This enables the back button in keyguard

import android.content.res.Resources;

import android.graphics.Canvas;

import android.os.UserManager;

import android.telephony.TelephonyManager;

import android.util.AttributeSet;

import android.util.Log;

import android.util.Slog;

import android.view.View;

import android.view.WindowManager;

import android.view.animation.AnimationUtils;

import android.widget.Button;

import android.widget.RemoteViews.OnClickHandler;

import android.widget.ViewFlipper;

import com.android.internal.widget.LockPatternUtils;

import java.io.File;

import java.util.ArrayList;

import java.util.List;

public class KeyguardHostView extends KeyguardViewBase {

        dialog.show();

    }

    @Override

    public boolean dispatchKeyEvent(KeyEvent event) {

        if (event.getAction() == KeyEvent.ACTION_UP

                && event.getKeyCode() == KeyEvent.KEYCODE_BACK

                && mCurrentSecuritySelection != SecurityMode.None) {

            mCallback.dismiss(false);

            return true;

        }

        return super.dispatchKeyEvent(event);

    }

    private void showTimeoutDialog() {

        int timeoutInSeconds = (int) LockPatternUtils.FAILED_ATTEMPT_TIMEOUT_MS / 1000;

        int messageId = 0;