如何在Android上使背景20％透明

本文翻译自：How to make a background 20% transparent on Android

我如何使Textview的背景大约20％透明（不完全透明），背景中是否有颜色（即白色）？

#1楼

参考：https://stackoom.com/question/lLzd/如何在Android上使背景-透明

#2楼

Use a color with an alpha value like #33------ , and set it as background of your editText using the XML attribute android:background=" " . 使用具有#33------这样的alpha值的颜色，并使用XML属性android:background=" "将其设置为editText的android:background=" " 。

0% (transparent) -> #00 in hex 0％（透明）->＃00（十六进制）
20% -> #33 20％->＃33
50% -> #80 50％->＃80
75% -> #C0 75％->＃C0
100% (opaque) -> #FF 100％（不透明）-> #FF

255 * 0.2 = 51 → in hex 33 255 * 0.2 = 51→十六进制33

#3楼

Make the color have 80% in the alpha channel. 使颜色在Alpha通道中占80％。 For example, for red use #CCFF0000 : 例如，对于红色，请使用#CCFF0000 ：

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

In the example, CC is the hexadecimal number for 255 * 0.8 = 204 . 在示例中， CC是255 * 0.8 = 204的十六进制数。 Note that the first two hexadecimal digits are for the alpha channel. 请注意，前两个十六进制数字用于alpha通道。 The format is #AARRGGBB , where AA is the alpha channel, RR is the red channel, GG is the green channel and BB is the blue channel. 格式为#AARRGGBB ，其中AA是Alpha通道， RR是红色通道， GG是绿色通道， BB是蓝色通道。

I'm assuming that 20% transparent means 80% opaque. 我假设20％的透明意味着80％的不透明。 If you meant the other way, instead of CC use 33 which is the hexadecimal for 255 * 0.2 = 51 . CC使用CC代替CC 33的十六进制值255 * 0.2 = 51 。

In order to calculate the proper value for an alpha transparency value you can follow this procedure: 为了计算Alpha透明度值的正确值，您可以按照以下步骤操作：

Given a transparency percentage, for example 20%, you know the opaque percentage value is 80% (this is 100-20=80 ) 给定透明度百分比，例如20％，您知道不透明百分比值为80％（这是100-20=80 ）
The range for the alpha channel is 8 bits ( 2^8=256 ), meaning the range goes from 0 to 255. alpha通道的范围是8位（ 2^8=256 ），这意味着范围从0到255。
Project the opaque percentage into the alpha range, that is, multiply the range (255) by the percentage. 将不透明百分比投影到Alpha范围内，即将范围（255）乘以百分比。 In this example 255 * 0.8 = 204 . 在此示例中255 * 0.8 = 204 。 Round to the nearest integer if needed. 根据需要舍入到最接近的整数。
Convert the value obtained in 3., which is in base 10, to hexadecimal (base 16). 将以10为底的3中获得的值转换为十六进制（以16为底）。 You can use Google for this or any calculator. 您可以将Google用于此计算器或任何计算器。 Using Google, type "204 to hexa" and it will give you the hexadecimal value. 使用Google，输入“ 204 to hexa”，它将为您提供十六进制值。 In this case it is 0xCC . 在这种情况下，它是0xCC 。
Prepend the value obtained in 4. to the desired color. 将在4.中获得的值添加到所需的颜色之前。 For example, for red, which is FF0000 , you will have CCFF0000 . 例如，对于红色，即FF0000 ，您将拥有CCFF0000 。

You can take a look at the Android documentation for colors . 您可以查看有关颜色的Android文档。

#4楼

You can try to do something like: 您可以尝试执行以下操作：

textView.getBackground().setAlpha(51);

Here you can set the opacity between 0 (fully transparent) to 255 (completely opaque). 在这里，您可以将不透明度设置为0（完全透明）到255（完全不透明）之间。 The 51 is exactly the 20% you want. 51正是您想要的20％。

#5楼

Use the below code for black: 将以下代码用于黑色：

<color name="black">#000000</color>

Now if I want to use opacity then you can use the below code: 现在，如果我要使用不透明度，则可以使用以下代码：

 <color name="black">#99000000</color> <!-- 99 is for alpha and others pairs zero's are for R G B -->

And below for opacity code: and all opacity level here 以下是不透明度代码：以及此处的所有不透明度级别

Hex Opacity Values 十六进制不透明度值

100% — FF
95% — F2
90% — E6
85% — D9
80% — CC
75% — BF
70% — B3
65% — A6
60% — 99
55% — 8C
50% — 80
45% — 73
40% — 66
35% — 59
30% — 4D
25% — 40
20% — 33
15% — 26
10% — 1A
5% — 0D
0% — 00

If you always to forget what code for transparency then you must have to see below link and no worry about to remember anything regarding transparent code :- 如果您始终忘记透明的代码，则必须查看以下链接，而不必担心记住任何有关透明代码的内容：

https://github.com/duggu-hcd/TransparentColorCode https://github.com/duggu-hcd/TransparentColorCode

textviewHeader.setTextColor(Color.parseColor(ColorTransparentUtils.transparentColor10(R.color.border_color)));

#6楼

I have taken three Views. 我已经采取了三种看法。 In the first view I set full (no alpha) color, on the second view I set half (0.5 alpha) color, and on the third view I set light color (0.2 alpha). 在第一个视图中，我设置了全色（无Alpha）颜色，在第二个视图中，我设置了一半（0.5 Alpha）颜色，在第三个视图中，我设置了浅色（0.2 Alpha）。

You can set any color and get color with alpha by using the below code: 您可以使用以下代码来设置任何颜色并使用alpha获取颜色：

File activity_main.xml 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" ><Viewandroid:id = "@+id/fullColorView"android:layout_width = "100dip"android:layout_height = "100dip" /><Viewandroid:id = "@+id/halfalphaColorView"android:layout_width = "100dip"android:layout_height = "100dip"android:layout_marginTop = "20dip" /><Viewandroid:id = "@+id/alphaColorView"android:layout_width = "100dip"android:layout_height = "100dip"android:layout_marginTop = "20dip" /></LinearLayout>

File MainActivity.java 文件MainActivity.java

public class MainActivity extends Activity {private View fullColorView, halfalphaColorView, alphaColorView;@Overrideprotected 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;}
}

Kotlin version: Kotlin版本：

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 完成