@Override

    public boolean onKeyDown(int keyCode, KeyEvent event)

    {

        if(keyCode == KeyEvent.KEYCODE_BACK)

        { //监控/拦截/屏蔽返回键

            dialog();

            return false; 

        } else if(keyCode == KeyEvent.KEYCODE_MENU)

        {

            if(isShowButton)

            {

                rly.setVisibility(View.VISIBLE);

                isShowButton = false;

            }else

            {

                rly.setVisibility(View.GONE);

                isShowButton = true;

            }

            return false;

        } else if(keyCode == KeyEvent.KEYCODE_HOME)

        {

            //由于Home键为系统键，此处不能捕获，需要重写onAttachedToWindow()

            return false;

        }

        return super.onKeyDown(keyCode, event);

     }

    protected void dialog()

    {

        AlertDialog.Builder builder = new Builder(WebActivity.this);

        builder.setMessage("确定要退出吗?");

        builder.setTitle("提示");

        builder.setPositiveButton("确认",

        new android.content.DialogInterface.OnClickListener()

        {

            public void onClick(DialogInterface dialog, int which)

            {

                dialog.dismiss();

                WebActivity.this.finish();

            }

        }); 

        builder.setNegativeButton("取消",

        new android.content.DialogInterface.OnClickListener()

        {

            public void onClick(DialogInterface dialog, int which)

            {

                dialog.dismiss();

            }

        }); 

        builder.create().show();

    } 

    /*

    // 拦截/屏蔽系统Home键

    public void onAttachedToWindow()

    {

        this.getWindow().setType(WindowManager.LayoutParams.TYPE_KEYGUARD);

        super.onAttachedToWindow();

    }

    */