Custom buttons on android with code for android version 4.0 and below

package com.blogspot.programer27android.stopwacth;
import android.content.DialogInterface;import android.support.v7.app.AlertDialog;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.view.KeyEvent;import android.view.WindowManager;
public class Activity extends AppCompatActivity {

    @Override    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);    }
    @Override    public boolean onKeyDown(int keyCode, KeyEvent event) {
        if ((keyCode == KeyEvent.KEYCODE_HOME)) {
            System.out.println("KEYCODE_HOME");            showDialog("'HOME'");            return true;        }
        if ((keyCode == KeyEvent.KEYCODE_BACK)) {
            System.out.println("KEYCODE_BACK");            showDialog("'BACK'");            return true;        }
        if ((keyCode == KeyEvent.KEYCODE_MENU)) {
            System.out.println("KEYCODE_MENU");            showDialog("'MENU'");            return true;        }
        return false;    }

    void showDialog(String the_key){
        AlertDialog.Builder builder = new AlertDialog.Builder(this);        builder.setMessage("You have pressed the " + the_key + " button. Would you like to exit the app?")
                .setCancelable(true)
                .setPositiveButton("OK", new DialogInterface.OnClickListener() {
                    public void onClick(DialogInterface dialog, int id) {
                        dialog.cancel();                        finish();                    }
                })
                .setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
                    public void onClick(DialogInterface dialog, int id) {
                        dialog.cancel();                    }
                });        AlertDialog alert = builder.create();        alert.setTitle("CoderzHeaven.");        alert.show();    }

    @Override    public void onAttachedToWindow() {
        super.onAttachedToWindow();        this.getWindow().setType(WindowManager.LayoutParams.TYPE_KEYGUARD_DIALOG);    }

    public void onUserLeaveHint() { // this only executes when Home is selected.        // do stuff        super.onUserLeaveHint();        System.out.println("HOMEEEEEEEEE");    }
}

is there a solution for android 4.0 and above.
the answer is ..

but only one possibility that we can do. just add code to the manifest ..

<activityandroid:name=".Activity"android:launchMode="singleInstance"><intent-filter>    <action android:name="android.intent.action.MAIN" />
    <category android:name="android.intent.category.HOME" />    <category android:name="android.intent.category.DEFAULT" /></intent-filter></activity>

dan anda harus menentukan apa yang akan dikerjakan oleh onCread() dan apa yang akan dikerjakan oleh onResume()

and you must specify the default application as launcher

thanks..