It's true that processing is consistent with these buttons. I'm trying to either (1) fix an error so that the app can be put in the background (via the home button) and still be restarted without a blacked-out screen or (2) override the home button so users cannot leave the app (though this is contrary to preferred design - android wants Home to bring the user home). The second item is more long-term; I am trying to baby-proof the phone just like Toddler Lock. I've searched Google and Stack Overflow - switching between activities via the Home button seems to be one of the more promising suggestions but I have yet to try it.

I'm using an HTC Incredible with 2.2.

This could be it's own question but I'll post an answer here for now. You cannot override the home button. At best you can detect it using the following but you can't override it.

Here's a workaround to override certain buttons for now, using Android's event methods, overriding the ones in Processing. If you use these, you'll want to take out your code in onKeyPressed() and put it in handleKeyPress();

UPDATE: Changed onKeyUp to onKeyDown. Some buttons, like the volume buttons, can't be canceled on key up, only on key down. Still can't get BACK to cancel though.

1. import android.view.*;
   
2. 
   
3.  public boolean onKeyDown(int code, KeyEvent event) {
4. 
       return handleKeyPress(code) || super.onKeyDown(code, event);
   
   }
   
   public boolean handleKeyPress(int keyCode) {
     println("pressed key: ");
      //switch (keyCode) { //(I don't know if it's because it's 3am, but I can't get the damn switch() statement to work!)
           //case KeyEvent.KEYCODE_SEARCH:
       if (keyCode == KeyEvent.KEYCODE_SEARCH){
             // do something here for the back button behavior
             // you'll need to set keyCode to 0 if you want to prevent quitting (see above)
            
             themeColor = max(themeColor - 50, 0);
            
              return true; //suppress default
       }
       if (keyCode == MENU) {
             // user hit the menu key, take action
            
             themeColor = min(themeColor + 50, 255);
              return true; //suppress default
       }
       if (keyCode == KeyEvent.KEYCODE_VOLUME_DOWN) {
              themeColor = max(themeColor - 50, 0);
             return true; //suppress default
       }
       if (keyCode ==  KeyEvent.KEYCODE_VOLUME_UP) {
             themeColor = min(themeColor + 50, 255);
              return true; //suppress default
         }
     
      return false;
   }

I've found that it doesn't work on VOLUME_UP on my Samsung Vibrant - still changes the volume and shows the graphic. It DID work to suppress the Search box for KEYCODE_SEARCH though.

Does exiting that way work for you to solve the black screen issue? Updating to 191 and using A3D worked for me. 

Using System.Exit() in onPause is not very clean, I think. onPause() is called when your activity has been put in the background, but not necessarily quit. onPause() is called when even a tiny popup window, or notification panel partially covers up the app. So your app can possibly still be visible while the user looks at the popup or whatever. Quitting then would be a bad idea (although for a Processing app it may be different).

From the dev docs:

Called when the system is about to start resuming a previous activity. This is typically used to commit unsaved changes to persistent data, stop animations and other things that may be consuming CPU, etc. Implementations of this method must be very quick because the next activity will not be resumed until this method returns.

In fact, I don't even think the System.Exit() function is used anywhere in an Android app. Android uses an interesting process model where it never actually exits anything, just frees up parts of the application if it needs to, and restarts others when you need them again. Exiting your entire application would mean Android would have to load EVERYTHING again.

System.Exit(0) does in fact "fix" a black screen issue. However, the app seems to occasionally quit when it's started. I'm not sure why. I've noticed System.Exit(0) seems to cause an issue if it's in the onPause() routine. Why is this?

I tend to forget there's a bug list. I'm adding my info now.