我的任务有问题。我应该使用JavaFX创建NFL草案，但从未使用过JavaFX我不知道如何解决任何问题。如果有人可以帮助我，那将是惊人的。我已经发布了我的代码以及所有堆栈跟踪错误。我知道其中一个错误是在代码的position.equals部分，我不知道如何解决这个问题。我对编码以及本网站都很陌生。
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$154(LauncherImpl.java:182)
at java.lang.Thread.run(Thread.java:748)
Caused by: java.lang.Error: Unresolved compilation problem:
position cannot be resolved
at application.Main.playerInfo(Main.java:80)
at application.Main.allPlayersVBoxList(Main.java:111)
at application.Main.main(Main.java:124)
at application.Main.start(Main.java:162)
at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$161(Launc.herImpl.java:863)
at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$174(PlatformImpl.java:326)
at com.sun.javafx.application.PlatformImpl.lambda$null$172(PlatformImpl.java:295)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.application.PlatformImpl.lambda$runLater$173(PlatformImpl.java:294)
at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
运行应用程序应用程序的异常。主要
package application;
import java.util.ArrayList;
import java.util.Optional;
import javafx.application.Application;
import javafx.geometry.Insets;
import javafx.geometry.Pos;
import javafx.stage.Stage;
import javafx.scene.Scene;
import javafx.scene.control.Alert;
import javafx.scene.control.Button;
import javafx.scene.control.ButtonType;
import javafx.scene.control.Label;
import javafx.scene.control.Alert.AlertType;
import javafx.scene.layout.HBox;
import javafx.scene.layout.VBox;
public class Main extends Application {
private static Stage primaryStage = new Stage();
private ArrayList<NFLPlayers> DRAFT_LIST = new ArrayList<>();
public HBox navigationBar() {
HBox navigationBtnsHBox = new HBox();
navigationBtnsHBox.setAlignment(Pos.CENTER);
Button btn1 = new Button("Main Menu");
Button btn2 = new Button("NFL PLayers");
btn1.setOnAction(e -> {
main();
});
btn2.setOnAction(e -> myDraft());
navigationBtnsHBox.getChildren().addAll(btn1, btn2);
return navigationBtnsHBox;
}
public HBox playerInfo (NFLPlayers player) {
HBox listOnePlayerHBox = new HBox();
Button removeBtn = new Button ("Remove Player");
Button addBtn = new Button("Add Player");
addBtn.setOnAction(e ->{
DRAFT_LIST.add(player);
listOnePlayerHBox.getChildren().remove(addBtn);
listOnePlayerHBox.getChildren().add(removeBtn);
Alert confirmAddingPlayer = new Alert(AlertType.INFORMATION);
confirmAddingPlayer.setHeaderText("You have added a new player!");
confirmAddingPlayer.setContentText(((NFLPlayers) player).getName() + "has been added to your NFL Draft.");
confirmAddingPlayer.show();
});
removeBtn.setOnAction(ae -> {
Alert confirmRemovePlayer = new Alert(AlertType.CONFIRMATION);
confirmRemovePlayer.setTitle("NFL Draft");
confirmRemovePlayer.setHeaderText("Are you sure you want to remove this player?");
confirmRemovePlayer.setContentText("Are you sure you want to remove this player?");
Optional<ButtonType> choice = confirmRemovePlayer.showAndWait();
if(choice.get() == ButtonType.OK) {
DRAFT_LIST.remove(player);
listOnePlayerHBox.getChildren().remove(removeBtn);
listOnePlayerHBox.getChildren().add(addBtn);
} else {
confirmRemovePlayer.close();
};
});
if (position.equals("offensive")) {
OffensivePlayers op = (OffensivePlayers)DRAFT_LIST.get(0);
System.out.print(op.getFumbles() + op.getYards() + op.getAverage() + op.getTouchdowns());
}
else {
DefensivePlayers dp = (DefensivePlayers) DRAFT_LIST.get(0);
System.out.println(dp.getTouchdowns() + dp.getInterceptions() + dp.getYards() + dp.getTackles() + dp.getAssists());
}
