以编程方式隐藏/显示上下文操作栏 [英] Hiding/showing the contextual action bar programmatically

问题描述

我的用例:

我有一个以 ViewPager 作为唯一视图元素的活动，为其三个页面设置了三个 Fragment(使用 FragmentPagerAdapter>).其中一个片段是 ListFragment，而另外两个常规 Fragment 包含一些信息图表.

I have an activity with a ViewPager as its only view element, set up with three Fragments for its three pages (using a FragmentPagerAdapter). One of these fragments is a ListFragment, while the other two regular Fragments containing some infographics.

ListFragment 中的列表允许检查"元素，检查元素会显示上下文操作栏，显示对选定/选中的项目可能执行的操作列表.

The list in the ListFragment allows "checking" elements, and checking elements brings up the contextual action bar, presenting a list of actions possible on the selected/checked items.

我的问题:

当我选择几个列表项时，CAB 就会出现.但是当我切换页面时，CAB 保持可见，显示操作.更糟糕的是，ViewPager 似乎有时会破坏列表片段的视图 - 因此选择操作会抛出 "java.lang.IllegalStateException: Content view not yet created" 例外.

When I select a couple of list items, the CAB shows up. But when I switch pages, the CAB stays visible, presenting the actions. To make matters worse, the ViewPager seems to sometimes destroy the view of the list fragment - hence selecting the actions throws a "java.lang.IllegalStateException: Content view not yet created" exception.

我的问题:

1. 当用户离开 ListFragment 页面时，如何让 CAB 消失?
2. (可选)当 ListFragment 返回且某些项目仍处于检查状态时，如何让 CAB 重新出现.

1. How do I get the CAB to disappear when the user moves away from the ListFragment page?
2. (optional) How do I get the CAB to reappear when the ListFragment back is and some items are still checked.

推荐答案

你需要先添加一个 ViewPager.OnPageChangeListener 和 ViewPager.OnPageChangeListener 到你的 viewPager.

You need to first add a ViewPager.OnPageChangeListener with ViewPager.OnPageChangeListener to your viewPager.

在 onPageSelected 方法中调用 ListFragment 中的方法来关闭 CAB.

In the onPageSelected method call a method in your ListFragment to dismiss your CAB.

要获取当前的活动片段，您可以使用它的标签.可以用这种方法计算标签:

To get the current active fragment you can use it's tag. The tag can be computated with this method:

private static String makeFragmentName(int viewId, int index) {
   return "android:switcher:" + viewId + ":" + index;
}

其中viewId是viewpager的id并索引标签索引(位置)

where viewId is the id of the viewpager and index the tab index (position)

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