popBack function
pop 返回简写 带参数 nullBack
=true navigator 返回为空 就继续返回上一页面
Implementation
void popBack(Future<dynamic> navigator,
{bool nullBack = false, bool useMaybePop = false}) {
final Future<dynamic> future = navigator;
future.then((dynamic value) {
if (nullBack) {
pop(value, useMaybePop);
} else {
if (value != null) pop(value, useMaybePop);
}
});
}