代码 复制 - 运行

private static Boolean isExit = false; 
    private static Boolean hasTask = false; 
    Timer tExit = new Timer(); 
    TimerTask task = new TimerTask() { 

        @Override 
        public void run() { 
            isExit = false; 
            hasTask = true; 
        } 
    }; 


public boolean onKeyDown(int keyCode, KeyEvent event) { 
                // TODO Auto-generated method stub 
                if(keyCode == KeyEvent.KEYCODE_BACK){ 
//                        System.out.println("user back down"); 
                        if(isExit == false ) { 
                                isExit = true; 
                                Toast.makeText(this, "再按一次退出程序", Toast.LENGTH_SHORT).show(); 
                                if(!hasTask) { 
                                        tExit.schedule(task, 2000); 
                                }} else { 
                                                                                } 
                                finish(); 
                                System.exit(0); 
                        } 
                }                         
                return false; 
        }