/**

     * 设置点击返回按钮，跳转到上一个html页面，而不是退出当前activity

     * @param keyCode

     * @param event

     * @return

     */

    @Override

    public boolean onKeyDown(int keyCode, KeyEvent event) {

        if (event.getKeyCode() == KeyEvent.KEYCODE_BACK) {

            if(webView.canGoBack()) {

                //获取webView的浏览记录

                WebBackForwardList mWebBackForwardList = webView.copyBackForwardList();

                //这里的判断是为了让页面在有上一个页面的情况下，跳转到上一个html页面，而不是退出当前activity

                if (mWebBackForwardList.getCurrentIndex() > ) {

                    String historyUrl = mWebBackForwardList.getItemAtIndex(mWebBackForwardList.getCurrentIndex() - ).getUrl();

                    if (!historyUrl.equals(url)) {

                        webView.goBack();

                        return true;

                    }

                }

            } else {

                return true;

            }

        }

        return super.onKeyDown(keyCode, event);

    }