将0到1之间的值转换为十六进制

Question

在我正在开发的应用程序中，我正在尝试创建一个实用程序方法。这种方法的想法是它采用#RRGGBB形式的int和介于0和1之间的浮点数来描述颜色的alpha值。然后该方法应返回#AARRGGBB形式的新int。实用方法目前看起来像这样：

public static int colorWithAlpha(int color, float alpha) {
    // Somehow convert alpha value between 0 and 1 to hexadecimal
    return color;
}

如何将alpha的0到1之间的值转换为alpha的十六进制值，我可以将其添加到颜色int？

Answer 1

试试这个

public static int colorWithAlpha(int color, float alpha) {
    return color | ((int)(alpha*255)<<24);
}

Answer 2

// you get the decimal value of the alpha here  
int alphaInt = (int)(alpha * 255);  
// check that the input color has no alpha ("left 8-bit-section" is 0)
bool colorAlreadyHasAlpha = (color & 0xff000000) == 0   

if((alphaInt <= 255 || alphaInt >= 0) && !colorAlreadyHasAlpha){
    // now add it to the "left 8-bit-section" of the integer
    return color |= alphaInt << 24;       
}
else{
    throw new IllegalArgumentException("color already has alpha, or provided alpha value is invalid");
}