Question

通常当我想制作动画时，我会通过绘制矩形重置所有图形屏幕：

@Override
public void paintComponent(Graphics g) {
    g.setColor(Color.white);
    g.fillRect(0,0,1000,1000);

    // now im drawing the animation on empty screen
}

绘制完Rect后，我可以在空白屏幕上绘制动画，这样动画就会移动而不是传播。现在我想在透明JFrame上绘制动画。如何从Precedings图纸中清空组件，并保持JFrame透明？

Answer 1

确保您的组件不透明
要使透明度有效，您无需在paintComponent()中执行任何操作（尤其是不使用WHITE填充矩形）
每当您想要重置所有内容时，请设置标志或条件并调用repaint()。在paintComponent()中，检查该标志或条件，如果为true，则不要绘制任何内容。

这是一个半透明框架的小型演示，可以在鼠标移动的任何地方画出一条线。无论何时单击框架，都会删除所有内容。

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Point;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.io.IOException;
import java.net.MalformedURLException;
import java.util.ArrayList;
import java.util.List;

import javax.swing.BorderFactory;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;

public class TestTransparentFrame {

    private class PaintPanel extends JPanel {
        private List<Point> points = new ArrayList<Point>();

        public PaintPanel() {
            setOpaque(false);
            MouseAdapter adapter = new MouseAdapter() {
                @Override
                public void mouseClicked(MouseEvent e) {
                    points.clear();
                    repaint();
                }

                @Override
                public void mouseMoved(MouseEvent e) {
                    points.add(e.getPoint());
                    repaint();
                }
            };
            addMouseListener(adapter);
            addMouseMotionListener(adapter);
            setBorder(BorderFactory.createLineBorder(Color.GREEN));
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            if (points.size() > 1) {
                g.setColor(Color.RED);
                Point p1 = points.get(0);

                for (int i = 1; i < points.size(); i++) {
                    Point p2 = points.get(i);
                    g.drawLine(p1.x, p1.y, p2.x, p2.y);
                    p1 = p2;
                }
            }
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(700, 500);
        }
    }

    protected void createAndShowGUI() throws MalformedURLException, IOException {
        JFrame frame = new JFrame("Test transparent painting");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setUndecorated(true);
        frame.setBackground(new Color(0, 0, 0, 50));
        frame.add(new PaintPanel());
        frame.pack();
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    new TestTransparentFrame().createAndShowGUI();
                } catch (MalformedURLException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
        });

    }

}

如何在透明JFrame上使用paintComponent重置图形？

1 个答案: