Android中的屏幕亮度值

Question

How do you get the current screen brightness of your activity?

Following method works fine for setting the brightness to max by calling setBrightness(100) :

private void setBrightness(int brightness) {
    WindowManager.LayoutParams layoutParams = getWindow().getAttributes();
    layoutParams.screenBrightness = brightness/100.0f;
    getWindow().setAttributes(layoutParams);
}

Im trying to achieve the following:

1. Start the activity and save the current brightness value
2. Set brightness to max
3. Reset brightness to the initial value on certain events

Many thanks!

Answer 1

Try

int curBrightnessValue = android.provider.Settings.System.getInt(getContentResolver(), android.provider.Settings.System.SCREEN_BRIGHTNESS);

and then

   WindowManager.LayoutParams layoutParams = getWindow().getAttributes();
    layoutParams.screenBrightness = curBrightnessValue/100.0f;
    getWindow().setAttributes(layoutParams);

Answer 2

To reset brightness to default value

WindowManager.LayoutParams layoutParams = getWindow().getAttributes();
layoutParams.screenBrightness = -1f;
getWindow().setAttributes(layoutParams);

A value of less than 0, the default, means to use the preferred screen brightness.

Refer http://developer.android.com/reference/android/view/WindowManager.LayoutParams.html#screenBrightness

Answer 3

I use this on Android 17+ (Probably works w/lower APIs)

    private void setScreenBrightnessTo(float brightness) {
        WindowManager.LayoutParams lp = getActivity().getWindow().getAttributes();
        if (lp.screenBrightness == brightness) {
            return;
        }

        lp.screenBrightness = brightness;
        getActivity().getWindow().setAttributes(lp);
    }

Usages:

To set screen to MAX Brightness (for example when you show a Barcode or something):

setScreenBrightnessTo(BRIGHTNESS_OVERRIDE_FULL);

To RESET back to whatever the user had before :

setScreenBrightnessTo(BRIGHTNESS_OVERRIDE_NONE);

Answer 4

There are distinct brightness values: 1) if you already set something for activity brightness, you can get this value. If not set it will be -1F 2) system value for brightness Example to get it:

    val activityBrightness = requireActivity().window.attributes.screenBrightness
    val systemBrightness = Settings.System.getInt(requireActivity().contentResolver, Settings.System.SCREEN_BRIGHTNESS) / 255
    currentBrightness = if (activityBrightness == -1F) systemBrightness.toFloat() * 100 else activityBrightness * 100

Example code to set brightness for activity window (bear in mind that value can be from 0.0 to 1.0):

    currentBrightness = if (currentBrightness < 0) 0.0F else if (currentBrightness > 100) 100.0F else currentBrightness
    val layoutParams = activity?.window?.attributes
    if (layoutParams != null) {
        layoutParams.screenBrightness = currentBrightness / 100
        requireActivity().window.attributes = layoutParams
    }