Java Graphics2D是否在下次调用paintComponent()时重置合成?为什么?
Graphics2D是否在每次调用paintComponent()时重置合成?为什么 比如说,Java Graphics2D是否在下次调用paintComponent()时重置合成?为什么?,java,swing,transparency,graphics2d,paintcomponent,Java,Swing,Transparency,Graphics2d,Paintcomponent,Graphics2D是否在每次调用paintComponent()时重置合成?为什么 比如说, public void paintComponent(Graphics g) { Graphics2D g2 = (Graphics2D)g; System.out.println(((AlphaComposite)g2.getComposite()).getAlpha()); //printing alpha value before setting composition
public void paintComponent(Graphics g)
{
Graphics2D g2 = (Graphics2D)g;
System.out.println(((AlphaComposite)g2.getComposite()).getAlpha()); //printing alpha value before setting composition
g.drawImage(background,0,0,500,500,null);
g2.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER, 0.5f));
g.setColor(Color.RED);
g.fillOval(x-100,y-100,200,200);
System.out.println(((AlphaComposite)g2.getComposite()).getAlpha()); //printing alpha value after setting composition
}
当多次调用paintComponent()时,上面的代码将打印以下内容
1.0
0.5
1.0
0.5
1.0
0.5
1.0
0.5
这是否意味着graphics2D在paintComponent()之后重置构图,为什么必须这样做?是;你的结果是预期的。其中,默认的组合
应用
AlphaComposite.SRC\u OVER
规则,该规则“相当于setComposite(new AlphaComposite.SrcOver)
”注意AlphaComposite.SrcOver
的alpha值为1.0f这是JFrame还是小程序