在循环中绘制矩形? [英] Drawing rectangle within the loop?

问题描述

我正在尝试根据按钮内for循环确定的坐标为矩形设置动画.这是我的 JComponent 类:

I'm trying to animate a rectangle based on a coordinate determined by for-loop, inside a button. Here is my JComponent Class:

public class Rect extends JComponent {
    public int x;
    public int y;
    public int w;
    public int h;
    
    public Rect (int x, int y, int w, int h) {
        this.x = x;
        this.y = y;
        this.w = w;
        this.h = h;
        repaint();
    }

    @Override
    public void paintComponent(Graphics g)  {
        Graphics2D g2 = (Graphics2D) g;
        super.paintComponent(g);
        g2.setColor(Color.green);
        g2.drawRect(x+15, y+15, w, h);
    }
}

这是 JFrame 类中的我的按钮和 button :

and here is my button and button inside JFrame class:

public class MainFrame extends JFrame {
    Rect R = new Rect(15, 15, 50, 50);
    JPanel lm = new JPanel();
    LayoutManager lay = new OverlayLayout(lm);
    JButton animate = new JButton("animate");

    public MainFrame () {
        setSize(1200, 700);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        lm.setLayout(lay);
        lm.add(R);
}
    animate.addActionListener(new ActionListener() {
           public void actionPerformed(ActionEvent e) { 
               for (int k = 0; k < 500; k+=50) {
                R = new Rect(k, k, 50, 50);
               validate();
               repaint();
               }
           }   
  });
}

但是当我运行代码并单击按钮时，什么也没有发生.怎么了?

But when I run the code and click the button, nothing happens. What's wrong?

我在主类中运行框架，如下所示:

I run the frame inside my main class like this:

public class OrImage {
    public static void main(String[] args) throws Exception
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                MainFrame mf = new MainFrame();
                mf.setVisible(true);
            }
        });   
    }
}

推荐答案

我更改了类 MainFrame 的代码，这样，当您按下 animate 按钮时，发生了什么，但我不知道这是否是您想要发生的事情.

I changed the code of class MainFrame such that when you press the animate button, something happens, but I don't know if that is what you want to happen.

我没有更改类 Rect ，而是在 MainFrame 中添加了 main()方法，只是为了将所有内容都保留在一个类中.

I did not change class Rect and I added main() method to MainFrame just to keep everything in one class.

import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.LayoutManager;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.OverlayLayout;

public class MainFrame extends JFrame {
    Rect R = new Rect(15, 15, 50, 50);
    JPanel lm = new JPanel();
    LayoutManager lay = new OverlayLayout(lm);
    JButton animate = new JButton("animate");

    public MainFrame () {
        setSize(1200, 700);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        lm.setLayout(lay);
        lm.add(R);
        animate.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) { 
                for (int k = 0; k < 500; k+=50) {
                    R = new Rect(k, k, 50, 50);
                    lm.add(R);
                }
                lm.revalidate();
                lm.repaint();
            }   
        });
        add(lm, BorderLayout.CENTER);
        add(animate, BorderLayout.PAGE_END);
        setLocationByPlatform(true);
        setVisible(true);
    }

    public static void main(String[] args) {
        EventQueue.invokeLater(() -> new MainFrame());
    }
}

主要更改是在方法 actionPerformed()中.您需要将 R 添加到 JPanel 中.您需要在 JPanel 上调用 revalidate()，因为您已经更改了其中包含的组件数.在调用 revalidate()之后，您应该调用 repaint()(同样在 JPanel 上)以使其重绘.

The main change is in method actionPerformed(). You need to add R to the JPanel. You need to call revalidate() on the JPanel because you have changed the number of components that it contains. And after calling revalidate() you should call repaint() (again, on the JPanel) to make it redraw itself.

这是按下 animate 之前的外观.

这是按下 animate

根据要求-带有动画.

import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.LayoutManager;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.OverlayLayout;
import javax.swing.Timer;

public class MainFrame extends JFrame {
    Rect R = new Rect(15, 15, 50, 50);
    JPanel lm = new JPanel();
    LayoutManager lay = new OverlayLayout(lm);
    JButton animate = new JButton("animate");
    private int  x;
    private int  y;
    private Timer  timer;

    public MainFrame () {
        setSize(1200, 700);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        lm.setLayout(lay);
        lm.add(R);
        timer = new Timer(500, event -> {
            if (x < 500) {
                lm.remove(R);
                x += 50;
                y += 50;
                R = new Rect(x, y, 50, 50);
                lm.add(R);
                lm.revalidate();
                lm.repaint();
            }
            else {
                timer.stop();
            }
        });
        timer.setInitialDelay(0);
        animate.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                timer.start();
            }   
        });
        add(lm, BorderLayout.CENTER);
        add(animate, BorderLayout.PAGE_END);
        setLocationByPlatform(true);
        setVisible(true);
    }

    public static void main(String[] args) {
        EventQueue.invokeLater(() -> new MainFrame());
    }
}

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