I came up with this using the other answers and some from elsewhere:
/**
* Checks device switch files to see if an HDMI device/MHL device is plugged in, returning true if so.
*/
private boolean isHdmiSwitchSet() {
// The file '/sys/devices/virtual/switch/hdmi/state' holds an int -- if it's 1 then an HDMI device is connected.
// An alternative file to check is '/sys/class/switch/hdmi/state' which exists instead on certain devices.
File switchFile = new File("/sys/devices/virtual/switch/hdmi/state");
if (!switchFile.exists()) {
switchFile = new File("/sys/class/switch/hdmi/state");
}
try {
Scanner switchFileScanner = new Scanner(switchFile);
int switchValue = switchFileScanner.nextInt();
switchFileScanner.close();
return switchValue > 0;
} catch (Exception e) {
return false;
}
}
If you’re checking often, you’d want to store the result and update it with @hamen’s listener.