多个 Graphics2D 对象

Question

我有一个 JPanel 的 Graphics 对象，并且工作正常：

import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.geom.Rectangle2D;
import javax.swing.JPanel;

public class GraphicsTest extends JPanel
{
    private Graphics2D g2d;
    private String state;
    private int x, y;

    @Override
    public void paintComponent(Graphics g)
    {
        super.paintComponent(g);
        g2d = (Graphics2D) g;
        g2d.setClip(0, 0, getWidth(), getHeight());

        g2d.setColor(Color.BLACK);
        g2d.drawString("STATE: " + state, 5, 15);
        g2d.drawString("Mouse Position: " + x + ", " + y, 5, 30);

        g2d.setColor(Color.red);
        Rectangle2D r2d = new Rectangle2D.Double(x,y,10,10);
        g2d.draw(r2d);
        Test t = new Test();
        super.add(t);

        repaint();
    }

    public void setState(String state) { this.state = state; }
    public String getState() { return state; }

    public void setX(int x) { this.x = x; }
    public void setY(int y) { this.y = y; }
}

我正在尝试一个新的 Graphics 组件，当我实例化一个新的 Test 并将其添加到 GraphicsTest 中时，什么也没有发生。我做错了什么？

import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.geom.Rectangle2D;
import javax.swing.JComponent;

public class Test extends JComponent
{
    private Graphics2D g2d;
    private String state;
    private int x, y;

    @Override
    public void paintComponent(Graphics g)
    {
        super.paintComponent(g);
        g2d = (Graphics2D) g.create();

        g2d.setColor(Color.GREEN);
        g2d.fill(new Rectangle2D.Double(60, 60,
                10, 10));

        repaint();
    }

    public void setState(String state) { this.state = state; }
    public String getState() { return state; }

    public void setX(int x) { this.x = x; }
    public void setY(int y) { this.y = y; }

}

谢谢！

Answer 1

您应该仅添加一次测试组件并设置布局：

public GraphicTest()
{
    super();
    setLayout(new BorderLayout());
    add(new Test(),BorderLayout.CENTER);
}

此外，不要保存 Graphics2D 对象，因为一旦 paintComponent 完成并且不调用 repaint，它们将无效 paintComponent 内。如果您需要动画并在 setXXX 方法中调用 repaint 来更改组件的外观，请使用计时器。