再按一次退出程序

功能简单：

package com.amaker.test;

import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.view.KeyEvent;
import android.widget.Toast;

public class SecondActivity extends Activity{
	private long exitTime = 0;
	protected void onCreate(Bundle savedInstanceState) {
		// TODO Auto-generated method stub
		super.onCreate(savedInstanceState);
		setContentView(R.layout.main);
	}
	
	public boolean onKeyDown(int keyCode, KeyEvent event) {
		if(keyCode == KeyEvent.KEYCODE_BACK && event.getAction() == KeyEvent.ACTION_DOWN){   
		    if((System.currentTimeMillis()-exitTime) > 2000){  
		    	Log.d("log", "----------------------->"+String.valueOf(System.currentTimeMillis()));
		        Toast.makeText(getApplicationContext(), "再按一次退出程序", Toast.LENGTH_SHORT).show();                                
		        exitTime = System.currentTimeMillis();   
		    }   
		    else{   
		       finish();   
		       System.exit(0);   
		    }   
		    return true;   
	    }
		return super.onKeyDown(keyCode, event);
	}
}