如果你想用kotlin制作50%透明的颜色，

val percentage = 50f/100 //50%
ColorUtils.setAlphaComponent(resources.getColor(R.color.whatEverColor), (percentage * 255).toInt())

使用一个带有alpha值的颜色，如#33------，并使用XML属性android:background=" "将其设置为editText的背景。

0%(透明)-> #00十六进制 20% -> #33 50% -> #80 75% -> # c0 100%(不透明)-> #FF

255 * 0.2 = 51→十六进制33

我知道，这是个很老的问题。

如果你想使用颜色值，你也可以使用#ARGB的简短版本。其中A是alpha通道的值。

在白色的情况下，有以下透明度值:

#FFFF  -     0%
#EFFF  -   6,7%
#DFFF  -  13,3%
#CFFF  -  20,0%
#BFFF  -  26,7%
#AFFF  -  33,3%
#9FFF  -  40,0%
#FFF8  -  46,7%
#7FFF  -  53,3%
#6FFF  -  60,0%
#5FFF  -  66,7%
#4FFF  -  73,3%
#3FFF  -  80,0%
#2FFF  -  86,7%
#1FFF  -  93,3%
#0FFF  - 100,0%

所以你可以为TextView添加以下行20%的透明度:

<TextView
    android:background="#CFFF"
    ... />

我们也可以用这种方法使透明。

白色颜色代码- FFFFFF

20%白色- #33FFFFFF

20%-33

70%白色- #B3FFFFFF

70% - b3

所有十六进制值从100%到0%

**100% —** **FF**,
99% — FC,
98% — FA,
97% — F7,
96% — F5,
95% — F2,
94% — F0,
93% — ED,
92% — EB,
91% — E8,
**90% —** **E6**,
89% — E3,
88% — E0,
87% — DE,
86% — DB,
85% — D9,
**84% —** **D6**,
83% — D4,
82% — D1,
81% — CF,
**80% —** **CC**,
79% — C9,
78% — C7,
77% — C4,
76% — C2,
75% — BF,
74% — BD,
73% — BA,
72% — B8,
71% — B5,
**70% — B3**,
69% — B0,
68% — **AD**,
67% — AB,
66% — A8,
65% — A6,
64% — A3,
63% — A1,
62% — 9E,
61% — 9C,
**60% —** **99**,
59% — 96,
58% — 94,
57% — 91,
56% — 8F,
55% — 8C,
54% — 8A,
53% — 87,
52% — 85,
51% — 82,
**50% —** **80**,
49% — 7D,
48% — 7A,
47% — 78,
46% — 75,
45% — 73,
44% — 70,
43% — 6E,
42% — 6B,
41% — 69,
**40% —** **66**,
39% — 63,
38% — 61,
37% — 5E,
36% — 5C,
35% — 59,
34% — 57,
33% — 54,
32% — 52,
31% — 4F,
**30% —** **4D**,
29% — 4A,
28% — 47,
27% — 45,
26% — 42,
25% — 40,
24% — 3D,
23% — 3B,
22% — 38,
21% — 36,
**20% — 33**,
19% — 30,
18% — **2E**,
17% — 2B,
16% — 29,
15% — 26,
14% — 24,
13% — 21,
12% — 1F,
11% — 1C,
**10% —** **1A**,
9% — 17,
8% — 14,
7% — 12,
6% — 0F,
5% — 0D,
4% — 0A,
3% — 08,
2% — 05,
1% — 03,
**0% —** **00**

使颜色在alpha通道中占80%。例如，对于红色，使用#CCFF0000:

<TextView
   ...
   android:background="#CCFF0000" />

在本例中，CC为255 * 0.8 = 204的十六进制数。注意，前两个十六进制数字是用于alpha通道的。格式为#AARRGGBB，其中AA为alpha通道，RR为红色通道，GG为绿色通道，BB为蓝色通道。

我假设20%透明意味着80%不透明。如果你的意思是另一种方式，用33代替CC，这是255 * 0.2 = 51的十六进制。

为了计算alpha透明度值的正确值，您可以遵循以下步骤:

Given a transparency percentage, for example 20%, you know the opaque percentage value is 80% (this is 100-20=80) The range for the alpha channel is 8 bits (2^8=256), meaning the range goes from 0 to 255. Project the opaque percentage into the alpha range, that is, multiply the range (255) by the percentage. In this example 255 * 0.8 = 204. Round to the nearest integer if needed. Convert the value obtained in 3., which is in base 10, to hexadecimal (base 16). You can use Google for this or any calculator. Using Google, type "204 to hexa" and it will give you the hexadecimal value. In this case it is 0xCC. Prepend the value obtained in 4. to the desired color. For example, for red, which is FF0000, you will have CCFF0000.

你可以看看Android的颜色文档。

下面是来自@Aromero的答案的编程解决方案，用于计算alpha通道的十六进制值。：）

 public static void main(String[] args) throws Exception {
    final Scanner scanner = new Scanner(System.in);
    int transPerc;
    float fPerc;
    System.out.println("Enter the transparency percentage without % symbol:");
    while((transPerc=scanner.nextInt())>=0 && transPerc <=100){
        fPerc = (float) transPerc / 100;
        transPerc = Math.round(255 * fPerc);
        System.out.println("= " + Integer.toHexString(transPerc));
        System.out.print("another one please : ");
    }
    scanner.close();
}