Question: I would like to know how to decrease the brightness of certain layout(I guess they did that)?
Like in this image:
[![enter image description here](https://i.stack.imgur.com/qwlDe.jpg)](https://i.stack.imgur.com/qwlDe.jpg)

I tried, setting the android:alpha to 0,6, but it isn't working.
I would appreciate any help.

**EDIT**
This is my layout, i am just testing.

```
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="debugging.transparenttest.MainActivity">

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!" />

</LinearLayout >

```

Answer: 
If you use autocompletion, it will hold your hand through this process.

[![enter image description here](https://i.stack.imgur.com/UqsDc.png)](https://i.stack.imgur.com/UqsDc.png)

And when you get to that field, hit enter, and then go to the end, enter a `.` (as it's clearly an enumeration), and you can see the options:

[![enter image description here](https://i.stack.imgur.com/xg0A9.png)](https://i.stack.imgur.com/xg0A9.png)

---

But it is:

```
var audioURL: URL = ...
var audioFileID: AudioFileID?
let status = AudioFileOpenURL(audioURL as CFURL, .readPermission, .allZeros, &audioFileID)

```
`CFURLRef` has been renamed to `CFURL`. `URL` is toll-free bridged to `CFURL`, all you need to do is cast an url to `CFURL` using `as`.

Here's the updated code for Swift 4:

```
let audioURL: URL = ...
var audioFile: AudioFileID?
let status = AudioFileOpenURL(audioURL as CFURL,
                              .readPermission,
                              0,
                              &audioFile)

```