那些遇到过的问题

How to use getWidth() and getHeight() to center the star shape in java

Jay*_*rio 1 java swing

I'm having problem centering the star shape. The problem is that I hard coded the points for each coordinate. And the problem with this is that Im not getting the right position although I created a perfect 5 star. On more problem is that what if I want to rescale the shape to make it bigger or small by clicking a button? Here's my code.

public void run() {
            DifferentShapes panel = new DifferentShapes();
            JFrame frame = new JFrame("Different Shapes");
            frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            frame.setSize(400,400);
            frame.setVisible(true);  
            frame.add(panel);
            frame.setJMenuBar(panel.getMenuBAr());
        }

    public void star(Graphics shape) {
    //        int sizeReq = 1;
    int [] starX =  new int[] {250, 262, 304, 268, 278, 250, 222, 232, 196, 238};
    int []starY =  new int[] {200, 236, 236, 254, 296, 272, 296, 254, 236, 236};
    shape.fillPolygon(starX, starY, starX.length);    

}
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Mad*_*mer 5

没有形状 API

您可能会花费大量时间手动转换多边形数组，但更好的解决方案可能是将多边形转换为0x0，以便上/左角位于0x0

基本上，我计算了每个数组的最小值/最大值，然后从所有值中减去“最小值”值......

protected static int[] minMax(int[] values) {
    int min = Integer.MAX_VALUE;
    int max = Integer.MIN_VALUE;
    for (int value : values) {
        min = Math.min(min, value);
        max = Math.max(max, value);
    }

    return new int[]{min, max};
}

protected static int[] normalise(int[] values, int min) {
    for (int index = 0; index < values.length; index++) {
        values[index] = values[index] - min;
    }
    return values;
}
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所以开始...

[250, 262, 304, 268, 278, 250, 222, 232, 196, 238]
[200, 236, 236, 254, 296, 272, 296, 254, 236, 236]
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翻译成……

[54, 66, 108, 72, 82, 54, 26, 36, 0, 42]
[0, 36, 36, 54, 96, 72, 96, 54, 36, 36]
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涂漆时，看起来像……

左上方

你现在可能在想，嗯，这不太好，我想要它在中心，但要进入中心，我们需要多边形的宽度和高度

为了实现这一点，我将转换后的数组传递给minMax方法并使用返回值的第二个元素，它给了我一个值108x96( widthx height)，现在我们有了使形状居中所需的信息

@Override
protected void paintComponent(Graphics g) {
    super.paintComponent(g);
    Graphics copy = g.create();
    int x = (getWidth() - maxWidth) / 2;
    int y = (getHeight() - maxHeight) / 2;
    copy.translate(x, y);
    copy.fillPolygon(starX, starY, starX.length);
    copy.dispose();
}
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基本上，所有这些都是使用maxWidth和maxHeight值来计算当前组件内的中心位置，将Graphics上下文转换为适当的偏移量并绘制多边形。平移移动原点位置（上下文的0x0点Graphics），这允许使用更改多边形的绘制位置。

中间的星星

import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.util.Arrays;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class Test {

    public static void main(String[] args) {
        new Test();
    }

    protected static int[] minMax(int[] values) {
        int min = Integer.MAX_VALUE;
        int max = Integer.MIN_VALUE;
        for (int value : values) {
            min = Math.min(min, value);
            max = Math.max(max, value);
        }

        return new int[]{min, max};
    }

    protected static int[] normalise(int[] values, int min) {
        for (int index = 0; index < values.length; index++) {
            values[index] = values[index] - min;
        }
        return values;
    }

    public Test() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                    ex.printStackTrace();
                }

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        private int starX[];
        private int starY[];

        private int maxWidth, maxHeight;

        public TestPane() {
            starX = new int[]{250, 262, 304, 268, 278, 250, 222, 232, 196, 238};
            starY = new int[]{200, 236, 236, 254, 296, 272, 296, 254, 236, 236};

            int[] minMaxX = minMax(starX);
            int[] minMaxY = minMax(starY);

            starX = normalise(starX, minMaxX[0]);
            starY = normalise(starY, minMaxY[0]);

            minMaxX = minMax(starX);
            minMaxY = minMax(starY);

            maxWidth = minMaxX[1];
            maxHeight = minMaxY[1];
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(200, 200);
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            Graphics copy = g.create();
            int x = (getWidth() - maxWidth) / 2;
            int y = (getHeight() - maxHeight) / 2;
            copy.translate(x, y);
            copy.fillPolygon(starX, starY, starX.length);
            copy.dispose();
        }

    }

}
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所以，关于知道，你应该看到0x0为你的形状使用原点的重要性。

查看2D 图形和变换形状、文本和图像以了解更多详细信息

缩放...

