Detect on/off Key Press Android

From Christian's answer to this question:

public boolean onKeyDown(int keyCode, KeyEvent event) {
    if (event.getKeyCode() == KeyEvent.KEYCODE_POWER) {
        // do what you want with the power button
        return true;
    }
    return super.onKeyDown(keyCode, event);
}

However Jake Basile is right. Unless you have a really good reason for doing something special when the Power Button is pressed, you should be using standard Android life-cycle functions.

When the Power Button is pressed it will call the onPause() method of your application, and when you unlock the device it will call onResume(). This is where you should be managing your thread to prevent the app from crashing.

The documentation on Activity's will give you a detailed description of life-cycle functions, when they are called, and how you should use them.

Use the onPause and onResume methods. These are called when your app is no longer in the foreground (when a lock screen comes up) or when the phone is put to sleep, and when your app is brought back to the foreground.

This is the standard process for the Activity life cycle in Android, that is more fully documented here.

A lot of the answers to this question ignore the fact that when writing an app, it is important to know which event caused a particular standard Android life cycle function to be called. There is a onBackPressed() function; why not have an onPowerPressed() and onHomePressed() as well? Apps often need to do different things in the standard life cycle functions depending upon which event caused them to be called. Right now it is a real pain to figure out whether a standard life cycle method was called as a result of a home button press or a power button press.