如何让绿色圆圈涂抹? [英] How to get the green circle to smear?

问题描述

我正在尝试制作一个简单的动画，其中一个绿色圆圈以污迹的对角线在名为 panel 的小部件上以涂抹的方式移动，该小部件是 class MyPanel 的一个实例扩展了 JPanel .

I am trying to do a simple animation, in which a green circle moves diagonally in a smeared pattern on a widget named panel which is an instance of a class MyPanel which extends JPanel.

JFrame 有一个开始按钮，当按下该按钮时，它应该通过调用 actionPerformed 方法(在此方法中称为animate方法，该动画方法调用动画来开始动画). repaint 方法，同时在本身是侦听器的主类中依次增加圆的x和y坐标.

The JFrame has a start button, which when pressed is supposed to start the animation by calling the actionPerformed method (in which I call the animate method, which calls the repaint method while successively incrementing the x and y coordinates of the circle) in the main class which itself is the listener.

相反，当按下按钮时，该圆在初始坐标处显示，然后在延迟之后另一个圆在最终坐标处显示.有人可以帮我弄清楚我要去哪里错吗?我是Java的初学者，几年前用C做过一些基本编程.

Instead when the button is pressed, the circle shows up at the initial coordinates, and then after a delay another circle shows up at the final coordinates. Could someone please help me figure out where I am going wrong? I am a beginner in Java, who has done some basic programming in C years ago.

先谢谢了.这是我的代码:

Thanks in advance. Here is my code:

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

public class Smear implements ActionListener{ 
    JFrame frame; 
    MyPanel panel; 
    JButton button; 
    Smear animgui1; 
    int x=70; 
    int y=70; 

    public static void main(String[] args) { 
        Smear animgui=new Smear(); 
        animgui.project(); 
        animgui.set(animgui); 
    } 

    public void set(Smear anim) { 
        animgui1=anim; 
    } 

    public void project() { 
        frame=new JFrame(); 
        panel=new MyPanel(); 
        button=new JButton("Start"); 
        button.addActionListener(this); 
        frame.getContentPane().add(BorderLayout.NORTH, button); 
        frame.getContentPane().add(BorderLayout.CENTER, panel); 
        frame.setSize(300,300); 
        frame.setVisible(true); 
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
    } 

    public void animate() { 
        while(x!=200) { 
            panel.repaint(); 
            x++; 
            y++; 
            System.out.println("++++"); 
            try { 
                Thread.sleep(50); 
            } 
            catch(Exception ex) {}; 
        } 
    } 

    public void actionPerformed(ActionEvent event) { 
        animgui1.animate(); 
    } 

    class MyPanel extends JPanel { 
        public void paintComponent(Graphics g) { 
            g.setColor(Color.green); 
            g.fillOval(x,y,40,40); 
        } 
    } 
}

但是，与此同时，我制作了另一个没有该按钮的程序SmearGui(我删除了与按钮和侦听器有关的代码)，并且可以按预期的方式工作；圆以涂抹模式缓慢移动.的代码是:

But at the same time, I have made another program SmearGui without that button(I removed the code pertaining to the button and the listener), and it works the way its intended to; the circle slowly moves in a smear pattern. The code for that is:

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

public class SmearGui{
    JFrame frame;
    MyPanel panel;
    //JButton button;
    SmearGui animgui1;
    int x=70;
    int y=70;

public static void main(String[] args){
        SmearGui animgui=new SmearGui();
        animgui.project();
        animgui.set(animgui);
        animgui.animate();
}
public void set(SmearGui anim){
        animgui1=anim;
}
public void project(){
        frame=new JFrame();
        panel=new MyPanel();
        //button=new JButton("Start");
        //button.addActionListener(this);
        //frame.getContentPane().add(BorderLayout.NORTH, button);
        frame.getContentPane().add(BorderLayout.CENTER, panel);
        frame.setSize(300,300);
        frame.setVisible(true);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
public void animate(){
    while(x!=200){
        panel.repaint();
        x++;
        y++;
        try{
        Thread.sleep(50);
        }
        catch(Exception ex){};
}
}
/*public void actionPerformed(ActionEvent event){
        animgui1.animate();
}*/
  class MyPanel extends JPanel{
      public void paintComponent(Graphics g){
        g.setColor(Color.green);
        g.fillOval(x,y,40,40);
}
}
}

上面的代码将animate方法放置在主体本身中.

The code above places the animate method in the main itself.

推荐答案

重新绘制是异步的，因此您的代码无需等待面板重新绘制即可继续.您的循环代码比重新绘制面板快得多.使用一个摆动计时器，该计时器在重绘发生的同一线程上执行，这样您就不会在计算时序和重绘时序上出现这种不匹配.

repaint is asynchronous, so your code doesn't wait for the panel to redraw before continuing. Your loop code is significantly faster than redrawing the panel. Use a swing timer which is executed on the same thread that the repaint occurs, so that you don't have this mismatch in calculation vs. redraw timings.

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