Change int color opacity in java/android
Wouldn't it be sufficient?
colorDrawerItemSelected = (colorDrawerItemSelected & 0x00FFFFFF) | 0x40000000;It saves the color value and sets the alpha to 25% of max.
First byte in the color int is responsible for the transparency: 0 - completely transparent, 255 (0xFF) – opaque. In the first part ("&" operation) we set the first byte to 0 and left other bytes untouched. In the second part we set the first byte to 0x40 which is the 25% of 0xFF (255 / 4 ≈ 64).
I use this approach in my app:
private int getTransparentColor(int color){ int alpha = Color.alpha(color); int red = Color.red(color); int green = Color.green(color); int blue = Color.blue(color); // Set alpha based on your logic, here I'm making it 25% of it's initial value. alpha *= 0.25; return Color.argb(alpha, red, green, blue);}You can also use ColorUtils.alphaComponent(color, alpha) from the support lib.
Use ColorUtils.setAlphaComponent(color, alpha) to set the alpha value to a color easy. The ColorUtils class is in the android support lib.