android 返回键两次退出

返回键两次退出

    private long exitTime = 0;
    @Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
        if(keyCode == KeyEvent.KEYCODE_BACK && event.getAction() == KeyEvent.ACTION_DOWN){   
            if((System.currentTimeMillis()-exitTime) > 2000){  
                Toast.makeText(getApplicationContext(), "再按一次退出程序", Toast.LENGTH_SHORT).show();                                
                exitTime = System.currentTimeMillis();   
            } else {
                finish();
                android.os.Process.killProcess(android.os.Process.myPid()); //获取PID 
                System.exit(0);
            }
            return true;   
        }
        return super.onKeyDown(keyCode, event);
    }