使用Java Swing绘制多行

问题描述

我正在学习使用Java Swing绘制线条以绘制迷宫。我可以在指定位置绘制一条线，它显示得很好。但是当我想画多行时，只有最后一行显示。我的代码：

I'm learning drawing lines with Java Swing in order to draw a labyrinth. I can draw one line at a specified position and it shows just fine. But when I want to draw multiple lines, only the last one shows. My code:

public class LabyrinthGUI extends JFrame {
...
Line line;
for (int i = 0; i < 10; i++) {
   line = new Line(i*25, 0, (i+1)*25, 50);
   this.getContentPane().add(line);
}
}

public class Line extends JPanel{
private int x1, y1, x2, y2;

public Line(int x1, int y1, int x2, int y2) {
    this.x1 = x1;
    this.y1 = y1;
    this.x2 = x2;
    this.y2 = y2;
}
public void paintComponent (Graphics g) {
    g.drawLine(x1, y1, x2, y2);

}

我可能需要刷新一些东西，才能显示所有行用for循环绘制，但不知道是什么。

I probably have to refresh something, to display all the lines drawn with for-loop, but don't know what.

推荐答案

为什么你的例子不起作用很简单; Swing使用布局管理器将添加到 Container 的每个组件放到屏幕上。这样，线条不重叠。

Why your example doesn't work is a simple one; Swing uses a layout manager to place every component added to a Container onto the screen. This way, the lines do not overlap.

而是使用一个组件，其中每一行都是绘制的。绘制迷宫的解决方案是：

Instead, use one Component in which every line is drawn. A solution for drawing a maze would be:

public class Labyrinth extends JPanel {

    private final ArrayList<Line> lines = new ArrayList<Line>();

    public void addLine(int x1, int y1, int x2, int y2) {
        this.lines.add(new Line(x1, y1, x2, y2));
    }

    public void paintComponent(Graphics g) {
        for(final Line r : lines) {
            r.paint(g);
        }
    }
}

public static class Line {
    public final int x1;
    public final int x2;
    public final int y1;
    public final int y2;
    public Line(int x1, int y1, int x2, int y2) {
        this.x1 = x1;
        this.x2 = x2;
        this.y1 = y1;
        this.y2 = y2;
    }
    public void paint(Graphics g) {
        g.drawLine(this.x1, this.y1, this.x2, this.y2);
    }
}

然后使用 Labyrinth。 addLine 将行添加到迷宫中。也;通过调用 setBounds 或类似来指定 Labyrinth 的宽度和高度，因为Swing可能会裁剪图形。

And then use Labyrinth.addLine to add lines to your labyrinth. Also; specify a width and height for your Labyrinth, by calling setBounds or similar, because Swing may be cropping the graphics.

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