AWT只描绘最后加帆布 [英] AWT paints only last-added Canvas

问题描述

我有一个非常简单的AWT绘画。只是在玩风靡做出更大的东西。但不能得到它的工作...

什么情况是，只有elypse2显示 - 无论重绘（）的ING与否

我也试过用Swing组件而不是AWT（JFrame的，JComponent的），但是这也没有改变什么。

时使用必要的布局管理器？但我只想绘制的图形组件，如弧，矩形，线，多线，麻生太郎...

下面是最主要的（）：

 公共静态无效的主要（字串[] args）{
  帧testFrame =新帧（GRAFX试验）;
  testFrame.setSize（300，200）;
  testFrame.setAlwaysOnTop（真）;  了java.awt.EventQueue.invokeLater（新的Runnable（）{
    @覆盖
    公共无效的run（）{
      testFrame.setVisible（真）;
    }
  }）;  Elypse elypse =新Elypse（新点（70，80），30，30，Color.BLUE，假）;
  testFrame.add（elypse）;  Elypse elypse2 =新Elypse（新点（70，50），50，30，Color.BLUE，真）;
  testFrame.add（elypse2）;
}
 

和这里所使用的类：

 公共类Elypse扩展画布{  私人点开始;
  私人诠释宽度;
  私人诠释高度;
  私人色彩℃;
  私人布尔填补;  公共Elypse（点开始，诠释的宽度，诠释高度，颜色C，布尔填写）{
    this.start =启动;
    this.width =宽度;
    this.height =高度;
    this.c = C;
    this.filled =填补;
  }  @覆盖
  公共无效漆（图形G）{
    g.setColor（C）;
    如果（填写）{
      g.fillOval（start.x，start.y，宽度，高度）;
    }
    其他{
      g.drawOval（start.x，start.y，宽度，高度）;
    }
  }
}
 

解决方案

您忽略了包（）封闭窗口。注意：在你原来的code中的典型症状：调整框架，它生成一个更新，使 elypse2 出现

附录：你可以看到的两个的 Elypse 使用布局，如网​​格布局。

  testFrame.setLayout（新的GridLayout（0,1））;
 

由于测试：

 进口java.awt.Canvas中;
进口java.awt.Color中;
进口java.awt.Dimension中;
进口java.awt.Frame中;
进口java.awt.Graphics;
进口java.awt.Point中;公共类的测试{    公共静态无效的主要（字串[] args）{
        帧testFrame =新帧（GRAFX试验）;
        testFrame.setAlwaysOnTop（真）;
        Elypse elypse =新Elypse（新点（70，80），30，30，Color.BLUE，假）;
        testFrame.add（elypse）;
        Elypse elypse2 =新Elypse（新点（70，50），50，30，Color.BLUE，真）;
        testFrame.add（elypse2）;
        testFrame.pack（）;
        testFrame.setVisible（真）;
    }    私有静态类Elypse扩展画布{        私人点开始;
        私人诠释宽度;
        私人诠释高度;
        私人色彩℃;
        私人布尔填补;        公共Elypse（点开始，诠释的宽度，诠释高度，颜色C，布尔填写）{
            this.start =启动;
            this.width =宽度;
            this.height =高度;
            this.c = C;
            this.filled =填补;
        }        @覆盖
        公共无效漆（图形G）{
            g.setColor（C）;
            如果（填写）{
                g.fillOval（start.x，start.y，宽度，高度）;
            }其他{
                g.drawOval（start.x，start.y，宽度，高度）;
            }
        }        @覆盖
        公共尺寸的get preferredSize（）{
            返回新尺寸（320，240）;
        }
    }
}
 

I've a VERY simple AWT Painting. Just playing aound to make something bigger. But can't get it working ...

What happens is that only elypse2 is shown - regardless of repaint()ing it or not.

I also tried to use Swing components instead of AWT (JFrame, JComponent) but this also changes nothing.

Is using a Layout Manager necessary? But I want to draw only graphical components, like arcs, rectangles, line, poly-lines, aso ...

Here's the main():

public static void main(String[] args) {
  Frame testFrame = new Frame("Grafx-Test");
  testFrame.setSize(300, 200);
  testFrame.setAlwaysOnTop(true);

  java.awt.EventQueue.invokeLater(new Runnable() {
    @Override
    public void run() {
      testFrame.setVisible(true);
    }
  });

  Elypse elypse = new Elypse(new Point(70, 80), 30, 30, Color.BLUE, false);
  testFrame.add(elypse);

  Elypse elypse2 = new Elypse(new Point(70, 50), 50, 30, Color.BLUE, true);
  testFrame.add(elypse2);
}

and here the used class:

public class Elypse extends Canvas {

  private Point start;
  private int width;
  private int height;
  private Color c;
  private boolean filled;

  public Elypse(Point start, int width, int height, Color c, boolean filled) {
    this.start = start;
    this.width = width;
    this.height = height;
    this.c = c;
    this.filled = filled;
  }

  @Override
  public void paint(Graphics g) {
    g.setColor(c);
    if (filled) {
      g.fillOval(start.x, start.y, width, height);
    }
    else {
      g.drawOval(start.x, start.y, width, height);
    }
  }
}

解决方案

You neglect to pack() the enclosing Window. Note the characteristic symptom in your original code: resizing the frame, which generates an update, causes elypse2 to appear.

Addendum: You can see both Elypse instances by using a layout such as GridLayout.

testFrame.setLayout(new GridLayout(0, 1));

As tested:

import java.awt.Canvas;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Frame;
import java.awt.Graphics;
import java.awt.Point;

public class Test {

    public static void main(String[] args) {
        Frame testFrame = new Frame("Grafx-Test");
        testFrame.setAlwaysOnTop(true);
        Elypse elypse = new Elypse(new Point(70, 80), 30, 30, Color.BLUE, false);
        testFrame.add(elypse);
        Elypse elypse2 = new Elypse(new Point(70, 50), 50, 30, Color.BLUE, true);
        testFrame.add(elypse2);
        testFrame.pack();
        testFrame.setVisible(true);
    }

    private static class Elypse extends Canvas {

        private Point start;
        private int width;
        private int height;
        private Color c;
        private boolean filled;

        public Elypse(Point start, int width, int height, Color c, boolean filled) {
            this.start = start;
            this.width = width;
            this.height = height;
            this.c = c;
            this.filled = filled;
        }

        @Override
        public void paint(Graphics g) {
            g.setColor(c);
            if (filled) {
                g.fillOval(start.x, start.y, width, height);
            } else {
                g.drawOval(start.x, start.y, width, height);
            }
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(320, 240);
        }
    }
}

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