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();
}

我已经接受了三个观点。在第一个视图中，我设置了全颜色(无alpha)，在第二个视图中，我设置了半颜色(0.5 alpha)，在第三个视图中，我设置了浅色(0.2 alpha)。

你可以使用下面的代码设置任何颜色并使用alpha获取颜色:

文件activity_main.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools = "http://schemas.android.com/tools"
    android:layout_width = "match_parent"
    android:layout_height = "match_parent"
    android:gravity = "center"
    android:orientation = "vertical"
    tools:context = "com.example.temp.MainActivity" >

    <View
        android:id = "@+id/fullColorView"
        android:layout_width = "100dip"
        android:layout_height = "100dip" />

    <View
        android:id = "@+id/halfalphaColorView"
        android:layout_width = "100dip"
        android:layout_height = "100dip"
        android:layout_marginTop = "20dip" />

    <View
        android:id = "@+id/alphaColorView"
        android:layout_width = "100dip"
        android:layout_height = "100dip"
        android:layout_marginTop = "20dip" />

</LinearLayout>

文件MainActivity.java

public class MainActivity extends Activity {

    private View fullColorView, halfalphaColorView, alphaColorView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        fullColorView = (View)findViewById(R.id.fullColorView);
        halfalphaColorView = (View)findViewById(R.id.halfalphaColorView);
        alphaColorView = (View)findViewById(R.id.alphaColorView);

        fullColorView.setBackgroundColor(Color.BLUE);
        halfalphaColorView.setBackgroundColor(getColorWithAlpha(Color.BLUE, 0.5f));
        alphaColorView.setBackgroundColor(getColorWithAlpha(Color.BLUE, 0.2f));
    }


    private int getColorWithAlpha(int color, float ratio) {
        int newColor = 0;
        int alpha = Math.round(Color.alpha(color) * ratio);
        int r = Color.red(color);
        int g = Color.green(color);
        int b = Color.blue(color);
        newColor = Color.argb(alpha, r, g, b);
        return newColor;
    }
}

芬兰湾的科特林版:

private fun getColorWithAlpha(color: Int, ratio: Float): Int {
  return Color.argb(Math.round(Color.alpha(color) * ratio), Color.red(color), Color.green(color), Color.blue(color))
}

Done

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**

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())

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"
    ... />

你可以尝试这样做:

textView.getBackground().setAlpha(51);

这里你可以将不透明度设置在0(完全透明)到255(完全不透明)之间。51就是你想要的20%