java图形如何使绘制的字符串透明？

Question

我尝试通过以下操作更改绘制字符串的alpha：

g2d.drawString("HelloWorld", 50, 50, alphaValue);

这导致编译错误

我所要做的就是让一条画好的线慢慢变透明

Answer 1

你需要设置颜色

Color curr = g2d.getColor();
// Color curr = Color.GREEN;
g2d.setColor(new Color(curr.getRed(), curr.getGreen(), curr.getBlue(), alphaValue));
g2d.drawString("HelloWorld", 50, 50);

Answer 2

正如Sergiy所说，您需要更改图形使用的Color的alpha

下面是一个可以淡出文本的方法的示例

import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
import javax.swing.Timer;

public class ExampleFrame extends JFrame {

    private JPanel drawPanel = new DrawPanel();
    private Timer timer;
    private int alpha = 255;
    private final int TIMER_TICK = 50;
    private final int ALPHA_TICK_VALUE = 3;

    private class DrawPanel extends JPanel {

        final int PANEL_HEIGHT = 80;
        final int PANEL_WIDTH = 100;
        final int TEXT_MARGIN = 20;

        DrawPanel() {
            setPreferredSize(new Dimension(PANEL_WIDTH, PANEL_HEIGHT));
        }

        @Override
        public void paintComponent(Graphics g) {
            super.paintComponent(g);
            Color color = new Color(0, 0, 0, alpha);
            g.setColor(color);
            g.drawString("Hello World", TEXT_MARGIN,
                    PANEL_HEIGHT / 2 + g.getFontMetrics().getHeight() / 2);
        }

    }

    public void createAndShow() {
        getContentPane().add(drawPanel);
        timer = new Timer(TIMER_TICK, new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                alpha -= ALPHA_TICK_VALUE;
                if (alpha >= 0) {
                    drawPanel.repaint();
                } else {
                    alpha = 0;
                    timer.stop();
                }
            }
        });
        pack();
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setVisible(true);
        timer.start();
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {

            @Override
            public void run() {
                ExampleFrame ef = new ExampleFrame();
                ef.createAndShow();
            }
        });
    }
}