VolumeCombination.java

package com.example

import android.util.Log;
import android.view.KeyEvent;

/**
 * Created by mat on 10/04/14.
 *
 * Allows a secret combination of volume up / volume down presses to trigger something.
 * I.E. reveal a hided debug menu when a combination is entered
 * In the example below 2431 would be triggered by pressing
 * down down, up up up up up, down down down, up
 *  or
 * up up, down, down, down, down, up, up, up, down
 */

  private VolumeCombination volumeCombination;
 
  // Create a new VolumeCombination with secret code and a listener for unlocking 
  volumeCombination = new VolumeCombination("2431", new VolumeCombination.UnlockListener() {
    @Override
    public void onUnlock() {
	Toast.makeText(StartActivity.this, "Unlocked ^_^", Toast.LENGTH_SHORT).show();
    }
  });
      
  // Override onKeyDown in your activtiy or fragment and pass the event to 
  @Override
  public boolean onKeyDown(int keyCode, KeyEvent event){
      if (volumeCombination.checkVolumeCombination(keyCode, event)) return true;
      return super.onKeyDown(keyCode, event);
  } 
 */
public class VolumeCombination {

    private static final long TIMEOUT_PREVIOUS_PRESS = 2000;
    public UnlockListener unlockListener;

    public String secretCode;
    public String currentAttempt = "";
    public long prevPress = 0;

    public int curNo = 0;
    public int prevKey = -1;

    public VolumeCombination(String secretCode, UnlockListener unlockListener){
        this.secretCode = secretCode;
        this.unlockListener = unlockListener;
    }

    interface UnlockListener{
        public void onUnlock();
    }

    public boolean checkVolumeCombination(int keyCode, KeyEvent keyEvent){
        if (keyCode == KeyEvent.KEYCODE_VOLUME_UP || keyCode == KeyEvent.KEYCODE_VOLUME_DOWN){
            if (System.currentTimeMillis()-prevPress>TIMEOUT_PREVIOUS_PRESS){
                // If user doesn't press a volume for a while, clear the attempt
                Log.i("VOLUME COMBINATION: ", "Timeout...");
                curNo=0;
                prevKey=-1;
                currentAttempt="";
            }
            if (prevKey==keyCode || prevKey==-1){
                // If it's the same key add one to current letter of code
                curNo++;
            }
            else{
                // If it's different move on to next letter
                currentAttempt += curNo;
                curNo=1;
            }
            Log.i("VOLUME COMBINATION: ", ""+currentAttempt+curNo);
            if (secretCode.equals(currentAttempt+curNo)){
                unlockListener.onUnlock();
            }
            // If our current string is too long, drop the start
            if (currentAttempt.length()==secretCode.length()) currentAttempt = currentAttempt.substring(1);
            prevKey = keyCode;
            prevPress = System.currentTimeMillis();
            return true;
        }
        return false;
    }
}