api.addEventListener({　　　　
            name: ‘keyback‘　　
        }, function(ret, err) {
            if (flag == 1) {
                api.closeWidget({
                    silent: true
                });
            }　
            else {
                flag = 1;
                api.toast({
                    msg: ‘再点一次退出应用‘,
                    duration: 2000,
                    location: ‘bottom‘
                });
                setTimeout(function() {
                    flag = 0;
                }, 2000);
            }
        });