We will use a mobile and build an app to work as a Bluetooth Server. This app will have 4 buttons (up, down, left and right), it will send a number from 1 to 8 according to those buttons are TouchDown or TouchUp.
Another mobile will be the Bluetooth Client, it will have an application with four circles, these circles will be filled with white or black depending on the button pressed on the Server.
we pack those four LDRs in a cardboard, leaving a hole as the following image indicates:
We put these four LDRs on the mobile screen, on the circles of the Client application, as the image indicates:
If we measure the resistance of an LDR with an ohmmeter we will observe that its value will change between 2 KΩ (when the circle is white) and 50 KΩ (when the circle is black) [Those values are just examples]
(Canned Response ABG - Bluetooth non-BLE SCAN Permission Blocks)
The easiest solution, for immediate relief
(from @Barry_Meaker) ...
I had the same issue. The problem is your app does not have permission to see nearby devices. The solution is to give your app permission on your phone (no code changes in your app).
on your phone,
goto settings
search for your app
in App Info for your app select Permissions
change Nearby Devices from Not Allowed to Allowed
Done
By the way, the very first time you run the app, Android will ask if you want to grant the app this permission. If you say no, or ignore the pop-up, the permission will be set as Denied. Android will not ask again.
A more complex approach, for professional app development:
It would really help if you provided a screenshot of your relevant blocks, so we can see what you are trying to do, and where the problem may be.
To get an image of your blocks, right click in the Blocks Editor and select "Download Blocks as Image". You might want to use an image editor to crop etc. if required. Then post it here in the community.
Taifun.