从另一个类调用时,Java重绘方法不起作用 [英] Java repaint method does not work when called from another class
问题描述
我已经用Netbeans编写Java大约一年了,并且写了很多数据操作代码,这些代码在屏幕上绘制图形.通常,我会在主窗口中植入一个JPanel对象,编写自定义绘画代码,然后根据需要调用repaint()方法.
I have been coding up Java with Netbeans for about a year now, and have written a lot of data manipulation code which plots graphs on-screen. I generally plant a JPanel object in my main window, write custom painting code, and call the repaint() method as needed.
但是,今天,我第一次尝试从包含面板的类(对象)之外的类(对象)上调用面板上的重绘.尽管编译器对此没有发现任何问题,但在调试模式下,它正确地单步执行了对外部重绘的调用,实际上没有发生重绘,并且代码也没有真正进入repaint方法.
But today, for the first time, I tried to invoke a repaint on a panel from a class (object) other than the one that contained the panel. Although the compiler found nothing wrong with this, and in debugging mode, it single-stepped properly to the exterior call to the repaint, no repaint actually occurred, and the code did not actually step into the repaint method.
我编写了一个简单的程序来演示该问题,如下所示(省略了Main,因为它仅包含用于设置两个屏幕面板的代码.)
I wrote a minimalist program to demonstrate the problem, as shown below (Main is ommitted, since it only contains code to set up the two on-screen panels.)
---类的描述,首先包含绘图表面,其他则重绘调用---
--- Description of classes, first contains the drawing surface, other the repaint call ---
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class Panel1 extends JComponent
{
GraphPnl graphPnl;
boolean colorFlag;
public Panel1()
{
setLayout(null);
colorFlag = true;
graphPnl = new GraphPnl();
graphPnl.setBounds(10, 10, 110, 110);
graphPnl.setBackground(Color.black);
add(graphPnl);
}//Panel1()
public class GraphPnl extends JPanel
{
//just draws a line segment, toggling color
@Override
public void paint(Graphics g)
{
super.paint(g);
Graphics2D g2 = (Graphics2D) g;
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
if (colorFlag) {g2.setColor(Color.red);} else {g2.setColor(Color.green);}
g2.drawLine(10, 10, 50, 50);
}//paint
}//GraphPnl
}//Panel1
import javax.swing.*;
import java.awt.event.*;
public class Panel2 extends JComponent
{
JButton testBtn;
TestAction testAction;
Panel1 p1;
public Panel2()
{
p1 = new Panel1();
testBtn = new JButton("Click");
testBtn.setBounds(10, 10, 80, 30);
add(testBtn);
testAction = new TestAction();
testBtn.addActionListener(testAction);
}//Panel2()
public class TestAction implements ActionListener
{
public void actionPerformed(ActionEvent evt)
{
p1.colorFlag = ! p1.colorFlag;
p1.graphPnl.repaint();
}
}//TestAction
}//Panel2
如果有人对此有任何见解或知道有解决方法,我将很高兴听到 从你那里.
If anyone has any insights into this, or knows of a workaround, I'd be very happy to hear from you.
预先感谢您提供任何见解.
Thanks in advance for any insights.
约翰·多纳(John Doner)
John Doner
推荐答案
我相信在绘制JComponent时,剪辑区域设置为该JComponent.因此,如果其他组件尝试绘制(或者您称其为重新绘制),则由于裁剪,它们将不会绘制.
I believe that when you are painting a JComponent, the clip region is set to that JComponent. So if other components try to paint (or if you call their repaint), they won't, because of the clipping.
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