按下时更改按钮上的数值 - javafx

Question

我正在寻找一种方法来改变按钮，然后说＃34;玩家1结束转弯＆＃34;到＆＃34;玩家2结束转弯＆＃34;按下时以下是我所拥有的：

private int pTurn = 1;
        Button turn = new Button();
            turn.setText("Player " + pTurn + " End Turn");
            turn.setOnAction(new turnButton());

//There is code between these two blocks, but it isn't important for
//this question I don't think

        class turnButton implements EventHandler<ActionEvent> {
        @Override
        public void handle(ActionEvent event) {
            pTurn++;
            if (pTurn == 3) {
                pTurn = 1;
            }
            turn.setText("Player " + pTurn + " End Turn");
        }

    }

当我运行此按钮时，我收到以下错误：

Executing /Users/bronsonlane/NetBeansProjects/FinalProject/dist/run1715909217/FinalProject.jar using platform /Library/Java/JavaVirtualMachines/jdk1.8.0_111.jdk/Contents/Home/jre/bin/java
Exception in thread "JavaFX Application Thread" java.lang.NullPointerException
at halma.Halma$turnButton.handle(Halma.java:234)
at halma.Halma$turnButton.handle(Halma.java:227)
at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)

Answer 1

您需要在按钮转动前声明pTurn变量。 pTurn未设置且返​​回null。

        int pTurn = 1;

        Button turn = new Button();
            turn.setText("Player " + pTurn + " End Turn");
            turn.setOnAction(new turnButton());

        class turnButton implements EventHandler<ActionEvent> {
        @Override
        public void handle(ActionEvent event) {
            pTurn++;
            if (pTurn == 3) {
                pTurn = 1;
            }
            turn.setText("Player " + pTurn + " End Turn");
        }

    }