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我正在使用线程来绘制一些动画，所以我需要为每一帧重新绘制标签。要做到这一点而不闪烁，我正在使用我的后缓冲图形对象更新标签（使用 lbl.update(bufferedGraphics); 方法），但是当我这样做时，标签会在 Graphics 对象的左上角重新绘制，而不是在哪里setLocation 已指定。

如何在图形中指定标签的位置，而不是在拥有标签的面板中？

这是一个SSCCE：

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

public class LabelSSCCE extends JApplet implements Runnable {
JPanel pnl;
JLabel lbl;
Image buffer;
Graphics bufferedGraphics;
Thread t;

public void init (){
    pnl = new JPanel (null);
    lbl = new JLabel ();

    lbl.setText ("Text");
    lbl.setOpaque(true);

    add(pnl);
    pnl.add (lbl);
    lbl.setLocation(100, 100);
    lbl.setBounds (100, 100, 200, 20);

    buffer = createImage (500, 500);
    bufferedGraphics = buffer.getGraphics ();

    t = new Thread (this, "Label");
    t.start ();
}// init method

public void paint (Graphics g){
    if (g != null)
        g.drawImage (buffer, 0, 0, this);
}//paint

public void update (Graphics g){
    paint (g);
}//update

public void render (){
    bufferedGraphics.setColor (Color.WHITE);
    bufferedGraphics.fillRect (0, 0, 500, 500);
    lbl.update (bufferedGraphics);

    update(getGraphics());
}//render

public void run (){
    while (true){
        try{
            render ();
            t.sleep (20);
        } catch (InterruptedException e){
            e.printStackTrace ();
        }//catch
    }//while
}//run
}//LabelSSCCE
4

1 回答 1

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首先，将 JLabel 转换为 BufferedImage：

    public BufferedImage componentToImage(Component component)
{
    BufferedImage img = new BufferedImage(component.getWidth(), component.getHeight(), BufferedImage.TYPE_INT_ARGB_PRE);
    Graphics g = img.getGraphics();
    g.setColor(component.getForeground());
    g.setFont(component.getFont());
    component.paintAll(g);
    Rectangle region = new Rectangle(0, 0, img.getWidth(), img.getHeight());
    return img.getSubimage(region.x, region.y, region.width, region.height);
}

然后，将渲染方法更改为如下所示：

public void render() {
    bufferedGraphics.setColor(Color.WHITE);
    bufferedGraphics.fillRect(0, 0, 500, 500);      
    BufferedImage bi = componentToImage(lbl);
    bufferedGraphics.drawImage(bi, lbl.getX(), lbl.getY(), null);

    update(getGraphics());
}
于 2013-09-06T21:48:37.030 回答