如何在半透明的小程序中绘制一个填充的矩形？

Question

如何在半透明/半透明的小程序中绘制一个填充的矩形？

Answer 1

Yup.

void foo(Graphics g) {
  g.setColor(new Color(.3f, .4f, .5f, .6f);
  g.fillRect(50, 50, 100, 100);
}

Answer 2

What API are you using? If you use Graphics from Java2D, when you create Color objects, you can add transparency to them as an alpha between 0 and 1.

Here's an old article on Java2D that has some examples

Answer 3

Paul Murray's answer is exactly right. But to clarify, the mixing and matching of the 4 color switches is what makes different colors. Here are some of the basics to help you get started.

g.setColor(new Color(1f, 0f, 0f, 1f)); //RED
g.setColor(new Color(0f, 1f, 0f, 1f)); //GREEN
g.setColor(new Color(0f, 0f, 1f, 1f)); //BLUE
g.setColor(new Color(0f, 0f, 0f, 1f)); //BLACK
g.setColor(new Color(1f, 1f, 1f, 1f)); //WHITE

and if you use decimal numbers you can make the color opaque. so:

g.setColor(new Color(.5f, 0f, 0f, .5f)); //RED

would be 50% opaque and red. then you can draw whatever with that opaque color. such as:

g.fillRect(50, 50, 100, 100);

as Paul stated