Question

I wrote a listener that does some actions onKeyDown basically I need to include it in all my activities but I’m new to Java and don’t know the best way to do it, I can of course just copy paste the code on every class but it would be a pain to keep every one updated.

@Override
public boolean onKeyDown(int keyCode, KeyEvent event)  {
    if(sharedPrefs.getBoolean("pref_disable_keydowns", true)) {
        System.out.println("Prevent keydown");
        return true; 
        }
    return super.onKeyDown(keyCode, event);
}

How can I include this in different .java files so I only have to modify it once to affect all classes it’s included?

Answer 1

Do not never under (nearly) no circumstances copy code from one method to another.

Now to your solution:

public class MyListerer implement KeyListener {

    public void onKeyDown(int keyCode, KeyEvent event){
        Toast.makeText(this, "Hey world!", Toast.LENGTH_LONG).show();
    }
}

Now you can make

object.addKeyListener(new MyListener());

I am pretty sure, that the Interface KeyListener may have a different Name, but I think you get the point.

update

Is it all about Android Activities? http://developer.android.com/reference/android/app/Activity.html

In that case you can implement it a different way. There is no event-listener in Android activites. You can do the following:

class MyActivity extends Activity {

    private MyListener delegate= new MyListener();

    // your existing code

    public boolean onKeyDown(int keyCode, KeyEvent event)  {
        delegate.onKeyDown(keyCode, event);
    }

}