error: more than one device/emulator

This error message appears when there are multiple devices or emulators connected to the computer at the same time and the command being executed is ambiguous as to which device to target.

To resolve this error, you need to specify which device or emulator to target by using the `-s` flag followed by the device ID or name. For example:

adb -s emulator-5554 install myapp.apk

This command installs the `myapp.apk` file on the emulator with the ID `emulator-5554`.

To get the list of connected devices and their IDs, you can use the `adb devices` command. This will display a list of all connected devices and emulators along with their unique IDs.

adb devices

Once you have identified the device or emulator you want to target, use the `-s` flag to specify it in the command.