缩放可以通过Graphics2D#scale...

规模

@Override
protected void paintComponent(Graphics g) {
    super.paintComponent(g);
    Graphics2D copy = (Graphics2D) g.create();
    double scale = slider.getValue() / 100d;
    int x = (getWidth() - maxWidth) / 2;
    int y = (getHeight() - maxHeight) / 2;
    copy.translate(x, y);
    copy.scale(scale, scale);
    copy.fillPolygon(starX, starY, starX.length);
    copy.dispose();
}
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但这会缩放像素，这可能不会给出您想要的结果。

在有人跳下我的喉咙之前，如果你想让它再次居中，你还需要缩放maxWidth和maxHeight值

使用形状 API

正如我在过去所说的，使用 2D 形状 API 会获得更好的结果，它们是自包含的，它们很容易移动，并且在缩放它们时会得到更好的结果

例如，使用上面的“翻译”值，您应该创建一个很好的自定义、可重用、类...

public class StarShape extends Path2D.Double {

    public StarShape() {
        moveTo(54, 0);
        lineTo(66, 36);
        lineTo(108, 36);
        lineTo(75, 54);
        lineTo(82, 96);
        lineTo(54, 72);
        lineTo(26, 96);
        lineTo(36, 54);
        lineTo(0, 36);
        lineTo(42, 36);
        closePath();
    }

}
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知道，我不了解你，但这更容易阅读，你可以轻松地在一些方格纸上绘制它。

现在它很容易通过做一些简单的事情来填充......

@Override
protected void paintComponent(Graphics g) {
    super.paintComponent(g);
    Graphics2D g2d = (Graphics2D) g.create();
    g2d.fill(new StarShape());
    g2d.dispose();
}
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但是，等等，我们希望它居中，一切都那么简单......

@Override
protected void paintComponent(Graphics g) {
    super.paintComponent(g);
    Graphics2D g2d = (Graphics2D) g.create();
    Rectangle bounds = starShape.getBounds();
    int x = (getWidth() - bounds.width) / 2;
    int y = (getHeight() - bounds.height) / 2;
    g2d.fill(starShape.createTransformedShape(AffineTransform.getTranslateInstance(x, y)));
    g2d.dispose();
}
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嗯，这比非形状 API 方法少了很多代码......

import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Rectangle;
import java.awt.geom.AffineTransform;
import java.awt.geom.Path2D;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class Test {

    public static void main(String[] args) {
        new Test();
    }

    public Test() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                    ex.printStackTrace();
                }

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class StarShape extends Path2D.Double {

        public StarShape() {
            moveTo(54, 0);
            lineTo(66, 36);
            lineTo(108, 36);
            lineTo(75, 54);
            lineTo(82, 96);
            lineTo(54, 72);
            lineTo(26, 96);
            lineTo(36, 54);
            lineTo(0, 36);
            lineTo(42, 36);
            closePath();
        }

    }

    public class TestPane extends JPanel {

        private StarShape starShape;

        public TestPane() {
            starShape = new StarShape();
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(200, 200);
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            Graphics2D g2d = (Graphics2D) g.create();
            Rectangle bounds = starShape.getBounds();
            int x = (getWidth() - bounds.width) / 2;
            int y = (getHeight() - bounds.height) / 2;
            g2d.fill(starShape.createTransformedShape(AffineTransform.getTranslateInstance(x, y)));
            g2d.dispose();
        }

    }

}
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缩放

一般来说，缩放使用与翻译相同的过程，但是，您得到的好处是您可以缩放 aShape然后单独翻译它，允许您独立获得Rectangle缩放的边界Shape。它还缩放矢量（点）而不是像素，这会给你一个更好的结果......

秤

@Override
protected void paintComponent(Graphics g) {
    super.paintComponent(g);
    Graphics2D g2d = (Graphics2D) g.create();
    double scale = slider.getValue() / 100d;
    Shape shape = starShape.createTransformedShape(AffineTransform.getScaleInstance(scale, scale));
    Rectangle bounds = shape.getBounds();
    int x = (getWidth() - bounds.width) / 2;
    int y = (getHeight() - bounds.height) / 2;
    GeneralPath path = new GeneralPath();
    path.append(shape.getPathIterator(AffineTransform.getTranslateInstance(x, y)), true);
    g2d.fill(path);
    g2d.dispose();
}
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所以，简短的回答是，使用 Shapes API，长的回答是，使用 Shapes API，你不需要为你面临的每个问题重新发明轮子

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