Android FragmentStatePagerAdapter，如何标记片段以便以后找到它 [英] Android FragmentStatePagerAdapter, how to tag a fragment to find it later

问题描述

当使用 FragmentStatePageAdapter 我得到这样的片段:

When using the FragmentStatePageAdapter I get the fragments like this:

    @Override
    public Fragment getItem(int position) {
        return new SuperCoolFragment();
    }

但是，稍后在我的代码中，我需要找到这个片段来设置属性.在我使用片段的应用程序的其他一些部分中，我基本上标记它们并使用 findFragmentByTag(TAG) 查找它们，但现在我不知道该怎么做.

However, later on my code I need to find this fragment to set a property. In some other parts of the app where I use fragments I basically tag them and look for them using findFragmentByTag(TAG) but with now I don't know how to do it.

如何使用 FragmentStatePageAdapter 找到片段?

How do can I find the fragments using the FragmentStatePageAdapter?

推荐答案

* EDIT *

正如@ElliotM 指出的，有一个更好的解决方案.无需更改适配器中的任何内容，只需获取片段:

As @ElliotM pointed out, there is a better solution. No need to change anything in your adapter, just get the fragment with:

Fragment myFragment = (Fragment) adapter.instantiateItem(viewPager, viewPager.getCurrentItem());

* 旧解决方案 *

最佳选择是这里的第二种解决方案:http://tamsler.blogspot.nl/2011/11/android-viewpager-and-fragments-part-ii.html

Best option is the second solution here: http://tamsler.blogspot.nl/2011/11/android-viewpager-and-fragments-part-ii.html

简而言之:您跟踪所有活动"片段页面.在这种情况下，您在 ViewPager 使用的 FragmentStatePagerAdapter 中跟踪片段页面.

In short: you keep track of all the "active" fragment pages. In this case, you keep track of the fragment pages in the FragmentStatePagerAdapter, which is used by the ViewPager..

public Fragment getItem(int index) {
    Fragment myFragment = MyFragment.newInstance();
    mPageReferenceMap.put(index, myFragment);
    return myFragment;
}

为了避免保留对非活动"片段页面的引用，我们需要实现 FragmentStatePagerAdapter 的 destroyItem(...) 方法:

To avoid keeping a reference to "inactive" fragment pages, we need to implement the FragmentStatePagerAdapter's destroyItem(...) method:

public void destroyItem(View container, int position, Object object) {
    super.destroyItem(container, position, object);
    mPageReferenceMap.remove(position);
}

...当您需要访问当前可见的页面时，您可以调用:

... and when you need to access the currently visible page, you then call:

int index = mViewPager.getCurrentItem();
MyAdapter adapter = ((MyAdapter)mViewPager.getAdapter());
MyFragment fragment = adapter.getFragment(index);

... MyAdapter 的 getFragment(int) 方法如下所示:

... where the MyAdapter's getFragment(int) method looks like this:

public MyFragment getFragment(int key) {
    return mPageReferenceMap.get(key);
}

---

在你的适配器中添加这个，在方向改变之后:

Also add this in your adapter, for after an orientation change:

/**
 * After an orientation change, the fragments are saved in the adapter, and
 * I don't want to double save them: I will retrieve them and put them in my
 * list again here.
 */
@Override
public Object instantiateItem(ViewGroup container, int position) {
    MyFragment fragment = (MyFragment) super.instantiateItem(container,
            position);
    mPageReferenceMap.put(position, fragment);
    return fragment;
}

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