How to detect if screen brightness has changed in Android?

问题

I have searched extensively and couldn't find a similar question.

I would like to know if there is any way to detect when the screen brightness of a mobile device has been changed.

I have already tried to store the old value when the app starts and repeatedly check usingSettings.System.getInt(getContentResolver(),Settings.System.SCREEN_BRIGHTNESS); to compare the initial and final value of screen brightness , which is not a good way of doing so.

Thanks

EDIT: This question states that I have already tried the solution of using Settings.System.SCREEN_BRIGHTNESS to get current screen values and periodically check for screen brightness changes. I am looking for a more efficient way of doing such an operation.

回答1:

There are no receivers provided to detect brightness change.

You have to run a Service or Thread to check the brightness change by yourself.

Settings.System.getInt(getContext().getContentResolver(), 
             Settings.System.SCREEN_BRIGHTNESS);

The above code will give you current system brightness level. Periodically detect the brightness and compare with the old one.

Note: If the system is in Auto Brightness mode, you can't get current brightness level. See this answer.

回答2:

yes, there is a way by using ContentObserver:

code:

// listen to the brightness system settings
val contentObserver = object:ContentObserver(Handler())
{
    override fun onChange(selfChange:Boolean)
    {
        // get system brightness level
        val brightnessAmount = Settings.System.getInt(
                contentResolver,Settings.System.SCREEN_BRIGHTNESS,0)

        // do something...
    }
}

// register the brightness listener upon starting
contentResolver.registerContentObserver(
        Settings.System.getUriFor(Settings.System.SCREEN_BRIGHTNESS),
        false,contentObserver)

// .....

// unregister the listener when we're done (e.g. activity destroyed)
contentResolver.unregisterContentObserver(contentObserver)

permission in AndroidManifest.xml:

<uses-permission android:name="android.permission.WRITE_SETTINGS"/>

for API >= 23, you need to request the permission through Settings Activity