlatformImpl.java:294)
at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.lambda$null$148(WinApplication.java:191)
... 1 more
Exception running application sup.Sup
最佳答案
您遇到的异常的根本原因是 NullPointerException
以及详细消息“需要位置”。
Caused by: java.lang.NullPointerException: Location is required.
我不会指导您如何阅读堆栈跟踪,请参阅 this question相反。
您收到“location is required”错误,因为您将 null
传递给 FXMLLoader.load()
方法。 null
值显然必须来自 getResource()
称呼。来自Class.getResource()
文档:
[...]
Returns:
AURL
object ornull
if no resource with this name is found[...]
所以你得到异常的原因必须是找不到具有给定名称的资源。
请验证以下内容:
- 如果您使用标准的 eclipse 项目布局:确保将
sample.fxml
放入与Sup.java
相同的目录中> 文件 如果您使用的是类似 maven 的目录结构,其中资源和来源的目录不同,请确保
sample.fxml
在资源中文件夹和与源文件相同的目录。示例:您的源文件
Sup.java
放在src/main/java/com/example/Sup.java
中。将sample.fxml
文件放入src/main/resources/com/example/sample.fxml
。如果您使用的是 eclipse,请清理并重建您的项目。构建工具有类似的选择(或者直接删除
build
/out
目录)
关于java - 应用程序启动方法中的异常,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/36250965/