我正在嘗試創建一個允許用戶購買門票和小吃的電影院預訂系統，并在每次點擊時刷新標簽。我有兩節課：public class DashboardUserController{ public Label subtotal; public static Double subtotalCounter = 0.0; public static Double filmPrice; @FXML public void onWaterBottleClick(){ subtotalCounter = subtotalCounter + 1.50; orderRecipt = orderRecipt + "Water Bottle 1.50￡ \n"; setSubtotal(); } // and similar methods for each type of snack public void setSubtotal(){ subtotal.setText(subtotalCounter.toString() + " ￡"); }// set the price for each click on the label public void addTicket() { System.out.println(subtotalCounter); subtotalCounter = subtotalCounter + filmPrice; setSubtotal(); } }另一個擴展了 DashboardUserController 的類public class TheatresController extends DashboardUserController { @FXML private void onClick(MouseEvent event) { //method for selection/deselection of seats ImageView imageView = (ImageView) event.getSource(); if (imageView.getImage() == redSeat) { Alert alert = new Alert(Alert.AlertType.CONFIRMATION, "Do you want to proceed with the unbooking?", ButtonType.YES, ButtonType.NO); if (alert.showAndWait().orElse(ButtonType.NO) == ButtonType.YES) { imageView.setImage(imageView.getImage() == redSeat ? greenSeat : redSeat); } } else { Alert alert = new Alert(Alert.AlertType.CONFIRMATION, "Do you want to proceed with the booking?", ButtonType.YES, ButtonType.NO); if (alert.showAndWait().orElse(ButtonType.NO) == ButtonType.YES) { imageView.setImage(imageView.getImage() == redSeat ? greenSeat : redSeat); addTicket(); } } } 這里奇怪的是，如果我再次單擊任何小吃，標簽會正確顯示所選食物的價格以及所選每個座位的電影價格。
1 回答
心有法竹
TA貢獻1866條經驗 獲得超5個贊
所以有很多錯誤（夸大效果），但你正在學習，所以我會盡力提供幫助。請在復制并粘貼到您的程序之前閱讀全部內容，以便您理解它
從你得到一個空指針的原因開始，你有一個事實，extend DashBoardUserController這意味著DashBoardUserController程序初始化時沒有與你交談TheatresController，當你嘗試訪問它時，它給了你一個空指針，因為沒有初始化在擴展類
所以第 1 步刪除extend DashBoardUserController
因此，既然它已經消失了，我們需要獲取DashBoardUserController對該類的引用，以便它可以調用必要的方法，我們可以在初始化時TheatresController這樣做
FXMLLoader loader = new FXMLLoader(getClass().getResource(resourceLocation));
Pane pane = loader.load();
TheatresController controller = loader.getController();
controller.setDashBoardUserControllerReference(this);//We'll get here
接下來是在中制作必要的方法和變量TheatresController
private DashboardUserController dashboardUserController;//Set at top of class
public void setDashBoardUserControllerReference(DashboardUserController dashboardUserController){
this.dashboardUserController = dashboardUserController;
}
完成這將修復空指針移動以生成您的方法，因為有很多代碼復制對您來說是不必要的輸入
@FXML
public void onjosephclick() {
//weekPickerInput(); //You can delete from here
//addFilmsInList();
//filmList.setShowLocation("Joseph P");
//System.out.println("joseph button pressed");
//try {
// Pane pane = FXMLLoader.load(getClass().getResource("scenes/josephpane.fxml"));
// seatsSelection.getChildren().setAll(pane);
//} catch (IOException e) {
// System.out.println(e);
//}
//setStuff();
//seatsavailable.setText(Integer.toString(seatsJoseph));
//filmPrice = filmList.searchFilm().get().getPrice();
//System.out.println("Price:"+filmPrice); //Down to here
genericOnClick("Joseph P","scenes/josephpane.fxml",seatsJoseph);
//change the strings for each call and remove the unnecessary stuff
//in the methods it will clean it up a lot
}
private void genericOnClick(String location, String resourceLocation, int seats) {
weekPickerInput();
addFilmsInList();
filmList.setShowLocation(location);
System.out.println("Location:"+location);
try {
FXMLLoader loader = new FXMLLoader(getClass().getResource(resourceLocation));
Pane pane = loader.load();
TheatresController controller = loader.getController();
controller.setDashBoardUserControllerReference(this);
seatsSelection.getChildren().setAll(pane);
} catch (IOException e) {
System.out.println(e);
}
setStuff();
seatsavailable.setText(Integer.toString(seats));
filmPrice = filmList.searchFilm().get().getPrice();
System.out.println("Price:"+filmPrice);
}
最終要學習的其他一些東西是 java 命名約定，處理代碼復制
祝好先生好運代碼。如果它不起作用，我可以發布完整的課程，但我認為您應該嘗試將其找出為它的好習慣，我給了您所有您需要的代碼，如果您需要更多幫助，請告訴我
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