transparency - How to make a background 20% transparent on Android -

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how make background of textview 20% transparent (not transparent), there color in background (i.e. white)?

make color have 80% in alpha channel. example, red use #ccff0000:

<textview    ...    android:background="#ccff0000" />

in example, cc hexadecimal number 255 * 0.8 = 204. note first 2 hexadecimal digits alpha channel. format #aarrggbb, aa alpha channel, rr red channel, gg green channel , bb blue channel.

i'm assuming 20% transparent means 80% opaque. if meant other way, instead of cc use 33 hexadecimal 255 * 0.2 = 51.

in order calculate proper value alpha transparency value can follow procedure:

  1. given transparency percentage, example 20%, know opaque percentage value 80% (this 100-20=80)
  2. the range alpha channel 8 bits (2^8=256), meaning range goes 0 255.
  3. project opaque percentage alpha range, is, multiply range (255) percentage. in example 255 * 0.8 = 204. round nearest integer if needed.
  4. convert value obtained in 3., in base 10, hexadecimal (base 16). can use google or calculator. using google, type "204 hexa" , give hexadecimal value. in case 0xcc.
  5. prepend value obtained in 4. desired color. example, red, ff0000, have ccff0000.

you can take @ android documentation colors.


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