Question

我试图让一个方框显示速度和角度的输入，以及显示球被射击的次数。它给了我一个运行时错误，我不知道为什么。导致错误的部分是JOptionPane.showInternalMessageDialog

import java.awt.Graphics2D;

import javax.swing.JFrame;
import javax.swing.JOptionPane;


public class CannonGame {

    private static final int WIDTH=800;
    private static final int HEIGHT=600;
    private static final int WAIT_TIME=10;

    public static void main(String[] args) {
        JFrame frame=new JFrame("Cannon Game");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(WIDTH,HEIGHT);
        MyComponent comp=new MyComponent();
        frame.add(comp);
        frame.setVisible(true);
        comp.initializeLocations();
        frame.repaint();
        boolean cont = true;
        //prompt user for angle and velocity

        while(cont){

            String vel=JOptionPane.showInputDialog(frame,"Enter the Velocity (1-100)");
            if(vel == null)
                System.exit(0);
            Double velocity=Double.parseDouble(vel);

            while(velocity < 0 || velocity > 100){
                String vel1 = JOptionPane.showInputDialog(frame,"Enter the Velocity (1-100)");
                if(vel == null)
                    System.exit(0);
                Double velocity1 = Double.parseDouble(vel1);
                velocity = velocity1;
            }

            String ang=JOptionPane.showInputDialog(frame,"Enter the angle (0-90)");
            if(ang == null)
                System.exit(0);
            Double angle=Math.PI*Double.parseDouble(ang)/180.0;

            while(angle < 0 || angle > 1.57111111111111){
                String ang1=JOptionPane.showInputDialog(frame,"Enter the angle (0-90)");
                if(ang == null)
                    System.exit(0);
                Double angle1=Math.PI*Double.parseDouble(ang1)/180.0;
                angle = angle1;
            }


            JOptionPane.showInternalMessageDialog(frame, "Balls fired: " + comp.getNumBallsFired(),
                    "velocity: " + velocity + "angle: " + angle, JOptionPane.INFORMATION_MESSAGE);

            //animate the cannonball until it hits the ground
            comp.getReadyForShot(angle,velocity);
            while(comp.stillInFlight()) {
                comp.update(System.currentTimeMillis());
                frame.repaint();
                try {
                    Thread.sleep(WAIT_TIME);
                } catch (InterruptedException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }

            //print how many tries and if they hit it
            if(comp.isTargetHit()){
                JOptionPane.showMessageDialog(frame, "You fired "+comp.getNumBallsFired()+" times\n and you "+
                        (comp.isTargetHit()?"":"did not")+" hit the target!");

                int answer = JOptionPane.showConfirmDialog(null,
                        "Would you like to fire again?", "choose one", JOptionPane.YES_NO_OPTION);

                if(answer == JOptionPane.YES_OPTION){
                    cont = true;
                    comp.initializeLocations();
                }
                else {
                    cont = false;
                    System.exit(0);
                }
            }else{
                JOptionPane.showMessageDialog(frame, "You fired "+comp.getNumBallsFired()+" times\n and you "+
                        (comp.isTargetHit()?"":"did not")+" hit the target!");

                int answer = JOptionPane.showConfirmDialog(null,
                        "Would you like to fire again?", "choose one", JOptionPane.YES_NO_OPTION);

                if(answer == JOptionPane.YES_OPTION){
                    cont = true;
                }
                else {
                    cont = false;
                    System.exit(0);
                }
            }

        }

    }
}

Answer 1

根据API，您应该将showInternalMessageDialog与JInternalFrames一起使用，而您不是这样做的。解决方案：不要使用此JOptionPane，而是使用其他更合适的一个，例如showMessageDialog。

Answer 2

您必须将JFrame的内容窗格作为方法中的第一个参数传递，而不仅仅是像现在这样的JFrame。所以你需要像这样调用你的消息语句（注意使用了frame.getContentPane()，而不只是框架）：

JOptionPane.showMessageDialog(frame.getContentPane(), "You fired "+comp.getNumBallsFired()+" times\n and you "+
                    (comp.isTargetHit()?"":"did not")+" hit the target!");

参考：Here。

JOptionPane.showInternalMessageDialog导致运行时错误

2 个答案: