填充栏（进度条）JApplet paint（）Thread（）

Question

垂直条应填充到小程序的高度。到达顶部时，新栏应该开始填充前一个栏。问题：当新栏开始填充时，前一个paint() /栏被清除

img如何：http://bayimg.com/DAEoeaagm

img应该如何：http://bayimg.com/dAeOgAaGm

代码：

import java.awt.Color;
import java.awt.Graphics;

import javax.swing.JApplet;


public class fillingbar extends JApplet implements Runnable{

    int shifting=0,filling=0;
    public void init()
    {
        Thread t= new Thread(this);
        t.start();
        setSize(400,250);
    }

    public void paint(Graphics g)
    {
        super.paint(g);

            g.setColor(Color.GREEN);
            g.fillRect(shifting,getHeight()-filling,20,filling);

            g.setColor(Color.BLACK);
            g.drawRect(shifting, getHeight()-filling, 20, filling);
    }

    public void run()
    {
        while(true)
        {
            repaint();
            try{
                if(shifting<getWidth())
                {
                    if(filling<getHeight())
                        filling+=10;                    
                    else {
                        shifting+=20;
                    filling=0;
                    }
                }       
                Thread.sleep(50);
            }catch(Exception E){
                System.out.println("Exception caught");
            }

        }
    }

}

Answer 1

1. 你只在paint方法中绘制一个矩形，因此只有一个会显示。
2. 如果您需要绘制更多内容，请使用循环遍历矩形ArrayList<Rectangle>的for循环。
3. 另一种方法是移动局部并在paintComponent中做一些简单的数学运算，以查看要绘制的内容和位置。例如，在for循环中绘制已完成的条形for (int i = 0; i < filling / getHeight(); i++) {，以及尚未完成的条形图，直至filling % getHeight()。
4. 您不应直接在JApplet中绘制，而应在JPanel的paintComponent方法中绘制。
5. Swing Timer比线程更容易使用（至少对我而言），并且可以更安全。

---

例如，可以通过以下代码创建：



import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.lang.reflect.InvocationTargetException;

import javax.swing.*;

@SuppressWarnings("serial")
public class FillingBar2 extends JApplet {
   @Override
   public void init() {
      try {
         SwingUtilities.invokeAndWait(new Runnable() {
            public void run() {
               FillingBarPanel fillingBarPanel = new FillingBarPanel();
               add(fillingBarPanel);
               add(new JButton(new StartAction(fillingBarPanel)), BorderLayout.PAGE_END);
               setSize(getPreferredSize());
            }
         });
      } catch (InvocationTargetException | InterruptedException e) {
         System.err.println("Big Problems");
         e.printStackTrace();
      }
   }
}

@SuppressWarnings("serial")
class StartAction extends AbstractAction {
   private FillingBarPanel fillingBarPanel;

   public StartAction(FillingBarPanel fillingBarPanel) {
      super("Start");
      putValue(MNEMONIC_KEY, KeyEvent.VK_S);
      this.fillingBarPanel = fillingBarPanel;
   }

   @Override
   public void actionPerformed(ActionEvent evt) {
      fillingBarPanel.start();
   }
}

@SuppressWarnings("serial")
class FillingBarPanel extends JPanel {
   private static final int BAR_WIDTH = 20;
   private static final int TIMER_DELAY = 100;
   private static final int PREF_W = 400;
   private static final int PREF_H = 250;
   private int filling = 0;
   private Timer timer;

   public FillingBarPanel() {
      timer = new Timer(TIMER_DELAY, new TimerListener());
   }

   public void start() {
      if (timer != null && !timer.isRunning()) {
         timer.start();
      }
   }

   @Override
   protected void paintComponent(Graphics g) {
      super.paintComponent(g);
      int shifting = 0;
      for (int i = 0; i < filling / getHeight(); i++) {
         shifting = i * BAR_WIDTH;
         g.setColor(Color.GREEN);
         g.fillRect(shifting, 0, BAR_WIDTH, getHeight());

         g.setColor(Color.BLACK);
         g.drawRect(shifting, 0, BAR_WIDTH, getHeight());
      }
      shifting = BAR_WIDTH * (filling / getHeight());
      g.setColor(Color.GREEN);
      g.fillRect(shifting, getHeight() - (filling % getHeight()), BAR_WIDTH, getHeight());

      g.setColor(Color.BLACK);
      g.drawRect(shifting, getHeight() - (filling % getHeight()), BAR_WIDTH, getHeight());
   }

   private class TimerListener implements ActionListener {
      @Override
      public void actionPerformed(ActionEvent evt) {
         filling += 10;
         repaint();
      }
   }

   @Override
   public Dimension getPreferredSize() {
      if (isPreferredSizeSet()) {
         return super.getPreferredSize();
      }
      return new Dimension(PREF_W, PREF_H);
   }

}