android 按两次返回键退出应用
private long mExitTime; @Override public boolean onKeyDown(int keyCode, KeyEvent event) { if (keyCode == KeyEvent.KEYCODE_BACK) { //设置回退 if ((System.currentTimeMillis() - mExitTime) > 2000) { Toast.makeText(this, "再按一次退出程序", Toast.LENGTH_SHORT).show(); mExitTime = System.currentTimeMillis(); } else { this.finish(); } return true; } return super.onKeyDown(keyCode, event); }