android back键处理

@Override

public boolean onKeyDown(int keyCode, KeyEvent event) {

if(keyCode == KeyEvent.KEYCODE_BACK){

if(System.currentTimeMillis() -lastback >2000){

ToastUtils.showToast("请再按一次退出");

            lastback = System.currentTimeMillis();

        }else {

finish();

        }

return false;

    }

return super.onKeyDown(keyCode, event);

}