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。

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。

现在Android Studio 3.3和更高版本提供了一个内置的功能来改变颜色的Alpha值，

只需在Android工作室编辑器中单击一种颜色，并提供Alpha值的百分比。

更多信息见下图

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**

试试这段代码:)

它是一个完全透明的十六进制代码-“#00000000”