It resides in the notification area and sets the volume to zero when the speaker volume is raised.
Tap on the notification, the menu dialog will appear, and you can enable the speaker for a specified time or until screen off.
Using the Quick Settings Tile, you can operate with notifications turned off. (Android 7.0 or later)
Quick Settings Tile
* Tap: Display menu (Disable speaker when speaker is enabled)
* Long press: Enable speaker until screen turns off
About Bluetooth earphone
Open the settings from the ⋮ button on the upper right corner of the menu dialog, and select the Bluetooth device to be treated as an earphone.
About permissions
Nearby Device (Android 12 or later): used to obtain Bluetooth earphone info
Notification (Android 13 or later): used to show notification
After installation, please check the following.
1. When raising the volume of the speaker where the earphone is not connected, will it automatically sets to zero?
2. Do you restart the terminal and DoNotSpeak automatically appears in the notification area?
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Details, Source codes and Feedback: https://github.com/diontools/DoNotSpeak