Mac OS X Java最初并未绘制

Question

尝试使用Java的基本功能总是给我带来问题。 当运行时创建JFrame时，最初没有绘制任何组件，您是否必须调整窗口大小才能明显调用paint（）？ 有没有我所缺少的简单解决方法？

import javax.swing.*;
import java.awt.event.*;
import java.awt.*;

public class LabTen extends JFrame{

    int x, y;

    public LabTen(){
        this.setSize(200,200);
        this.setVisible(true);
        this.setDefaultCloseOperation(EXIT_ON_CLOSE);
        this.getContentPane().add(new Board()); //do this in the constructor    
    }

    public static void main(String[] args){
        LabTen one = new LabTen();
        one.repaint();
    }       
}
//mouseListener has more things when we're going in and out so you should have it too
//write on the component or pannel, not the frame
class Board extends JComponent implements MouseListener, MouseMotionListener{

    int mouseX, mouseY;

    public Board(){
        addMouseListener(this);
        addMouseMotionListener(this);
    }

    public void mouseMoved(MouseEvent e){           
        this.mouseX = e.getX();
        this.mouseY = e.getY();
        this.repaint(); 
    }

    public void mouseDragged(MouseEvent e){
        //do nothing...
    }

    public void mouseClicked(MouseEvent e){         
    }

    public void mouseEntered(MouseEvent e){         
    }

    public void mouseExited(MouseEvent e){
    }

    public void mousePressed(MouseEvent e){         
    }

    public void mouseReleased(MouseEvent e){
    }

    public void paintComponent(Graphics g){
        //g.drawString("(" + this.mouseX + ", " + this.mouseY +  ")", this.mouseX,this.mouseY);
        //this uses the default way
        // g.drawLine(this.getWidth()/2, this.getHeight()/2, this.mouseX, this.mouseY);

        double distance = Math.sqrt(Math.pow(this.mouseX - this.getWidth()/2, 2) + Math.pow(this.mouseY - this.getHeight()/2, 2));          
        int centerX = this.getWidth()/2;
        int centerY = this.getHeight()/2;

        for(int i = 0; i < 20; i++){
            double distanceX = 
            g.drawLine(centerX, centerY, (centerX))
        }           
    }
}

Answer 1

您完全按照错误的顺序进行操作。 这样做：

1. 添加组件

    this.add(new Board()); 

2. 设置首选尺寸

    this.setPreferredSize(new Dimension(200, 200)); 

3. 包装框架

    this.pack(); 

4. 将框架设置为可见。

    this.setVisible(true); 

当然， this是您的JFrame。

Answer 2

设置完JFrame ，您应该调用jFrame.pack()和jFrame.setVisible(true) 。

Answer 3

在实现之前，所有组件都需要添加到容器中。