Label playerInformation = new Label ("Player Name: " + player.getName() + "\n" + "Player age: " + player.getAge() + "\n" + "Player height: "+ player.getHeight() + "\n" + "Player weight: " + player.getWeight() + "\n" + "Player position: " + player.getPosition() + "\n" +"Player's college: " + player.getCollege() + player.getTeam() + player.getExperienceInYears() + ((OffensivePlayers) player).getFumbles() + ((OffensivePlayers) player).getYards() + "\n" + "Offensive layer's Average: " +((OffensivePlayers) player).getAverage() + "\n" + "Offensive Player's Touchdowns: " + ((OffensivePlayers) player).getTouchdowns() +"\n" + "Defensive Player's Interceptions: " + ((DefensivePlayers) player).getInterceptions() + "\n" + "Defensive Player's Yards: " + ((DefensivePlayers) player).getYards() + "\n" + "Defensive Player's Touchdowns: " + ((DefensivePlayers) player).getTouchdowns() + "\n" + "Defensive Player's Assists: " + ((DefensivePlayers) player).getAssists() + "\n" + "Defensive Player's Tackles: " + ((DefensivePlayers) player).getTackles());
playerInformation.setPadding(new Insets(0, 0, 25, 25));
playerInformation.setMinWidth(150);
if (DRAFT_LIST.contains(player))
listOnePlayerHBox.getChildren().addAll(playerInformation, addBtn);
else
listOnePlayerHBox.getChildren().addAll(playerInformation, removeBtn);
return listOnePlayerHBox;
}
public VBox allPlayersVBoxList(ArrayList<NFLPlayers> list) {
VBox playersList = new VBox();
playersList.setMinWidth(555);
for (int i=0; i< list.size(); i++) {
playersList.getChildren().add(playerInfo(list.get(i)));
}
return playersList;
}
public void main(){
VBox mainVBox = new VBox();
mainVBox.setAlignment(Pos.CENTER);
Label aTitle = new Label("NFL Draft");
HBox mainNavigationBar = navigationBar();
mainVBox.getChildren().addAll(aTitle, allPlayersVBoxList(PlayerManager.PLAYERS_LIST), mainNavigationBar);
Scene scene = new Scene(mainVBox, 600, 700);
primaryStage.setScene(scene);
primaryStage.setTitle("NFL Draft");
primaryStage.show();
}
public void myDraft() {
VBox myDraftMainVBox = new VBox();
myDraftMainVBox.setAlignment(Pos.TOP_CENTER);
Label draftTitle = new Label("My Team");
draftTitle.setPadding(new Insets (25, 0, 50, 0));
HBox navBar = navigationBar();
navBar.getChildren().remove(1);
if(DRAFT_LIST.size() > 0) {
myDraftMainVBox.getChildren().addAll(draftTitle, allPlayersVBoxList(DRAFT_LIST), navBar);
myDraftMainVBox.setPadding(new Insets(0, 0, 25, 25));
}
else {
Label emptyList = new Label ("Browse Players And Add Them To Your Draft!");
myDraftMainVBox.getChildren().addAll(draftTitle, emptyList, navBar);
}
Scene scene = new Scene(myDraftMainVBox, 500, 700);
primaryStage.setScene(scene);
primaryStage.setTitle("NFL Draft");
primaryStage.show();
}
@Override
public void start(Stage primaryStage) {
try {
PlayerManager playerManager = new PlayerManager();
main();
} catch(Exception e) {
e.printStackTrace();
}
}
public static void main(String[] args) {
launch(args);
}
答案 0 :(得分：1)
您在position方法中使用playerInfo(NFLPlayers)的方式不正确。目前，position未定义。
在您提及的问题评论中，您在position课程中定义了NFLPlayers。但是，您不能使用NFLPlayers方法参数（名为player）来访问position。假设position的{{1}}字段NFLPlayers对Main可见，则更改：
if (position.equals("offensive") {
到
if (player.position.equals("offensive") {
就像我说的，这假设您的NFLPlayers类被定义为：
public class NFLPlayers {
public String position;
// Or...
// String position; <--- depending on if NFLPLayers is in the same package as Main
}
如果封装position（更好，或至少更多Java方式），如：
public class NFLPLayers {
private String position;
public String getPosition() {
return position;
}
// if position is writable
public void setPosition(String position) {
this.position = position;
}
}
然后if语句应为：
if (player.getPosition().equals("offensive")) {
或者，甚至更好，因为如果NullPointerException返回getPosition()，则可以避免潜在的null：
if ("offensive".equals(player.getPosition()) {